Effects of Date of Sowing on the Yield and Yield Components of ...


Effects of Date of Sowing on the Yield and Yield Components of ...

Wheat Special Report No. 23aong>Effectsong> ong>ofong>ong>Dateong> ong>ofong> ong>Sowingong> on the Yieldand Yield Components ong>ofong> Spring Wheatand their Relationship with Solar Radiationand Temperature at Ludhiana, Punjab, Indias.s. Dhillon and J.1. Ortiz-Monasterio R.November 1993

ContentsivivPrefaceAcknowledgments1 Introduction3 Materials and Methods3 Effect ong>ofong> genotype, planting date, and year on yield, yield components, andphenology ,3 Effect ong>ofong> PTQ, temperature, and solar radiation on yield and GM2 duringpre-anthesis4 Absolute and relative losses with delayed sowing7 Results and Discussion7 Statistical analysis ,8 Effect ong>ofong> genotype, planting date, and year on yield, yield components,and phenology10 Effect ong>ofong> PTQ, temperature, and solar radiation on yield and GM2 duringpre-anthesis12 Effect ong>ofong> temperature and solar radiation during post-anthesis period on grainyield and TGW12 Use ong>ofong> the PTQ for explaining year effects13Absolute and relative losses with delayed sowing13 Conclusions14 References15 Figure 1. Yield response ong>ofong> three spring wheat genotypes to seven dates ong>ofong> planting16 Figure 2. Yield response over 4 years to seven dates ong>ofong> planting17 Figure 3. GM2 response ong>ofong> three wheat genotypes to seven dates ong>ofong> planting18 Figure 4. Changes in TGW and days to heading ong>ofong> three wheat genotypes over 4years and seven dates ong>ofong> planting19 Figure 5. Changes in days to maturity and grain-filling days ong>ofong> three wheatgenotypes over 4 years and seven dates ong>ofong> planting20 Figure 6. Relationship between grain yield and PTQ2 and grain yield and meantemperature in three wheat genotypes21 Figure 7. Relationship between grain yield and solar radiation and grain yield andGM2 in three wheat genotypes22 Figure 8. Relationship between GM2 and PTQ2 and GM2 and mean temperature(-20H to +lOH) in three wheat genotypes23 Figure 9. Relationship between GM2 and solar radiation and yield and PTQ(+lOH to +40H) in three wheat genotypes24 Figure 10. Relationship between grain yield and mean temperature (+ lOH to +40H)and grain yield and solar radiation (+ lOH to +40H)25 Figure 11. Relationship between grain yield and TGW and TGW and PTQ (+ lOH to+40H) in three wheat genotypes26 Figure 12. Relationship between TGW and mean temperature (+lOH to +40H) andTGW and solar radiation (+10H to +40H) in three wheat genotypes27 Figure 13. Relationship between TGW and mean temperature (+lOH to +40H)over 4 years in three wheat genotypesii

PrefaceThis Wheat Special Report analyzes the effects ong>ofong> radiation and temperature on the date ong>ofong>flowering and grain yield ong>ofong> spring bread wheat cropped under optimum conditions. Theexperiments were conducted at Ludhiana, Punjab, India, over 7 years and using a range ong>ofong>genotypes. The optimum flowering date for maximization ong>ofong> wheat grain yields is confirmedto be when the ratio ong>ofong> radiation to temperature (PTQ) is at its maximum. The individualeffects ong>ofong> radiation and temperature on yield and yield components at various stages ong>ofong> cropdevelopment are also examined.We hope that the concepts validated here will be useful elements ong>ofong> wheat componentagronomy in the development ong>ofong> new spring wheat varieties and better agronomic practicesfor wheat grown under irrigation (Mega-environment 1).This short version (No. 23a) does not include the raw data that may be ong>ofong> interest to somescientists. This information (Le., correlation coefficients for the three genotypes used in theexperiments, means averaged across reps, and climatic data) is provided in Appendices 2through 5, which are included in No. 23b.S.S. Dhillon is an agronomist with the Department ong>ofong> Plant Breeding, Punjab AgriculturalUniversity, Ludhiana, India, and J.1. Ortiz-Monasterio R. is an agronomist, with the WheatProgram, Crop Management and Physiology Subprogram, CIMMYT, Mexico.E. AcevedoLeaderCrop Management and Physiology SubprogramCIMMYT Wheat ProgramAcknowledgmentsWe wish to thank especially Dr. R.A. Fischer for his guidance and suggestions during dataanalysis and Drs. E. Acevedo and K.D. Sayre for their discussions and suggestions on thetopic.iv

IntroductionWheat is the main cereal crop ong>ofong> the Indian Punjab. The main objectives ong>ofong> the India'swheat production programs are to increase production to achieve self-sufficiency in foodgrains, and to step up and establish production at a higher level. During 1965-66, wheatacreage in India was 12.79 million hectares; this area increased to 24.0 million hectaresduring 1991-92, an 88% increase. Wheat production for this same period increased from10.7 million tons to 54.5 million tons, 409% increase. As shown in Table 1, yieldincreases contributed significantly to the production increase.Similarly, in the Punjab, while the area has doubled since 1965-66, production hasincreased more than sixfold (Table 2). This is explained by the increase in yield from1104 kglha in 1965-66 to 3715 kglha in 1990-91.Table 1. Area, production, and yield or wheat in India rrom 1965 to 1992.Year Area (000 ha) Production (000 tons) Yield (tll1a)1965-66 12.79 10.72 0.841970-71 17.89 23.24 1.231975-76 20.11 28.33 1.411980-81 22.10 36.46 1.651985-86 23.07 46.89 2.031990-91 23.50 49.90 2.121991-92 24.00 54.50 2.27Table 2. Area, production and yield ong>ofong> wheat in Punjab from 1965 to 1991.Area Production YieldYear (000 ha) (000 tons) (tll1a)1965-66 1548 1916 1.101970-71 2299 5145 2.241975-76 2449 5809 2.371980-81 2808 7669 2.731985-86 3113 10992 3.531990-91 3272 12155 3.72Intensive crop rotations have been widely adopted due to the availability ong>ofong> moreirrigation facilities. Wheat occupies a dominant place in double and multiple croppingsystems. Approximately 80% ong>ofong> the total cropped area during the rabi (winter) season inPunjab is sown under wheat. Thus, wheat follows practically all kharif (summer) crops inPunjab. The most common rotations involving wheat are:1

Rice-WheatCotton-WheatMaize-WheatRice-Wheat-Sesbania (Green Manure)MaizelRice-Potato-WheatGround nut-WheatRice- Pea-WheatMaize fodder- Brassica-WheatKhari f Pulses-WheatDepending upon the maturity and harvesting ong>ofong> the previous summer crop, the time ong>ofong>sowing wheat is extended from the end ong>ofong> October to the end ong>ofong> December. Losses ingrain yield with delayed planting have been reported in Punjab (Randhawa et al. 1981).The wheat crop is greatly influenced by temperature and radiation prevailing during theseason, particularly when water and nitrogen are not limiting. Nix (1976) showed thattemperature and radiation influence plant processes differently, but there combined effectcan be usefully described as a photothermal quotient (PTO). PTO is defined as the ratioong>ofong> daily total solar radiation in MJ/m 2 /day divided by the mean daily temperature minus4.5 0 C (base temperature). Midmore et al. (1984) and Fischer (1985) observed thatgrains/m 2 (GM2) in wheat was associated with PTO over 30 days preceding anthesis.Grain yield reductions with delayed sowing under optimal conditions ong>ofong> water andnitrogen have been attributed to reduced GM2 caused by higher pre-anthesistemperatures (Fischer and Maurer 1976) and to reduced thousand grain weight (TGW)caused by higher post anthesis temperatures (Song>ofong>ield et aJ. 1977, McDonald et aJ. 1983),even though the irradiance levels also increased in each case. The wheat crop seems to besource-limited during the pre-anthesis phase when GM2 is being determined--particularlyduring the phase ong>ofong> rapid spike growth and development, which occurs 20 to 30 daysprior to anthesis.It has been demonstrated that the number ong>ofong> grains is determined by the carbohydratesupply to the crop during this phase. Specifically, it has been estimated that 10 mg ong>ofong>carbohydrates directed to the growing spike are required during rapid spike growth tokeep a potential grain from aborting (Fischer 1984), for wheat crops that do not sufferfrom nutrient or water stress and without competition from weed, diseases, and pests. Thetheory behind the PTO is based on the assumption that radiation (assuming close to fulllight interception) and temperature are the driving forces in assimilate production anddevelopment rate, respectively, during this critical phase. High radiation values, througha larger assimilate production and low temperatures, by extending the crop durationduring this critical phase. Therefore, high PTO values should result in a larger number ong>ofong>GM2. Fischer (1985) specifically applied the PTO concept to explain the effects ong>ofong>radiation and temperature on kernel number in wheat crops. He confirmed that dry matteraccumulation under conditions at Ciudad Obregon, Sonora, Mexico (January to March)was linearly related to absorbed photosynthetic radiation (slope ong>ofong> 3 g/MJ PARA; PARA= 0.45 * incident solar radiation for full ground cover). He also inferred mainlyfrom theliterature that rate ong>ofong> development during the terminal spikelet to anthesis period waslinear with respect to average temperature (max + minl2) minus a base temperature ong>ofong>4.S°C.The PrO was calculated on a daily basis with the following algorithm:if T mean> 10 PrO= solar radiation/«max + min)/2)ifT mean

The last relationship means that, for a given solar radiation, maximum PTQ is reached atT mean =10, but PTQ rapidly and linearly drops to zero at T mean =4.5.The field studies in Ludhiana were undertaken from 1985-86 to 1991-92 with threeobjectives:• To find the optimum planting date for wheat in the Punjab.• To find the absolute and relative losses in grain yield, GM2 and TGW, withdelay in sowing from the optimum time.• Understand the first two objectives in terms ong>ofong> the effect ong>ofong> temperature andradiation combined and separately on yield, GM2, and TGW.Materials and MethodsField experiments were conducted from 1985 through 1992 on a loamy sand soil atPunjab Agricultural University, Ludhiana. Ludhiana is situated at 30 0 54' N latitude and75 0 48' E longitude and 247 mas!. Sixty-six genotypes having spring growth habit and tendates ong>ofong> planting were studied, although not all genotypes and planting dates were studiedeach year. The genotypes and planting dates sown each year are given in Table 3. Theplots were managed under optimal conditions ong>ofong> fertilizer and irrigation. Broad leaf andother grassy weeds were completely controlled by hand hoeing. The net plot areaharvested for each genotype was 7.36 m 2 in each year. The seeding density used in allgenotypes, planting dates, and years was 100 kglha. Heading date was defined as the datewhen about 75% ong>ofong> the spikes had fully emerged from the boot and maturity date when100% ong>ofong> the spikes were without green color. GM2 was calculated from grain yield andTGW. The treatment design was a factorial combination ong>ofong> planting dates and genotypesarranged as a split-plot design with three replications. Main plots were planting dates andsubplots were genotypes.Effect ong>ofong> genotype, planting date, and year on yield, yield components,and phenologyThe statistical analysis was done first by years for all the planting dates and genotypes.Then a combined analysis ong>ofong> an orthogonal subset ong>ofong> data was done for 4 years (1987-88,1988-89, 1989-90, and 1991-92), three replications, three genotypes [PBW 34 (longseason), PBW 154 (medium season) and PBW 226 (medium to short season)], and sevenplanting dates (Oct. 25, Nov. 5, Nov. 15, Nov. 25, Dec. 5, Dec. 15, and Dec. 25) to studythe interactions ong>ofong> genotype x year, planting date x year and genotype x planting date xyear. Replications and experiments were considered as random effects and genotype andplanting dates as fixed effects.Effect ong>ofong> PTQ, temperature, and solar radiation on yield and GM2 during thepre-anthesis periodTo evaluate the effect ong>ofong> temperature and radiation on yield, GM2, and TGW, thecomplete data set (all years and dates) ong>ofong> the selected genotypes was used. Weathervariables, such as temperature, radiation, etc., were recorded at a weather station less than1 km from the experimental plots. The following PrQs were generated by calculating thedaily PTQ and averaging them for different periods:PTQ1: -30 days to heading,PTQ2: From -20 days to heading to +10 days after heading,PTQ3: -20 days to heading,3

PTQ4: From -20 days to heading to +20 days after heading,PTQ TGW: From heading +10 days to heading +40 days.The PTQs were expressed as MJ/m 2 /dayf'C. The correlations between PTQs for theabove periods and yield and GM2 are given in Appendix 1. Out ong>ofong> the four PTQs, PTQ2calculated in the pre-heading phase was more consistent for predicting GM2 and wasselected for further use. The post-anthesis photothermal quotient (PTQ TGW), calculatedfrom heading +10 to heading +40 days period, was used with TGW.Absolute and relative losses with delayed sowingTo calculate the absolute and relative losses caused by delayed planting date, only datafrom the optimum planting date to 25DEC were used. The optimum planting dates were05NOV for PBW34 and NOV15 for PBW154 and PBW 226. Then absolute and relativelosses were calculated from that date to 25DEC for all three genotypes. The 25DEC datewas selected because there are basically no farmers planting beyond this planting date.Data from a different number ong>ofong> years were available for each genotype; PBW 34(average ong>ofong> 6 years) PBW 154, (average ong>ofong> 7 years), and PBW 226 (average ong>ofong> 5 years).The method ong>ofong> analysis to estimate yield losses due to delays in planting date was donewith the following regression functions:Yi = a + bPDi + u absolute ( 1 )In(Yi) = a + bPDi + u relative ( 2 )where Yi is the yield in kg/ha ong>ofong> planting date i, In(Yj) is the natural log ong>ofong> Yi' and PDi isthe Julian date for the planting date i. The linear speCification (function 1) provides anestimate ong>ofong> the yield reduction due to delays in planting dates in absolute terms (Le., bmeasures kg/halday yield loss) while the logarithmic specification in function (2) givesthe relative yield reduction (i.e., 100 (dq/dVi)ri =100b measures the percent per dayyield loss) (Gujarati 1988).Table 3. Detail ong>ofong> genotypes and planting dates used in the experiments from 1985­86 to 1991-92.Exp. Year ong>Sowingong> ong>Dateong>s GenotypesCalendarJulian1 1985-86 150cr 288 WL711250cr 298 PBW3405NOV 308 PBW 12015NOV 318 PBW5425NOV 328 PBW 13805DEC 338 PBW 15415DEC 348 PBW 15925DEC 358 PBW 17905JAN 5 PBW 18115JAN 15 SKAMLIHD2285TL12104

Table 3. Continued.Exp.YearCalendarong>Sowingong> ong>Dateong>sJulianGenotypes2 1986-87150cr250cr05NOV15NOV25NOV050EC150EC250EC05JAN15JAN288298308318328338348358515WL 711PBW 120PBW 138PBW 154PBW 188PBW 189PBW34PBW 206SKAMLI3 1987-884 1988·89150cr25NOV.05NOV15NOV25NOV050EC150EC250EC250cr05NOV.15NOV25NOV050EC150EC250EC288298308318328338348358298308318328338348358WL 711PBW 154PBW 222PBW 226PBW 230SKAMLIPBW34POW 212TL2603WL 1562PBW 222PBW 226POW215POW 218HO 2329HO 2428PBW 138PBW 154PBW345 1989-90150CT25OCT05NOV15NOV25NOV050EC150EC250EC288298308318328338348358PBW 154PBW222PBW226POW 215PBW34HO 2329POW 22061990·91200CT25OCT05NOV15NOV25NOV050EC150EC293298308318328338348PBW 154PBW222PBW226POW 215POW 225POW 227HD 23295

Table 3. Continued.Exp. Year ong>Sowingong> ong>Dateong>s GenotypesCalendarJulian25DEC 35805JAN 57. 1991-92 200CT 293 PBW 154250CT 298 PBW 22205NOV 308 PBW 13815NOV 318 PBW 22625NOV 328 HD 232905DEC 338 HD 228515DEC 348 CPAN300425DEC 358 WH54205JAN 5 POW 215POW 233PBW 234PBW34Table 4 shows a summary ong>ofong> the climatic data for the years ong>ofong> this study. The year 1988­89 had the lowest mean temperatures for the months ong>ofong> January and February comparedto other years. The solar radiation during February was the highest 18.05 MJ/m 2 in 1988­89 and the lowest 11.13 MJ/m 2 in 1989-90. There was not much variation in othermonths ong>ofong> the various years under study except that in 1988 April was the hottest both formaximum and minimum temperatures. The year 1988-89 can be considered climaticallyas the better year among all given the low temperatures and high radiation levels in thepre-anthesis phase, as shown by the PTQ values in the month ong>ofong> February.Table 4. Maximum, minimum, solar radiation, and PTQ values for Ludhiana, India(30° 54') for the wheat seasons studied.Year Oct. Nov. Dec. Jan. Feb. March AprilMaximum temperature (0C)1985-86 29.9 26.2 21.2 18.8 20.4 25.3 33.41986-87 30.4 26.6 19.5 19.6 22.9 26.8 34.91987-88 32.2 27.8 21.6 19.5 22.8 26.1 36.11988-89 31.8 26.5 21.1 17.7 20.7 ~6.2 32.91989-90 32.8 26.1 18.8 19.7 19.7 .24.6 34.21990-91 30.7 26.9 20.2 18.3 21.2 25.8 31.91991-92 31.8 26.0 20.0 17.7 19.7 25.3 33.16

Table 4. Continued.Year Oct. Nov. Dec. Jan. Feb. March AprilMinimum temperature (0C)1985-86 17.1 :0.1 8.2 4.2 6.4 11.6 17.21986-87 16.8 11.7 6.1 5.7 9.1 12.8 17.71987-88 18.1 10.1 6.0 6.4 7.8 12.3 17.91988-89 16.2 11.7 7.1 4.8 6.3 11.5 15.21989-90 16.0 11.6 7.6 7.7 9.3 11.2 16.81990-91 16.4 11.5 7.4 5.3 8.6 12.0 16.21991-92 15.0 10.1 7.6 7.2 7.4 11.8 16.8Solar radiation (MJ/m 2 )1985-86 17.17 13.31 10.34 12.52 14.05 19.41 23.361986-87 16.39 11.99 11.40 11.14 14.48 17.31 22.391987-88 16.28 13.97 11.64 11.69 15.87 18.62 21.951988-89 17.74 12.81 10.42 11.55 18.05 18.78 24.461989-90 16.67 13.15 9.36 11.22 11.13 18.49 22.881990-91 9.42 12.17 13.25 16.92 19.971991-92 15.42 12.06 8.98 8.47 13.23 15.45 16.58PTQ (MJ/M1Jday/°C)1985-86 0.91 0.99 1.08 1.77 1.56 1.42 1.151986-87 0.87 0.83 1.48 1.39 1.28 1.14 1.061987-88 0.81 0.98 1.28 1.44 1.52 1.30 0.981988-89 0.91 0.90 1.10 1.72 2.18 1.36 1.301989-90 0.84 0.93 1.05 1.23 1.17 1.48 1.111990-91 1.01 1.60 1.37 1.20 1.041991-92 0.82 0.90 1.02 1.12 1.56 1.15 0.84Results and DiscussionStatistical analysisThe statistical analysis ong>ofong> individual years for yield, GM2, and TGW revealed thatsowing dates and genotypes had significant effect on yield and yield components in allthe years (Table 5). However, the interaction between sowing dates and genotypes wasnot significant for yield in three years (1985-86, 1986-87, and 1991-92) and GM2 in 2years (1987-88 and 1990-91).The combined analysis ong>ofong> the orthogonal subset ong>ofong> data for four years, three genotypesand seven planting dates revealed that planting date x genotype interactions weresignificant for yield and GM2 (Table 6). Also the year x planting date interaction wassignificant for grain yield. The year x planting date x genotype interaction was significant7

Table 5. Statistical analysis by years for yield, GM2, and TGW.Year ong>Dateong>s Genotype ong>Dateong> x SEb a CV%Genotype1985-86 Yield (kglha)GM2TGW (g)••••••••••••••••••211.91534.910.57012.0412.082.491986-87 Yield •• •• .* 205.16 10.81GM2 .* *. ** 517.70 10.82TGW *. ** ** 0.595 2.611987-88 Yield •• .* NS 218.76 10.46GM2 ***NS 561.16 11.15TGW ••**** 0.582 2.40-1988-89 Yield ** .* NS 311.42 11.64GM2 -* ** 693.39 11.77TGW •• -* ** 0.612 2.341989-90 Yield ** ** • 191.31 8.77GM2 ** ** •• 466.29 9.16TGW ** ** ** 0.629 2.54_.1990-91 Yield ** NS 220.61 10.88GM2 .* ** NS 541.77 11.38TGW ** ** ** 0.669 2.75.*1991-92 Yield ** ** 302.97 12.80GM2 * ** * 777.71 13.05TGW ** ** ** 0.606 2.62... Significant at P « =0.05); ** Significant at P « =0.01); NS =nonsignificant.a Standard error ong>ofong> the difference between two means for comparison ong>ofong> two subplot means at the samemain plot level.for TGW, days to heading (Days H), days to maturity (Days M), and grain-filling days(Days H-M).Effect ong>ofong> genotype, planting date and year on yield, yield components,and phenologyYield--As the combined analysis shows, the three-way interaction between year, plantingdate, and genotype was not significant. This suggests that the genotype by planting dateinteraction, which was significant, was independent ong>ofong> the year effect. The mean grainyield across years at the earliest planting date (250CI) was 4354, 4505, and 4133 kglhafor PBW 34, PBW 154, and PBW 226, respectively. By delaying the planting date to05NOV and 15NOV, the yield ong>ofong> all three genotypes improved except for PBW 34,which produced the highest yield on the 05NOV planting date (Figure 1). The 15NOV8

Table 6. Combined analysis ong>ofong> orthogonal subset ong>ofong> data 4 years, three replications,three genotypes, and seven planting dates.Source ong>ofong> variation df Yield GM2 TGW Days Days Days(kglha) (g) H M H-MY 3 ** NS ** ** * **Rep(Y)8Planting date 6 ** ** ** ** ** **Y x P date 18 ** NS ** ** ** **Y x rep x P date48Genotype 2 ** ** NS ** ** **Y x genotype 6 NS NS ** ** ** **P date x genotype 12 ** ** NS ** ** **Y x P date x genotype 36 NS NS ** ** * **Error112Standard error'l 136 415 1.42 1.80 0.64 1 1.80* significant at P « = 0.05); ** significant at P « = 0.01); NS non significanta Standard error ong>ofong> the difference between two means for comparison ong>ofong> two subplotmeans at the same main plot level.planting date produced the highest yield for paw 226 (5050 kg/ha) followed by paw154 (4744 kg/ha) and paw 34 (4138 kg/ha). With further delay in planting date, theyield ong>ofong> all the three genotypes decreased. However, the rate ong>ofong> reduction was moresevere in paw 34 compared to PBW 154 and PBW 226 (Figure 1). Therefore, thegenotype by planting date interaction can be explained by the earlier optimum plantingdate ong>ofong> PBW34 as well as the faster decline in yield ong>ofong> this genotype compared toPBW154 and PBW 226. A significant interaction for yield between years and plantingdate revealed that 1988-89 was the highest yield year for all genotypes at all the plantingdates except 25DEC. At this planting date, 1991-92 produced 3502 kglha compared to3351 kglha in 1988-89 (Figure 2). As mentioned before, 1988-89 had the lowesttemperature and the highest radiation and PrQ in the pre-anthesis period.Yield componenls--The response ong>ofong> GM2 was very similar to that ong>ofong> yield, in contrast toTGW. The three-way interaction for GM2, between year, planting date, and genotypewas not significant. However, the genotype by planting date interaction was significant.The number ong>ofong> GM2 for all three genotypes, averaged across the years under differentplanting dates, had a similar trend to that ong>ofong> yield, which shows the predominant role ong>ofong>GM2 in determining final yield (Figure 3). For TGW, the genotype by planting dateinteraction also interacted with year. TGW for all three genotypes decreased with anydelay in planting date after 150CT in all the years (Figure 4a). However, among years,1988-89 produced heavier grains compared to others in all genotypes at almost allplanting dates. In addition, 1987-88 had a different pattern ong>ofong> TGW reduction with delaysin planting date compared to the other years. The ranges ong>ofong>TGW across years and dateswere 45-56, 44-52, and 44-48g for PBW 34, PBW 154, and PBW 226, respectively.Phenology--The interaction between genotype, planting date, and year was significant fordays to heading, days to maturity, and grain-filling days. The ranges ong>ofong> number ong>ofong> days to9

headi ng across years and dates were 99-111, 90-100, and 88-93 for PBW 34, PBW 154,and PBW 226, respectively (Figure 4b). It is also clear from the data that PBW 34 tookthe maximum days to heading when planted on 250cr; for the other two genotypes, themaximum was reached usually on 15NOV. The number ong>ofong> days to heading was reducedwith further delays in sowing in all the genotypes. The number ong>ofong> days to maturity weredrastically reduced with any delay in planting after 150cr for all three genotypes and inall four years (Figure Sa). In general, the number ong>ofong> grain-filling days was reduced withany delay in planting date for all genotypes, however, for PBW 34 the rate ong>ofong> reductionwas slower than for the other two genotypes (Figure 5b). Undoubtedly, PBW34 reachedheading later than the other genotypes in early plantings. The steadily increasingmaximum and minimum temperatures (Table 4) during February, March, and April mayhave caused the late planting date to produce lower number ong>ofong> GM2, lower TGW, andultimately lower yields. Radiation increases should, however, have compensated to someextent for the increase in temperature. The next section examines these relationships.Effect ong>ofong>PTQ, temperature, and solar radiation on yield and GM2 during the preanthesisperiodEffect on grain yie/d--Grain yield across planting dates was linearly and positivelycorrelated with the pre-anthesis photothermal quotient (-20 H to +10 H) for all threegenotypes (Figure 6a). The correlation coefficient values were 0.95, 0.70, and 0.64 forPBW 34, PBW 154, and PBW 226, respectively, including all points in the graph.Generally, grain yield increased with the increase in PTO values--except in the 15JANlate planting in genotypes PBW 34 and PBW 154 (there was no 15JAN planting for PBW226) where the PTO values were relatively high, but grain yield was not. It is believedthat in the 15JAN planting the crops were exposed to high temperatures around meiosisand anthesis causing spike sterility, resulting in a lower number ong>ofong> GM2 and, in turn,yield for a given PTO value. The other possible explanation is that, in the 15JANplanting, PBW34 and PBW 154 did not reach full light interception, therefore they couldnot efficiently use the available radiation. Thus, although PTO values were relativelyhigh, yield and GM2 were low. The effect ong>ofong> temperature during the pre-anthesis period(-20 H to +10 H) was found to be negatively correlated with yield across planting datesfor all the genotypes, PBW 34 (r = -0.92), PBW 154 (r = -0.86), and PBW 226 (r = -0.86)(Figure 6b). Similarly, yield was also found to be negatively correlated with solarradiation during the pre-anthesis period for PBW 34 (r = -0.86), PBW 154 (r = -0.71),and PBW 226 (r = -0.40) (Figure 7a). PBW 34 was found to be relatively more sensitiveto higher temperature and solar radiation conditions. We would expect solar radiation tobe positively correlated with yield, however, due to the high autocorrelation betweensolar radiation and temperature, this correlation becomes negative (Table 7).Effect on GM2--For all three genotypes, GM2 was positively correlated with grain yieldacross planting dates. The correlation coefficients (r) were 0.97,0.97, and 0.84 for PBW34, PBW 154, and PBW 226, respectively (Figure 7b). GM2 was positively correlatedwith PTO during the pre-anthesis period (-20 H to +10 H). The number ong>ofong> GM2 rangedfrom 3790 to 11,550 and PTOs from 1.08 to 1.58 MJ/m 2 /dayPC. The correlationcoefficients (r) were 0.89,0.72, and 0.94 for PBW 34, PBW 154, and PBW 226,respectively (Figure 8a). GM2 increased as PTO increased, except for the 15JANplanting. See the above explanation on yield.GM2 was negatively correlated with mean temperature during the pre-anthesis period (­20 H to +10 H) for all three genotypes, PBW34 (r=-0.81), PBW154 (r=-0.73), and PBW226 (r =-0.48) (Figure 8b).The number ong>ofong> grains were also negatively correlated with solar radiation during the preanthesis(-20 H to +10 H) period, for PBW 34 (r = -0.73), and PBW 154 (r =-0.55).10

Table 7. Correlation using values averaged across year for yield, yield components, and climaticvariables in three genotypes.PBW34Days Yield GM2 TGW MTIGW RADTGW PTQTGW MTGM2 RADGM2 PTQ2Days 1.000Yield -0.953 1.000GM2 -0.868 0.971 1.000TGW -0.994 0.938 0.834 1.000MTIGW 0.991 -0.907 -0.797 -0.991 1.000RADTGW 0.963 ·0.852 -0.719 -0.968 0.988 1.000PTQTGW -0.985 0.896 0.787 0.985 -0.992 -0.969 1.000MTGM2 0.990 -0.924 -0.814 -0.992 0.995 0.985 -0.982 1.000RADGM2 0.954 -0.855 -0.730 -0.959 0.972 0.981 -0.965 0.975 1.000PTQ2 -0.943 0.949 0.885 0.939 -0.920 -0.878 0.898 -0.930 -0.826 1.000PBW 154Days Yield GM2 TGW MTIGW RADTGW PTQTGW MTGM2 RADGM2 PTQ2Days 1.000Yield -0.849 1.000GM2 -0.721 0.974 1.000TGW -0.973 0.919 0.811 1.000MTIGW 0.991 -0.781 -0.634 -0.951 1.000RADTGW 0.976 -0.731 -0.576 -0.928 0.994 1.000PTQTGW -0.963 0.706 0.538 0.918 -0.988 -0.986 1.000MTGM2 0.970 -0.862 -0.727 -0.974 0.962 0.942 -0.947 1.000RADGM2 0.961 -0.709 -0.547 . -0.921 0.986 0.996 -0.987 0.940 1.000PTQ2 -0.386 0.703 0.717 0.501 -0.294 -0.213 0.248 -0.512 -0.194 1.000PBW 226Days Yield GM2 TGW MTTGW RADTGW PTQTGW MTGM2 RADGM2 PTQ2Days 1.000Yield -0.587 1.000GM2 -0.067 0.841 1.000TGW -0.992 0.601 0.076 1.000MTTGW 0.987 -0.516 0.026 -0.993 1.000RADTGW 0.899 -0.214 0.332 -0.882 0.924 1.000PTQTGW -0.658 0.770 0.454 0.735 -0.686 -0.386 1.000MTGM2 0.847 -0.858 -0.476 -0.876 0.836 0.607 -0.886 1.000RADGM2 0.902 -0.397 0.147 -0.933 0.956 0.912 -0.695 0.783 1.000PTQ2 0.187 0.637 0.936 -0.196 0.291 0.539 0.181 -0.224 0.426 1.000Note: Ten planting dates used in the correlation for PBW 34 and PBW 154 and nine planting dates used (150Cf to 05JAN) forcorrelations ong>ofong> PBW 226.11

However, in the case ong>ofong> PBW 226, the number ong>ofong> grains was not much affected bychanges in solar radiation (r = 0015), so PBW 226 was found to be relatively moretolerant to the changes in temperature and solar radiation compared to PBW 154 andPBW 340 Solar radiation was expected to have a positive effect on GM20 However, dueto the high correlation between temperature and radiation, i.e., 0.98, 0.94, and 0.78 forPBW 34, PBW 154, and PBW 226, respectively (temperature having a negativerelationship with GM2, Table 7), there was a negative relationship between solarradiation and GM2 in two ong>ofong> the genotypes studied (Figure 9a).The above analysis shows that GM2 is affected by both solar radiation and temperatureduring the pre-anthesis period. This can be observed by the improvement in therelationship between GM2 and PTQ (which uses both solar radiation and temperature)when compared to either solar radiation or temperature alone.Effect ong>ofong> temperature and solar radiation during the post-anthesis period on grainyield and TGWEffect on grain yield--For all three genotypes, grain yield across planting date means waspositively and linearly correlated with the combined effect ong>ofong> temperature and solarradiation (PTQ) during the post-anthesis period (+ 10 H to +40 H). The correlation wasstronger for PBW 34 (r = 0.90) than for PBW 154 (r = 0.71) and PBW 226 (r = 0.77)(Figure 9b). Grain yields ranged from 1393 to 4356 kg/ha, 1545 to 4555 kg/ha, and 2933to 4905 kg/ha with the corresponding ranges in PTQ values from 1.08 to 1.43, 1.09 to1.50, and 1.00 to 1.55 for PBW 34, PBW 154, and paw 226, respectively.The increasing mean temperature during the post-anthesis period had a strong effect ongrain yield. The yield ong>ofong> all three genotypes decreased with an increase in meantemperature. However, increasing mean temperature had more a negative effect on yieldfor paw 34 (r = -0.91) compared to PBW 154 (r = -0.78) and PBW 226 (r=-0.52)(Figure lOa). Similarly, the grain yield ong>ofong> PBW 34 was more severely affected byincreasing solar radiation during the post-anthesis period (H+10 to H+40) (r = -0.86)compared to paw 154 (r = -0.73) and paw 226 (r = -0.21) (Figure lOb). PBW 226 andpaw 154, being short and mid-season genotypes, were found to be relatively moretolerant to increases in mean temperature and solar radiation conditions during the postanthesisperiod.Effect on TGW--Grain yield was positively correlated with TGW for all three genotypes(Figure 11a): paw 34 (r =0.94), paw 154 (r =0.92), and paw 226 (r = 0.60). In PBW34, TGW was found to be positively correlated with the photothermal quotient during thepost-anthesis period (H +10 to H +40), however, it was highly negatively correlated withthe separate effect ong>ofong> temperature and solar radi ation; the correlation coefficient (r)values were 0.99, -0.99, and -0.97 for TGW vs PTQ, mean temperature, and meanradiation, respectively. A similar trend was observed in PBW 154 and paw 226. Thecorrelation coefficient (r) values were 0.92, -0.95, and -0.93, for TGW vs PTQ, meantemperature, and solar radiation for paw 154 and 0.74, -0.99, and -0.88 for paw 226,respectively (Figures lib, 12&, 12b). The best correlations with TGW occurred withmean temperature, without any improvement by adding radiation alone or together withmean temperature (PTQTGW), suggesting that TGW is solely affected by temperatureunder Ludhiana conditions. When the relationship between TGW and mean temperaturewas plotted by year, we can still observe a strong relationship between these two factors(Figure 13).Use ong>ofong> the PTQ for explaining year effectsPTQ was useful in explaining part ong>ofong> the year x planting date variability in yield andGM2. Although the correlations were not as high as with date ong>ofong> planting means, the12

values are significant and demonstrate how variability among years can also be explainedby PTQ. This can be seen in Figures 14a and 14b where the year 1988-89 had higherPTQ values with correspondingly higher GM2 and yield values. The higher variabilityobserved by using the yearly data could be explained by soil differences over the years.Absolute and relative losses with delayed sowingThe grain yield ong>ofong> all three genotypes decreased with a delay in sowing. However, theoptimum date varied with the genotype. Calculating for delays after the optimum date,grain yields decreased at rates ong>ofong> 41,35, and 36 kg/ha/day for PBW 34, PBW 154, andPBW 226, respectively; the corresponding values on a relative basis for these genotypeswere 1.2,0.9, and 0.9%/ha/day.With a delay in sowing from 05NOV to 25DEC for PBW 34 and from 15NOV to 25DECfor PBW 154 and PBW 226, GM2 on an absolute basis decreased at a rate ong>ofong> 61,58, and56/day for PBW 34, PBW 154, and PBW 226, respectively, and the corresponding valueswere 0.8, 0.6, and 0.5%/day on a relative basis for PBW 34, PBW 154, and PBW 226.For PBW 34, the number ong>ofong> GM2 decreased at the rate ong>ofong> 749 grains/m2pC with anincrease in mean temperature from 14.50 to 18.45 0 C during the pre-anthesis period (-20H to +10H). The number ong>ofong> grains decreased at the rate ong>ofong> 599 grains/m 2 PC and554/grains/m 2 PC with increases in mean temperatures from 14.35 to 18.17 0 C and from13.76 to 17.70 0 C for PBW 154 and PBW 226, respectively.With a delay in sowing from 05NOV to 25DEC for PBW 34 and from 15NOV to 25DECfor PBW 154 and PBW 226, TGW was reduced at rates ong>ofong> 0.18,0.13, and 0.13 glday ong>ofong>planting delay for PBW 34, PBW 154, and PBW 226, respectively. On a relative basis,the values were 0.4, 0.3, and 0.3%/day for PBW 34, PBW 154, and PBW 226,respectively.For PBW 34, TGW was reduced at a rate ong>ofong> 1.52 g;Oc with a corresponding increase inmean temperature from 18.70 to 24.52 0 C during the post-anthesis period (H+10 toH+40). For PBW 154, TGW decreased at a rate ong>ofong> 1.03 g;Oc with a correspondingincrease in mean temperature from 18.47 to 23.68 0 C during the post-anthesis period.Similarly, for PBW 226, TGW was reduced at a rate ong>ofong> 1.05 gjOc with a correspondingincrease in mean temperature from 17.26 to 22.23 0 C.ConclusionsThe results ong>ofong> these studies suggest that time ong>ofong> sowing is a very important factor fordetermining yield. The optimum planting dates were 05NOV for PBW 34 and 15NOVfor PBW154 and PBW 226. Delay in sowing beyond these dates caused severereductions in GM2, TGW, and yield. High post-anthesis temperatures had a highlynegative effect on TGW and yield on all genotypes.All three genotypes maximized their yield when the PTQ value was highest between 20days before heading to 10 days after heading. This suggests that all genotypes shouldmaximize their yield by flowering during the highest PTQ in the growing season. PBW34 is a longer season genotype compared to the other two and the highest PTQ valueoccurs at a given time during the year. Therefore, PBW 34 will have to be planted earlierthan the other two so that all three genotypes flower at about the same time to takeadvantage ong>ofong> the high PTQ values. It can be seen clearly that this was the case for PBW34 and PBW 154 (Figure 15). However, that did not hold true for PBW 226 (shortseasongenotype).13

If we analyze GM2, we can observe that PBW 34 and PBW 154 have a period ong>ofong> 10 days(between Julian dates 50 and 60--about 20 and 28 Feb.) when GM2 is maximized(Figure 16). However, for PBW 226 the optimum is around Julian date 40 (Feb. 10) andthen there is a sharp drop after this date. This may be explained by a possible inability ong>ofong>PBW 226 to reach full light interception after Julian date 40.GM2 could be better explained by the combination ong>ofong> solar radiation and temperature(PTQ2) than by either ong>ofong> the two alone during the pre-anthesis phase, while TGW couldbe better explained only by temperature in the post-anthesis phase.These results suggest that it would be useful to look at long-term climatic data andcalculate probabilities ong>ofong> when the highest PTQ occurs and use that as the target optimumflowering date from which the optimum planting date could be calculated.The PTQ2 pre-anthesis seems to be able to predict which will be high yielding years.There is a 1.2, 0.9, and 0.9%/ha/day yield loss after the optimum planting date for PBW34 (long season), PBW 154 (medium season), and PBW 226 (short season), respectively.ReferencesFischer, R.A. 1984. Physiological limitations to producing wheat in semitropical andtropical environments and possible selection criteria. In pages 209-230, Wheat for MoreTropical Environments, A Proceedings ong>ofong> the International Symposium, Sept. 24-28,1984. Mexico, D.F.: CIMMYT.Fischer, R.A. 1985. Number ong>ofong> kernels in wheat crops and the influence ong>ofong> solar radiationand temperature. J. Agric. Sci. 105:447-61.Fischer, R.A., and R. Maurer. 1976. Crop temperature modification and yield potential ina spring wheat. Crop Sci. 16:855-9.Gujarati, D.M. 1988. Basic Econometrics. Second Edition. Mc Graw-Hill BookCompany.McDonald, G.K., B.G. Sutton, and F.W. Ellison. 1983. The effects ong>ofong> time ong>ofong> sowing onthe grain yield ong>ofong> irrigated wheat in the Namoy Valley, New South Wales. Aust. J. Agric.Res. 34:229-40.Midmore, DJ., P.M. Cartwright, and R.A. Fischer. 1984. Wheat in tropicalenvironments. II. Crop growth and grain yield. Field Crops Res. 8:207-27.Nix, M.A. 1976. Climate and crop productivity in Australia. In pages 495-507, S.Yoshida, ed., Climate and Rice. Int. Rice Res. Inst., Los Banos, Philippines.Randhawa, A.S., S.S. Dhillon, and W. Singh. 1981. Productivity ong>ofong> wheat varieties, asinfluenced by the time ong>ofong> sowing. J. Res. Punjab Agric. Univ. 18(3):227-33.Song>ofong>ield, G., L.T. Evans, M.G. Cook, and G.F. Wardlaw. 1977. Factors influencing therate and duration ong>ofong> grain-filling in wheat. Aust. J. Plant Physio\. 4:785-97.14

6000 .-----r---...,....---.--------r---.---...,--~,._-___,55005000r-. 4500«I""-.2S 4000o-...JW>- .3500.3000o PBW34• PBW154\l PBW2262000I- > > > u u UC.l 0 0 0 w w w() -,.Z "- Z 0 0 0In In In In In In L()1"1 (''J NPlanting DoteFigure 1. Yield response ong>ofong> three spring wheat genotypes to seven dates ong>ofong> planting.15

6000 .-----r-I---r,-----,I---l.----..---I--.....I-------,I--~,o········q5500 f- , ­,, , ,, ,5000 '- o ­_--'7 O."\7"-----' ,r---- 4500 I- ........ ­« ........ "f': ......... ,I ......................... """ ·v.. ,,""­, ,C) ~ .. , ,'\7 ,,2S 4000 I- ­.........bo' ...... --........~w ............... ..... ',____ ". '7--. '>- 3500 I- --........:.: -'~--'7 ­.~ "0-....3000 - ° 88/89­.... 89/90'\7 91/922500 - ­,• 87/88 .....•::-.2000I I I I I I I0 I--- -~ > > u u uu 0 0 0 w w w0 Z Z Z 0 0 0vi lJ) lJ) lJ) lJ) lJ) lJ)l'-.,J N NPlanting ong>Dateong> ....Figure 2. Yield response over 4 years to seven dates ong>ofong> planting.16

12000, "N11000.------_:.,,. "~....','.....'9,.......\7.,10000,, ,,....,' e,'\7" ........9000 :~o.•.-......•\780007000 \7 PBW226~,"0 PBW34• PBW154 ~.o--06000I- > > > u u uu 0 0 0 w w w() Z Z Z 0 0 0u) l,{) l,{) l,{) l,{) l,{) l,{)N N NPlanting ong>Dateong>Figure 3. GM2 response ong>ofong> three wheat genotypes to seven dates ong>ofong> planting.17

3:c.:>l­60 I I I I I I IPBW3450403020l-I-i­°,• 0•~\7 '0".... . ~: """'" ~i( '.­"'y."eI I I I I I I 50I I I I I I I------3:()I­605040.3020f­'­f-II'pBW 1!540"0,~o--o--o... "'1 """'''''''''­ 0~f:.~.........• 87/88 "''''.",.",0 88/89'" 89/90\7 91/92I I I I I I III---c.:>z0«wI0I­(f)>­«012011010090;30706050PBW154,g:;B,::..(J.:.~9',0 ""':/.~.;-"'\7. 0r·\... ··:·• 87/88 .--eo 88/89... 89/90\7 91/9260 120I I I I I I I I I I I I I IPBW226110 _ • 87/88 PBW226_o o 88/B9-50 - ~"O,z100 _ ... 89/90\7 91/92.:~~. '0"Q" ".0 _40-\j"" "'~i::~,,~.. 0.......~-.• 87/88 ...o 88/8930 -'" 89/90\7 91/9220~ >. :>U 0 0o z z­-o«wI90ong>ofong>­ aa(f)~o70 f­-'­ - Q~:.;~:.:g-"-\7p': \' "°'.,.~ -:/', . . ...,.,:-'-,;' .-e60 '­ 0 -I I I I I I I I I I I I I IL()"'lIf) L() L()"'l> u uo w wZOOuw0L() L() L()"'lt)f"i:'?'6o } Z zL()C'JL() L() Lf)"'lu u uw w w000L() If) lO"'lPlonting ong>Dateong>PIC] nting DoteFigure 4. Changes in TGW and days to heading ong>ofong> three wheat genotypes over 4years and seven dates ong>ofong> planting.18

170~ 1600::::JI-- 1,30~" PBW154~"I­I- 11300::::JI­.:.( 15020l- 140(/)?;(01.30120~ PBW226~t,'~~.·T. •"V"''Y'0.. 0I- > > > u u uu 0 0 0 w w w0 Z Z Z 0 0 0In I.n If) If)U') L{) L{)C'-l ('.J ('.JIf) L{) l.() l.() L{) If) L{)('l N C'-lPlonting ong>Dateong>Plonting ong>Dateong>Figure S. Changes in days to maturity and grain-filling days ong>ofong> three wheatgenotypes over 4 years and seven dates ong>ofong> planting.19

,-....~'--'0-lW>­6000 I I I I,PBW3450004000300020001000----r=O.95I••• •I-I I-•• ..­• --I,-....~'--'0-lw>­600050004000030002000IUOU-PBW34•• •• •••1'=-0.92• • •,-....~........"0-lW>­600050004000300020001000""'"""'"""'"""'"I I I I IPBW154." ."r=O.70 ."."."."~."I I I I I-" ---,-....«I............0~'-'0-.Jw>­6UOO50004000.:iODO20001000--f­-I T IPBW154." TT TT1'=-0.861 I ITTITTTI----,-....~........"0....Jw>­60005000400030002000""'"--""'"10001.0I1.1I•••r=O.64II1.2IPBW226•• •I1.3II1.4I.­ • .---I1.5 1.6,-....«I"--"0~'--'0-lw>­600050004UUU30002000IUUU-iIIc-f­""'"10I I IPBW226• •• ••• •r=-O.86I12I14I16I--• •I--18 20PTQ2 (MJ/M2/DAY/ C) ME',L\I\j TEMF' -20H + IOH ( C)Figure 6. Relationship between grain yield and PTQ2 and grain yield and meantemperature in three wheat genotypes.20

6000-­500040JO300e20001000~;rIPBW:34• • • •r= -086•• ••~I• •I~«I"'--­0:cs:::0-lw>­600050004000300020001000II r~[r=0.97PBW34•• •• •••IIIIIII16000 I I I I~«I',,-­0:cs:::'--"0-.Jw>­5000 I­...4000 f'Y3000 I­2000 I­1000PBW154... ... ... ... ......r=-0.71 ...I I II...----~«I"'--­0:cs:::'--"0-lW>­600050004000300020001000I­,...'-­-I I IPBW 154...Wr=0.97.................. ...I I I I--J-'6000 I I I I«I~"'--­0~'--"0-.Jw>­PBW2265000 -• •4000 •I­•3000 -•r= -OAO2000 -• ••,I I I100010 12 14 16 18RADIATION - 20H +10H(MJ/M2/DAY/ C)----20~«I"'--­0~'--"0-.Jw>­600050004000 r=0.B4-.•PBW2263000•200010002000400060008000100002000GM2•:FIgure 7. Relationship between grain yield and solar radiation and grain yield andGM2 in three wheat genotypes.21

12000 I 12000,tI10000 ~I10eoo '­PBW34 PBW34Ii8CO] ;-, r=0.89 r • ••• • •..~• • .1ir=0.81•1!8000 --;( ,j! r'-J•~\J I •0• !i6000 60004000 40002000 2000i12000I I I I I12000.. PBW154 ~.. .." .. ..I10000 -.. .... •10000.. PBW154J.. .. I.. .. 18000 - - 8000r"JN2 :2u..ur=0.726000 - - 60004000 i- - 4000·lI I I I I2000 2000r=073N•••I.12000 I I I12000I I IPBW22610000PBW226• • ..- 10000 ••l-i-• •••• • •• ­8000 - - 8000 I- ­N2 :20 06000 - - 6000r=0.94I- ­r=0.484000 - - 4000 - ­I I I I I I I I I2000 20001.0 1.1 1.2 1.3 1.4 1.5 1.6 10 12 14 16 18 20PTQ2 (MJ/M2/DAY/ C) MEAN TEMPERATURE ( C)Figure 8. Relationship between GM% and PTQ% and GM% aDd mean temperature (­%OH to +1011) in three wheat genotypes.22

! :rJOOl : (JOOOi30JO6000 LI4000 ~II2000 I••r=-0.7312000 ,----,-----,--------,.----,----,......... PBW15410000 I: ... .........:::: ll!­4000r= -0.55o-.JW6000 l IPBW345000 --j3000,rf .:II•• •• • • l !>-2000r=090~10006000PBW15415000«... ... ... 1I...~ 4000(,) ... ...~"-'... ...o 3000-.JW...>­2000r=0711000 '------'-_--'--_--'--_'----------'-_-.JI20001200010000800060004000••r=0.15.'•• PBW226•••200010 12 14 16 18 20RADIATION (MJ/M2/DAY)6000 r---'-I--r-I-'-I-~Ir--'--I--'PBW2265000 - ­..---.« •I•d 4000- ,..~"-'•o .3000 4~-.JW>­. ­-r=0.772000 - ­1000 I I I I I1.0 1.1 1.2 1.3 1.4 1.5 1.6PTa + 10 H +40H(MJ/M2/DAY/ C)Figure 9. Relationship between GM2 and solar radiation and yield and PTQ (+10 to+40) In three wheat genotypes.23

,~«I2i.:>:::c~w'­6000 'I-----,--,--....,-------,.-.-------,-------r-JIPBW345000 ~ I400030002000iOOOr • • •• ~~ r~-O.91 ••••••o.....Ji...J..j>=60005000400030002000IiririPBW34• • • •r= -0.86i ....,I.....J• i5000PBW 1545000PBW154... ...... ... ...... ... ... ... ...l-Io.....JW>­30002000r=-0.'78o~w>­300020001000r= -0.'73... 110006000 I I I I I Ir--.«I~o:c.:::o.....JW>­60005000400030002000PBW226• • •••••r=0.521000 '-----L..-----'---------'-_~--l....-__'_-----'--_12 14 16 18 20 22 24 26 28r--.«I0':::s:::"---"o.....JW>­5000 I­4000 e­ •3000 e­2000 I­PBW226• • •••••r= -0.211000 L-_.l.--I_.l.--I_.l.--I_.l.--I_.l.--I_L-I.--J10 12 14 16 18 20 22 24RADIATION + 1OH +40H----MEAN TEMP + 10H +40H ( C)(MJ/M2/DAY)Figure 10. Relationship between grain yield and mean temperature (+108 to +408)and grain yield and solar radiation (+108 to +408).24

"""«I'­C)::::s::::.--../0---.JLJ>­6(',('0vv I 55':0004DOO3DOO20001000~~if • •PBW:34••••••• r=094I1I!~.0"SC)f­504540351i-II~I•••PBW34•• • •• •r=099II---1Iil,.---...,«I'-,'­C)::::s::::"'-.-/0---.JLJ>­600050004000300020001000f-I-f-f­...I I I IPBW154... ......... ... ...... ...... r=0.92I I I I----0""'-.-/SCJf­5550454035... ...~...PBW154...~... ... ...r=O.92,IJi ,I~~~,.---...,«I.........CJ::::s::::"'-.-/0---.Jw>­6000 I I I I 555000400030002000l-l­--1000I35PBW226••• ••• ••r=0.60I40I45I----0""'-.-/SC)f­50454035PBW226• • e• •J•• r~O.74 J50 55 1.0 1. 1 1.2 1.3 1.4 1.5 1.6TGW (g) PTQTGW (MJ/M2/DAY/ C)Figure 11. Relationship between grain yield and TGW and TGW and PTQ (+108 to+408) in three wheat genotypes.2S

55 55 I1PBW34I • 50 •C'I•'----' 45r •3': •0 •f-40 •35r=-0.99• PBW3450 ~ • •CJ1 I'-.../ 45 r- • J3':0f-40•Jr= -0.9? • II-I35 --iI'-.../55 II I IPBW15450 ~ ­...~ ­...CJ145 ... ...~0f- .........40 ~ ­r=-095 ......35 I- ­I • I , , ...55 T --, I IPBW15450 ~ ­...'-.../ 45 ...CJ1 I- ...­3': ...0f- ......40 ~35...... -Ir=-0.93...I- ­I I I I ...55I I IPBW22650 ~ ­.----.-.CJ1'-../ 45 ~ ­ -.3':0 •f-40 l­•­35r=-0.99•• ••l- ­I I I I12 16 20 24 28MEAN TEMPERATURE ( C)55 T T T IPBW22650 ~ ­...----.-.CJ1 ~'-../•~0 •r= -0.88 •••45 ­f-40 ~ ­35 •~ ­I I I I9 12 15 18 21 24RADIATION (MJ/M2/DAY/ C)Figure 11. Relationship between TGW and mean temperature (+108 to +4(8) andTGW and solar radiation (+108 to +408) in three wheat geROtypes.26

60• 88-89•~ 89-90•• 90-91• .. • ~•55 • • 87-8850~....(J'l"---/v 3:45I...••40PBW34 .­I-I35 r=-O 75•l30~(J'l"---/60 I I I 1 1 I I I• 88-8955PBW154f- 87-88 ­89-9090-9150 ..... • • ­~ ••••.3=

~­70006000 I­5000 -4000 r­3000 l­2000 I­1000 I­00.5IPBW2260~[] ~EJ~c8o 00r=O.54I1.0 1.5III-•• ••-• 88-89 -o 87-8889-90 -90-91-I2.0 2.5-N::2l)14000-I I IPBW2260~rn8000 I­ EJO06000 - 0 • 88-8912000 I­-.o ~.10000 I­o 87-884000 -89-90r=065 90-912000I I I0.5 1.0 1.5 2.0PTQ2 (MJ/M2/DAY/ C) PTQ2 (MJ/M2/DAY/ C)-----,..., c::L.->Figure 14. Relationship between PTQ2 and yield and PTQ2 and GM2 over 4 yearsin three wheat genotypes.28

1 10 ,----,---,----r--,---,--------r--....-------,-------,10090C'J2 ~~C)w> 80r­

Appendix 1. Correlation coefficients for three genotypes between yield and grains per metersquare vs four different PTQ values during 7 years at Punjab Agricultural University inLudhiana, India.PBW34 PBW 154 PBW 226Year Yield GM2 Yield GM2 Yield GM21985-86 PTQl .58 .56 .06 .11PTQ2 .60 .61 .48 .50PTQ3 .65 .68 .69 .64PTQ4 .63 .65 .53 .541986-87 PTQl .82 .77 .34 .30PTQ2 .81 .79 .85 .79PTQ3 .57 .59 .51 .45PTQ4 .74 .72 .79 .711987-88 PTQl .62 .84 -.63 .49 -.40 .30PTQ2 .86 .12 -.24 .43 .12 .71PTQ3 .48 -.22 -.49 .08 -.10 .59PTQ4 .67 -.22 .09 .38 .25 .871988-89 PTQI .58 .41 .68 .82 .33 .82PTQ2 .88 .74 .96 .92 .70 .93PTQ3 .72 .63 .86 .96 .52 .79PTQ4 .88 .71 .91 .80 .75 .891989-90 PTQI -.96 -.94 -.52 .19 .05 .76PTQ2 -.81 -.89 -.45 .20 -.25 .59PTQ3 -~82 -.86 -.42 .04 -.13 .61PTQ4 -.87 -.80 -.19 .48 -.24 .531990-91 PTQI .44 .46 .12 .22PTQ2 .88 .83 .68 .74PTQ3 .68 .67 .38 .49PTQ4 .96 .93 .90 .861991-92 PTQl .13 .35 .00 .59 .40 .67PTQ2 .85 .81 .69 .57 .63 .73PTQ3 .31 .55 .33 .41 .40 .57PTQ4 .95 .74 .87 .67 .69 .63PTQI:PTQ2:PTQ3:PTQ4:-30 HFrom -20 H to + 10 H-20 HFrom -20 H to +20 H31

CIMMYT Wheat Special Reports Completed or In Press(As ong>ofong> Nov. 10, 1993)Wheat Special Report No.1. Burnett, P.A., J. Robinson, B. Skovmand, A. Mujeeb­Kazi, and G.P. Hettel. 1991. Russian Wheat Aphid Research at CIMMYT: Current Statusand Future Goals. 27 pages.Wheat Special Report No.2. He Zhonghu and Chen Tianyou. 1991. Wheat and WheatBreeding in China. 14 pages.Wheat Special Report No.3. Meisner, CA. 1992. Impact ong>ofong> Crop ManagementResearch in Bangladesh: Implications ong>ofong> CIMMYT's Involvement Since 1983. 15 pages.Wheat Special Report No.4. Skovmand, B. 1994. Wheat Cultivar Abbreviations. Paperand diskette versions. In press.Wheat Special Report No.5. Rajaram, S., and M. van Ginkel. 1993 (rev.). A Guide tothe CIMMYT Bread Wheat Section. 52 pages.Wheat Special Report No.6. Meisner, CA., E. Acevedo, D. Flores, K. Sayre, I. Ortiz­Monasterio, and D. Byerlee. 1992. Wheat Production and Grower Practices in the YaquiValley, Sonora, Mexico. 75 pages.Wheat Special Report No. 7a. Fuentes-Davila, G. and G.P. Hettel, eds. 1992. Update onKamal Bunt Research in Mexico. 38 pages.Reporte Especial de Trigo No. 7b. Fuentes-Davila, G., y G.P. Hettel, eds. 1992. Estadoactual de la investigacion sobre el carbon parcial en Mexico. 41 pages.Wheat Special Report No.8. Fox, P.N., and G.P. Hettel, eds. 1992. Management andUse ong>ofong> International Trial Data for Improving Breeding Efficiency. 100 pages.Wheat Special Report No.9. Rajaram, S., E.E. Saari, and G.P. Hettel, eds. 1992. DurumWheats: Challenges and Opportunities. 190 pages.Wheat Special Report No. 10. Rees, D., K. Sayre, E. Acevedo, T. Nava Sanchez, Z. Lu,E. Zeiger, and A. Limon. 1993. Canopy Temperatures ong>ofong> Wheat: Relationship with Yieldand Potential as a Technique for Early Generation Selection. 32 pages.Wheat Special Report No. 11. Mann, C.E., and B. Rerkasem, eds. 1992. Borondeficiency in Wheat. 132 pages.Wheat Special Report No. 12. Acevedo, E. 1992. Developing the Yield Potential ong>ofong>Irrigated Bread Wheat: Basis for Physiological Research at CIMMYT. 18 pages.Wheat Special Report No. 13. Morgunov, A.I. 1992. Wheat Breeding in the FormerUSSR. 34 pages.Wheat Special Report No. 14. Reynolds, M., E. Acevedo, O.A.A. Ageeb, S. Ahmed,L.J.CB. Carvalho, M. Balata, R.A. Fischer, E. Ghanem, R.R. Hanchinal, C.E. Mann, L.Okuyama, L.B. Olegbemi, G. Ortiz-Ferrara, M.A. Razzaque, and J.P. Tandon. 1992.Results ong>ofong> the 1st International Heat Stress Genotype Experiment. 19 pages.32

Wheat Special Report No. 15. Bertschinger, L. 1993. Research on BYD Viruses: ABrief State ong>ofong> the Art ong>ofong> CIMMYT's Program on BYD and Its Future ResearchGuidelines. In press.Wheat Special Report No. 16. Acevedo, E., and G.P. Hettel, eds. A Guide to theCIMMYT Wheat Crop Management & Physiology Subprogram. 161 pages.Wheat Special Report No. 17. Huerta, J., and A.P. Roelfs. 1993. The VirulenceAnalysis ong>ofong> Wheat Leaf and Stem Rust on a Worldwide Basis. In press.Wheat Special Report No. 18. Bell, M.A., and R.A. Fischer. 1993. Guide to SoilMeasurements for Agronomic and Physiological Research in Small Grain Cereals. 40pages.Wheat Special Report No. 19. Woolston, J.E. 1993. Wheat, Barley, and TriticaleCultivars: A List ong>ofong> Publications in Which National Cereal Breeders Have Noted theCooperation or Germplasm They Received from CIMMYT. 68 pagesWheat Special Report No. 20. Balota, M., I. Amani, M.P. Reynolds, and E. Acevedo.1993. An Evaluation ong>ofong> Membrane Thermostability and Canopy Temperature Depressionas Screening Traits for Heat Tolerance in Wheat. 26 pages.Reporte Especial de Trigo No. 21a. Moreno, J.I., y L. Gilchrist S. 1993. La rona 0 tiz6nla espicga del trigo. In press.Wheat Special Report No. 21b. Moreno, J.I., and L. Gilchrist S. 1993. Fusarium headblight ong>ofong> wheat. In press.Wheat Special Report No. 22. Stefany, P. 1993. Vernalization Requirement andResponse to Day Length in Guiding Development in Wheat. 39 pages.Wheat Special Report No. 23a (short version). Dhillon, S.S., and I. Ortiz-MonasterioR. 1993. ong>Effectsong> ong>ofong> ong>Dateong> ong>ofong> ong>Sowingong> on the Yield and Yield Components ong>ofong> Spring Wheatand Their Relationships with Solar Radiation and Temperature at Ludhiana (Punjab),India. 33 pages.Wheat Special Report No. 23b (long version). Dhillon, S.S., and I. Ortiz-Monasterio R.1993. ong>Effectsong> ong>ofong> ong>Dateong> ong>ofong> ong>Sowingong> on the Yield and Yield Components ong>ofong> Spring Wheatand Their Relationships with Solar Radiation and Temperature at Ludhiana (Punjab),India. 83 pages.Wheat Special Report No. 24. Saari, E.E., and G.P. Hettel, eds. 1993. Guide to theCIMMYT Wheat Crop Protection Subprogram. In press.Wheat Special Report No. 25. Reynolds, M.P., E. Acevedo, K.D. Sayre, and R.A.Fischer. 1993. Adaptation ong>ofong> Wheat to the Canopy Environment: Physiological Evidencethat Selection for Vigor or Random Selection May Reduce the Frequency ong>ofong> HighYielding Genotypes. 17 pages.Wheat Special Report No. 26. Reynolds, M.P., K.D. Sayre, and H.E. Vivar. 1993.Intercropping Cereals with N-Fixing Legume Species: A Method for Conserving SoilResources in Low-Input Systems. 14 pages.33

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