12 Agriculture 7(2001) Table 1. Pleiotropic effect of Rht 3 dwarfing gene dosage on plant, seed and flour characteristics (the two year average: Kri`evci, 1991 and 1995) Tablica 1. Pleiotropni u~inak Rht 3 gena za patuljastu stabljiku na svojstva biljke, sjemena i bra{na (prosjek od dvije godine: Kri`evci, 1991. i 1995.) **, *, NS = difference significant at 0,01; 0,05 level or not significant respectively - razlika zna~ajna uz vjerojatnost 1% i 5%, odnosno nezna~ajna
Agriculture 7 (2001) 13 class by gravimetric method (Kvet and Marshall, 1971). After harvest the other plant characteristics (ear length, number of spikelets/ear, number of kernels/ear, grain weight/ear, grain weight/plant) were determined. The differences between the two means were calculated and their significancy tested by t-test. The kernel and quality characteristics (moisture, test weight, thousand kernel weight, grain protein, milling, flour ash, and flour amylogram) were determined on average samples, without possibility of statistical measuring of differences between the means. RESULTS AND DISCUSSION A problem in explanation of this type of investigations is frequent disability to distinguish the primary effect of dwarfing genes and the secondary effect of other reduced values - source capacity, for instance. Beside this, till now reported results often disagree in findings. One reason could be frequent use of near-isogenic lines, and ’inter-cultivar’ rather than ’inter-gene’ comparisons. In this experiment we tried to avoid this misleading procedure by using true-isogenic lines and ’inter-gene’ comparison. The main effect of Rht 3 gene is significant shortening of plant stature by about 54% and 28% in double and single gene dosage respectively, as well as significant decrease of a-amylase activity (determined by amylograph) in double gene dosage only (Tab.1). In double gene dosage decreased spike fertility (number of kernels per spike for -25.04%, TKW for -16.06% and test weight for -4.08%) could not be compensated by slightly increase in number of tillers per plant (9,69%) and spikes per plant (12,18%). As a result, grain yield per plant, in space planting, was strongly lowered by -26.56 and -7.02% in double and single gene dosage respectively in environmental conditions of Croatia. This negative effect could be compensated to some extent in dense planting due to better lodging resistance of dwarf and semi-dwarf plants. Even in this case, too dense distribution of leaves in double gene full dwarf, and bad light interception into canopy, seems to be unfavorable for photosynthesis. However, our findings disagree with the results obtained recently by Borner and Worland (1994). According to them, in Britain conditions, a higher number of grains per ear was accompanied by a lower grain weight, but depending on the climatic conditions in a particular year, the increase in grain number was sufficient to compensate for the reduction in grain size and resulted in higher yields. Obviously, the environmental conditions of Croatia is to worm in period of heading and flowering, resulting in empty, non-fertilized flowers, and consequently lower grain number per head. On the contrary, single gene dosage (heterozygous genotype - Rht 3 rht 3 ) seems more acceptable when plant stature is in question (semi-dwarf of 83 cm). Lower grain yield per plant in experiment (space planing) for about 7% could be compensated by dense population in commercial planting. However, this type could be exploited only as F 1 hybrid due to its heterozygous stage. In this way, the F 1 seed production could be more efficient due to the difference in plant height (dwarf mother plant and tall pollinator plant) and hybrid vigor could be expressed beneficially on grain yield of semi-dwarf F 1 plants. REFERENCES 1. Allan, R.E. (1986): Agronomic comparisons among wheat lines nearly isogenic for three reduced-height genes. Crop Sci. 26:257-286. 2. Allan, R.E. (1989): Agronomic comparisons between Rht1 and Rht2 semidwarf genes in winter wheat. Crop Sci. 29:1103-1108. 3. Atkins, I.M., Mangelsdorf, P.C. (1942): The isolation of isogenic lines as a means of measuring the effects of awns and other characters in small grains. Jour. Amer. Soc. Agron., 34:667-668. 4. Borner, A., Worland, A.J. (1994): Breeding for lodging resistance in wheat and the utilization of dwarfing genes. Abstracts of EUCARPIA Symp. on Prospectives of Cereal Breeding in Europe, Landquart, Switzerland, p. 169-170. 5. Fasoulas, A. (1988): The honeycomb method of plant breeding. Aristotelian University of Thesaloniki, Greece, p. 167. 6. Gale, M. D., Marshall, G.A. (1973): Insensitivity to gibberellin in dwarf wheats. Ann Bot. 37:729-735. 7. Gale, M.D., Law, C.N. , Worland, A.J. (1975): The chromosomal location and a major dwarfing gene from Norin 10 in new British semi-dwarf wheats. Heredity, 35(3):417-421. 8. Gale, M.D., Marshall, G.A. (1976): The chromosomal location of Gai 1 and Rht 1, genes for gibberellin insensitivity and semidwarfism, in a derivative of Norin 10 wheat. Heredity. 37(2):283-289. 9. Gale, M.D. (1979): The effects of Norin 10 dwarfing genes on yield. Proc. 5th Int. Wheat Genet. Simp., New Delhi, p. 978-987. 10. Gale, M. D., Youssefian, S. (1984): Pleiotropic effects of the Norin 10 dwarfing genes, Rht1 and Rht2, and interactions in response to chlormequat. Proc. 6 th Int. Wheat Genet. Symp. Kyoto, p. 271-277. 11. Gale, M.D., Salter, A.M., Angus, W.J. (1989): The effect of dwarfing genes on the expression of heterozis for grain yield in F 1 hybrid wheat. In: Maluszynski, M.(Ed.), Current options for cereal improvement. Doubled haploids, mutants and heterozis. p. 49-61. 12. Gent, P.N.M., Kiyomoto, R.K. (1998): Physiological and agronomic consequences of Rht genes in wheat. J.Crop Prod. 1(1):27-46. 13. Kertesz, Z., Flintham, J.E., Gale, M.D. (1991): Effects of Rht dwarfing genes on wheat grain yield and its components under Eastern European Conditions. Cereal Res. Comm. 19:297-304. 14. Kvet, J., Marshall, J. K. (1971): Relationships between linear measurements and leaf area. In: Sestak et al. (Eds.), Plant photosynthetic production - Manual of methods. Dr. W.Junk N.V. Publishers, The Hague, p. 526-532.
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