Hema Kasinathan Thesis May 1 2012.pdf - Atrium - University of ...

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and a green stemmed, squat or canton type. The green stemmed type is Shanghai pakchoy and white stemmed type is buk choy (Lovatt 2010). It is also a cool season cropthat is either transplanted or direct sown. The plant tops are usually harvested 35–55 daysafter seeding, depending upon the variety (OMAFRA 2011b). Many Asian Brassicavegetables have a short days-to-harvest and several crops are often grown in successionwithout any crop rotation (McDonald and Westerveld 2008). In Ontario, they are usuallygrown from mid-April to mid-October (OMAFRA 2011a).1.4 Factors that affect development of Plasmodiophora brassicae1.4.1 TemperatureTemperature plays an important role in the pathogenicity of P. brassicae, as itdoes for most plant pathogens. The optimum temperature for club development has beenreported to be between 18°C and 24°C (Karling 1968). The influence of air temperature,in association with various other factors under greenhouse conditions, was studied and atemperature range of 18° to 25°C and a mean of 23°C were required for clubrootsymptom development (Colhoun 1952). Others observed that a mean temperature of19.5°C was required for the entire period of crop growth for maximum disease severityand club development under controlled environment conditions (Buczacki et al. 1978). Afield study conducted on muck soil showed that soil temperature and moisture werepositively correlated with clubroot development in radish and that the highest diseaselevels were observed at an optimum temperature of 20°–22° C (Thuma et al. 1983).In studies with Asian Brassica crops at the Holland Marsh, the highest severitywas observed on Shanghai pak choy and Chinese flowering cabbage crops harvested in14
July and August. The temperature during the optimum infection period ranged from 20°–22°C. Little or no symptom development occurred when the crop was harvested inOctober, when air temperatures were below 12°C (McDonald and Westerveld 2008). In asubsequent study, the highest levels of clubroot occurred in Shanghai pak choy harvestedduring July, when the mean temperature was 20°C (Adhikari 2010). Trials undercontrolled conditions estimated that the optimum range for clubroot incidence andseverity is 19.6° to 25.5°C for both canola and pak choy. Further studies on pak choyunder controlled environmental conditions showed that optimum infection occurred at26°C. The maximum root hair infection and clubroot severity was observed at 25°Cfollowed by 20°C and 30°C. Little or no infection occurred at 10° and 15°C (Sharma etal. 2011a).1.4.2 Soil pHThe term pH (potential of hydrogen) is the measure of the hydrogen ion [H + ion]concentration in a solution. It is expressed as the negative logarithm of hydrogen ionconcentration and the scale ranges from 0–14. Higher H + ion concentration in a solutionleads to acidity (pH < 7) and lower to alkalinity (pH > 7) (Buck et al. 2002).The ability of an organism to grow, multiply, and complete its lifecycle dependson its ability to develop and persist in its environment. Microorganisms require aparticular pH range in their environment to proliferate, metabolize and to secreteenzymes (Penalva 2008). Soil pH plays a vital role in the development of P. brassicae.Bremer (1924) reported that germination of resting spores was highest, at 37%, in wetacid soils, but was only 1–2% in wet alkaline soils (cited in Karling 1968). Resting sporescan germinate within 2 days in soil at pH 6. However, addition of calcium salts resulted15
Page 1 and 2: Influence of pH, Temperature, and B
Page 3 and 4: and Lee). The mean clubroot inciden
Page 5 and 6: TABLE OF CONTENTSACKNOWLEDGEMENTS .
Page 7: 6 APPENDIX: 2 SUPPLEMENTARY TABLES
Page 10 and 11: LIST OF ACRONYMSANOVABDCIAnalysis o
Page 12 and 13: pathogen in the Holland Marsh area
Page 14 and 15: 1.2.1 PathotypesHonig (1931) was th
Page 16: were distinguished using only three
Page 19 and 20: 1.3 HostsIn general, hosts of P. br
Page 21 and 22: erucic acid and 30 µmoles glucosin
Page 23: Table 1.2. Economically important B
Page 27 and 28: (Colhoun 1953). Studies on differen
Page 29 and 30: Soil compaction, which has been ass
Page 31 and 32: calcium source resulted in a small
Page 33 and 34: effective against P. brassicae has
Page 35 and 36: are filamentous rod-shaped gram-pos
Page 37 and 38: another study, the biofungicides Se
Page 39 and 40: Oomycetes and plasmodiophorids at v
Page 41 and 42: has been no systematic study of the
Page 43 and 44: 2 CHAPTER 2INFLUENCE OF pH AND TEMP
Page 45 and 46: The optimum temperatures for clubro
Page 47 and 48: When the cotyledons were fully expa
Page 49 and 50: the plants were watered with deioni
Page 51 and 52: dehisced sporangia looked like empt
Page 53 and 54: epetition. There was no repetition
Page 55 and 56: RHI = -169.14 + 27.54 (temp°) - 0.
Page 57 and 58: on canola seedlings at 12 days afte
Page 59 and 60: The individual regression analysis
Page 61 and 62: Multiple regression equations were
Page 63 and 64: hair infection was strongly and pos
Page 65 and 66: (Macfarlane and Last 1959, Myers an
Page 67 and 68: temperature (Adhikari, 2010, Gossen
Page 69 and 70: 3.2 IntroductionClubroot of crucife
Page 71 and 72: organic soil, whereas only 25% wate
Page 73 and 74: (1.34% Bacillus subtilis QST 713),
Page 75 and 76:
2. To assess the interaction of pat
Page 77 and 78:
and the spray width was approximate
Page 79 and 80:
3.3.2 Field trials - Napa cabbageTw
Page 81 and 82:
Four types of growth media were ass
Page 83 and 84:
treatments (described in detail in
Page 85 and 86:
Field capacity (%) =(Initial weight
Page 87 and 88:
3.4 Data analysisThe data were anal
Page 89 and 90:
Analysis of variance was conducted
Page 91 and 92:
etween clubroot severity and cumula
Page 93 and 94:
growth medium) for severity, but no
Page 95 and 96:
B) Saturated canola - Clubroot inci
Page 97 and 98:
10080A) Drained trialab ab bcaabPos
Page 99 and 100:
3.6.2 Experiment 2 - Shanghai pak c
Page 101 and 102:
Table 3.5 Analysis of variance for
Page 103 and 104:
A three-way interaction (biofungici
Page 105 and 106:
correlated with micro-pore volume.
Page 107 and 108:
negative correlation between clubro
Page 109 and 110:
that a greater number of assessment
Page 111 and 112:
supports the observations of previo
Page 113 and 114:
In Experiment 3, both Prestop and S
Page 115 and 116:
depending on factors such as soil m
Page 117 and 118:
growth room trials, up to 6 x 10 9
Page 119 and 120:
Biofungicides have been included as
Page 121 and 122:
esults indicate that application of
Page 123 and 124:
growth in rhizopshere zone (Mikkels
Page 125 and 126:
iofungicides varies with the growth
Page 127 and 128:
Bremer, H., B. Wehnelt, and E. Bran
Page 129 and 130:
Dobson, R., R. L. Gabrielson, and A
Page 131 and 132:
Hwang, S. F., S. E. Strelkov, B. D.
Page 133 and 134:
Mitani, S., K. Sugimoto, H. Hayashi
Page 135 and 136:
PMRA 2008. Registration Decision fo
Page 137 and 138:
Tommerup, I. C., and D. S. Ingram.
Page 139 and 140:
5 APPENDIX 1: ANOVA TABLES FOR CHAP
Page 141 and 142:
Clubroot severity: Multiple regress
Page 143 and 144:
7 APPENDIX 3: ANOVA TABLES FOR CHAP
Page 145 and 146:
2011 - Root weight of 10 plantsSour
Page 147 and 148:
Runs 1 and 2 combined DSIRandom eff
Page 149 and 150:
Table. A3.9 Interaction of biofungi
Page 151 and 152:
9 APPENDIX: 5 RAW DATA FOR CHAPTER
Page 153 and 154:
CI- Clubroot incidence (%); - Not d
Page 155 and 156:
25 7.0 3 43.66 4.33 15.89 20.33 56.
Page 157 and 158:
10 APPENDIX 6 RAW DATA FOR CHAPTER
Page 159 and 160:
Raw data for growth room trials Exp
Page 161 and 162:
Soilless P6 Prestop 1 6.67 10.00 24
Page 163 and 164:
Sand P3 Prestop 1 86.11 100.00 80.0
Page 165 and 166:
Mineral T5 - 1 80.00 50.00 70.00 43
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