Garg Harsh, Sivasithamparam Krishnapillai, Barbetti Martin J
School of Plant Biology, Faculty of Natural and Agricultural Sciences, The University of Western Australia, Crawley, WA, 6009, Australia.
School of Plant Biology, Faculty of Natural and Agricultural Sciences, The University of Western Australia, Crawley, and Department of Agriculture and Food Western Australia, South Perth, WA, 6151, Australia.
Plant Dis. 2010 Aug;94(8):1041-1047. doi: 10.1094/PDIS-94-8-1041.
Ascospores of Sclerotinia sclerotiorum are the primary source of inoculum for disease epidemics in many economically important crops. Mass production of ascospores under laboratory conditions is required to prepare inoculum for use in selection of genotypes with resistance against Sclerotinia diseases. A study was undertaken, first, to investigate the effect on carpogenic germination of scarifying sclerotia from two S. sclerotiorum isolates taken from canola (Brassica napus) and, second, to identify environmental factors that enhance carpogenic germination. Seven different environmental treatments were applied to scarified and unscarified sclerotia: (i) sterilized distilled water for 4 months at 15°C, (ii) aerated water for 4 months at 4°C, (iii) constant rinsing with tap water for 8 weeks at 4°C, (iv) cold-conditioning for 4 weeks at 4°C and subsequent transfer into moist unsterilized compost at 15°C, (v) incubation in sterilized river sand at 15°C, (vi) air drying for 2 weeks followed by subsequent transfer into sterilized moist river sand at 15°C, or (vii) placed into 0.5% water agar and incubated at 15°C. Carpogenic germination of scarified sclerotia was significantly greater (P < 0.05) than for unscarified sclerotia. There was significant interaction (P < 0.001) between scarification and the different environmental treatments in relation to the carpogenic germination. Carpogenic germination of scarified sclerotia was enhanced by incubation of sclerotia in compost or in sterilized river sand. Further, overall carpogenic germination of both scarified and unscarified sclerotia occurred to the greatest extent when sclerotia of either of the two isolates were subjected to constant rinsing with tap water. We believe this to be the first report of both the enhanced carpogenic germination by scarification in S. sclerotiorum and the environmental factors we report that enhance carpogenic germination of scarified sclerotia. The progression of carpogenic germination in all the environmental treatments was also monitored as a part of this study across the two consecutive years for the same two isolates. The majority of sclerotia of both isolates germinated between the months of June and September in both years, a period which coincides with the main part of the cropping season when Sclerotinia stem rot is normally observed in rainfed canola in Western Australia. These data suggested the existence of a seasonal rhythm-like pattern in relation to the carpogenic germination of this pathogen.
核盘菌的子囊孢子是许多经济作物病害流行的主要接种源。为了制备用于筛选抗核盘菌病基因型的接种物，需要在实验室条件下大量生产子囊孢子。本研究首先调查了对来自油菜（甘蓝型油菜）的两种核盘菌分离株的菌核进行划破处理对其产孢萌发的影响，其次是确定促进产孢萌发的环境因素。对划破和未划破的菌核应用了七种不同的环境处理：（i）在15°C下用灭菌蒸馏水培养4个月，（ii）在4°C下用曝气水培养4个月，（iii）在4°C下用自来水持续冲洗8周，（iv）在4°C下冷处理4周，随后转移到15°C的未灭菌潮湿堆肥中，（v）在15°C的灭菌河沙中培养，（vi）风干2周，随后转移到15°C的灭菌潮湿河沙中，或（vii）放入0.5%的水琼脂中并在15°C下培养。划破菌核的产孢萌发显著高于未划破的菌核（P < 0.05）。在产孢萌发方面，划破处理与不同环境处理之间存在显著的交互作用（P < 0.001）。将菌核在堆肥或灭菌河沙中培养可提高划破菌核的产孢萌发率。此外，当对两种分离株中的任何一种菌核用自来水持续冲洗时，划破和未划破菌核的总体产孢萌发率最高。我们认为这是关于核盘菌划破处理增强产孢萌发以及我们所报道的促进划破菌核产孢萌发的环境因素的首次报告。作为本研究的一部分，还对这两种分离株连续两年在所有环境处理中产孢萌发的进程进行了监测。在这两年中两种分离株的大多数菌核都在6月至9月间萌发，这一时期与西澳大利亚雨养油菜通常观察到核盘菌茎腐病的作物生长季节的主要部分相吻合。这些数据表明该病原菌的产孢萌发存在季节性节律样模式。
