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Reference Report for SoyBase3998300
Title:First report of sclerotium production by Sclerotinia sclerotiorum in soil on infected soybean seeds
Authors:Yang, X.B., Workneh, F., Lundeen, P.
Source:Plant Dis. 1998, 82(2):264-264
Abstract:Experiments were conducted to determine if sclerotia are formed in soils from internally infected (S. sclerotiorum) soyabean seeds. Soyabean seeds from a field with 70% disease severity were collected and sorted into 3 classes: (i) normal quality seed which included moderate or good seed, (ii) poor quality seed (shrivelled and/or whitish) and (iii) seed of regular size with visible mycelial mats (S. sclerotiorum or Peronospora manshurica) on the seed coat. Transfer of surface-disinfested seeds to potato dextrose agar and subsequent production of sclerotia showed that 2, 44 and 6% of the seed from each respective class were infested with S. sclerotiorum. One hundred seeds from each of these classes were planted into sterilized and non-sterilized soil at a rate of 5 seeds/pot. Pots were placed in growth chambers under 2 temperature regimes: (a) at 20°C and (b) at 10° for 10 days and then raised to 20°. Two weeks after planting seeds were examined for formation of sclerotia and the percentages of seeds from which sclerotia were formed were calculated. One to two sclerotia were found in place of each seed that did not germinate. Sclerotia were mainly found from seeds of poor quality, with an average of 12% seeds that produced sclerotia. The frequency of sclerotia found in normal quality seeds was 0.4% and no sclerotia were found from seeds with mycelial mats. Sclerotial production frequencies were 11.4 and 15.4% for temperature regimes (a) and (b), respectively. Higher percentages of sclerotium production were found in sterilized soil (15.6%) than non-sterilized soil (7.5%). These results indicate the possibility of internally infested soyabean seeds as a means for field-to-field dissemination of S. sclerotiorum.






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