Abstract:

Abstract Sclerotinia stem rot, caused by Sclerotinia sclerotiorum (Lib) de Bary, is one of the most damaging fungal diseases of oilseed rape worldwide. The pathogen is dispersed by airborne ascospores, which usually infect plants via petals deposited on leaves or stems. A modified Steadman’s media with two different pH indicators were used to check the infection of petals by S. sclerotiorum. Petals of oilseed rape were sampled in March and April 2006 from two fields in Hefei, Anhui Province, China. Petals were collected every day during a flowering period and cultured on both media under room temperature. The percentage of infected petals was calculated from all samples. The results showed that petals were infected during the whole flowering period, except one day on one field only. Petals were less infected at the beginning of a flowering period. From full blossom stage to the end of a flowering period the infection of petals was high. The results obtained using different media varied by ca. 10% for the benefit of one pH indicator. The percent of petal infection in the first field accounted for 32.00 and 40.19% and in the second field it was 27.34 and 35.69% respectively. Disease incidence and index in the first field accounted for 2.74% and 1.78. In the second field the respective values were 1.47% and 0.37. There was a significant positive correlation between the number of infected petals and subsequent disease development (r=0.829,r0.05=0.811). The experiment had demonstrated that studies of petal infection may help in making decisions on the timing of fungicide applications.