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The cause of virulence decline of hypovirulent isolate Ep-1PN of Sclerotinia sclerotiorum (Lib.) de Bary has been studied through transmitting test and analysing its offsprings derived from single ascospore. When the colony of a normal strain Ep-1PNA 183 intermingled with the colony of Ep-1PN, its margin became abnormal, just like Ep-1PN. Cultures isolated from top-tip of the colony of Ep-1PNA 183 showed the hypovirulence and its associated properties of Ep-1PN. Moreover, a series of cultures which have characteristics between Ep-1PN and normal strain could be isolated from stipes of Ep-1PN. More than 200 offsprings derived from single ascospore of Ep-1PN were normal strains. According to those results, there exists a transmissible cytoplasmic hypovirulent element in hypovirulent isolate Ep-1PN of S. sclerotiorum.
The cause of virulence decline of hypovirulent isolate Ep-1 PN of Sclerotinia sclerotiorum (Lib.) De Bary has been studied through transmitting test and analysing its offsprings derived from single ascospore. When the colony of a normal strain Ep-1 PNA 183 intermingled with the colony of Ep-1PN, its margin became abnormal, just like Ep-1PN. Cultures isolated from top-tip of the colony of Ep-1 PNA 183 showed the hypovirulence and its associated properties of Ep-1 PN. Characteristics between Ep-1PN and normal strain could be isolated from stipes of Ep-1PN. More than 200 offsprings derived from single ascospore of Ep-1PN were normal strains. According to those results, there exists a transmissible cytoplasmic hypovirulent element in hypovirulent isolate Ep -1PN of S. sclerotiorum.