LAUSR

Collapsed sweet potato vines observed in Hangzhou fields in September 2019 were found to be due to Sclerotinia sclerotiorum based on its morphology and ITS rDNA sequence . Here, the chitinase gene chit42 from Trichoderma harzianum was introduced into Ipomoea batatas using Agrobacterium -mediated transformation to evaluate the effect against subsequent disease severity from S. sclerotiorum . PCR analysis detected the transgene in 23 transformants with a transformation efficiency of 5.1%. RT-PCR analysis showed transgene mRNA expression in all four selected lines harboring chit42 . Enzymatic tests showed a significant increase in the activity of endochitinase in extracts from leaf tissues of chit42 -transgenic 75-day sweet potato lines. Virulence of three genetically different isolates was markedly reduced on leaves of 75-day-old chit42- transgenic plants compared with the controls. To our knowledge, this is the first report of S. sclerotiorum on sweet potato plants in China.