[Construction and pathogenicity tests of a mutated specific fragment SCF73 in Verticillium dahliae]

To identify preliminarily the specific fragment SCF73's function in Verticillium dahlia virulence.

The specific fragment SCF73 exposed to be existed in the high-virulent V. dahliae strain VDG1 and not in the mild one VDG2. The SCF73 fragment was obtained from comparatively aligned genome sequences of the two strains and its existence was confirmed using PCR method. According to SCF73's DNA sequence, a homologous recombination plasmid was constructed to knock out the fragment. The Agrobacterium tumefaciens-mediated transformation technique was used to initiate the mutant deltaSCF73, followed by antibiotic resistance screening, and PCR verification. The mutant's ability to secrete carbohydrate hydrolase was analyzed using pectin, cellulose and starch media and its virulence to the susceptible cotton cultivar Gossypium hirsutum cv. Junmian1 was assessed.

SCF73 (27.1 kb) contains 5 genes, two of them have glycosyl hydrolase activity. Although the, mutant deltaSCF73's carbohydrate hydrolase secretion was not significantly different from the control VDG1, virulence of the mutant to cotton plants decreased significantly accompanied with disease outburst delay.

The specific fragment SCF73 plays an important role in the virulence of V. dahlia towards its cotton host plants.