Expression of pathogenesis-related genes in cotton stems in response to infection by Verticillium dahliae

The levels of mRNA transcripts of genes for several pathogenesis-related proteins were examined in cotton stems after infection of the plants with the soil-borne, vascular wilt pathogen Verticillium dahliae. Reverse transcription PCR sas used to estimate mRNA levels corresponding to particular transcripts. In order ro determine if differences in timing or level a of gene activation were likely to account for differences in the susceptibility of Gossypium hirsutum cultivars to Verticillium wilt, we compared the gene activation patterns in the relatively resistant commercial cultivar, Sicala V2 with those exhibited by the susceptible cultivar. CS50. A non-defoliating, Australian isolate of V. dahliae was used and infection was achieved by stempuncture inoculation with a conidial suspension of the pathogen. Levels of mRNA for genes for cadinene synthase, acidic chitinase, basic chitinase, beta -1,3-glucanase, and at least orle member of the family of cotton Ypr10 gene homologues coding ibr potential PRIG proteins increased after inoculation with V. dahliae, while levels of mRNA for a gene for phenylalanine ammonia lyase were similar in all samples. Even though leaf necrosis symptoms were found to be less severe in Sicala V2 after V. dahliae infection, no differences in the timing or in the extent or activation of gene repression were observed between the two cultivars used. Significant activation was not observed after treatment of CS50 with bion(R) (benzo-(1,2,3)- thiadiazole-7-carbothioc acid S-methyl ester, BTH) or methyl jasmonate, but there was a reduction in the severity of leaf necrosis of both cultivars after bion(R) treatment, which was malgrinai in CS50 but clearly evident in Sicala V2. Thus the enhanced partial resistance of cotton to Verticillium wilt observed here, whether due to cultivar or bion(R) treatment, is not accompanied by a change in the tinting or levels of expression of the genes investigated. Therefore it is: likely that some other factors are responsible For the degree of resistance observed. (C) 2001 Academic Press.