Molecular Characters And Detection Of Three Pathogenic Fungi Of Vegetable Diseases

Tomato and cucumber are widely cultivated in China. The yield and quality would be reduced destructively if they were attacked by diseases. Tomato gray mould, cucumber downy mildew and cucumber powdery mildew are very popular in vegetable planting fields. They always cause destructive production failure because they are difficult to diagnose at the earlier affection. The pathogens of the three vegetable diseases are all fungi.It has been commonly accepted that the pathogen of the tomato gray mould is Botrytis cinerea while the cucumber downy mildew is Pseudoperonospora cubensis. The pathogen of cucumber powdery mildew is Sphaerotheca cucurbitae or Erysiphe cucurbitacearum, according to "Fauna Sinica of Fungi, Erysiphales". But in this study, it was identified by morphologic characters as Sphaerotheca fuliginea by providers in College of Agriculture and Biology, Shanghai Jiaotong University.In the paper, the molecular characters of Botrytis cinerea, Pseudoperonospora cubensis and Sphaerotheca fuliginea were screened and analyzed, and molecular diagnostic method was established and evaluated. The results were listed as follows:1. rDNA-ITS of 4 strains of Botrytis cinerea was amplified and sequenced. The PCR fragments were clear and bright. The rDNA-ITS was sequenced, as the length was 424 bp, GC content was 44.81 %(hml), 45.28 %(hm2/hm3) and 45.05 % (hm4), respectively. The parts of rDNA were determined by reference, with partial ITSl as site 1-120, total 5.8S as site 121-267, partial ITS2 as site 268-424. The sequences alignments were made among the 4 strains of Botrytis cinerea, and among with its 10 sibling species, which got from GenBank. The inter-strains sequences of ITS2 and 5.8S regions were the same; there were 3 sites differences in ITSl region. The divergence between Botrytis cinerea and Botrytis fabae, Botrytis tulipae and Sclerotinia tetraspora were minor. There was only 1 base pair different between hm4 and Botrytis fabae and Botrytis tulipae; and there was 8 base pair different between hm4 and Sderotinia tetraspora. The divergence between Botrytis cinerea and the other 7 sibling species was...