Studies On Guummy Stem Blight And Test Of Resistance In Melon

Melon gummy stem blight, a serious disease at the middle-late Stage of melon growth,often causes seedling growth retardation. It damages the crop production much moreseriously than both Fusarium wilt and Phytophthora blight do. The plant death rate reachesat 30%～40% if the disease can't be effect controlled. It directly results in the yield drop andquality deterioration. Farmers can't find a correct method to control or prevent the diseasesince they don't clearly understand it, or lack resistant disease varieties. So the authorconducted the research on the etiology and disease for melon gummy stem blight. The mainresults are following:1. We study the variations on yield, single fruit weight, width of fruit flesh, fruit shapeindex, sugar content, and reticulate pattern formation after plants infect the disease, thedisease results in not only fruit yield fall but also commercial appearance deterioration.2. We separated and cultured four pathogenic fungus strains collected at different areasin Jiangsu Province, the fungi are assorted to Phoma cucurbitacearum (Fr.) Sacc.Temperature is main factor for it growth, its optimum temperate is 25℃, it stops growthover 35℃, the results are according to the general fungus growth characters. The sournessis not important for its growth, there is no obvious difference for its development when theenvironmental sourness range changes from pH 5.0 to pH 8.0. The pathogenic fungiexhibits higher sensitivity to Prochloraz but lower sensitivity to Thiophanate-methyl which isused widely in muskmelon production.3. The categorization status is further nailed down by PCR sequencing strategy. Wefound the pathogenic strains from both Nanjing and Haimen belong to Didymellacucurbitacearum of Didymella Sacc, its asexual type is assorted to Phoma cucurbitacearum(Fr.) Sacc. The sequences comparing among four strains released their IET sequences arevery conserved, and without obvious genetic diversity.4. The pathogenic abilities of five gummy stem blight strains are identified byinoculated with mycelium and conidiophore respectively. The result indicated that abovetwo inoculation methods are consistency. The wound inoculation by mycelium is ofquickness and simple, but this should conduct under low humidity. TMK-3 strain from Jiangning area of the strongest pathogenic ability among five strains.5. Twenty six melon germplasms were tested for ability resistance to gummy stemblight by wound mycelium inoculation. M-28 and other 5 materials, whose PODisoenzyme bands increase and produce new bands after inoculation, exhibit strongerresistant power, but the most are sensitive to the disease.