The Gray Correlation Analysis Among Coffee Seedling Breeding Measures and Control Effect of Rhizoctonia solani Disease

The relationship among each step of the coffee seedling breeding measures and the control effect of Rhizoctonia solani disease in Yunnan Province was studied by means of gray correlation analysis. The results showed that the relational grade between every step of coffee seedling breeding and the control effect of Rhizoctonia solani disease was as follows: seed bed preparation (substrate material for seed bed) 0.7549, seed soaking (yes or no) 0.4823, seed dressing（yes or no）0.7045, sowing (sowing density) 0.6687, seed covering (the covering material) 0.8489, water retention (the material) 0.7432, seed bed management (the frequency of pesticide spray) 0.6501. The relational grade and its weighted power of the seedling breeding measures was ordered as seed covering ＞ seed bed preparation ＞ water retention ＞ seed dressing ＞ sowing ＞ seed bed management ＞ seed soaking. The study showed that the seed bed preparation, seed covering and water retention measures had the greatest influence on the control effect of Rhizoctonia solani disease. The infestation rate of Rhizoctonia solani disease might be reduced by promoting the clearness of seedling breeding materials.