Sorghum Seedborne Fungal Diseases in Kinmen District

• Main Authors: Souleman Konate, 柯索孟
• Other Authors: Ho, Wang-Ching
• Format: Others
• Language: en_US
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/84535860476645087429

碩士 === 國立屏東科技大學 === 熱帶農業暨國際合作研究所 === 93 === Sorghum is an important food crops in many developing countries. The yield of sorghum is, however, low in most of these areas and sorghum diseases are one of the major contributors to this “yield gap”. In Taiwan, survey conducted at Kinmen district in 2003, showed that: leaf spot caused by Curvularia lunata and sheath and stalk rot caused by Fusarium moniliforme were most prevalent on sorghum variety Kinmen No.9 and Taichung No.5, and leaf spot caused by Phoma sorghina also could be found in some locations. These three fungi and Alternaria alternata could be isolated from sorghum kernels collected from fields at the same time. The roles of sorghum seedborne pathogens in the disease severity of sorghum plants were, therefore, evaluated. The deep frozen blotter method gave higher counts and detected more kinds of pathogenic fungi on the seeds than blotter method. It was therefore, used for detection of the seedborne fungi of sorghum collected from field kept under storage conditions. Using deep frozen blotter method four kinds of pathogenic fungi (C. lunata, F. moniliforme, A. alternata and P. sorghina) were isolated from the sorghum seeds while only two pathogenic fungi (C. lunata, F. moniliforme) were isolated with the blotter method. C. lunata, F. moniliforme, A. alternata, P. sorghina, Aspergillus spp. and Penicillium spp. could be detected on seeds of the sorghum varieties Taichung No. 5 and Kinmen No. 9. Disease transmission from seeds to seedlings was evaluated by the rolled paper towel method and pot test. The germination rates of sorghum seeds were low. The diseases on seedlings or plants could be detected on rolled paper towel or on potted plants in the greenhouse. The incidence of a certain disease on plants was directly correlated with the infection rate of the pathogen on sorghum seeds. Leaf spot caused by C. lunata and sheath and stalk rot caused by F. monilforme were found to be the most important seedborne diseases on sorghum in Kinmen District and could be the limiting factors for sorghum production. The pathogenicity tests of sorghum seedborne pathogens (C. lunata, F. moniliforme, P. sorghina, A. alternata) at inoculum densities of 100, 102, 104 and 106 spores / ml were conducted by using rolled paper towel and pot test methods. With rolled paper towel method, C. lunata and P. sorghina were the most virulent pathogenic fungi at densities of 102,104 and 106 spores / ml on unsterilized sorghum seeds but on sterilized sorghum seeds the most virulent pathogenic fungi were C. lunata and P. sorghina at densities of 102 and 104 spores / ml. With pot test, A. alternata and F. moniliforme were the most virulent pathogenic fungi at densities of 102, 104 and 106 spores / ml on sterilized sorghum seeds but on unsterilized sorghum seeds C. lunata and A. alternata were the most virulent pathogenic fungi at densities of 102 and 104 spores / ml. Results showed that seedlings that developed from seeds inoculated with different pathogens showed typical symptoms as they occur in nature. The optimum temperature for disease development from C. lunata, F. moniliforme, P. sorghina, A. alternata ranged from 20 to 280C. For the six fungicides (80% Thiram; 50% Benlate; 21.2% Imazalil; 23.7% Rovral; 23% Bayfidan and 25% Prochloraz) applied as inhibitors of conidial germination on micro slides and as seed dressing in the control of sorghum seedborne fungi, 80% Thiram; 50% Benlate; 21.2% Imazalil and 23.7% Rovral were most effective in controlling the spore germination. Seeds treated with these fungicides reduced the incidence of diseases and increased the germination rate and hence, could improve the yield and production of sorghum in Kinmen district.