| STUDIES ON EPIDEMIOLOG OF MAIZE SHEATH BLIGHT IN FILED ,RELATIONSHIP BIOCHEMICAL FACTORS ON STAGE RESISTANCE, AND RESISTANCE EVOLUATION OF MAIZE SHEATH BLIGHT Tang Li (Sichuan Agricultural University ,Ya?an,Sichuan,625 01 4,China) Abstract The dynamic of maize sheath blight was systematically monitored under field conditions by interval sowing. The stage resistance and the relationship between the stage resistance and change in content of nitrogen were studied. Sixty-five cultivators or lines of maize were evaluated for the resistance to the disease. The results are as follows: 1. The disease developments in natural conditions included horizontal and vertical expansion. The horizontal developmental curve was ??type. The vertical development curve was different with varying target. The progress rate of maize sheath blight was influenced by the stage of corn, the position of sheath and the climate factors. At early and late growth stage , the disease progressed slowly. The lesion of middle sheathes progressed rapider than the upper and lower sheathes. Temperature was the key factor which influenced the initial time of disease. High humidity and prolonged rainfall promoted the disease developments. 2. The resistance of corn to the disease was higher at early and late growth stage than that at middle growth stage. The resistance of middle sheathes to the disease was lower than that of upper and lower sheathes. 3. Resistance of maize was influenced by types and content of nitrogen. The change in content of soluble protein and free amino acid was related to 53 resistance change of stage resistance, which became high while content of soluble protein and free amino acid declined. 4. There were only two high resistance cultivators among sixty-five evaluated cultivators (lines). The ratio, which the lesion height divides the height of corn ear could be used to identify the resistance of corn to maize sheath blight. |
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