| Corn is one of the main crops in our country, which plays an important role in the development of national economy. In our country the objects of com breeding are: stabilizing the cultivated area, increasing per unit-area yield significantly as the foundation, improving quality as the center, strengthening resistance as the guarantee, and showing totally the contribution of com to the field of edibility feed, process export and so on.Nowadays per unit-area yield of corn has already reached the higher level in China, and people pay more and more attention to quality, at the same time, breeding for stress tolerance particularly breeding for disease resistance has also obtained a certain progress. But in the recent decade, sheath blight spreads quickly in corn production, and makes the loss bigger and bigger. It has become the restrictive factor that affects com production.Although some production departments and research institutions have showed much concern on corn sheath blight, there are only few people having made some reports about its biological character and aetiology. Up to the present, there is no relevant report about inherited mechanism of resistance to com sheath blight at home and abroad, therefore, corn breeding for resistance to sheath blight is progressing slowly. This experiment uses 6 generations as its materials which are from complete diallel cross of 5 corn inbred lines whose resistance to sheath blight is different. Inoculate by sheath blight, get the grade of disorder after inoculation, and analyze the regulation of inheritance of resistance to corn sheath blight. Main results are summarized as follows:(1) It exists genes which can resist sheath blight in com gene pool. Among 5 inbred lines, resistance to sheath blight of U8112 and Shuang er huang is strong, while that ofB77, RA and Huang zao 4 is weak.(2) 10 combinations from complete diallel cross of 5 corn inbred lines and their reciprocal cross, analysis of variance of parents and F1 reaches significant difference, which implies that the resistance to corn sheath blight is controlled by hereditary basis of its genotype.(3) There are 5 combinations that can not be examined apparent cytoplasm effect of resistance to sheath blight in t test of F1 , but in t test of F2 there are only 3 combinations whose resistance to sheath blight is not affected by the cytoplasm. Although the result of these two kinds of tests is not completely alike, both show that different combinations have different hereditary basis of resistance to corn sheath blight (same to the conclusion that follows). Resistance to corn sheath blight is primarily controlled by cell nucleus, generally not affected by cytoplasm effect, but some combinations may be suffered by the cytoplasm effect.(4) The heritability in broad sense of resistance to com sheath blight is higher, mostly above 45%, variation of resistance in the population of separated generation is mainly caused by hereditary variation.(5) The analysis of variance of combining ability of resistance to com sheath blight shows, the whole population is not submitted to the influence of cytoplasm. In this experiment, resistance to sheath blight of inbred lines of general combining ability (GCA) and special combining ability (SCA) effect exist significant difference. Further analysis of GCA shows, resistant GCA of U8112 and Shuang er huang is high, that of RA B77 and Huang zao 4 is weak, it is consistent with analysis of resistance above. The further analysis of SCA shows, U8112 can deliver resistance stably to all cross combinations, but Shuang er huang can form special and highly resistant combinations.(6) The genetic analysis of resistance of F2 and 6 genetions shows, different combinations have different genetic regulation of resistance. Some are controlled by major gene, some are controlled by polygene, and others are operated by major geneand polygene together. Dominance effect exists among allele, and interaction exists among non-allelic genes.(7) Inheritance...
|
PDF Full Text Request