不同穗型粳稻品种(系)稻曲病粒在穗内粒位上的分布

为了寻找稻曲病(Ustilaginoidea viresns)的发病原因及其与穗型的关系,利用54个直立、半直立和弯曲穗型粳稻品种(系),研究不同穗型品种(系)稻曲病粒在穗内不同粒位的分布。结果表明,直立穗型品种(系)的发病机率较大,而且发病严重,损失较大。直立穗型品种(系)每穗稻曲病粒数最多,半直立穗型品种(系)次之,弯穗型品种(系)最少,差异达到了显著水平。3种穗型品种(系)的2次枝梗上总病粒数都比1次枝梗上的多。直立和半直立穗型品种(系)病粒数表现为穗中部穗下部穗上部,而弯穗型品种(系)则是穗下部穗中部穗上部。3种穗型品种(系)的病粒数在穗上6个部位的分布规律极为相似,都是在中部2次枝梗上分布的最多,上部1次枝梗上分布的最少;在穗上33个粒位的分布规律也很相似,病粒数都是在中部2次枝梗第一、第二、第三粒位和下部2次枝梗上第一、第二粒位上分布的较多,其中穗中部2次枝梗第一粒位上病粒数最多,而在上部1次枝梗上第一、第六、第七粒位分布的最少。每穗粒数过多,尤其是2次枝梗粒数所占比例多是利于稻曲病发生的主要原因,而与穗型特点并无必然联系。

Grain Position Distribution of Diseased Grain of False Smut (Ustilaginoidea viresns) within A Panicle in Different Panicle Type Japonica Rice Varieties

In order to find the relationship between false smut of rice and rice plant type, 54 typical type cultivars including erect-panicle type, semi-erect-panicle type and curved-panicle type were applied as materials to study diseased grain distribution of false smut (Ustilaginoidea viresns) within a panicle in different panicle type japonica rice varieties. The results showed that disease incidence of erect panicle type varieties was higher than other panicle type varieties, and the disease was more serious, the loss was bigger. The order of diseased grain number of rice false smut per panicle in three different panicle type varieties was erect-panicle type>semi-erect-panicle type >curved-panicle type, indicating significant differences. Total diseased grain number for the grains on a secondary branch in three panicle type rice cultivars were more than those on a primary branch. The order of total diseased grain number for the grains on different panicle position in erect-panicle type and semi-erect-panicle type varieties was at middle part>at bottom part>at top part, but the trend of the diseased grain number of curved panicle type varieties was at bottom part>at middle part>at top part. Diseased grain number in the grains among six parts had similar regularity that diseased grain number in the grains on a secondary branch at middle part was the most, and diseased grain number in the grains on a primary branch at top part was the least. Diseased grain number for the grains on 33 grain positions had the similar regularity that number of the diseased grain distributed in the grain 1 on a secondary branch at middle part was the most, but number of the diseased grain distributed in the grain 1, 6, and 7 on a primary branch at top part was the least. Too much grain number per panicle, especially higher ratio of grain number on secondary branch to total grain number was the main cause of disease happening, which was no connection with panicle type.