水稻株形对纹枯病抗性的影响

利用240份源于珍汕97B/明恢63的重组自交系水稻(Oryza sativa L.)群体,连续2年调查纹枯病病级与水稻生育期、株高和叶片长宽等18个株形性状的关系.对株形性状与纹枯病病级进行了偏相关分析.实验结果,只有植株松紧度与病级表型偏相关两年中都达到了显著或极显著水平,倒2叶基角、穗层整齐度等8个性状与病级之间的偏相关只有一年达显著或极显著水平.结合构建的分子标记遗传连锁图谱,对各性状进行QTL定位.在抗纹枯病QTL相近区间仅检测到控制分蘖角、植株松紧度和倒2叶基角的QTLS,未发现其余株形性状QTLs与抗纹枯病QTLs分布在同一染色体上.结果表明,水稻对纹枯病的抗性主要是由本身抗性基因控制,株形对纹枯病抗性表达的影响主要是间接影响,即通过改变田间小气候而影响发病程度.抗纹枯病育种在累加主效抗纹枯病QTLs的同时,也要注重选择不利于纹枯病发展的株形性状.

Effect of Morphological Traits on Sheath Blight Resistance in Rice

Sheath blight, caused by the Rhizoctonia solani Kü hn, is one of the most serious diseases of rice (Oryza sativa L.). The relationship between morphological traits and sheath blight resistance was investigated in 1999 and 2000 by using a segregant population consisting of 240 inbred recombination lines, derived from an elite combination of Zhenshan 97×Minghui 63. Partial correlation analysis between phenotypic data (morphological characteristics and heading date (HD)) and sheath blight ratings (SBR) showed that only one trait, plant compactness, was significantly correlated with resistance to sheath blight in both 1999 and 2000, eight traits, such as plant height, heading date, and penultimate leaf angle, were significantly correlated with SBR in either of the two years, and the remaining 10 morphological traits were not consistently associated with SBR in the two years. A major quantitative trait locus (QTL) controlling plant compactness was found to be in the site on chromosome 9 adjacent to the region responsible for qSB9, a major QTLs conferring sheath blight resistance. One out of the three QTLs contributing to a penultimate leaf angle was mapped approximately on the same region as another sheath blight resistance QTL, qSB5, located on chromosome 5. Whereas, no QTLs underlying most other traits was detected on the chromosomal region correlated with sheath blight resistance QTL. The results in the present study suggested that the morphological traits were not the main factors responsible for the SBR separation among the recombinant inbred lines (RILs) population. Nevertheless, some morphological characteristics had some indirect influence on expression of sheath blight resistance genes through altering a microcli-mate on paddy field so as to influence the infection of the pathogen and development of the disease. An efficient approach in resistance breeding to sheath blight was recommended by pyramiding major QTLs for sheath blight resistance and selecting those morphological traits that favor resistance gene expression.