关键词: 水稻, 种质创新, 资源评价

Abstract:

【Objective】In order to avoid the influences of unknown genes, genetic background and other uncontrollable factors in breeding practice, experiments were conducted to create new high-quality rice germplasm using an improved method, which integrated high-throughput SNP genotyping with traditional breeding to improve breeding efficiency. 【Method】 Two varieties of rice (Jianzhen 2 and Ezhong 5) were used as parents to make a cross (Ezhong 5/Jianzhen 2), and Ezhong 5 was used as recurrent parent to obtain backcross generations, whose progenies were selected by pedigree method. Rice qualities were evaluated in generations from BC₁F₂ to BC₁F₄. An elite line, 4W1-056, was screened in the generation of BC₁F₇. DNA segments from Jianzhen 2, Ezhong 5 and 66 plants of 4W1-056 were PCR-amplified and sequenced using capture sequencing technologies, and 908 SNP sites were analyzed. Phylogenetic analyses were performed based on genotypes of SNP sites using p-distance method in software MEGA7. Novel lines were selected and evaluated based on agronomic traits and rice qualities in combination with the results from phylogenetic analyses. 【Result】An elite line 4W1-056 was obtained by means of crossing, backcrossing and selfing, which has desirable plant type, strong tillering ability, good lodging resistance for stocky stems, excellent appearance quality and preliminarily stable in agronomic traits. Sixty-six plants selected from 4W1-056 were clustered into three groups based on the results from phylogenetic analyses. The base substitution rate among cluster Ⅰ, Ⅱ and cluster Ⅲ was 0.1398, and that between cluster I and Ⅱ was 0.0662. The base substitution rate within any of these clusters was 0, which suggested that there were no genetic differences among individual plants within the same cluster. Cluster II was designated ZY56 as a new line based on its agronomic traits and rice qualities, and its appearance quality is better than that of 4W1-056, with a chalkiness score of 0.9, which is closer to the appearance quality performance of Ezhong 5. ZY56 and its original parents were detected using 8K RICE SNP chips, the results showed that 14.13% of ZY56’s chromosome segments were from Jianzhen 2 and 85.87% were from Ezhong 5, Chip detection further showed that most of the genes in ZY56 originated from Ezhong 5, and verified the selection results after crossing, backcrossing and selfing. The minimum effective accumulated temperature needed for basic vegetative growth in ZY56 was 760.5℃, the critical light length for reproductive growth was 14 h 13 min, and the effective accumulated temperature needed for panicle differentiation was above 711.5℃. The results of quality analyses from experiments at different sowing dates showed that ZY56 responded to light length significantly weaker than Ezhong 5, its photosensitivity was weak and growth was stable, which was conducive to the development of rice qualities, and the rice qualities of ZY56 were more stable than Ezhong 5. 【Conclusion】We proposed a new method for the selection in higher generations of a germplasm development program, in which high-throughput SNP genotyping technology was used to screen plants for genetic consistency, and eventually to find out the strains that conform to breeding targets. This method overcame the difficulty in the selection for agronomic traits by means of traditional pedigree in advanced generations, and circumvented the problems that similar types of strains were repeatedly selected and different types were missed. The method saved efforts of selection in higher generations, while increased the efficiency of selection, so it had value of popularization.

Key words: rice, germplasm improvement, resources evaluation