Study on breeding and photosynthetic characteristics of new polyploidy variety for leaf and fruit-producing mulberry(morus l) | 果叶兼用多倍体新桑品种的选育及其光合特性研究

Chinese. 【目的】选育果叶兼用多倍体新桑品种,使桑树利用多元化,提高桑树的经济效益;探讨桑树多倍化以后光合特性,为桑树多倍体育种提供理论指导。【方法】采用单株选优与化学诱变相结合的染色体工程,选育果叶兼用多倍体桑树品种(2n=4X=56);测定多倍体与无性系亲本二倍体桑的形态性状,光合日变化和叶绿素含量,对叶绿体超微结构进行观察。【结果】该品种年平均桑产叶量和产果量较对照品种‘红果2号’（2n=2X=28）分别高38%和45.89%。该品种桑叶养蚕成绩中的万头蚕产茧量、万头蚕产茧层量和4―5龄每100 kg桑叶产茧量较对照叶用桑‘湖桑32号’分别高4.65%、4.35%和5.2%。于2009年通过重庆市蚕桑品种审定。四倍体叶绿素含量、RuBPcase羧化活性提高,叶绿素a与叶绿素b的比值降低,叶绿体内部基粒片层和基质片层丰富,垛叠疏松,排列有序,净光合速率（Pn）高于无性系亲本二倍体。【结论】多倍体新桑品种不但桑叶产量和质量高,且产果量高;体细胞染色体加倍以后,光合性能增强。

English. 【Objective】 The purpose of this experiment was to breed new polyploidy varieties of leafy and fruit-producing mulberry for its diverse utilization, improve economic profit and study the effects of different ploidy on the photosynthetic characteristics of mulberry,thus providing a theoretical basis for its breeding. 【Method】 Individual excellent selection associated with chemical induction were adopted. The morphological characters, daily changes of photosynthetic rate and chlorophyll content were measured and ultrastructural changes of chloroplasts were observed. 【Result】 Results of three regional experiments showed that fruits yield of new variety was 45.8% higher than the control cultivar Hongguo2 and the mean leaves yield were 40% and 13% higher than the control cultivars ‘Hongguo2’ and ‘Husang 32’, respectively. The results of rearing silkworm showed that cocoon crop per 10 000 four-instar silkworm, cocoon shell weight per 10 000 four-instar silkworm and cocoon crop per 100 kg leaves were higher than only leave-producing control cultivar Husang32, increased by 4.65%, 4.35%, and 5.2%, respectively. This variety was registered and released for commercial production in Chongqing in 2009. Compared to clonal diploidy parent, synthetic character performance of tetraploid was superer and net photosynthetic rate and chlorophyll content increased, the number of the thylakoid per granum increased and the granum thylakoid piled up loosely and arranged orderly．【Conclusion】 The increase of number of the somatic chromosome of mulberry would in favor of the enhancement of leaf photosynthetic capacity and the new polyploidy variety of leafy and fruit-producing mulberry could not only increase the yield and quality of leaves, but also increase the yield and quality of fruits.