| Medicago polymorpha is an important forage resource in southern agricultural system as an annual medic in China. It is very useful for green manure, crop rotation, planting forage in winter fallow field, and also eaten as vegetable in Jiangsu and Zhejiang region. But there is little research about it and especially is lack of genetic breeding background. This study was started from collecting resources of M.polymorpha in Jiangsu. The main contents were about that how photoperiod effected early-flowering and genetic analysis of M. polymorpha and in order to provide a basis for genetic breeding.The main results are as follows:(1) Resources of M. polymorpha were collected through field investigation in Jiangsu Province, and evaluated by field experiment and SSR to find out the germplasm characters. The results showed that 17 cities (counties) within 26 collection sites were investigated, and 8 M. polymorpha resources were collected from Luoshe, Yinguoan, Jiangdu, Runyang, Yangzhong, Dafeng, Haian,Haimen in Jiangsu Province. The germplasm from Yinguoan of Wuxi City performed very well in more than one character, which the length of main branch was the longest reaching 129.64 cm, the growth rate was the fastest reaching 1.82 cm·d-1, the numbers of nodes were the most reaching 11.1; compared with other materials, the germplasm from Runyang of Yangzhou City in multiple trait index have reached significant difference (P< 0.05). There were molecular differences between germplasm from Yangzhong and Haian, and the percentage of polymorphic primers was 8%. The distribution of M. polymorpha in Jiangsu showed obvious biogeographical characteristic, which distributed northward to Dafeng of Yancheng City and southward to everywhere. This was related to the climate which was getting gradually cold in Jiangsu Province. There was significant difference in length of main branch,growth rate, numbers of nodes and branch, leaf area and fresh hay yield; the polymorphism was low within M. polymorpha germplasm, even no polymorphism existed within some germplasm.(2) In artificial climate chamber, different photoperiods were setted to study the affection on early-flowering time of M. polymorpha, find out differences of photoperiod sensitivity between resources. The results showed that the photoperiod sensitivity of different M. polymorpha germplasm varied significantly. The MP-2-14 from Haian, Jiangsu had an LD-FHR value of 45.56%, which was significantly higher than the other germplasm (P<0.05), and was sensitive to photoperiod; the MP-1-14 from Wenling, Zhejiang had an LD-FHR value of 11.34%, which was significantly lower than the other germplasm (.P<0.05), and was insensitive to photoperiod. When the germplasm were the same, the effect of daylight (13 h, 16 h) on the early-flowering time for the vast majority of germplasm was not significant. In addition, early-flowering time of burr medic were affected significantly by germplasm characters and photoperiod, and there was a significant interaction between them. The photoperiod had larger influence on the early-flowering time, which indicated that the germplasm characters had special adaptability to photoperiod, that is, different photoperiod was the main external factor for the differences in early-flowering time of burr medic germplasm.(3) Based on the main basis of photoperiod sensitivity and evaluation of field experiment, the suitable parents were selected. Using stereo microscope to hybridize M. polymorpha indoors, technical method for hybridizing M. polymorpha was created out,and the first genetic populations of M polymorpha were constructed. The results showed that the PCR amplification procedure of Medicago truncatula was applicable to M. polymorpha. The polymorphic primer MtB18 could identify successfully Fi of’MP-2-14’(male) x’MP-1-14’ (female) as true hybrids. F1 possessed the paternal characteristic bands. F2 was generated by F1 selfing.2 populations of 124 individual plants and 91 individual plants were constructed respectively.(4) The major gene-poly gene blending inheritance model method was used to study inter-generational genetic analysis of early-flowering under long daylight and short daylight conditions for P1, P2, F1, F2 populations. The results showed that under long and short daylight the early flowering genetic parameter estimates were different. The average values of each generation were more than 120 d under SD and more than 50 d under LD. The value of σ2e was 110.25 and the σ2p was 110.86 under SD, the value of σ2v was 13.39 and the 0% was 19.84 under LD. The early-flowering of M. polymorpha under LD was controlled by poly genes and genetic effect was additive-dominant-epistatic, without effect of major gene. The early-flowering of M. polymorpha under SD was controlled by 2 equivalent dominant gene plus additive dominant poly gene. But the heritability of major gene was low, which was 15.37%. |
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