J Syst Evol ›› 2008, Vol. 46 ›› Issue (6): 856-860.DOI: 10.3724/SP.J.1002.2008.08072

• Research Articles • Previous Articles     Next Articles

The cross-fertilization mechanism and reproductive interference of self-pollen of Medicago varia ‘Xinmu No. 1’

1Ai-Qin ZHANG; 2Dun-Yan TAN; 2Jin-Zhong ZHU   

  1. 1(Life Science College, Xinjiang University, Ürümqi 830046, China)
    2(Xinjiang Key Laboratory of Grassland Resources and Ecology, College of Grassland and Environment Sciences, Xinjiang Agricultural University, Ürümqi 830052, China)zaql@sohu.com
  • Received:2008-05-16 Published:2008-11-18

Abstract: Some control tests and a technique employing the fluorescent properties of pollen and pollen tube stained with aniline blue dye were utilized to study the stigma receptivity, the optimum pollination period, the self-pollen clogging effect, pollen germination and the pollen tube growth state in alfalfa. The results can be summarized as follows: (1) The stigma receptivity and flower longevity barely overlap. On the first day after pollination, the pollination efficiency was the highest, with a pod-seting rate per raceme of 65.17%±2.01% (P<0.01). The period of the highest pollination efficiency was the same as the peak of stigma receptivity. When pollination was on the fourth day after flowering, the pod-setting percentage per raceme was still 34.25%±6.73%. (2) Self-pollination led to a lower pollen germination frequency and a lower pollen tube growth rate than cross-pollination. When artificial cross-pollination was applied after self-pollen grains on the stigma was re-moved, the pod-setting percentage per raceme was 72.31%±6.24%, and the number of seed per pod was 3.46±0.25, In contrast, these two values were 51.76%±5.37% (P<0.01) and 2.11%±0.18 respectively (P<0.01) when the self-pollen grains were not removbed in the artificial cross-pollination experiements. Hence, the clog-ging effect of self-pollen to stigma was significant. (3) In the breeding system of alfalfa, there are two mecha-nisms that help the plants to avoid self-fertilization: dichogamy and self-incompatibility. However, due to the structure of flowers, they were not effective enough to improve cross-fertilization rate, even if the stamen matured earlier than the stigma. The typical self-incompatibility system guaranteed the lower self-fertilization rate, but cannot avoid the reproductive interference of self-pollen.

Key words: alfalfa, cross-fertilization mechanism, reproductive interference, clogging effect .