Diversity Of Seed Yield And Its Components In Alfalfa Varieties

Alfalfa (Medicago sativa L.) is important legume forage in farming and stock in the world. It is widely adaptable to diverse environmental conditions partly because of its deeply penetrable root system and its ability to fix atmospheric nitrogen in symbiosis with Rhizobium meliloti.Genetic diversity of seed yield characteristics was studied with different varieties of alfalfas using morphological. A field study was conducted from 2005 to 2006 in Linze County of Zhangye city, Gansu Province, Genetic diversity of seed yield and its components were investigated in 62 alfalfa germplasm resources which belong to 55 varieties which grew in the fourth year under row sowing condition. The effect of fertile shoot/m~2, inflorescences/fertile shoot, flowers/inflorescence, pods/inflorescence, seeds/pod, 1000seed weight and the vertical height of plants on seed yield, and the quality of seed in 2005 and 2006 were also evaluated. The relation between actual seed yields and potential seed yields was studied in two years.Percentage of hard seed varied greatly in two years.The results showed as follows:Variation of seed yields was large among varieties. The mean seed production of all varieties was different between two years, 54.7 kg/hm~2 in 2005 and 169 kg/hm~2 in 2006, respectively. Most of them were different significantly (P <0.01), therefore, all the 55 varieties were classified into five groups according to the seed yield of 2006 by Hierarchical Cluster.Seed yield of some varieties were higher than others significantly (P< 0.01). such as, Xinjiang daye,Tianshui,Indian,L33,CaoyuanNO.2,Sitel,BearNo.1,Longzhong,PL55,WL323 and Dingxi. The mean percentage of actual seed yield accounted for potential seed yield (ASY/PSY) was from 0.22 % to 5.06 % in 2005 and from 0.44 % to 4.64 % in 2006. Almost all of them less than 4 %, and most of them was between 1 % and 2 %, difference significantly was found among varieties and between years.The two years results also showed that each of the seed yield components among varieties and between years vaired greatly. All the seed yield components varied among varieties, and there were significantly differences between native varieties and introduced varieties except number of seeds per pod.The correlation between the seed yield and the yield components among the germplasm resources were not similar in the two years. The statistical order of the correlations between the two years is as follows: inflorescences/fertile shoot > fertile shoot/m~2 > seeds/pod > pods/inflorescence > flowers/ inflorescence > thousand seed weight in 2005, and inflorescences/fertile shoot > seeds/pod > flowers/inflorescence > pods/inflorescence > fertile shoot/m~2 > thousand seed weight in 2006. The number of inflorescences per fertile shoot was significantly correlated with seed yield in two years. It was stressed that the number of inflorescences fer fertile shoot could be an useful character to be used as a selection criterion for increasing the seed yield potential of alfalfa row sowing condition.However, 1000seed weight was not positively correlated with seed yield. 1000seed weight of almost of all germplasm resources were larger in 2006 than in 2005. But 1000seed weight were different significantly among all native sources but not different in introduced sources.Dormancy character of alfalfa varieties were studied in the two years and the percentage of hard seed were different significantly in varieties and in different year. The influence of the seed parent on dormancy was more consistent than the influence of the pollen parent, but the environment was the first important to it. The seeds were stored in a period of half of years before it is used to test. The percentage of hard seed of 12 varieties decreased from 72 % to 37 %, and when the seeds were treated with liquid-nitrogen about 20 min after harvested soon, percentage of hard seed dcrased to 5 %. The hard seed had been mostly released.