Study On Co-tolerance For Varieties Of Alfalfa And Italian Ryegrass

(1)A seed germination experiment was conducted to investigate effects of cobalt stress on germination rate and growth of twenty-seven Italian ryegrass varieties and thirty five Alfalfa varieties to explore differences of Co2+tolerance among sixty two varieties. The results indicated that the germination rate, germination energy and germination index of Italian ryegrass and Alfalfa were superior to the control at low level of Co2+treatments. However, the germination rate, germination energy, germination index and radical/embryo ratio all decreased with the increase of the Cobalt concentration. According to the calculated Co2+tolerance indexes for the sixty two varieties, the strongest Co2+tolerance materials were Zhongxu-1021and Victoria of Italian ryegrass varieties and Mobo and Saidi-10of Alfalfa varieties, and the weakest Co2+-tolerance materials were Zhuoyue and Bufei of Italian ryegrass varieties and Shanxi and San Miguelite of Alfalfa varieties.(2) Relative survival rate,relative plant height, relative aboveground biomass, Relative electrical conductivity, chlorophyll content and proline content were measured under different Co2+stress at seeding stage.Co2+tolerance in27Italian ryegrass varieties and35Alfalfa varieties was comprehensively analyzed by principal component analysis and subordinative function.The results showed that the strongest Co2+tolerance materials were Aowaxun and Morsanskij of Italian ryegrass varieties and Weibo and Xifeng of Alfalfa, and the weakest Co2+tolerance materials were kangaroo valley and Pakeer of Italian ryegrass varieties and WF-101and Mandan of Alfalfa.(3)The enrichment features of Italian ryegrass varieties and Alfalfa under Co2+stress were studied. In general,(BCF) of Co from soil to different parts of Italian ryegrass varieties and Alfalfa were increased with the increase in added Co to the soil. BCFs of Co of all parts of the strongest Co2+tolerance materials were greater than those of the weakest Co2+tolerance materials. At low Co addition, the transfer factors (TF) of Co from root to shoot for Italian ryegrass varieties and Alfalfa were increased with increasing Co addition. At high Co addition, TF of Co in Italian ryegrass varieties and Alfalfa tended to decrease with increasing Co addition.