Response Of Different Alfalfa (Medicago Sativa L.) Genotypes On Arbuscular Mycorrhizal (AM) Fungi And Studies On The Propagation Of AM Fungi

The costs and benefits of maintaining a symbiosis with AMF can differ significantly for plants, and the plant responses can vary widely. Plant growth responses may range from positive (mutualism) to neutral (commensalism) and even to negative (parasitism). Thus, the symbiosis could more accurately be defined as a continuum from parasitism to mutualism. Whether plants benefit from the association depends on a number of factors, including the genotypes of the organisms, and the environmental conditions under which they interacted. A better understanding of the factors that influence the positioning of AM fungi along the parasitism-mutualism continuum would lead to a better indicator of the roles of AM fungi in natural ecosystems.The experiments were carried out in glasshouese experiments to discover the relationship between AM fungi and plants, and the response and dependence of different alfalfa (Medicago sativa L.) genotypes to inoculate with native or exotic arbuscular mycorrhizal (AM) fungi and studies on the propagation conditions of AM fungi.1) Results showed that the mycorrhizal colonization rates of 30 different alfalfa cultivars ranged from 56.36% to 91.80%. All cultivars of alfalfa were dependent on the native arbuscular mycorrhizal fungis for shoot P uptake and growth (Dependency of P uptake on arbuscular mycorrhizal fungi was 36%-99%, dependency of growth on arbuscular mycorrhizal fungi was 46%-98%). There were negative correlations between specific P uptake of non-mycorrhizal plants and dependency of P uptake (r=-0.547**) or shoot growth (r=-0.574**). Gannong No.1, West Giant, Zhungeer, Gongnong No.1, America, Purpose, Caoyuan No.2, Xinjiangdaye, Graze, Tianshui, Giant201+Z, Huanghua, Concept, Wudi, USSR-2- are highly mycotrophic cultivars. Dependency of P uptake and growth on arbuscular mycorrhizal fungi was higher than other cultivars.2) Forty five differernt alfalfa cultivars responsed to colonization by Glomus versiforme can range from highly positive to highly negative. Percentage mycorrhizal colonisation ranged from 26% to 67%. Dependency of P uptake on Glomus versiforme was -91%～65%, dependency of growth on Glomus versiforme was 46%～98%. Glomus versiforme significantly promote the shoot dry mass and shoot P content of Dayushan, Keshansaertu, Gannong No.1, Gannong No.3, Zhonglan No.1. Dependency of their growth were respectively 33%,50%,50%,61%,73%; dependency of their P uptake were respectively 26%,46%,36%,54% and 65%, which were higher than other cultivars. Zhonglan No.1 and Gannong No.3 were the first and second. So, appropriate cultivar-AM fungi combinations need to be identified in order to derive the utmost benefit from symbiosis.3) Results showed that different plant species and different densities caused significant influence on the colonization and spores reproduction of G. versiforme and the biomass of host plants (P<0.05). The extents of AM colonizaion and spore densities in 10 plants per pot were much higher than the treatments of 5 plants per pot (P<0.05). Our studies suggested that maize, which has the highest biomass with high density, was suitable for propagation of Glomus versiforme.