Genotypic Variation in Responses of Citrus spp. to Arbuscular Mycorrhizal Fungi

Thailand is part of Southeast Asia that covers the center of diversity of citrus species, where various species of thegenus are widely grown. One of the most common is tangerine (Citrus reticulata), which is commonly grown bygrafting on rootstocks of different tangerine varieties or other citrus species. The objective of this study is to investigateresponses of some Citrus spp. seedlings to arbuscular mycorrhizal (AM) fungi, and thus their potential as rootstocks.The experiment was done with four tangerine varieties, Cleopatra, Fremont, Ocean and Sainamphung; and four othercitrus species, lime (C. aurantifolia), pomelo (C. maxima), sweet orange (C. sinensis) and Troyer citrange (Citrussinensis????Poncirus trifoliata), in pots for five months. Roots of non-inoculated plants were not infected with AM fungi,while inoculated plants were heavily infected with AM fungi, and contained 14-28 AM spores per 10????g of rhizospheresoil. Most of the citrus responded positively to AM fungi, but with different magnitudes among the varieties and species.Lime and pomelo seedlings were fast growing compared to other citrus species. Total dry weight and N, P, K and Mgcontents were increased most strongly by AM fungi in lime, pomelo and tangerine varieties Ocean, Fremont andSainamphung, but little or none in Cleopatra, Troyer and sweet orange. Lime was the most outstanding in the responseto AM fungi, followed by Ocean tangerine and pomelo. The potential of lime, pomelo and Ocean tangerine as rootstockfor tangerine should be further investigated.