Growth Studies in Mangosteen (Garcinia mangostana L.). II. Activation of seedling growth in Mangosteen using Arbuscular Mycorrhizal Fungi and Azospirillum

An experiment was undertaken in the central orchard at the main campus of the Kerala Agricultural University to address the slow growth in mangosteen, a highly potential crop of the humid tropics. Glomus mosseae, Glomus fasciculatum and Azospirillum individually and in combinations, as well as a control, formed the treatments. The treatments were adequately replicated in a completely randomized design. The best treatments for activating seedling growth were the combinations of Glomus fasciculatum (5 g) + Azospirillum (10 g) + single super phosphate (10 g) followed by Glomus fasciculatum (5 g) + Azospirillum (20 g) + single super phosphate(10 g) per plant. A rhythmic pattern was observed with the treatments giving the best seedling growth also yielding higher values of nitrogen, phosphorus, potassium, crude protein, chlorophyll a, b, total chlorophyll, total phenol total carbohydrates and abscisic acid content; treatments with intermediate growth recording also gave intermediate values except in the case of sodium. Control plants gave values that fell beween those of intermediate and the least growth. The highest spore count was observed in plants inoculated with Glomus fasciculatum (20 g) + single super phosphate (10 g) followed by Glomus fasciculatum (20 g) + Azospirillum (20 g) + single super phosphate (10 g). With regard to root infection, plants inoculated with Glomus fasciculatum (5 g) + Azospirillum (20 g) + single super phosphate (10 g) per plant and Glomus fasciculatum (20 g) + Azospirillum (10 g) + single super phosphate (10 g) revealed the maximum percentage of infection. The Azospirillum population was highest in the plants inoculated with Glomus fasciculatum (5 g) + Azospirillum (10 g) + followed by Glomus mosseae (20 g) + Azospirillum (20 g) + single super phosphate (10 g). The standard procedure for identification and quantification of abscisic acid was modified, as clear banding patterns were not obtained. Using the modified procedure, the characteristic-banding pattern corresponding to standard abscisic acid was obtained and confirmed when standards of abscisic acid were also simultaneously used with samples. Banding patterns and quantification of samples of the treatment with Arbuscuar mycorrhizal fungi and Azospirillum-inoculated plants were also successfully obtained and are presented. Growth measurements at the end of the first year revealed that all characters recorded were far superior to the established selection indices for the purpose.