Vesicular - arbuscular mycorrhiza research for tropical agriculture

This state-of-the-art report (1930-78) outlines the relation of VA mycorrhiza to agriculture and ecology, notes research trends, and considers the application of research on VA mycorrhiza to tropical soils and conditions. The authors first present an overview of the VA mycorrhizal system, including the structure of arbuscles, vesicles, and external mycelium and the classification and distribution of the fungi. Next explored is the manner in which VA mycorrhiza promote plant uptake of P and the resulting effect on plant growth. Methods for inoculating nonsterile soils are presented. Also outlined are the other functions of VA mycorrhiza, i.e., the promotion of plant uptake of zinc, sulfur, and nitrogen and the beneficial effects on soil aggregation. Emphasizing the importance in the natural ecosystem of VA mycorrhiza, the authors investigate the possible applications of mycorrhizal research to crop production in the tropics, particularly in the areas of improving utilization of applied fertilizer, improving nodulation and nitrogen fixation by grain and forage legumes, reestablishing infection in sterilized soils, and controlling erosion. Constraints to large-scale inoculation are discussed. Finally, the authors recommend that future research center on: field experimentation on P uptake; developing a workable method for estimating the numbers and efficiency of endophytes at particular sites; the effects of VA mycorrhiza on uptake of sodium, chlorine, aluminum, and manganese and the effect of these ions on VA endophytes; and hormone production by endophytes. Appendices include a 348-item bibliography (1926-81) and lists of important growth responses to VA mycorrhiza inoculation by crop and of other important subtropical and tropical VA mycorrhiza hosts.