Responce of Snap Bean Plants (Phaseolus vulgare) to Mycorrhizal Fungi Under Different Levels of Phosphate

Abstract

The effect of arbuscular mycorrhizal (AM) fungus and soil phosphorus levels (P) sole or combined application were studied on growth parameters, total chlorophyll, chemical concentrations, yield and quality as well as mycorrhizal dependency (MD) of snap bean grown at El-Baramoun Farm, Mansoura Horticulture Research Station, Dakahlia Governorate, Egypt, during two successive seasons of 2014 and 2015. A factorial design 2X3 experiment was designed and conducted to characterize the relationships between three soil phosphorus levels (0, 50% and 100% of recommended P fertilization) and two vesiculararbuscular mycorrhizal (VAM) fungi treatments which were without mycorrhizae (NAMF) and with mycorrhizae (AMF). Mycorrhizal inoculation significantly increased all studied parameters compared with nonmycorrhizal plants. Addition of soluble phosphate improved all growth parameters, photosynthetic pigment, mineral composition (N, P and K), yield (yield/plant and early and total yield/feddan) and pod quality expressed as TSS, protein and fiber percentages.The interaction results between mycorrhizal bean and P amendment had higher growth records i.e., plant height, dry weight and leaf area, but no significant differences between 50% and 100%P were observed in both seasons. IN addition, 50%P was more superior in increasing total chlorophyll, chemical concentrations and yield component in AMF bean plants, except P concentration in the first season. In addition, pod characteristics was enhanced with increasing P level combined with AMF inoculation and the highest records of pod weight, length and diameter were obtained with inoculation with AMF and 50% of the recommended dose of P fertilizer. TSS and protein percentages of pods were significantly increased, whereas, fiber% was significantly decreased in mycorrhizal bean compared with nonmycorhizal one at the same levels of P. Mycorrhizal inoculation was more superior in improving pod quality of plants supplemented with 50%P.In general, growth, photosynthetic pigments, nutrition, yield and pod quality of snap bean plants showed a high degree of dependency on the mycorrhizal fungus in nonfertilized soil and 50%P when compared with the soil fertilized with100% P.The economic feasibility of snap bean cultivation shows that the highest net return and benefit-cost ratio (13353 LE fed-1 and 2.39, respectively) were obtained with mycorrhizal bean amended with half dose of phosphorus recommendation compared with other treatments under the condition of this study.This study confirmed that Bronco variety showed better vigorous growth of plants with higher pod yield and its quality in response to bio-fertilizer application(arbuscular vesicular mycorrhizal fungi) with the two levels of P (50,100%) and 50%P was more superior under high pH soil conditions of Nile Delta soils, where P availability is low.