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Abstract

Low availability of Phosphorus (P) is one of the most serious factors limiting onion (Allium cepa L.) production, especially on calcareous soils. In the current investigation, we studied the impact of three indigenous isolates of arbuscular mycorrhizal fungi (AMF), Glomus mossae, Glomus hoi, and Glomus intraradices, on physiological attributes, antioxidant metabolism and yield of onion at reduced phosphorus availability. Isolates were sourced from onion rhizosphere soils in Pakistan and identified morphologically before use. Treatments included three AMF species alone, phosphorus (100% recommended dose or R.D. and 50% R.D.) and their combinations and were arranged in a completely randomized design with three replicates. Compared to control (without inoculation), AMF inoculation significantly increased root colonization, spore counts, P content, carbohydrate accumulation, antioxidant activity, phenolics and flavonoids production and yield attributes. Responses were mostly consistent with the isolate G. intraradices showing the maximum effect on all parameters. AMF application with 50% recommended dose of P showed highest bulb yield (83% higher than control), dry matter content and significantly increased antioxidant activity and total phenolics. Application of P alone only increased P uptake without showing any integrated physiological and biochemical improvement over non-inoculated controls. Therefore, indigenous AMF could play a promising role in improving P-use efficiency, bulb quality and yield of onion under P-deficient conditions. Furthermore, inoculation with indigenous AMF along with reduced application of chemical fertilizers might prove beneficial in decreasing agrochemical inputs.

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