Indigenous AM fungi and Azotobacter isolates, and their screening from citrus seedlings at different levels of inorganic fertilizers application.

摘要

Arbuscular mycorrhizal fungi (AMF) and Azotobacter chroococcum association in citrus orchards grown in nine different plantation areas of north-western Himalayan region (NWHR) of India was investigated. Twelve AMF species of genera viz., Glomus, Gigaspora, Scutellospora and Entrophospora and two strains of Azotobacter chroococcum viz., Azotobacter strain-I (AZ₁) and Azotobacter strain-II (AZ₂) were isolated and identified. The species of Glomus namely G. fasciculatum (Thaxter) Gerdemann and Trappe and G. mosseae (Nicol. Gerd.) Gerdemann and Trappe were the most abundant in the majority of the experimental sites. The mycorrhizal spore population was maximum at Daad and minimum at Dashlera. Root colonization percentage oscillated between 24.6 and 30.5%. Inoculation study was carried out with the aim to select the most efficient native AMF species and Azotobacter strain for sustainable citrus nursery management. The impact of two most frequently occurring AM species viz., G. fasciculatum (Thaxter) Gerdemann & Trappe and G. mosseae (Nicol. & Gerd.) Gerdemann & Trappe and Azotobacter strains viz., AZ₁ and AZ₂ at alone and in combination with different levels of N and P was evaluated on growth and development status of citrus seedlings under controlled atmospheric conditions. The significant increase in growth parameters namely, height, diameter, root length and leaf area was more evident for the seedlings inoculated with G. fasciculatum (Thaxter) Gerdemann & Trappe followed by G. mosseae (Nicol. & Gerd.) Gerdemann & Trappe, AZ₁ alone and in combination with 2/3rd dose of N+P.