Arbuscular mycorrhizal fungi induced biochemical changes in pea (Pisum sativum) and their effect on powdery mildew (Erysiphe pisi)

Colonization of Glomus mosseae and Pseudomonas fluorescens (mutant Pf2) increased the growth of three pea (Pisum sarivum) cultivars such as 'Rachna', 'HUDP16' and 'HUP2'. When colonized with mutant Pf2, all the three cultivars exhibited maximum biomass accumulation in terms of shoot and root weight. Treatment with Pf2 mutant also resulted in greater nodulation, e. g., 31, 33 and 34 nodules/ plant in 'Rachna', 'HUDP16', 'HUP2', respectively, as compared to mycorrhizal and control plants. Plants colonized with G. mosseae gave greater yield. Various levels of qualitative as well as quantitative accumulation of phenolic acids were observed in pea plants in response to the colonization with G. mosseae and mutant Pf2. Qualitatively, certain phenolic acids, namely, tannic, gallic, vanillic and ferulic acids, were identified with more prominent quantitative variations. Plants of all the cultivars showed greater accumulation of phenolic acids in treatments than the control. In all the cultivars, mycorrhizal colonization occurred irrespective of whether the plants were infected with Erysiphe pisi. About 70 % colonization of G. mosseae was observed in the above pea cultivars. In plants infected by E pisi, maximum content of total phenolics was recorded in 'HUP2' followed by 'Rachna' and 'HUDP16'. Mycorrhizal colonization and total phenolic accumulation were closely correlated with disease intensity (D.I.) on pea plants. Control plants of 'Rachna' showed maximum D.I. (55.2 %) followed by 'HUP2' and 'HUDP16', whereas mycorrhizal plants of 'HUDP16' showed minimum D.I. (28.7 %) as compared to 'HUP2' and 'Rachna'.