Effect of Zinc Oxide Nanoparticles and Rhizobium leguminosarum on Growth, Photosynthetic Pigments and Blight Disease Complex of Pea

Effects of zinc oxide nanoparticles (ZnO NPs) and Rhizobium leguminosarum alone and in combination were observed on the disease complex of pea caused by Meloidogyne incognita and Pseudomonas syringae pv. pisi. Plants inoculated with M. incognita and P. syringae pv. pisi, alone or in combination, showed a significant reduction in plant growth, chlorophyll and carotenoid content compared to uninoculated controls. Use of ZnO NPs (0.10 ml⁻¹) as seed priming resulted in a greater increase in plant growth than 0.10 ml⁻¹ foliar spray. Plants inoculated with R. leguminosarum had better plant growth, chlorophyll and carotenoid content than plants without R. leguminosarum. Greater plant growth, chlorophyll and carotenoid content were observed when NPs primed seeds were grown with R. leguminosarum than the use of NPs foliar spray plus R. leguminosarum. Plants inoculated with R. leguminosarum showed higher root nodulation while only few nodules were observed in plants without R. leguminosarum. Both tested pathogens had adverse effect on nodulation, while use of ZnO NPs with R. leguminosarum also reduced nodulation. ZnO NPs and R. leguminosarum reduced blight disease indices, galling and nematode population. Use of ZnO NPs primed seeds with R. leguminosarum resulted in the highest reduction in disease indices, galling and nematode population. The segregation of various treatments in the biplot of principal component analysis demonstrates a suppressive role of ZnO NPs on blight disease complex of pea.