Phytoplasmal diseases in India and its management

Phytoplasmas are phloem-limited pleomorphic bacteria which lacks the cell wall, mainly transmitted through leafhoppers but also by plant propagation materials and seeds. In India evidences showed that phytoplasma have been found associated with 129 plant species including Cereals, vegetables, fruits, trees, ornamental, sugarcane, grasses and weeds which is increasing at alarming rate. Sesame phyllody, brinjal little leaf, sugarcane grassy shoot, sandal spike, coconut root wilt, areca nut yellow leaf and many diseases in ornamental plants which causes the most severe economic losses in India. In earlier days, very few phytoplasma diseases were identified in India merely based on the bright-field, fluorescence, electron microscope observations, tetracycline treatment and to a lesser extent by serological assays. Recently detection of phytoplasma based on molecular methods including nested PCR assays are efficiently carried out and on that basis several plant species are reported to have phytoplasma infections. Identified phytoplasmas are related to ‘Candidatus Phytoplasma asteris’, ‘Ca. P. pruni’, ‘Ca. P. ziziphi’, ‘Ca. P. trifolii’, ‘Ca. P. solani’, ‘Ca. P. cynodontis’, ‘Ca. P. oryzae’, ‘Ca. P. phoenicium’, ‘Ca. P. australasia’ and ‘Ca. P. pini’. At present the suggested effective management practices in India includes growing resistant varieties, control of insect vectors, weed species as alternative hosts and use of healthy planting materials. It is moreover essential to understand the molecular basis of phytoplasma-vector interaction and other factors involved in disease development in order to reduce the outbreak of phytoplasma. In this chapter, we have discussed overall progress on phytoplasma disease on plant species in India in terms of detection, transmission and management of phytoplasma.