Chapter 5 - Update on phytoplasma diseases associated with legumes in Asia

Abstract

Legume grains as a significant source of protein dietary fiber, carbohydrates, and dietary mineral are primarily grown for their seed, animal feed, and silage, and as soil-enhancing green manure in Asian countries. The major legume grains are common bean, chickpea, garden peas, lentil, cowpea, mung bean, urd bean, and pigeon pea in Asia. In addition, there are many minor pulses that are also grown and used as food all around Asia. Diseases and pests are major constraints to legume production, especially in the tropics and subtropics. Phytoplasmas, as emerging pathogens, have caused significant losses in several grain legume crops throughout Asia. To date, phytoplasmas belonging to five different ribosomal groups, i.e., 16SrI, 16SrII, 16SrVI, 16SrXIV, and 16SrIX have been reported in chickpea, cowpea, faba bean, lentil, mung bean, urd bean, pigeon pea, soybean, and cluster bean in Asia. Among the phytoplasma strains identified in legumes, 16SrII group is the dominant. Various leafhopper vectors and alternate hosts have also been identified as natural reservoirs of legume phytoplasma strains. This chapter provides an overview of phytoplasma diseases affecting legume and pulse crops with an emphasis on geographical distribution, identification, epidemiology, and impacts in Asian countries.