Brinjal Little Leaf Disease Epidemiology in Insect Proof Conditions

Abstract

Eggplant or brinjal is one of the most consumed and important nutrient-dense tropical solanaceous vegetable crops grown worldwide. Little leaf is a disease especially widespread in brinjal in India where it is associated with the presence of phytoplasmas. To clarify the epidemiology of this disease and verify its seed transmission potential, seedlings and their progeny derived from symptomatic mother plants field-collected in Dharwad district of Karnataka State, India, were sowed under insect proof conditions in greenhouse. The resulting first- and second-generation seedlings obtained were tested at different times after germination by DNA extraction and amplification of 16S rRNA gene of phytoplasmas. Tissues from field collected symptomatic brinjal plants were also tested following the same procedure. The amplicons obtained were subjected to restriction fragment length polymorphism (RFLP) analysis and sequencing for phytoplasma identification. The detected phytoplasmas belonged to 16SrI, 16SrII, 16SrIII, 16SrV, 16SrVI, and 16SrXII groups. Several fruits produced from the first-generation seedlings showed germination of the seeds inside the fruit and resulted to be phytoplasma positive. This demonstrates the seed transmission of phytoplasmas in eggplants for two subsequent generations. This finding highlights the risk of additional source of infection represented by asymptomatic and infected seedlings under field conditions and contribute to explain the epidemic spread of phytoplasmas in brinjal cultivations in India and in the other eggplant growing areas of the world.