Phytoplasma on Sesame: Etiology, Insect Vectors, Molecular Characterization, Transmission and Integrated Management

Sesame phyllody disease is of serious concern in many sesame-growing areas. It significantly diminishes crop production, especially in warm environments causing up to 80% yield loss. We observed various symptoms of phyllody disease, viz. flowery phyllody, virescence, flower bud proliferation, ovivipary and cracking of seed capsules. Orosius albicinctus (Distant) was identified as the vector of sesame phyllody. Sesame phyllody phytoplasma 16SrI strain sequences of India, Egypt and Thailand were associated in one group; 16SrII strains were grouped separately, comprising sequences from India, Iran, Taiwan, Turkey and Oman. 16SrIX stains of Iran (MW27256, KF774193 and MW272565) and Turkey (KC139791) sequences were clearly distinguished from the phylogenetic tree. This result clearly shows the presence of different sesame phyllody phytoplasma strains and diversity in the Indian subcontinent. Sesame phytoplasma was effectively transmitted to the healthy plants from infected plants of sesame through O. albicinctus, grafting and dodder. The most sustainable and viable alternative for managing sesame phyllody can be an integrated strategy by combining cultural, host plant resistance, biological, physical and chemical methods. Sesame phyllody has become a potential threat to sesame cultivation. Hence, it is necessary to take steps to reduce its further spread. In this article, extensive details on distribution, taxonomy, symptomatology, etiology, transmission, molecular characterization, genetic diversity, host plant resistance and management methods on phytoplasma infecting sesame are provided.