Studies on host range and management of Tomato leaf curl virus

Abstract

Thesis Title: “Studies on host range and management of Tomato Leaf curl virus” Tomato (Solanum lycopersicon L.) belong to genus Lycopersicon under family Solanaceae. Tomato is an important and most widely grown vegetable crop in both tropics and sub tropics of the world. It ranks second in the importance among vegetables. India is a second largest tomato producing country. The estimated area and production of tomato in India (during 2013-2014) was 0.88 million hectares with a total production of 18.73 million tones (productivity 21.2 mt/ha), respectively (National Horticultural Board Database, 2014). Among all the diseases of tomato, the tomato leaf curl virus (ToLCV) disease is cited to be the most devastating both in terms of quantitative and qualitative yield losses. Often, the loss reaches to the extent of 100% during summer throughout India. The present investigations entitled “Studies on host range and management of tomato leaf curl virus” during 2015-16. The virus associated with tomato leaf curl disease was detected by PCR using coat protein specific primers. The results confirmed the presence of TLCD caused by tomato leaf curl virus. For management of virus vector white flies (Bemisia tabaci) different plant leaf extracts, seed kernel extract, plant oils and chemicals were used. The effect of plant leaf extracts, seed kernel extract, plant oils bio agent and chemicals were found to be effective for reducing whiteflies population. The maximum decrease number of whitefly was recorded 3.00, 3.67, 1.67, 2.33 in acetamiprid followed by neem seed kernel extract 4.00, 4.33, 2.67, 3.00 after 7 and 14 days of first and second spray. Whereas, untreated control was recorded with 13.00, 14.67, 15.00, 16.00 respectively. Several measures have been taken to control the vector Whitefly. However, it has not been very effective in preventing epidemics and yield losses due to these viruses. Hence, the present investigations were carried out with potent rhizobacterial isolates alone and, along with elicitor molecules such as chitosan to determine its ability to control ToLCV in tomato. Different formulations of PGPR and chitosan were evaluated for controlling ToLCV and growth promotion of tomato. It was found that the application of Pseudomonas fluorescens in combination with chitosan reduces the severity of the ToLCV disease by 80 - 90 per cent. Application of chitosan and bacterial inoculant alone was not effective to control the severity of ToLCV disease. However, the plants inoculated with the chitosan based formulation of Pseudomonas fluorescens Pf1 and Pf2 recorded maximum plant height, fruit number and yield/plant over the diseased control. The results, thus, indicate that addition of chitosan has enhanced the biocontrol efficacy of Pseudomonas fluorescens against ToLCV