Tomato Yellow Leaf Curl Virus (TYLCV) Alters the Phytochemical Constituents in Tomato Fruits (Report‪)‬

Introduction Tomato (Lycopersicon esculentum Miller.) is the world's second most extensively grown horticultural crop after potato. Present world production is about 100 million tons fresh fruit produced on 3.7 million hectares. The production has been reported for 144 countries (FAOSTAT Database, 2004). Unfortunately, plants in nature are constantly challenged by a diverse array of plant pathogenic microorganisms. Many viruses like tomato yellow leaf curl virus (TYLCV), tomato leaf curl virus, tobacco mosaic virus (TMV), potato virus X, potato virus Y, cucumber mosaic virus, beet curly top, etc. are known to infect tomato plants (Navas-Castillo, 1999; Moriones and Navas-Castillo, 2000). Among them, TYLCV is prevalent and widely distributed in many Mediterranean, Middle Eastern, African, and Asian countries including Bangladesh, causes a dramatic yield loss to the crop and poses a great threat to commercial tomato cultivation. Infection levels range from 5 to 100% of plants (Rybicki et al., 2000). Losses from plant diseases can have a significant economic impact, causing a reduction in income for crop producers, distributors, and higher prices for consumers. As TYLCV continues to spread, many isolates have been described in different parts of the world. However, this disease has not been properly investigated in Bangladesh. The biochemical alterations of cellular constituents are reported to be directly related to morphological deviation of virus infected plants and the extent of crop loss is largely determined by visible symptoms (Levy and Marco, 1982). The symptoms specificity and its severity are concerned with the changes of specific cellular components due to virus infection (Sreenivasulu et al., 1989). A dramatic biochemical changes in virus infected plants result in decrease of both quality and quantity of infected crops (Al-Musa, 1982). Various reports suggest that virus multiplication inside the plant cell alters different biochemical constituents of plants and disrupt the physiological process like photosynthesis, transpiration and respiration of the infected plants which affect the growth and yield (Fraser, 1987). They also reported that the determination of cellular constituents in virus infected plant is very important to understand the activities of the host cell and the nature and extent of damage caused by the virus. TYLCV is transmitted exclusively by a single insect species, the whitefly Bemisia tabaci in a circulative manner (Ghanim and Czosnek, 2000). The virus differs in nature of survival, host range, transmission and field epidemiology. Although not systematically studied, it is assumed that the disease may be one of the major causes of poor yield to tomato in Bangladesh. Scientists in recent years showed keen interests to find out the biochemical impact of viruses. Al-Musa and Monsour (1983) reported that TYLCV cause the prevalent disease characterized by stunting, chlorosis, curling, rosette, enations, and distortion on leaves, flowers and fruits. Alam et al. (1996) noticed biochemical alterations only in leaves of tomato caused by different viruses. Makkouk et al. (1979) and Al-Musa (1982) reported quantitative and qualitative reductions in yield in infected plants compared to healthy. So far, there is no information regarding biochemical status of the fruits which may cause yield reduction in tomato by TYLCV. Physiological and genetic base for the organic acid, nucleic acid and auxin accumulation in fruits of infected tomato plants have not properly been investigated by researchers. In view of its importance, the present study was undertaken to follow the changes in ascorbic acids, nucleic acids, auxin, and individual organic acids in fruits of tomato plants after TYLCV infection. The nutritional status and yield in fruits of infected tomato caused by TYLCV were compared to healthy plants.