Relationship between Disease Incidence of Chlorosis and Leaf Curl and Two Species of Whitefly in Tomato Crop

Abstract

Crinivirus and Begomoviruses have been reported to cause serious diseases in a number of economic crops in the world, especially in tomato crop. Crinivirus (Tomato infectious chlorosis virus/TICV and Tomato chlorosis virus/ToCV) causes chlorosis while Begomovirus (Tomato yellow leaf curl virus/TYLCV) causes curl diseases. TICV and ToCV are transmitted by vector insects in semipersistent, but TYLCV in persistent manner. The diseases have been found in Indonesia, especially in West Java. Information about the infecstation of both diseases in tomato crops are still limited. The spread of both diseases on tomato crops based on vector insect abundance in various altitude in Indonesia was evaluated in this study. The study consists of three main activities: (1) a field survey on disease incidence conducted in various altitudes from 100 to 1500 meters above sea level (m asl), which observed variables as follows: (a) diseases incidence, (b) climate condition (temperature and relative humidity (RH)), (c) abundaces of Trialeurodes vaporariorum and Bemisia tabaci, and (d) cropping condition, such as age of plant, varieties, and planting system; (2) the detection and identification of viruses and whiteflies; and (3) the analysis of the relationship between disease incidence and its determinant factors. Minor coat protein gene of Crinivirus (360 bp and 417 bp) and coat protein gene of Begomovirus (780 bp) from symptomed samples in all studied altitudes were successfully amplified by PCR. Some stadia of T. vaporariorum and B. tabaci found during observations had also been identified. The chlorosis and curl diseases infected tomato crops in altitude above 1200 m asl until 1500 m asl. Also, B. tabaci was found at those altitudeswhich previously only found at altitudes below 1200 m asl. The result of regression analysis showed there were positive correlations between the incidence of chlorosis and curl diseases with the presence of the two whitfly spesieses and the increase in altitude. Other factors such as relative humidity, tomato varieties, and plant age did not show significant contributions to the change in the incidence of both diseases.