Evaluation of Round and Roma-type Tomato Varieties and Advanced Breeding Lines Resistant to Tomato Yellow Leaf Curl Virus in Florida

Tomato yellow leaf curl virus (TYLCV) is considered to be the most damaging tomato (Solanum lycopersicum) virus worldwide. Management of TYLCV has relied primarily on insecticidal control targeting the vector sweetpotato whitefly [SPW (Bemisia tabaci)]. However, resistance of the SPW to insecticides; increased length of the growing season, due in part to increased plantings of grape tomato; and asymptomatic hosts of TYLCV such as pepper (Capsicum annuum) have increased the need for wider use of TYLCV-resistant (TYLCV-R) varieties. The objective of this study was to evaluate horticultural characteristics of commercially available TYLCV-R varieties/advanced breeding lines of round and Roma-type tomato varieties in Florida. Sweetpotato whitefly populations and incidence of TYLCV were greater in 2007 than 2008. Under high TYLCV pressure, most of the TYLCV-R varieties/advanced breeding lines produced higher yield than susceptible varieties. In contrast, no clear advantage was found by using TYLCV-R varieties under low TYLCV pressure. Additionally, TYLCV-R varieties produced a high percentage of unmarketable fruit due to rough blossom end scars (BES), zippering, catfacing, sunscald, yellow shoulders, off shapes, and radial or concentric cracking compared with susceptible varieties in both years. Visual assessment of TYLCV-R varieties/advanced breeding lines for horticultural traits showed that ‘Security 28’, Sak 5443, and ‘Shanty’ were the best overall varieties/ advanced breeding lines based on participants combined score rating, although ‘Tygress’ and Sak 5808 performed best based on empirical evaluation (numerical data) of total marketable yields and low unmarketable yield. T omato yellow leaf curl virus, a begomovirus, was first described in Israel in 1939 (Pico et al., 1996), and subsequently became a major constraint to tomato production in the entire Mediterranean basin (Czosnek et al., 1990). TYLCV is transmitted by the SPW and considered the most damaging virus of tomato worldwide (Pico et al., 1996). After acquiring the virus, the SPW remains viruliferous for life, with symptoms appearing 2 to 3 weeks after inoculation (Lapidot and Polston, 2006). In the western hemisphere, TYLCV was first detected in Cuba in 1990, the Dominican Republic in 1992, and Florida in 1997 (Polston et al., 1999). TYLCV is now endemic throughout most of the southern tier of the United States, including Florida, Georgia, North Carolina, Louisiana, Texas, and California (Isakeit et al., 2007; Moriones and Navas-Castillo, 2010; Polston and Schuster, 2000; Rojas et al., 2007). Symptoms of TYLCV infection include dwarfed leaves that are up-curled, thick and crumpled, and have chlorotic margins. Up to 90% of flowers may abscise after infection, resulting in poor fruit set and yield, especially when infections occur early in the season (Schuster et al., 1996). Tomato growers in Florida have largely focused on controlling the SPW vector to reduce yield losses from TYLCV (Polston, 2003; Schuster et al., 1996). Management of SPW and TYLCV can be achieved through applications of insecticides, particularly systemic neonicotinoids. However, SPW resistance has developed to this class of insecticides in Florida (Schuster et al., 2008, 2010) and elsewhere (Horowitz et al., 2007). An effective cultural control program would include reduction of vector populations by initiating timely crop destruction after harvest followed by maintenance of a host-free period over one or more SPW generations (Hilje et al., 2001;