PRELIMINARY PERFORMANCE OF TOMATO BREEDING LINES FOR YIELD, FRUIT QUALITY, AND RESISTANCE TO TOMATO YELLOW LEAF CURL DISEASE

Abstract

Tomato (Solanum lycopersicum L.) is an important vegetable crop in West Africa. It is grown during all seasons and the ripe fruit is consumed fresh or dried. Although production has increased in the region over the past decade, yield has stagnated at less than 20 t/ha. This situation is attributable mainly to the lack of cultivars with high commercial yield, heat tolerance, long shelf-life, and resistance to Tomato yellow leaf curl disease (TYLCD). This disease has threatened tomato production for many years, often leading farmers in hotspot areas to misuse pesticides or abandon production during peak disease periods. In this study we assessed the preliminary performance of 13 tomato lines for horticultural traits and resistance to TYLCD. Our objectives were to identify promising lines for earliness, total and commercial fruit yields, fruit characteristics (size, firmness, and general appearance) and resistance to TYLCD. Some of the lines are known to carry resistance genes. All entries were grown during a period of high TYLCD pressure during the dry season (November-May) in Mali. The trial was conducted on-station using a randomized complete block design with three replicates and 24 plants per replicate. Disease assessment was done 3 and 11 weeks after transplanting on 24 individual plants/plot using a 0 (no symptoms)-4 (severe yellowing and stunting) scale. Except for total yield, significant differences existed among lines for all traits. Although 100% disease incidence occurred for most lines by three weeks after transplanting, the highest severity was scored 11 weeks after transplanting. Commercial yield ranged from 19-54 t/ha and averaged 35 t/ha. Superior lines for earliness, high commercial yield, fruit firmness, general appearance, and disease resistance were identified. Three lines carrying TYLCD resistance (‘CLN3022F2-37-13-0-0’, ‘CLN3022F2-154-11-0-0’, and ‘CLN3022F2-154-44-0-0’) had the lowest disease severity indices (1.35-1.72 and 2.57-2.88, 3 and 11 weeks after transplanting, respectively). In addition, they out-yielded the commercial check, ‘Xina’, by 24-35 t/ha, which corresponded to 125-183% yield advantage. These three lines hold promise for use in Mali and in other West African countries, especially as a component of an integrated pest management strategy. However, further multilocation trials are needed to confirm our results. Trials including a broader range of resistant breeding lines are now being conducted in Taiwan, Mali, and across West and North Africa.