Genetic improvement of processing tomatoes: A 20 years perspective

Over the past 20 years replicated field trials have been conducted on processing tomato varieties by the California Tomato Research Institute and the Israeli Ministry of Agriculture with the objective of identifying superior varieties. Because common check varieties were included in consecutive years, environmental effects could be factored out allowing an estimate of the genetic improvement due to breeding. The results indicate an average genetic gain for yield of 1.54%/yr for California and of 0.4%/yr for Israel. No significant genetic gain in brix was found for California, whereas for Israel, the data indicate an average increase of 0.53%/yr. For the derived trait brix x yield, the overall genetic gain ranged from 0.9%/yr in Israel to 1.5%/yr in California. A significant genetic gain of 1.15%/yr was determined for fruit color in California for the period 1977-87 and of 2.73%/yr for Israel during the years 1985-1995. The improvement in yield is partially due to the increase in the proportion of hybrids in the trials starting from the mid 1980's. The implications of the results for future tomato breeding are discussed.