TOMATO IRREGULAR RIPENING IN THE CULIACAN VALLEY, MEXICO

In Mexico, tomato (Solanum lycopersicum L.) is the most exported vegetable, and it is also of utmost importance in local markets; however, silverleaf whitefly (Bemisia argentifolii Bellows & Perring) attacks reduce production from 30 to 70 %. Although Mexican farmers use different technologies to grow tomato plants, irregular ripening is a generalized concern for adequate yield and product quality. Previous reports on tomato irregular ripening (TIR) associate it to the presence of silverleaf whitefly and low temperatures during harvest. Silverleaf whitefly incidence and temperature effects were measured to establish a relationship to TIR at one of the largest Mexican areas of tomato production. Experiments were carried out on 16 tomato hybrids sowed at the INIFAP Experiment Station in the Culiacan Valley, Mexico. Yield and commercial fruits size were measured, as they are important factors that determine commercialization and destination market (e.g. industrial process, export or domestic market). Silverleaf whitefly incidence and temperature effects on TIR were also analyzed on the basis of yield. TIR symptoms, both temporary (TIRt) and permanent (TIRp) were observed. The term TIRt described fruits that resumed their maturation process during the storage after harvest and reached full ripening after 7 d at 25 ºC. Consistent with previous reports, it was observed that TIRt symptoms were associated to low temperatures ( ≤ 8 ºC) during early harvest dates. TIRp damaged more fruits and associated to the effect of silverleaf whitefly at high population densities (0.77 to 0.93 adults cm-2), to high temperatures during the harvest season and to susceptible tomato genotypes.