Maturação pós-colheita de híbridos de tomate heterozigotos no loco alcobaça

Abstract

There is a direct relationship between the postharvest quality of tomatoes and preharvest factors, notably the choice of ideal hybrid. The behavior of three pairs of nearing isogenics hybrids of tomatoes of plurilocular group during its maturation was studied and the effect of the alcobaça loci in heterozygosis on its conservation and postharvest quality was evaluated. The trial was carried out in UFLA, MG, with a randomized complete block design. The pairs of hybrids (Stevens x Flora Dade and Stevens xTOM-559; Piedmont x Flora Dade and Piedmont xTOM-559; NC-8276 x Flora Dade and NC-8276 xTOM-559) were evaluated in four stages of maturation (breaker, pink, light-red and red) in four replications. The hybrids where the Flora Dade was the genitor corresponded to the normal genotype (+/+) while the hybrid where the TOM-559 was the genitor corresponded to the heterozygous genotype to alcobaça (+/alc). The quality of the fruits was determined through physical, physico-chemical, chemical and biochemical analyses. For the alcobaça allele in heterozygous, the postharvest life of the fruits stored under room temperature was extended for two days, without changes in pigmentation and levels of pH as well as the titrable total acidity (TTA). The levels of total soluble solids (TSS), total soluble sugars and TSS/TTA ratio in the alcobaça fruits were, in average, higher compared to the values observed for the control, while the activities of the pectinmethylesterase (PME) and polygalacturonase (PG) enzymes and solubilization percentage of pectic substances were less pronounced. The texture and the cell wall compounds were not affected by the alcobaça allele in pre-determined stages of maturation. The behavior of alcobaça hybrids, during the maturation, was similar to that of the normal ones, characterized by intense softening associated with an increase in PG activity, solubilization and depolymerization of pectic substances and turnover of neutral sugars of hemicellulosic fraction. The use of the alcobaça allele in heterozygous in the genetic breeding presented as aviable instrument in the obtention of hybrids of high commercial value.