Genetic analysis of selected tomato (Lycopersicon esculentum Mill.) traits in crosses between cultivated lines and the nor mutant
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The aim of the study was to investigate the delayed ripening caused by the nor gene and its possible interaction with selected traits observed in two combinations, namely, Dw4 x nor and C36 x nor. The lines Dw4 and C36 differed from each other in the majority of examined characters. There was no significant effect of reciprocal crosses on these characters (total yield, number of fruits, fruit weight, locule number, earliness and fruit shelf life). In Dw4 x nor fruit weight was inherited with incomplete dominance of small fruit, while in C36 x nor the inheritance proved to be intermediate. This important statement made it possible to distinguish the hybrids characterised by fruit weight intermediate in relation to the parental forms. The experiments attested to the high significance of additive effects for fruit weight, periods from sowing to ripening and from flowering to ripening in both combinations and for locule number in Dw4 x nor. It was also found that the nor gene slightly delayed the onset of fruit ripening but did not affect such traits as total yield, number and weight of fruits, locule number and period from sowing to flowering. In its homozygous state the nor gene totally inhibited fruit ripening. However, as a heterozygote it revealed an intermediate action, slowing down fruit ripening and prolonging shelf life 2-3 times as compared with standard tomato. The expression of the nor gene was also found to be dependent on the genetic background. Line C36 positively influenced the flavour and firmness of hybrid fruits, while Dw4 had a negative effect on fruit quality.
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K. Niemirowicz-Szczytt, Department of Plant Genetics, Breeding and Biotechnology, Warsaw Agricultural University, ul. Nowoursynowska 166, 02-787 Warszawa, Poland