Intra and interlocus interactions between alcobaça (alc), crimson (og c ), and high pigment (hp) loci in tomato Lycopersicon esculentum Mill.

The ripening mutant allele alcobaça (alc/alc) may be deployed to extend shelf life in tomatoes, but has reportedly negative effects on fruit colour development. Colour enhancing mutants crimson (og ^c /og ^c) and high pigment (hp/hp) could potentially overcome this limitation, but a detailed account of their interactions with alc is not available. In this paper, we report on intra-allelic (additive and dominant) interactions within these 3 loci, and on their possible interallelic (epistatic) interactions. Eight near-isogenic (NIL) tomato lines in background Flora-Dade were obtained, representing all possible 2ⁿhomozygous combinations in the n = 3 loci. The 8 NIL were crossed in all possible combinations (reciprocals excluded), to obtain 28 hybrids that were heterozygous in at least one locus. The 36 treatments (= 8NIL + 28 hybrids) were grown in a randomized complete block design with 4replications, and the following traits were evaluated: total yield, average fruit mass, fruit firmness at harvest (= breakerstage) and 6 days after harvest (d.a.h)., % coloured fruit surface, fruit lycopene and beta-carotene contents, fruit % soluble solids and solids/acidity ratio, internal and external fruit colour. The loci alcobaça, crimson and high pigment or their epistatic interactions had significant influence on the expression of all traits measured. Epistatic effects were responsible for most of the variation among genotypes (with a minimum of 48.1%of the total sum of squares for % coloured fruit surface and a maximum of 82.8% for total yield). External fruit colour was defficient in all alc/alc genotypes, and their commercial use is impaired, in spite of improvements in fruit internal and external colour brought about by deployment of specific genotypic constitutions in lociog ^c and hp. Some but not all alc ⁺ /alc genotypes were firmer and showed improved fruit quality over the normal Flora-Dade (alc ⁺ /alc ⁺ og ^c+ /og ^c+ hp ⁺ /hp ⁺) background. The following genotypic combinations represented good compromises between yield, long shelf life and fruit quality traits: alc ⁺ /alc og ^c+ /og ^c hp ⁺ /hp, alc ⁺ /alc og ^c /og ^c hp ⁺ /hp ⁺ and alc ⁺/alc og ^c+/og ^c+ hp ⁺ /hp