MATERIAL AND GENIC CYTOPLASMIC DIFFERENCES IN RECIPROCALLY CROSSED TOMATOES

Abstract

A series of generations was synthesized to study reciprocal differences for three developmental periods, early yield and fruit size in tomatoes. A small fruited early cultivar, Johnny Jumpup, and a large fruited later cultivar, Bounty, were used as parents. From individual cloned parent plants and their reciprocal F₁'s, all possible first backcross and F₂lines were derived. Maternal effects were demonstrated in BC₁lines for each of three periods and for early yield. Increased earliness was expressed rather uniformly by BC₁lines derived from F₁females over those derived from either of the parental females.Genic-cytoplasmic differences were demonstrated in BC₁lines for each of three development periods and for early yield. Earliness for each of these characters was associated with lines having common cytoplasmic-recurrent parentage, over those not having common such parentage. Magnitudinally, the differences were more closely associated with the Johnny Jumpup cytoplasmic-Bounty recurrent parent line than with the converse.Similarity in direction and magnitude of differences in F₁and F₂lines indicated that matroclinous reciprocal F₁differences for the development periods and early yield were persistent through the F₂. Therefore, the association of cytoplasm with an F₁genotype, rather than maternal effects, appears to be the primary cause of differences for earliness in F₁'s resulting from reciprocal crosses. The larger fruited, earlier parent should be used as the female in F₁hybrid seed production, if other considerations do not predominate.