Breeding biology and cross compatibility of close wild relatives of brinjal (Solanum melongena L.)

Abstract

The present study entitled “Breeding biology and cross compatibility of close wild relatives of brinjal (Solanum melongena L.)” was carried out in the Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, during 2014 – 2016. The objective of the study was to elucidate the reproductive biology of the related wild species of brinjal and to ascertain their cross compatibility with the cultivated species. Four wild species variants of Solanum viz., viarum, gilo, incanum and indicum, collected from NBPGR, RS, Vellanikkara along with S. melongena varieties Haritha and Surya formed the material for the study. These genotypes were evaluated for various vegetative, floral and fruit characters following the descriptor developed by IPGRI (1988) and clustering was done. Study of the reproductive biology revealed that flowering was profuse in S. viarum, S.incanum and S. gilo. However S. indicum did not flower during the entire experiment period and hence could not be utilized in the programme. The flowers of Solanum species were found to be positively geotropic with a floral formula of ♀∕K(5)C(5)A(5)G(2). In all the species evaluated, flowers were pedicellate, zygomorphic, bisexual and complete. Irrespective of species, long, medium and short styled flowers were observed. However, the frequency of medium styled flowers were very low. Unlike in the case of S. gilo and S. melongena variety Haritha, a change in colour of the corolla was observed in S. viarum, S. incanum and S. melongena variety Surya on the day prior to anthesis. The time of anther dehiscence was found to vary with the species. The pollen grains dehisced nearly two to five hours after flower opening in S. viarum and S. incanum. However, in the cultivated varieties, Haritha and Surya, anther dehiscence commenced along with the opening of flowers. Among the different species protandry was observed only in S. gilo. The dehiscence continued for three days in all the species. Irrespective of species, pollen grains were remained fertile for three days. The change in the colour of the stigmatic surface from glossy green to deep yellow, at the time of initiation of stigma receptivity was a unique feature of S. gilo. In all the other wild species of Solanum as well as the cultivated varieties Haritha and Surya, the colour of the stigmatic surface was glossy green at the time of receptivity. The colour was found to fade with the decline in receptivity. Studies to assess the mode of pollination revealed that cross pollination is the rule in Solanum species. Cross compatibility studies were undertaken between the three wild species which flowered and the two cultivated types under S. melongena. Among the twelve crosses attempted, Surya x S. viarum, S. viarum x Surya, Surya x S. incanum, Haritha x S. incanum, S. incanum x Haritha, S. viarum x Haritha were the successful ones. Out of these, the progeny of three crosses viz., Surya x S. viarum, S. viarum x Surya and Surya x S. incanum established in the field. The progeny of the cross Surya x S. viarum was found to be superior with respect to fruit weight as well as absence of prickles on leaf and fruit pedicel. Even though one of the parents of this cross, Surya was susceptible to most of the common pests and diseases of brinjal, no incidence of pests and diseases was noticed in the progeny population