Applications of biotechnology in eggplant

Eggplant (Solanum melongena L.), an economically important vegetable crop i n many countries in Asia and Africa, often has insufficient levels of resis tance to biotic and abiotic stresses. Genetic resources of eggplant have be en assessed for resistance against its most serious diseases and pests (bac terial and fungal wilts, nematodes and shoot and fruit borer). Attempts at crossing eggplant with its wild relatives resulted in limited success due t o sexual incompatibilities. However, the ability of eggplant to respond wel l in tissue culture, notably plant regeneration, has allowed the applicatio n of biotechnology, particularly the exploitation of somaclonal variation, haploidisation, somatic hybridisation and genetic transformation for gene t ransfer. Somaclonal variation has been used to obtain lines with increased resistance to salt and little leaf disease. Traits of resistance against ba cterial and fungal wilts have successfully been introduced into the cultiva ted eggplant through somatic hybridisation. However, most somatic hybrids w ere sterile when the parental lines were distantly related. In contrast, th e use of close relatives as fusion partners or highly asymmetric fusion res ulted in the production of fertile hybrids with resistance traits and a mor phology close to the cultivated eggplant, thus avoiding the series of backc rosses necessary for introgression of desired traits into eggplant. As far as molecular markers and genetic engineering are concerned, the information available for eggplant is very scanty. Two genetic linkage maps have been established by using RAPD and RFLP markers. In order to analyse the genetic relationships between eggplant and its relatives, some studies based on AF LP and ctDNA analyses have also been conducted. So far only resistance agai nst insects, and parthenocarpic fruit development have successfully been de veloped in eggplant using Agrobacterium tumefasciens transformation. Howeve r, some work on genetic engineering of eggplant for other biotic and abioti c stresses has recently been initiated.