Applications of biotechnology in eggplant

Eggplant (Solanum melongena L.), an economically important vegetable crop in many countries in Asia and Africa, often has insufficient levels of resistance to biotic and abiotic stresses. Genetic resources of eggplant have been assessed for resistance against its most serious diseases and pests (bacterial and fungal wilts, nematodes and shoot and fruit borer). Attempts at crossing eggplant with its wild relatives resulted in limited success due to sexual incompatibilities. However, the ability of eggplant to respond well in tissue culture, notably plant regeneration, has allowed the application of biotechnology, particularly the exploitation of somaclonal variation, haploidisation, somatic hybridisation and genetic transformation for gene transfer. Somaclonal variation has been used to obtain lines with increased resistance to salt and little leaf disease. Traits of resistance against bacterial and fungal wilts have successfully been introduced into the cultivated eggplant through somatic hybridisation. However, most somatic hybrids were sterile when the parental lines were distantly related. In contrast, the use of close relatives as fusion partners or highly asymmetric fusion resulted in the production of fertile hybrids with resistance traits and a morphology close to the cultivated eggplant, thus avoiding the series of backcrosses 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 AFLP and ctDNA analyses have also been conducted. So far only resistance against insects, and parthenocarpic fruit development have successfully been developed in eggplant using Agrobacterium tumefasciens transformation. However, some work on genetic engineering of eggplant for other biotic and abiotic stresses has recently been initiated.