Potential, Challenges and Strategies Involved in Gene Introgression from Wild Relatives of Vegetable Crops: A Review

Wide hybridization is an important plant breeding method as it helps in broadening the gene pool of a crop when the desired variation is not sufficient or absent within the same gene pool. Wild genetic resources are the potential source of desirable genes for various characters of crop plants. It plays a significant role in transferring traits of interest like disease and insect resistance, improved quality, earliness, dwarfness, increased yield, abiotic stress tolerance and manipulation in mode of reproduction etc. in crop plants. It has been instrumental in transferring disease resistance from wild species into many vegetable crops. For example, resistance to late blight, leaf roll and potato virus X, yellow vein mosaic virus and powdery mildew in okra, bacterial wilt, tomato leaf curl virus, early and late blight in tomato has been transferred from wild species into cultivated species. Wild species has been used to improve the quality traits of some crops like carotenoid content in carrot and tomato, starch content in potato etc. Sometimes distant hybridization leads to creation of entirely new crop species. Chromosome elimination technique followed by wide hybridization has been successfully used in the production of double haploids in some crops. However there are some lacunae in wide hybridization such as cross incompatibility, hybrid inviability, hybrid sterility and hybrid breakdown. Some special techniques viz. ploidy manipulation, pistil manipulation, growth regulators treatments, bridge crossing, grafting and embryo rescue have to be adopted to make distant hybridization successful in such cases.