Abstract
Background and Objectives
Eggplant (Solanum melongena L.) is an economically important crop with a wide range of fruit shapes and colors. Breeding programs in eggplant focus mainly on fruit quality. Production of commercial triploid cultivars and emission of seeds in fruits may increase acceptability by consumer and increase fruit quality. Induced tetraploidy and cross between di and tetraploid parental line is a conventional method used in different fruits and vegetables like watermelon. The current study aim to find how may induced tetraploidy affect pollen grain quality, its fertility, seed and transplant vigor in different eggplant cultivars.
Materials and Methods
Aiming to investigate autotetraploidy in four qultivars of Solanum melongena L., Keshtzar, Yalda, Chahboland and Passargad on fertility, number of days till fruit-set, germination rate and percentage and successful transplanting percentage, a survey was done in a completely randomized design. Tetraploid plants were derived from seed maceration/shoot tip treatment (0.5, 1 and 2 percent of colchicine). To ensure ploidy level, chromosome counting of root tips and flow-cytometry was done during the experiment. To quantify germination percentage and rate, 15 seeds of each cultivar in each ploidy level were placed in petri-dishes in three replications. The seeds of each ploidy form were sown in seedling trays and after seedling period, plugs were transplanted in field for evaluation of characteristics in different ploidy levels. Growth and development rate of plant in seedling stage observed since seeds were cultivated. As soon as hypocotyl appeared on the surface, they were counted. Then seedling emergence and rate were calculated. To test viability of pollen grains, they were stained using acetocarmen. In order to find best parental lines, 18 plants from each cultivar and in each ploidy level were cultivated in the greenhouse condition in three replications. Then all plants were crossed competley (direct and reciprocal). Di and tetraploid plants were tested to find out which one would be better as which parent.
Results
Number of days till fruit-set, characteristics of seed and seedling and growth rate in seedling stage were significantly (P≤5%) influenced by changes on levels of poloidy. Pollen grain staining with acetocarmine for evaluation of fertility percentage in pollen grains showed that with an increase in ploidy level, fertility may significantly increase (P≤5%). In an effort to triploid plant production, none of the crosses between di and tetraploid plant could bear fruit.
Discussion
With the overall results, despite slower growth, can be tetraploid plant, due to improved germination and seedling emergence, survival and reproductive capabilities, higher transplanting success in this category of plants, induced increase in the number of chromosomal bundles can be considered as a good way to create genetic variation and prepare parental lines with desirable traits for use in the breeding programs.