Genetic engineering of parthenocarpic vegetable crops

Abstract

Parthenocarpy, referred to as the ability to develop fruits in absence of fertilization, is a desirable genetic trait in vegetable crops grown for the commercial value of their fruits. The advantages conferred by parthenocarpy are fruit production under environmental condition prohibitive for fertilization and production of seedless fruit. Methods for achieving parthenocarpic development use either synthetic growth factors, genetic mutants, or plant altered in their ploidy level. Nevertheless, parthenocarpic cultivars have so far been available only to a limited degree. Therefore, flower buds treatment with synthetic phytohormones is commonly used to induce parthenocarpic vegetable fruit development for early or late production under protected cultivation. Transgenic parthenocarpic tobacco, eggplant and tomato plants are described which contain in their genome the coding region of the iaaM gene from Pseudomonas syringae pv. savastanoi under the control of the plaçental- ovule-specific defh9 gene regulator sequences from Anthirrhinum majus. Expression of the chimeric defH9- iaaM transgene starts during early flower development and causes production of marketable eggplant and tomato fruits from both emasculated and pollinated flowers under environmental conditions prohibitive for fruit setting in the untransformed controls, which did not set fruit at all. Under normal environmental conditions, production of marketable fruits took place from pollinated and unplanted transgenic flowers, while untransformed plants produced fruits of marketable size only from fertilized flowers. Field tests, performed in a cold plastic-greenhouse in the Mediterranean area, showed that three experimental transgenic parthenocarpic eggplant hybrids were able to give satisfactory winter production without need of phytohormones treatment.