Influence of the stage for anther excision and heterostyly in embryogenesis induction from eggplant anther cultures

In this work we address two aspects of eggplant flower biology potentially involved on the efficiency of anther culture: the selection of the best floral stage to extract anthers for culture, and the effect of heterostyly in the identification of suitable buds and anthers. For 12 different accessions, we determined morphological criteria (length ranges) to identify buds and anthers enriched in vacuolate microspores and young bicellular pollen, the stages most responsive to embryogenesis induction. While these microspore/pollen stages were the most responsive when isolated and cultured in liquid medium, we observed that culture of anthers containing these stages is not the best choice. Instead, the highest response was found for younger anthers, containing mostly young and mid microspores. We analyzed eggplant anther walls and found that their particular thickness may be behind this apparent discrepancy, since they may delay the diffusion of inducing factors to the anther locule, reducing their effect over inducible microspores. Thus, the culture of younger anthers would allow for younger microspores to grow up to the inducible stages while factors are entering the locule. We also analyzed the embryogenic response of short and long-styled buds present in Cristal, a heterostylic cultivar. Our results demonstrated that each floral morph produced buds and anthers of different lengths, but equally useful for anther culture, since similar amounts of embryos were produced. The practical application of these results may improve the efficiency of anther culture not only in these cultivars, but in others also presenting thick anther walls and heterostyly.