Sex and ploidy of anther culture derived papaya (Carica papaya L.) plants

Summary To improve the efficiency of papaya anther culture, we investigated (1) hormonal medium conditions for inducing haploids or dihaploids; (2) identified the sex of established plantlets using a sex-specific DNA molecular marker and (3) estimated their ploidy by flow cytometry analysis of DNA content. Anthers with a mixture of uninucleate, mitotic, and binucleate microspores were collected from a male plant, and cultured on MS agar medium with different concentrations of CPPU and NAA. An embryo induction rate of 13.8% was attained on MS agar medium with 0.01 mg l⁻¹ CPPU and 0.1 mg l⁻¹ NAA. The induced embryos were subcultured on medium with 0.0025 mg l⁻¹ CPPU. Rooting of the developed shoots was promoted by treating their basal parts with 1500 mg l⁻¹ IBA in a 50% ethanol solution for about 10 seconds. All the embryo-derived plantlets (27 plants) were identified as female, implying that they were derived from microspores. In addition, 26 plants were determined to be triploids and one to be tetraploids. We also observed a wide range of morphological variation (e.g., in tree height and fruit size) among the established plants. Based on the results, we discussed a potential value of anther culture techniques for the breeding of papaya.