Evaluation of regenerated strains from six Cucurbita interspecific hybrids obtained through anther and ovule in vitro cultures

Homozygous plants can be obtained in a single generation using doubled haploid technology, which can tremendously facilitate breeding programs. The present study reports on in vitro regeneration and production of double haploid plants through anther and ovule cultures resulting from the hybridization of cultivated species of Cucurbita pepo L. with three other Cucurbita species i.e. C. moschata L., C. ficifolia and C. martinezii L. Among six sucrose-2,4-Dichlorophenoxyacetic acid (2,4-D) combinations tested, the addition of 90 g l^sup -1^ sucrose and 1 mg l^sup -1^ 2,4-D into the medium was found to be more suitable for callus regeneration from anthers. Anthers from the hybrid C. pepo L. (Queen F^sub 1^) × C. moschata L. regenerated the highest percentage (40%) of plantlets from callus and highest average number of plantlets per callus (7.5) when the culture medium was supplemented with the aforementioned concentrations of sucrose and 2,4-D. Ovules collected from the hybrid C. pepo L. (MHTC77 F^sub 1^) × C. moschata L. produced the highest percentage of regenerated plantlets (25.33%), the highest percentage of responded ovules (18.67%) and the highest average number of plantlets per ovule (3.37). Cold pretreatment had negative effects on gynogenesis with the exception of the hybrid C. pepo L. (MHTC77 F^sub 1^) × C. moschata L. Chromosome counting in the root tips of androgenic plantlets revealed 50% of haploid and (n = x = 20) and 50% of dihaploid plantlets (2n = 2x = 40). The assessment of root tips from gynogenic plantlets resulted in 60% haploid (2n = x = 20) and 40% diploid (2n = 2x = 40) plants. The androgenic strains were evaluated for their vegetative and reproductive traits compared with open local cultivar C. pepo L. (Eskandarani cv.). While the majority of regenerated strains were intermediate between the cultivated species of C. pepo L. and other Cucurbita species, two regenerated strains proved superior to the local cultivar 'Eskandarani' in number of fruits (early and total yield/plot) as well as in total fruit yield per plot. Keywords: Anther culture, Cucurbitaceae, Genotype, Haploid, Ovule culture. Abbreviations: 2,4-D - 2,4-Dichlorophenoxyacetic acid; MS - Murashige and Skoog's medium; NAA - 1-Naphthalene acetic acid; PGR - plant growth regulators; PPF- photosynthetic photon flux .

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