Genetic Control of Haploidy in <i>Capsicum frutescens</i> L.

Abstract

An autodiploid line of Capsicum frutescens L., G168A, produced an unusually high frequency of haploid-diploid twin seedlings. Another autodiploid line, P1A, had a low frequency of polyembryony and yielded only diploiddiploid twins. The two autodiploid lines were utilized as female parents and crossed with untreated and X-rayed pollen of the variety Floral Gem. Floral Gem produced few twin seedlings and had pungent, yellow immature fruits in contrast to the nonpungent, dark green immature fruits of the autodiploids. The contrasting fruit characters of the parents permitted identification of the origin of resulting twin seedlings and haploids.Autodiploid G168A, characterized by a high frequency of haploidy in association with the formation of twin embryos following self-pollination, retained this attribute following crosses with pollen from the low frequency variety Floral Gem. Typical twin seedlings produced when G168A was utilized as the female parent had a smaller maternal haploid member in association with a larger sexual diploid. The reciprocal cross, Floral Gem×G168A, produced no haploids. Crosses of G168A with pollen of Floral Gem X-rayed with 500r, 1, 000r and 2, 000r did not result in significant variations in the frequencies and types of multiple seedlings in the X1 in comparison with the control population. Similarly, cytogenetic alteration of the pollen of Floral Gem by the same X-ray treatments did not significantly alter the incidence and kind of multiple seedlings produced when P1A was utilized as the female parent. These results suggest that the development of maternal haploid embryos in the formation of polyembryonic seeds is controlled by the genotype of the female parent.Seventeen monoembryonic haploids were isolated from the X1 populations of G168A×Floral Gem. All of the haploids occurred following treatment of the pollen with 1, 000r or 2, 000r. The frequencies of monoembryonic haploid parthenogenesis following the two pollen treatments were not significantly different. All of the haploids bore fruits, which enabled them to be classified as maternal in origin. A single monoembryonic haploid, paternal in origin, occurred in the F1 of P1A×Floral Gem; none was found in the X1 populations.An estimated five percent of the viable seeds from G168A crossed with pollen exposed to 1, 000r produced maternal monoembryonic haploids or maternal haploid members of twin seedlings. No haploids occurred following crosses of P1A with pollen irradiated at 1, 000r. These results show that the genotype of the female parent must be considered in experiments designed to induce haploidy.