Paternity Assignment in White Guinea Yam (Dioscorea Rotundata) Half-Sib Progenies from Polycross Mating Design Using SNP Markers

Abstract

White Guinea yam is mostly a dioecious outcrossing crop with male and female flowers produced on distinct plants. Fertile parents produce high fruit set in an open pollination polycross block, which is a cost-effective and convenient way of generating variability in yam breeding. However, the pollen parent of progeny from polycross mating is usually unknown. This study aimed to determine paternity in white Guinea yam half-sib progenies from polycross mating design. A total of 394 half-sib progenies from random open pollination involving nine female and three male parents was genotyped with 6602 SNP markers from DArTSeq platform to recover full pedigree. A higher proportion of expected heterozygosity, allelic richness, and evenness were observed in the half-sib progenies. A complete pedigree was established for all progenies from two families (TDr1685 and TDr1688) with 100% accuracy, while in the remaining families, paternity was assigned successfully only for 56 to 98% of the progenies. Our results indicated unequal paternal contribution under natural open pollination in yam, suggesting unequal pollen migrations or gene flow among the crossing parents. A total of 3.8% of progenies lacking paternal identity due to foreign pollen contamination outside the polycross block was observed. This study established the efficient determination of parental reconstruction and allelic contributions in the white Guinea yam half-sib progenies generated from open pollination polycross using SNP markers. Findings are useful for parental reconstruction, accurate dissection of the genetic effects, and selection in white Guinea yam breeding program utilizing polycross mating design.

Floral Biology and Pollination Efficiency in Yam (Dioscorea spp.)

“…The majority of flowering yam genotypes is dioecious, with male (staminate) and female (pistillate) flowers borne on separate plants [1,19,22] but monoecious genotypes that produce staminate and pistillate flowers on the same plant exist [19,23] (Figures 2 and 3). Due to its predominantly dioecious nature, yam is mostly an outcrossing crop [13,23]. The rate of flowering is generally low among cultivated yams.…”

“…When targeting natural pollination, male and female individual plants are grown closer to each other and their vines staked to the same supports to facilitate insect pollination, mostly by thrips [21,40]. Open pollination is cost-effective and convenient, especially when using profuse flowering, fertile, and compatible parents; although the progenies' male parent usually needs verification [13,40].…”

“…Yam breeding uses both sexual and asexual reproductive mechanisms. Sexual reproduction involves an artificial hand or natural open pollination during flowering to generate genetically variable offspring for selection [13]. This step starts with selecting parents with desirable traits.…”

“…Agriculture 2020, 10, x FOR PEER REVIEW 2 of 23 choice is based on a breeding program's objective, technical and financial capacity. Progenies with desirable traits such as yield stability, superior resistance to disease and pests, and higher tuber quality are then selected and advanced vegetatively for several generations and across locations before releasing as new varieties [3,13]. Therefore, plant breeding programs' success relies on genetic variation for traits of interest and successful transfer of the genetic allele of traits from source germplasm to the agronomically preferred background.…”

Breeding synthetic varieties in annual caraway: observations on the outcrossing rate in a polycross using a high-throughput genotyping system

“…Definitely, we will never reach this ideal situation in a practical breeding approach. Several studies on various species found unequal distribution of paternity after mating in a polycross (Moriguchi et al 2009;Norman et al 2020;Riday et al 2013;Tew and Pan 2010). We evaluated how far we missed completely random pollination in the conducted polycross.…”