Effects of photoperiod sensitivity genes Ppd‐B1 and Ppd‐D1 on spike fertility and related traits in bread wheat

Abstract

Increasing grain yield is a key breeding goal in bread wheat. Several authors have suggested that a spike fertility index (SF), that is the quotient between grain number per unit spike (GNS) and spike chaff dry weight (SCDW), could be used as a yield-related selection criterion, especially if molecular markers were available. Here, the effects of Ppd-B1 and Ppd-D1 genes on SFm, GNSm and SCDWm (measured at maturity) and the relationship between these variables were analysed in field experiments carried out during three crop seasons at Balcarce, Argentina, on an association mapping population of 100 bread wheat cultivars of diverse origin released in Argentina between 1927 and 2010. Results show that both Ppd-B1 and Ppd-D1 are associated with SFm with similar effects. Cultivars with insensitive alleles at both genes showed a mean SFm 9.2% greater than those with sensitive alleles at both genes; at each gene, difference in SFm between insensitive and sensitive alleles was~4.5%. In turn, each gene showed a differential effect on GNSm and SCDWm, as Ppd-B1 was more related to SCDWm, whereas Ppd-D1 was only related to GNSm. Although more research needs to be carried out in order to ascertain the physiological pathway by which these genes affect spike fertility, this study represents a first approximation in order to elucidate the molecular and genetic basis underlying SF and related physiological traits. K E Y W O R D S breeding, fruiting efficiency, grain yield, selection 1 | INTRODUCTION Bread wheat (Triticum aestivum L.) is the most widely grown crop at a global scale and a major source of carbohydrates and proteins in human nutrition (Mahjourimajd et al., 2016), and current and future prospects indicate that its demand will continue to grow. This implies Additional Supporting Information may be found online in the supporting information section at the end of the article. How to cite this article: Ramirez IA, Abbate PE, Redi IW, Pontaroli AC. Effects of photoperiod sensitivity genes Ppd-B1and Ppd-D1 on spike fertility and related traits in bread wheat.

Selection for high spike fertility index in early generations increases grain number per unit area (and yield) of advanced breeding lines in bread wheat.

“…The first thing we did was to determine the correlation between FEm values as taken in F2, F3 and RILs (advanced lines without selection). As a result, positive, significant correlations were observed (rF2-F3=0.46; rF2-RILs=0.32; rF3-RILs=0.32; P<0.05); this was not surprising, considering the high heritability of the trait (González et al, 2011;Martino et al, 2015;Mirabella et al, 2016;Alonso et al, 2018b;Ramirez et al, 2018;Pretini et al, 2020;Pontaroli et al, 2021). Nevertheless, it was encouraging to find these correlations considering that F2 and F3 plants are highly heterozygous, and measurements were taken on individual plants or rows as opposed to the sampling done in advanced generations, which entailed drawing a random spike sample from yield plots in homozygous lines.…”

QTL mapping of spike fertility index in bread wheat

“…The effect of the Ppd genes, reported by Ramirez et al (2018) as being associated with SF, could not be evaluated in this population because their parents, B10 and KCJ, are monomorphic for these genes (Vanzetti et al 2013). Table S1.…”

“…As for SF at maturity, Guo et al (2017) found a QTL on chromosome 2A, with a relatively small effect. Ramirez et al (2018) reported significant yet small effects of Ppd-B1 and Ppd-D1 on SF at maturity that were independent from those on the flowering date. Recently, a GWAS conducted by Pradhan et al (2019) allowed identification of 15 markertrait associations (MTAs) with SF in chromosomes 1B, 3B, 4A, 6B, and 7D.…”

Photoperiod and vernalization alleles and their combinations greatly affected phenological and agronomic traits in bread wheat under autumn and spring sowing conditions

“…However, PPD-D1 was found to have an impact on SF under SSC, with Ppd-D1a allele increasing SF by 10.6%. In a study examining the impact of photoperiod sensitivity on SF, the PPD-B1 and PPD-D1 genes’ insensitive alleles were found to be linked to an increase in SF (Ramírez et al, 2018).…”

“…Therefore, understanding whether there are differences in the effects of the allelic variants of VRN-1 and PPD-1 genes on phenology and agronomical traits across autumn and spring sowing conditions, will be important for their proper utilization. Unfortunately, only few studies have been carried out in this regard (Steinfort et al, 2017; Ramírez et al, 2018).…”