Abstract
Wheat (Triticum aestivum L.) is a self-pollinating crop whose hybrids offer the potential to provide a major boost in yield. Male sterility induced by the cytoplasm of Triticum timopheevii is a powerful method for hybrid seed production. Hybrids produced by this method are often partially sterile, and full fertility restoration is crucial for wheat production using hybrid cultivars. To identify the genetic loci controlling fertility restoration in wheat, we produced two cytoplasmic male-sterile (CMS) backcross (BC1) mapping populations. The restorer lines Gerek 79 and 71R1203 were used to pollinate the male-sterile winter wheat line CMS-Sperber. Seed set and numbers of sterile spikelets per spike were evaluated in 340 and 206 individuals of the populations derived from Gerek 79 and 71R1203, respectively. Genetic maps were constructed using 930 and 994 single nucleotide polymorphism (SNP) markers, spanning 2,160 and 2,328 cM over 21 linkage groups in the two populations, respectively. Twelve quantitative trait loci (QTL) controlled fertility restoration in both BC1 populations, including a novel restorer-of-fertility (Rf) locus flanked by the SNP markers IWB72413 and IWB1550 on chromosome 6AS. The locus was mapped as a qualitative trait in the BC1 Gerek 79 population and was designated Rf9. One hundred-nineteen putative candidate genes were predicted within the QTL region on chromosome 6AS. Among them were genes encoding mitochondrial transcription termination factor and pentatricopeptide repeat-containing proteins that are known to be associated with fertility restoration. This finding is a promising step to better understand the functions of genes for improving fertility restoration in hybrid wheat.
Highlights
Since the discovery of male sterility and restoration systems in the 1960s, hybrid wheat triggered attention due to its potential for improved grain and straw productivity and yield stability under harsh and marginal environments (Longin et al, 2012)
Whereas a 1:1 segregation ratio for fertile to sterile lines was observed in both BC1 Gerek 79 (174:166) and BC1 71R1203 (100:106), the average seed set was higher in BC1Gerek 79 (0.5) than in BC1 71R1203 (0.3)
Number of sterile spikelets per spike showed a negative correlation with seed set in both BC1 Gerek 79 (r = −0.65) and BC1 71R1203 (r = −0.87)
Summary
Since the discovery of male sterility and restoration systems in the 1960s, hybrid wheat triggered attention due to its potential for improved grain and straw productivity and yield stability under harsh and marginal environments (Longin et al, 2012). Wilson and Ross (1962) were the first to describe a workable cytoplasmic male sterile of T. timopheevii with largely neutral effects on the agronomic and quality characteristics This CMS system has gained widespread use due to the deleterious effects of other cytoplasms of the genera Triticum and Aegilops on various traits, and because no advantage existed over the T. timopheevii system (Virmani and Edwards, 1983). It uses three different breeding lines: a CMS line, maintainer line, and restorer line. Incomplete fertility restoration poses a major bottleneck for hybrid wheat breeding, as it compromises the heterotic gain for grain yield and the uniformity or quality of end-use products
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