Assessing the agronomic and quality value of genetic introgressions from wild Triticum species for wheat improvement

Wheat (Triticum sp.) is among the most important crops in the world. Its polyploid nature has imposed restrictions on its genetic variability added to the domestication process. Plant breeding has been criticized for causing an overall reduction in the genetic diversity of crop germplasm. Studies of the genetic variation at the DNA level of modern wheat cultivars confirm this criticism. However, recent efforts to expand the genetic basis of the cultivated wheat gene pool have resulted in increases in the genetic diversity of newly developed cultivars. Wild Triticeae species are critical to increase the genetic diversity of cultivated wheat. The incorporation of novel genes from wild Triticeae species is fundamental to meet the challenges imposed by an increasing wheat demand for human and animal consumption. The transfer of alien genes into cultivated wheat usually involves the introgression of large chromosome segments that can produce deleterious effects on agronomic and quality traits. Here we describe the impact of two alien introgressions on agronomic and quality traits of wheat. The introgressions studied were the leaf rust resistance gene Lr47 from Triticum speltoides on hexaploid wheat, and the high-grain protein content gene Gpc-B1 from T. turgidum ssp. dicoccoides on both hexaploid and tetraploid wheat. The Lr47 introgression was associated with a 3.8% reduction in grain yield that varied significantly across genotypes and environments, as well as a consistently lower test weight. Lines with the alien Lr47 segment showed consistent increases in grain (GPC) and flour protein concentration (P<0.01) but also highly significant decreases in flour yield (P<0.001) and increases in flour ash (P <0.01). In one of the experiments, the presence of the Lr47 T. speltoides segment was associated with improved lodging resistance. The Gpc-B1 introgression was associated with highly significant (P<0.05) increases in GPC in all 9 genotypes studied. Despite a consistent decrease in grain weight associated with the Gpc-B1 introgression, the differences in grain yield between the Gpc-B1 and control NILs were not significant. As a result, protein yield was increased in the Gpc-B1 NILs of both hexaploid (P<0.0001) and tetraploid (P=0.06) wheat. The Gpc-B1 introgression in hexaploid NILs resulted in significantly (P<0.01) lower straw N concentration at maturity and higher NHI which suggest that the functional Gpc-B1 allele improves N remobilization. As expected from the increase in GPC, the Gpc-B1 introgression was associated with an improvement in the bread- and pasta-making parameters such as increased mixing time, water absorption, loaf volume and gluten strength. On the negative side, the Gpc-B1 introgression was associated in some varieties with a significant reduction in flour yield and significant increases in ash concentration that are probably due to the decrease in grain size and test weight observed in the Gpc-B1 NILs. For most traits, significant gene x environment and gene x genotype interactions were found, stressing the need of evaluating the effect of the Gpc-B1 introgression in particular genotypes and environments. Knowledge of the beneficial or deleterious effects associated with these introgressions is essential for breeding programs to make informed decisions about the deployment of these genes into their germplasm and in selecting appropriate gene combinations to express their potential benefits and limit the unfavorable outcomes.