Expression of barley yellow dwarf virus and Russian wheat aphid resistance genes in and fertility of spring wheat × triticale hybrids and backcross lines

Abstract

The Barley Yellow Dwarf Virus disease (BYDV) and the Russian wheat aphid (RWA) Diuraphis noxia (Mordvilko) have caused significant losses to wheat and barley in several areas of the world . Important sources of resistance to both BYDV and RWA have been found in Triticale . Different generations of interspecific wheat x Triticale crosses were produced and the progenies were screened for BYDV and RWA tolerance . Plants with equal chromosome numbers showed different levels of fertility. A significant correlation was observed between pollen fertility and seed set in primary florets (r -0 .57) . In general, pollen fertility, seed set and the number of euploid plants (2n = 42) increased from one generation to the next. The expression of BYDV tolerance varied from population to population . Additive effects were predominant in F1 and some backcross populations . A dominant effect of rye tolerance genes was also observed in few populations . A monogenic trait or a quantitative (polygenic) character would not agree with the observed segregation patterns . The heritability of this oligogenic tolerance was quite different between populations and in many populations the tolerance genes were only partially expressed . Some transgressive segregation for tolerance and sensitivity was demonstrated . The genes controlling tolerance ; to RWA in Triticale lines, Muskox 658 and Nord Kivu were not expressed in advanced lines resistant to BYDV . This indicates that tolerance genes for BYDV and RWA in these lines are located on different chromosomes .

The influence of genetic background on resistance to the cabbage aphid (Brevicoryne brassicae) in Kale (Brassica oleracea var. acephala)

“…Our primary aim in this work was to determine whether the background into which a factor for resistance to B. brassicae is introgressed influences the phenotypic expression of that resistance. Previous reports have indicated that the choice of 'genetic background' can influence the expression of resistance (Luig & Rajaram, 1972;Walkey et al, 1985;Nkongolo, 1996;Potgieter, Marais & Du Toit, 1991). In the present study we wanted to determine whether the choice of 'susceptible' parent influenced the expression of resistance to B. brassicae in the F2.…”

“…Faster flowering B. oleracea genotypes exist and it was decided to attempt to transfer the resistance of the three kale accessions into a 'rapid flowering' background which would be more amenable for experimental studies. However, the choice of plant line, and therefore the genetic background, that disease and pest resistance is introduced into has been shown to influence the expression of resistance (Luig & Rajaram, 1972;Walkey, Ward & Phelps, 1985;Pretorious, Rijkenberg & Wilcoxson, 1990;Nkongolo, 1996;Warnock, Davis & Gingera, 1998). This paper reports the results of investigations into the influence of genetic background on resistance to B. brassicae derived from the cv.…”