Resistance to Helminthosporium leaf blight and agronomic performance of spring wheat genotypes of diverse origins

Abstract

Helminthosporium leaf blight (HLB), caused by a complex of Cochliobolus sativus (Ito & Kurib.) Drechsler ex Dastur and Pyrenophora tritici-repentis Died, is a serious disease of wheat (Triticum aestivum L.) in the warm lowlands of South Asia. Wheat cultivars grown in the area are either susceptible to HLB or possess low levels of resistance to it. A replicated field study was conducted in 1999 and 2000 at two sites in Nepal to determine the level of HLB resistance and other desirable traits in 60 wheat genotypes of diverse origin. The test genotypes were planted in main strips divided into two strips one of which was sprayed four times with Tilt TM (a.i. propiconazole) @ 125 g of a.i. ha −1 . Four readings of HLB were recorded to calculate the area under the disease progress curve (AUDPC). Other traits under investigation included biomass yield (BY), grain yield (GY), 1000-kernel weight (TKW), harvest index (HI), days to heading (DH) and maturity (DM), plant height (PHT), and effective tiller number (ETN). Wheat genotypes differed significantly for all traits. Mean AUDPC values ranged from 45 to 1268. A few exotic genotypes were highly resistant to HLB. Losses in GY due to HLB ranged from 2 to 26%, and TKW was reduced by up to 33%. A few genotypes showed HLB tolerance, i.e., relatively smaller GY and TKW reductions despite high levels of HLB. In general, medium to late maturity and higher levels of HLB resistance and low to high GY and TKW characterized genotypes exotic to South Asia. Biplot analysis identified several genotypes that were HLB-resistant and agronomically superior. Results suggest it is possible to improve HLB resistance of local wheat cultivars based on selective breeding using this pool of germplasm.

Heritability estimates of spot blotch resistance and its association with other traits in spring wheat crosses

“…Weather conditions were optimal for wheat cultivation and grain yields of commercially grown cultivars were normal. The response levels of the six parents show the appropriateness of selecting them for genetic study and confirm the previous report by Sharma et al (2004b).…”

“…The four resistant wheat parents included in this study are being widely used in the region's wheat breeding programs to improve resistance to spot blotch (Sharma et al, 2004c). Besides being resistant to spot blotch, they also possess acceptable plant type, kernel weight, and plant height, but are late in maturity (Sharma et al, 2004b).…”

“…A set of 14 F 2 -derived F 5 populations resulting from crossing six semidwarf wheat parents, differing in spot blotch response, plant type, maturity, yield potential, and genetic background (Sharma et al, 2004b), was selected for the study (Table 1). The crosses were made in the 1998-1999 wheat season (November to March), and the F 1 s were selfed to produce the F 2 generation in a summer nursery in 1999 at a hill location in Nepal.…”

Development and characterization of the 4th CSISA-spot blotch nursery of bread wheat

“…Additional resistance sources were reported in SA (Singh et al 1998;Joshi et al 2004Joshi et al , 2007aSharma et al 2004b;Sharma and Duveiller 2007). These resistant materials were extensively used and more elite varieties with higher levels of resistance were selected (Sharma et al 2004a;Siddique et al 2006;Joshi et al 2007b). Duveiller and Sharma (2009a) published a comprehensive list of SB resistant varieties; but sources with a high level of resistance seem to be limited.…”

Wheat grain yield and stability assessed through regional trials in the Eastern Gangetic Plains of South Asia

“…Sonalika is an early maturing cultivar with high susceptibility to HLB and other foliar diseases in South Asia Joshi et al 2007b). PBW343, Bhrikuti, and Kanchan are considered resistant, moderately resistant, and susceptible to HLB (Bhushan et al 2002;Sharma et al 2004b). …”