Tag: rusts

Identification of Genomic Associations for Adult Plant Resistance in the Background of Popular South Asian Wheat Cultivar, PBW343

Rusts, a fungal disease as old as its host plant wheat, an enemy as old as wheat, has caused havoc for over 8,000 years. As the rust pathogens can evolve into new virulent races which quickly defeat to qualitative or vertical the resistance that primarily rely on race specificity over time, adult plant resistance (APR) has often been found to be race non-specific and hence is considered have been proven to be a more to be a more reliable and durable strategy to combat this malady. Over decades sets of donor lines have been identified at International Maize and Wheat Improvement Center (CIMMYT) representing a wide range of APR sources in wheat. In this study, using nine donors and a common parent ‘PBW343’, a popular Green Revolution variety at CIMMYT, the nested association mapping (NAM) population of 1122 lines was constructed to understand the APR genetics underlying these founder lines. Thirty-four QTL were associated with APR to rusts, and 20 of 34 QTL had pleiotropic effects on SR, YR and LR resistance. Three chromosomal regions, associated with known APR genes (Sr58/Yr29/Lr46, Sr2/Yr30/Lr27, and Sr57/Yr18/Lr34), were also identified, 13 previously reported QTL regions were validated. Of the 18 QTL first detected in this study, 7 were pleiotropic QTL, distributing on chromosomes 3A, 3B, 6B, 3D, and 6D. The present investigation revealed the genetic relationship of historical APR donor lines, the novel knowledge on APR, as well as the new analytical methodologies to facilitate the applications of NAM design in crop genetics. Results shown in this study will aid the parental selection for hybridization in wheat breeding, and envision the future rust management breeding for addressing potential threat to wheat production and food security.

Source: Frontiers | Identification of Genomic Associations for Adult Plant Resistance in the Background of Popular South Asian Wheat Cultivar, PBW343 | Plant Science

Linkage analysis and map construction in genetic populations of clonal F1 and double cross

57985Authors: Manickavelu, A.; Joukhadar, R.; Jighly, A.; Caixia Lan; Huerta-Espino, J.; Ahmad Shah Stanikzai; Kilian, A.; Singh, R.P.; Ban, T.

Published in: Plant Science, 2016, vol.252, p.222-229

Mining of new genetic resources is of paramount importance to combat the alarming spread of stripe rustdisease and breakdown of major resistance genes in wheat. We conducted a genome wide associationstudy on 352 un-utilized Afghan wheat landraces against stripe rust resistance in eight locations. Highlevel of disease variation was observed among locations and a core-set of germplasm showed consis-tence performance. Linkage disequilibrium (LD) decayed rapidly (R2≈ 0.16 at 0 cM) due to germplasmpeerless diversity. The mixed linear model resulted in ten marker-trait associations (MTAs) across allenvironments representing five QTL. The extensively short LD blocks required us to repeat the analysiswith less diverse subset of 220 landraces in which R2decayed below 0.2 at 0.3 cM. The subset GWASresulted in 36 MTAs clustered in nine QTL. The subset analysis validated three QTL previously detectedin the full list analysis. Overall, the study revealed that stripe rust epidemics in the geographical originof this germplasm through time have permitted for selecting novel resistance loci.

Genetic protection of wheat from rusts and development of resistant varieties in Russia and Ukraine

Published in Euphytica 179(2): 297-311, 2011

Genetic protection of wheat from rusts and development of resistant varieties in Russia and Ukraine

A. Morgounov, I. Ablova, O. Babayants, L. Babayants, L. Bespalova, Zh. Khudokormov, N. Litvinenko, V. Shamanin and V. Syukov

Leaf rust represents the major threat to wheat production in Russia and Ukraine. It has been present for many years and epidemics of the pathogen occur in different regions on both winter and spring wheat. In some regions there is evidence of more frequent epidemics, probably due to higher precipitation as a result of climate change. There is evidence that the virulence of the leaf rust population in Ukraine and European Russia and on winter wheat and spring wheat is similar. The pathogen population structure in Western Siberia is also similar to the European part, although there are some significant differences based on the genes employed in different regions. Ukrainian wheat breeders mostly rely on major resistance genes from wide crosses and have succeeded in developing resistant varieties. The North Caucasus winter wheat breeding programs apply the strategy of deploying varieties with different types of resistance and genes. This approach resulted in decreased leaf rust incidence in the region. Genes Lr23 and Lr19 deployed in spring wheat in the Volga region were rapidly overcome by the pathogen. There are continuing efforts to incorporate resistance from wild species. The first spring wheat leaf rust resistant varieties released in Western Siberia possessed gene LrTR which protected the crop for 10–15 years, but was eventually broken in 2007. Slow rusting is being utilized in several breeding programs in Russia and Ukraine, but has not become a major strategy.