Genetic variation for tolerance to the downy mildew pathogenPeronospora variabilisin genetic resources of quinoa (Chenopodium quinoa)

Abstract

Background: Quinoa (Chenopodium quinoa Willd.) is an ancient grain crop that is tolerant to abiotic stress and has favorable nutritional properties. Downy mildew is the main disease of quinoa and is caused by infections of the biotrophic oomycete Peronospora variabilis Gaüm. Since the disease causes major yield losses, identifying sources of downy mildew tolerance in genetic resources and understanding its genetic basis are important goals in quinoa breeding. Results: We infected 132 South American genotypes, three Danish cultivars and the weedy relative C. album with a single isolate of P. variabilis under greenhouse conditions and observed a large variation in disease traits like severity of infection, which ranged from 5% to 83%. Linear mixed models revealed a significant effect of genotypes on disease traits with high heritabilities (0.72 to 0.81). Factors like altitude at site of origin or seed saponin content did not correlate with mildew tolerance, but stomatal width was weakly correlated with severity of infection. Despite the strong genotypic effects on mildew tolerance, genome-wide association mapping with 88 genotypes failed to identify significant marker-trait associations indicating a polygenic architecture of mildew tolerance. Conclusions: The strong genetic effects on mildew tolerance allow to identify genetic resources, which are valuable sources of resistance in future quinoa breeding.

Quantitative resistance differences between and within natural populations of Solanum chilense against the oomycete pathogen Phytophthora infestans

“…In a study with a panel of six domesticated and six wild tomato accessions, infection severity of 97 Botrytis cinerea isolates was shown to be determined by complexity of both host and pathogen genotype and a few pathogen genes associated with host preferences (Soltis et al., 2019). Similar multigenic effects has been indicated in a genome‐wide association mapping analysis of 88 genotypes of quinoa, Chenopodium quinoa , showing large variation in disease traits upon inoculation with one isolate of the downy mildew pathogen Peronospora variabilis (Colque‐Little et al., 2021). With the recent availability of a reference genome sequence for S .…”

Genome-wide association study in the pseudocereal quinoa reveals selection pattern typical for crops with a short breeding history

“…A recent study attempted identification of genes based on a GWAS analysis. However, no significant associations were found, probably due to the lack of power because of the small number of accessions used (61 and 88) 48 . In our study, a strong MTA suggests that the NBS-LRR gene on chromosome Cq2A contributes to downy mildew resistance in quinoa.…”

Genetic composition and diversity of Arabica coffee in the crop’s centre of origin and its impact on four major fungal diseases

“…One striking example is the wipe-out of monoclonal banana plantations by Fusarium wilt (Dita et al, 2018). Existence of genetic variation in crops is important for resistance or tolerance to biotic stresses such as diseases (Colque-Little et al, 2021;Rodenburg et al, 2017). Therefore, a better understanding and management of genetic variation in crops is essential to optimize the conservation and use of crop genetic resources in breeding programs (Brozynska et al, 2016;Fu, 2015;Zhou et al, 2002).…”