Mining and genomic characterization of resistance to tan spot, Stagonospora nodorum blotch (SNB), and Fusarium head blight in Watkins core collection of wheat landraces

Abstract

Background: In the late 1920s, A. E. Watkins collected about 7000 landrace cultivars (LCs) of bread wheat (Triticum aestivum L.) from 32 different countries around the world. Among which 826 LCs remain viable and could be a valuable source of superior/favorable alleles to enhance disease resistance in wheat. In the present study, a core set of 121 LCs, which captures the majority of the genetic diversity of Watkins collection, was evaluated for identifying novel sources of resistance against tan spot, Stagonospora nodorum blotch (SNB), and Fusarium Head Blight (FHB). Results: A diverse response was observed in 121 LCs for all three diseases. The majority of LCs were moderately susceptible to susceptible to tan spot Ptr race 1 (84%) and FHB (96%) whereas a large number of LCs were resistant or moderately resistant against tan spot Ptr race 5 (95%) and SNB (54%). Thirteen LCs were identified in this study could be a valuable source for multiple resistance to tan spot Ptr races 1 and 5, and SNB, and another five LCs could be a potential source for FHB resistance. GWAS analysis was carried out using disease phenotyping score and 8807 SNPs data of 118 LCs, which identified 30 significant marker-trait associations (MTAs) with-log10 (p-value) > 3.0. Ten, five, and five genomic regions were found to be associated with resistance to tan spot Ptr race 1, race 5, and SNB, respectively in this study. In addition to Tsn1, several novel genomic regions Q.Ts1.sdsu-4BS and Q.Ts1.sdsu-5BS (tan spot Ptr race 1) and Q.Ts5.sdsu-1BL, Q.Ts5.sdsu-2DL, Q.Ts5.sdsu-3AL, and Q.Ts5.sdsu-6BL (tan spot Ptr race 5) were also identified. Our results indicate that these putative genomic regions contain several genes that play an important role in plant defense mechanisms. Conclusion: Our results suggest the existence of valuable resistant alleles against leaf spot diseases in Watkins LCs. The single-nucleotide polymorphism (SNP) markers linked to the quantitative trait loci (QTLs) for tan spot and SNB resistance along with LCs harboring multiple disease resistance could be useful for future wheat breeding.

Genome-Wide Association Study of Tan Spot Resistance in a Hexaploid Wheat Collection From Kazakhstan

“…Nevertheless, 25 lines (13%) resistant to both races (Race 1 and Race 5) have been identified in the present study. Regarding toxin sensitivities of the genotypes, a low but positive correlation was observed between Ptr ToxA sensitivity of the genotypes and disease susceptibility in the field, which is in contrast with the observations made by Friesen et al (2003) ; Faris and Friesen (2005) , Noriel et al (2011) , and Halder et al (2019) . We did not obtain any significant correlations between days to heading and plant height with Ptr resistance in field, suggesting that none of these phenological traits significantly affected tan spot resistance in the germplasm investigated.…”

“…Most wheat entries evaluated in the study showed a susceptible response to Race 1 (72.6%), whereas for Race 5, 67.5% of lines were resistant. It is a common observation in most germplasm collections ( Liu et al, 2015 ; Halder et al, 2019 ), and our results reinforce that finding resistance against Ptr Race 1 is very challenging compared to other races. Race 1 is the most prevalent worldwide ( Ali and Francl, 2003 ; Abdullah et al, 2017 ) and is reported to contain the virulence of Races 2 and 3, making it more aggressive than other races ( Lamari et al, 2003 ).…”

“…Regarding MTA identified for AUDPC scores, most associations except the one on chromosome 3AL were identified within 2–3 Mb genomic region of the markers associated with seedling resistance to Races 1 and 5 or insensitivities to toxins Ptr ToxA and Ptr ToxB in the present study, thus confirming to be major genes ( tsn 1 , tsc2 ). Three associations on chromosomes 2BS, 4AL, and 6BS overlap with minor QTL reported for tan spot resistance in previous studies ( Gurung et al, 2011 ; Halder et al, 2019 ). The QTL found on chromosome 3AL is likely new for adult plant resistance, which was identified only at adult plant stage in the present study.…”

“…For resistance to Race 1, MTA on chromosomes 4BS and 3BS also showed strong effects. Halder et al (2019) recently reported a novel QTL on 4BS for resistance to Race 1 in the United Kingdom Watkins core collection, and the associated marker identified here on chromosome 4BS corresponds to this QTL. No gene or QTL has so far been reported on chromosome 3BS for resistance to Race 1.…”

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“…Regarding MTA identified for AUDPC scores, most associations except the one on chromosome 3AL were identified within 2-3 Mb genomic region of the markers associated with seedling resistance to Races 1 and 5 or insensitivities to toxins Ptr ToxA and Ptr ToxB in the present study, thus confirming to be major genes (tsn 1, tsc2). Three associations on chromosomes 2BS, 4AL, and 6BS overlap with minor QTL reported for tan spot resistance in previous studies (Gurung et al, 2011;Halder et al, 2019). The QTL found on chromosome 3AL is likely new for adult plant resistance, which was identified only at adult plant stage in the present study.…”