H. Randy Kutcher

A major quantitative trait locus conferring adult plant partial resistance to crown rust in oat

BackgroundCrown rust, caused by Puccinia coronata f. sp. avenae, is the most important disease of oat worldwide. Adult plant resistance (APR), based upon partial resistance, has proven to be a durable rust management strategy in other cereal rust pathosystems. The crown rust APR in the oat line MN841801 has been effective for more than 30 years. The genetic basis of this APR was studied under field conditions in three recombinant inbred line (RIL) populations: 1) AC Assiniboia/MN841801, 2) AC Medallion/MN841801, and 3) Makuru/MN841801. The populations were evaluated for crown rust resistance with the crown rust isolate CR251 (race BRBB) in multiple environments. The 6 K oat and 90 K wheat Illumina Infinium single nucleotide polymorphism (SNP) arrays were used for genotyping the AC Assiniboia/MN841801 population. KASP assays were designed for selected SNPs and genotyped on the other two populations.ResultsThis study reports a high density genetic linkage map constructed with oat and wheat SNP markers in the AC Assiniboia/MN841801 RIL population. Most wheat SNPs were monomorphic in the oat population. However the polymorphic wheat SNPs could be scored accurately and integrated well into the linkage map. A major quantitative trait locus (QTL) on oat chromosome 14D, designated QPc.crc-14D, explained up to 76% of the APR phenotypic variance. This QTL is flanked by two SNP markers, GMI_GBS_90753 and GMI_ES14_c1439_83. QPc.crc-14D was validated in the populations AC Medallion/MN841801 and Makuru/MN841801.ConclusionsWe report the first APR QTL in oat with a large and consistent effect. QPc.crc-14D was statistically significant in all environments tested in each of the three oat populations. QPc.crc-14D is a suitable candidate for use in marker-assisted breeding and also an excellent target for map-based cloning. This is also the first study to use the 90 K wheat Infinium SNP array on oat for marker development and comparative mapping. The Infinium SNP array is a useful tool for saturating oat maps with markers. Synteny with wheat suggests that QPc.crc-14D is orthologous with the stripe rust APR gene Yr16 in wheat.

Virulence of Pyrenophora teres populations in western Canada

Abstract Net blotch, caused by Pyrenophora teres, is an economically important disease of barley. The pathogen has two morphologically similar but genetically distinct forms: P. teres f. teres (Ptt) and P. teres f. maculata (Ptm), which cause net form net blotch (NFNB) and spot form net blotch (SFNB), respectively. The virulence of a collection of 39 Ptt and 27 Ptm isolates collected from western Canada was evaluated by inoculating these isolates onto sets of barley differential hosts. One week following inoculation, the second and third leaves of each plant were rated for disease severity on scales of 1–10 (for Ptt) or 1–9 (for Ptm). Plants rated <5 and ≥5 were scored as resistant and susceptible to Ptt, respectively, while plants rated 1–3 and >3 were scored as resistant and susceptible to Ptm. The experiment was repeated. Cluster analysis revealed 16 and 13 distinct pathotype groups, respectively, among the 39 and 27 representative Ptt and Ptm isolates. The barley differentials CI 5791 and CI 9820 were resistant to all isolates of Ptt except one, whilst the differential CI 9214 was resistant to all isolates of Ptm except two. Therefore, the differential lines CI 5791 and CI 9820, for Ptt, and CI 9214, for Ptm, can still be considered as potentially useful sources of resistance for Canadian barley breeding programmes.

Prevalence of mating type idiomorphs in Pyrenophora teres f. teres and P. teres f. maculata populations from the Canadian prairies

Abstract The fungus Pyrenophora teres Drechs. occurs as two morphologically similar but genetically distinct forms, P. teres f. teres (Ptt) and P. teres f. maculata (Ptm), which cause the net form and spot form of net blotch of barley, respectively. A collection of 220 isolates from the Canadian prairie provinces (Alberta, Saskatchewan and Manitoba) was evaluated for mating type (MAT) idiomorph distribution and frequency. Fungal isolates were classified as Ptt or Ptm using form-specific polymerase chain reaction (PCR) primers. PCR analysis with MAT-specific primers indicated that the MAT1 and MAT2 idiomorphs of Ptt and Ptm could be identified within the same field, on the same plant, and on the same leaf. There was no significant departure from the expected 1:1 MAT1/MAT2 ratio for both forms in all three provinces or in the Canadian prairies population as a whole. Polymorphic simple sequence repeat primers were used to detect evidence of possible recombination between the two forms. Cluster analysis revealed that all P. teres isolates, including 30 isolates causing intermediate symptoms, clustered in two distinct groups conforming to either Ptt or Ptm. Therefore, hybridization was not detectable from the 220 isolates collected in western Canada. Pyrenophora teres f. teres is still the dominant form (58%) of the net blotch pathogen, and the data suggest both Ptt and Ptm go through regular cycles of sexual reproduction in the Canadian prairies.

Lentil enhances agroecosystem productivity with increased residual soil water and nitrogen

Lentil ( Lens culinaris Medikus) may have a potential to enhance the productivity of agroecosystems in dry areas where water and nutrients are limited. This study quantified soil water, residual soil nitrogen (N), and crop yields in lentil-based systems in comparison with continuous cereal and conventional summerfallow systems. A 3-yr cropping sequence study was conducted for three cycles in Saskatchewan (50.28°N, 107.79°W) from 2007 to 2011. On average, soil retained 187, 196 and 337 mm of water in the 0–1.2 m depth at crop harvest in 2008, 2009 and 2010, respectively. Summerfallow contained the same amounts of water as the cropped treatments at the harvest in 2009 and 2010. However, in 2008, summerfallow contained more soil water than the cropped treatments. The effect of lentil cultivar on soil water conservation varied with years; the cultivars Glamis, Laird and Sedley conserved highest amounts of soil water by the planting time of 2009 and 2010, but no differences were found among cultivars in 2011. Soil available N (NO 3 − + NH 4 + ) at spring planting time was 50.4 kg ha −1 in the preceding lentil treatments, which was 44% higher compared with preceding barley or flax, but was 25% lower compared with preceding summerfallow. Lentil cultivars had a similar amount of soil residual N. Grain production in the 3-yr rotation averaged 6.3 t ha −1 per rotation for the wheat–lentil–durum system and 6.8 t ha −1 for the wheat–cereal–durum monoculture, averaging 36% greater compared with wheat–summerfallow–durum system. The lentil system increased total grain production through the access of residual soil water and biologically fixed N, whereas continuous cereal system relies on inorganic fertilizer input for yield. Summerfallow system relies on ‘mining’ the soil for nutrients. We conclude that the adoption of lentil systems will enhance grain production through the use of residual soil water and available N.

Sensitivity of western Canadian Pyrenophora teres f. teres and P. teres f. maculata isolates to propiconazole and pyraclostrobin

Abstract Pyrenophora teres f. teres (Ptt) and Pyrenophora teres f. maculata (Ptm), the causal agents of the net and spot forms of net blotch of barley, respectively, can be managed in western Canada with fungicides containing propiconazole and pyraclostrobin. Given the potential for development of fungicide resistance, the sensitivity of a collection of Ptt and Ptm isolates to propiconazole and pyraclostrobin was evaluated using microtitre plate bioassays. The concentration of propiconazole needed to inhibit fungal growth by 50% (EC50) was 1.5 mg L−1 for Ptt and 2.3 mg L−1 for Ptm, while the EC50 of pyraclostrobin was 0.015 mg L−1 for Ptt and 0.024 mg L−1 for Ptm. Subsequently, 39 Ptt and 27 Ptm isolates were screened with discriminatory doses of 5 mg propiconazole L−1 and 0.15 mg pyraclostrobin L−1. Inhibition of growth as a result of propiconazole was 12–95% for Ptt and 48–92% for Ptm; growth inhibition as a result of pyraclostrobin was 40–100% and 24–100%, respectively. Two Ptt isolates were insensitive to propiconazole, while one Ptm isolate was insensitive to pyraclostrobin. The latter also showed decreased sensitivity to propiconazole. The identification of net blotch isolates insensitive to these fungicides emphasizes the need for farmers to employ integrated crop management strategies to avoid fungicide resistance build-up.