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Crop wild relatives (CWRs) are an important source of genetic diversity for crop improvement. The aim of this study was to assess the usefulness of deploying CWRs in durum wheat [Triticum turgidum L. subsp. durum (Desf.) van Slageren] breeding. A set of 60 accessions was selected to include cultivars from nine countries, top lines obtained via elite-by-elite crossing, and CWR-derived lines. These accessions were screened for resistance against four major fungal diseases to reveal that CWR-derived lines are a good source of resistance against Septoria leaf blotch (Zymoseptoria tritici), while they were highly susceptible to tan spot (Pyrenophora tritici-repentis). Drought tolerance was assessed at eight environments with contrasting nitrogen levels and tillage practices to reveal a clear superiority of CWR-derived lines for grain size as well as higher grain yield (GY) under low nitrogen and normal tillage (NT). Temperature-stress tolerance was assessed at four heat-stressed environments along the Senegal River to confirm CWR-derived had up to 42% yield advantage and a higher grain number per spike (GNspk). Combined testing under plastic heat tunnels imposed at the time of flowering also revealed good performance of CWR-derived lines. However, the CWR-derived lines had low gluten sedimentation index and poor yellow color compared with cultivars and elite germplasm. High genetic diversity was found in CWR-derived lines with 75% of individuals having minor allele frequency (MAF) of 40-44% for frequent alleles but low genetic diversity for alleles with low frequency. In addition, 8-13% of the CWR parent genome

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We studied the genetics of the resistance to leaf rust (LR) (caused by Puccinia hordei) and spot blotch (SB) (caused by Cochliobolus sativus) in barley using a doubled-haploid population derived from the cross BCD47 · Baronesse. BCD47 has low SB severity and high susceptibility to LR, while Baronesse is susceptible to SB and has low LR severity. Resistance to both diseases is expressed at the adult plant stage. The population was phenotyped in eight field environments for SB and nine for LR. Ten quantitative trait loci (QTLs) were detected for SB. None were significant in more than three environments, and both parents contributed resistance alleles. Five QTLs were detected for LR. The most consistent quantitative trait locus (QTL) (significant in seven environments) was on chromosome 6H (located on the Bmag173-Bmag009 interval) with Baronesse contributing the resistance allele. Coincident QTL effects for SB were also detected in this region with resistance alleles to the two diseases in repulsion. These results illustrate the difficulties of resistance gene detection in the complex disease environments found under field conditions.

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Much effort is being made to breed barley with durable resistance to leaf spot blotch incited by Bipolaris sorokiniana (teleomorph: Cochliobolus sativus). We hypothesized that susceptibility and resistance traits in 11 diverse barley genotypes inoculated with a single C. sativus isolate might specify a range of distinct host cell responses. Quantitative descriptions of interaction microphenotypes exhibited by different barley genotype seedlings after infection with C. sativus are provided. Early oxidative responses occurring in epidermis and mesophyll leaf tissue were monitored by histochemical analysis of H2O2 accumulation at 8, 24, and 48 h after inoculation. Cell wall apposition (CWA) in epidermal cells and hypersensitive reaction (HR) of epidermal or mesophyll tissue were early defenses in both resistant and susceptible genotypes. There were differences in level, duration, and frequency of occurrence for CWA and HR for the different barley genotypes. Occurrence of HR in epidermal cells at post-penetration stages was indicative of compatibility. Patterns of cell responses were microphenotypically diverse between different resistant and susceptible genotypes. This suggests that timing and level of response are key features of microphenotypic diversity that distinguish different functional mechanisms of resistance and susceptibility present in barley.