Summary Bipolaris sorokiniana (teleomorph Cochliobolus sativus ) is the causal agent of common root rot, leaf spot disease, seedling blight, head blight, and black point of wheat and barley. The fungus is one of the most serious foliar disease constraints for both crops in warmer growing areas and causes significant yield losses. High temperature and high relative humidity favour the outbreak of the disease, in particular in South Asia's intensive ‘irrigated wheat–rice’ production systems. In this article, we review the taxonomy and worldwide distribution, as well as strategies to counteract the disease as an emerging threat to cereal production systems. We also review the current understanding of the cytological and molecular aspects of the interaction of the fungus with its cereal hosts, which makes B. sorokiniana a model organism for studying plant defence responses to hemibiotrophic pathogens. The contrasting roles of cell death and H 2O2 generation in plant defence during biotrophic and necrotrophic fungal growth phases are discussed.

In search of new durable disease resistance traits in barley to control leaf spot blotch disease caused by the necrotrophic fungus Bipolaris sorokiniana (teleomorph: Cochliobolus sativus), we developed macroscopic and microscopic scales to judge spot blotch disease development on barley. Infection of barley was associated with cell wall penetration and accumulation of hydrogen peroxide. The latter appeared to take place in cell wall swellings under fungal penetration attempts as well as during cell death provoked by the necrotrophic pathogen. Additionally, we tested the influence of a compromised Mlo pathway that confers broad resistance against powdery mildew fungus (Blumeria graminis f. sp. hordei). Powdery mildew-resistant genotypes with mutations at the Mlo locus (mlo genotypes) showed a higher sensitivity to infiltration of toxic culture filtrate of Bipolaris sorokiniana as compared with wild-type barley. Mutants defective in Ror, a gene required for mlo-specified powdery mildew resistance, were also more sensitive to Bipolaris sorokiniana toxins than wild-type barley but showed less symptoms than mlo5 parents. Fungal culture filtrates induced an H2O2 burst in all mutants, whereas wild-type (Mlo) barley was less sensitive. The results support the hypothesis that the barley Mlo gene product functions as a suppresser of cell death. Therefore, a compromised Mlo pathway is effective for control of biotrophic powdery mildew fungus but not for necrotrophic Bipolaris sorokiniana. We discuss the problem of finding resistance traits that are effective against both biotrophic and necrotrophic pathogens with emphasis on the role of the anti-oxidative system of plant cells.

Isoflavones are naturally occurring compounds found in soybean [Glycine max (L.) Merr.]. Soybean isoflavone, as a quantitative trait, is subject to significant genotype × environment interaction, which makes breeding for this trait difficult. Thirty F4:7 soybean lines, derived from crosses of ‘RCAT Angora’ × CK‐01 and ‘Heinong 35’ × RCAT Angora were classified within each population as high, intermediate, or low isoflavone. The lines, parents, and two maturity checks were grown in four locations in 2005 and six locations in 2006 across Ontario and Quebec, Canada. Isoflavone content of the mature seed was determined by near‐infrared reflectance. The effects of genotype, environment, and the genotype × environment (G × E) interaction were significant. Consistently performing genotypes from the two populations were identified by several stability parameters. Genotype–genotype × environment (GGE) biplot demonstrated an ability to provide information on both the genotypes and the environments in which they were evaluated. The identification of genotypes with consistent placement in either the high‐ and low‐isoflavone classes suggested that breeding for relative isoflavone content in soybean is possible, although breeding for absolute stability remains a challenge, given the large environmental influence on soybean isoflavone levels.

A comprehensive germplasm evaluation study of wheat accessions conserved in the Indian National Genebank was conducted to identify sources of rust and spot blotch resistance. Genebank accessions comprising three species of wheat–Triticum aestivum, T. durum and T. dicoccum were screened sequentially at multiple disease hotspots, during the 2011–14 crop seasons, carrying only resistant accessions to the next step of evaluation. Wheat accessions which were found to be resistant in the field were then assayed for seedling resistance and profiled using molecular markers. In the primary evaluation, 19,460 accessions were screened at Wellington (Tamil Nadu), a hotspot for wheat rusts. We identified 4925 accessions to be resistant and these were further evaluated at Gurdaspur (Punjab), a hotspot for stripe rust and at Cooch Behar (West Bengal), a hotspot for spot blotch. The second round evaluation identified 498 accessions potentially resistant to multiple rusts and 868 accessions potentially resistant to spot blotch. Evaluation of rust resistant accessions for seedling resistance against seven virulent pathotypes of three rusts under artificial epiphytotic conditions identified 137 accessions potentially resistant to multiple rusts. Molecular analysis to identify different combinations of genetic loci imparting resistance to leaf rust, stem rust, stripe rust and spot blotch using linked molecular markers, identified 45 wheat accessions containing known resistance genes against all three rusts as well as a QTL for spot blotch resistance. The resistant germplasm accessions, particularly against stripe rust, identified in this study can be excellent potential candidates to be employed for breeding resistance into the background of high yielding wheat cultivars through conventional or molecular breeding approaches, and are expected to contribute toward food security at national and global levels.

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Phenylpropanoids are a diverse chemical class with immense health benefits that are biosynthesized from the aromatic amino acid L-phenylalanine. This article reviews the progress for accessing variation in phenylpropanoids in germplasm collections, the genetic and molecular basis of phenylpropanoid biosynthesis, and the development of cultivars dense in seed-phenylpropanoids. Progress is also reviewed on high-throughput assays, factors that influence phenylpropanoids, the site of phenylpropanoids accumulation in seed, Genotype × Environment interactions, and on consumer attitudes for the acceptance of staple foods rich in phenylpropanoids. A paradigm shift was noted in barley, maize, rice, sorghum, soybean, and wheat, wherein cultivars rich in phenylpropanoids are grown in Europe and North and Central America. Studies have highlighted some biological constraints that need to be addressed for development of high-yielding cultivars that are rich in phenylpropanoids. Genomics-assisted breeding is expected to facilitate rapid introgression into improved genetic backgrounds by minimizing linkage drag. More research is needed to systematically characterize germplasm pools for assessing variation to support crop genetic enhancement, and assess consumer attitudes to foods rich in phenylpropanoids.

. 2009. Association of seed and agronomic traits with isoflavone levels in soybean. Can. J. Plant Sci. 89: 477Á484. Soybean, Glycine max (L.) Merr., seeds contain isoflavones, compounds with potential human health benefits. This study investigated the association of seed and agronomic traits with isoflavone level in a genetically diverse group of soybean genotypes to provide more information for cultivar development. F 4:7 lines derived from several crosses were grown in four locations in 2005 and six locations in 2006 across Ontario and Quebec. Seed protein, oil and isoflavone contents were measured using near-infrared reflectance (NIR) on a plot basis. Seed yield was determined at 13% moisture and days to maturity (R8) were recorded. GGE genotype-bytrait biplots were generated to describe the relationships among all variables. Isoflavone content was not correlated with yield, indicating that potential exists for development of high or low isoflavone cultivars without sacrificing yield. Isoflavone content was negatively correlated with protein content, however high isoflavone lines were identified with moderate protein content. Isoflavone content was correlated with maturity suggesting that delayed planting and/or the use of later maturing varieties could be a successful strategy to increase isoflavone content. The results of this study support the potential for the development of either high or low isoflavone soybean cultivars with acceptable agronomic and seed quality traits.Key words: Soybean, isoflavone, protein, oil, yield, maturity Murphy, S. E., Lee, E. A., Woodrow, L., Seguin, P., Kumar, J., Rajcan, I. et Ablett, G. R. 2009. Relation des caracte`res grainiers et agronomiques avec la concentration d'isoflavones chez le soja. Can. J. Plant Sci. 89: 477Á484. Les graines du soja, Glycine max (L.) Merr., contiennent des isoflavones, compose´susceptible d'avoir des effets be´ne´fiques sur la sante´. L'e´tude examinait les liens qui existent entre la concentration d'isoflavones et les caracte`res grainiers et agronomiques dans un groupe de varie´te´s de soja ge´ne´tiquement varie´, dans le but de fournir plus d'informations en vue de cre´er de nouveaux cultivars. Les ligne´es F 4:7 issues de plusieurs croisements ont e´te´cultive´es a`quatre endroits en Ontario et au Que´bec, en 2005, et a`six, en 2006. La teneur en prote´ines, en huile et en isoflavones des graines a e´te´e´tablie par re´flectance dans le proche infrarouge, dans les parcelles. Le rendement grainier a e´te´mesure´a`13 % de teneur en eau et on a enregistre´le nombre de jours jusqu'a`maturite´(R8). L'analyse GGE par double projection du ge´notype et des caracte`res a permis de de´crire les liens entre les variables. La concentration d'isoflavones n'est pas corre´le´e au rendement, signe qu'on pourrait cre´er des cultivars a`faible ou a`forte concentration d'isoflavones sans que le rendement en souffre. La concentration d'isoflavones pre´sente une corre´lation ne´gative avec la teneur en prote´ines, mais les ligne´es produisant beaucoup d'isoflav...

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