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Summary: The fungal pathogen, Magnaporthe oryzae Triticum pathotype, causing wheat blast disease was first identified in South America and recently spread across continents to South Asia and Africa. Here, we studied the genetic relationship among isolates found on the three continents.Magnaporthe oryzae strains closely related to a South American field isolate B71 were found to have caused the wheat blast outbreaks in South Asia and Africa. Genomic variation among isolates from the three continents was examined using an improved B71 reference genome and whole‐genome sequences.We found strong evidence to support that the outbreaks in Bangladesh and Zambia were caused by the introductions of genetically separated isolates, although they were all close to B71 and, therefore, collectively referred to as the B71 branch. In addition, B71 branch strains carried at least one supernumerary mini‐chromosome. Genome assembly of a Zambian strain revealed that its mini‐chromosome was similar to the B71 mini‐chromosome but with a high level of structural variation.Our findings show that while core genomes of the multiple introductions are highly similar, the mini‐chromosomes have undergone marked diversification. The maintenance of the mini‐chromosome and rapid genomic changes suggest the mini‐chromosomes may serve important virulence or niche adaptation roles under diverse environmental conditions. [ABSTRACT FROM AUTHOR]

Resistance to wheat spike blast (WSB), caused by the Magnaporthe oryzae triticum pathotype (MoT), has relied upon a single major source: the 2NvS translocation introgressed from the wild relative Aegilops ventricosa Tausch. However, this resistance is partial and recently partially overcome by newer MoT races. To characterize potential novel loci conferring resistance to WSB, we conducted a genome‐wide association study (GWAS) using a diverse panel of 384 wheat genotypes phenotyped under three controlled‐environment conditions using MoT isolates T‐25 (301 genotypes), B‐71 (87 genotypes), and 008 (49 genotypes). Genotyping‐by‐sequencing identified 13,175 single nucleotide polymorphisms (SNPs) after filtering. Principal components analysis (PCA) identified two clusters based on the presence or absence of the 2NvS translocation, and the first three PCAs explained 13% of the genetic variation. Three individual analyses were performed (full [all genotypes combined], 2NvS genotypes only, and non‐2NvS genotypes only) using a linear mixed model and a threshold of significance of false discovery rate at 5%. Association analysis detected 25 significant SNPs for the full GWAS with isolate T‐25, in which 21 were mapped on chromosome 2A in the same physical position as the 2NvS translocation. Highly significant linkage disequilibrium among these SNPs suggested they might tag the same quantitative trait locus (QTL). No significant associations were identified with isolates B‐71 and 008, likely due to the small sample size. A QTL pyramiding analysis showed that the combination of multiple QTL was not statistically different from the individual effect of the 2A QTL. Further validation of these genomic regions can aid breeding for broad spectrum and durable WSB resistance. [ABSTRACT FROM AUTHOR]

Phytopathogenic microorganisms, including the fungal pathogen Magnaporthe oryzae, secrete a myriad of effector proteins to facilitate infection. Utilizing the transient expression of candidate effectors in the leaves of the model plant Nicotiana benthamiana, we identified 11 suppressors of plant cell death (SPD) effectors from M. oryzae that were able to block the host cell death reaction induced by Nep1. Ten of these 11 were also able to suppress BAX-mediated plant cell death. Five of the 11 SPD genes have been identified previously as either essential for the pathogenicity of M. oryzae, secreted into the plant during disease development, or as suppressors or homologues of other characterized suppressors. In addition, of the remaining six, we showed that SPD8 (previously identified as BAS162) was localized to the rice cytoplasm in invaded and surrounding uninvaded cells during biotrophic invasion. Sequence analysis of the 11 SPD genes across 43 re-sequenced M. oryzae genomes revealed that SPD2, SPD4 and SPD7 have nucleotide polymorphisms amongst the isolates. SPD4 exhibited the highest level of nucleotide diversity of any currently known effector from M. oryzae in addition to the presence/absence polymorphisms, suggesting that this gene is potentially undergoing selection to avoid recognition by the host. Taken together, we have identified a series of effectors, some of which were previously unknown or whose function was unknown, that probably act at different stages of the infection process and contribute to the virulence of M. oryzae. [ABSTRACT FROM AUTHOR]

India has more than 215 million food-insecure people, many of whom are farmers. Genetically modified (GM) crops have the potential to alleviate this problem by increasing food supplies and strengthening farmer livelihoods. For this to occur, twofactors are critical: (i) a change in the regulatory status of GM crops, and (ii) consumer acceptance of GM foods. There are generally two classifications of GM crops based on how they are bred: cisgenically bred, containing only DNA sequences from sexually compatible organisms; and transgenically bred, including DNA sequences from sexually incompatible organisms. Consumers may view cisgenic foods as more natural than those produced via transgenesis, thus influencing consumer acceptance. This premise was the catalyst for our study-would Indian consumers accept cisgenically bred rice and if so, how would they value cisgenics compared to conventionally bred rice, GM-labelled rice and 'nofungicide' rice? In this willingness-to-pay study, respondents did not view cisgenic and GM rice differently. However, participants were willing-to-pay a premium for any aforementioned rice with a 'nofungicide' attribute, which cisgenics and GM could provide. Although not significantly different (P = 0.16), 76% and 73% of respondents stated a willingness-to-consume GM and cisgenic foods, respectively. [ABSTRACT FROM AUTHOR]

Rice expressing the Pi-ta gene is resistant to strains of the rice blast fungus, Magnaporthe grisea, expressing AVR-Pita in a gene-for-gent relationship. Pi-ta encodes a putative cytoplasmic receptor with a centrally localized nucleotide-binding site and leucine-rich domain (LRD) at the C-terminus. AVR-Pita is predicted to encode a metalloprotease with an N-terminal secretary signal and pro-protein sequences. AVR-Pita176 lacks the secretary and proprotein sequences. We report here that transient expression of AVR-Pita176 inside plant cells results in a Pi-ta-dependent resistance response. AVR-Pita176 protein is shown to bind specifically to the LRD of the Pi-ta protein, both in the yeast two-hybrid system and in an in vitro binding assay. Single amino acid substitutions in the Pi-ta LRD or in the AVR-Pita176 protease motif that result in loss of resistance in the plant also disrupt the physical interaction, both in yeast and in vitro. These data suggest that the AVR-Pita176 protein binds directly to the Pi-ta LRD region inside the plant cell to initiate a Pi-ta-mediated defense response. [ABSTRACT FROM AUTHOR]