Wheat blast, caused by Magnaporthe oryzae, is an important disease across central and southern Brazil. Control has relied mainly on strobilurin fungicides (quinone-outside inhibitors [QoIs]). Here, we report the widespread distribution of QoI resistance in M. oryzae populations sampled from wheat fields and poaceous hosts across central and southern Brazil and the evolution of the cytochrome b (cyt b) gene. Sequence analysis of the cyt b gene distinguished nine haplotypes, with four haplotypes carrying the G143A mutation associated with QoI resistance and two haplotypes shared between isolates sampled from wheat and other poaceous hosts. The frequency of the G143A mutation in the wheat-infecting population increased from 36% in 2005 to 90% in 2012. The G143A mutation was found in many different nuclear genetic backgrounds of M. oryzae. Our findings indicate an urgent need to reexamine the use of strobilurins to manage fungal wheat diseases in Brazil.

Genetic similarity among soybean genotypes was studied by applying the amplified fragment length polymorphism (AFLP) technique to 317 soybean cultivars released in Brazil from 1962 to 1998. Genetic similarity (GS) coefficients were estimated using the coefficient of Nei and Li (Nei and Li 1979), and the cultivars were clustered using the unweighted pair-group method with averages (UPGMA). The parentage coefficients of 100 cultivars released between 1984 and 1998 were calculated and correlated with the genetic similarity obtained by the markers. The genetic similarity coefficients varied from 0.17 to 0.97 (x = 0.61), with 56.8% of the coefficients being above 0.60 and only 9.7% equal to or less than 0.50. The similarity coefficients have remained constant during the last three decades. Dendrogram interpretation was hindered by the large number of cultivars used, but it was possible to detect groups of cultivars formed as expected from their genealogy. Another dendrogram, composed of 63 cultivars, allowed a better interpretation of the groups. Parentage coefficients among the 100 cultivars varied from zero to one (x = 0.21). However, no significant correlation (r = 0.12) was detected among the parentage coefficients and the AFLP genetic similarity. The results show the efficiency of AFLP markers in large scale studies of genetic similarity and are discussed in relation to soybean breeding in Brazil.

25The wheat blast disease has been a serious constraint for wheat production in Latin America 26 since the late 1980s. We used a population genomics analysis including 95 genome 27 sequences of the wheat blast pathogen Pyricularia graminis-tritici (Pygt) and other 28Pyricularia species to show that Pygt is a distinct, highly diverse pathogen species with a 29 broad host range. We assayed 11 neutral SSR loci in 526 Pygt isolates sampled from wheat 30 and other grasses distributed across the wheat-growing region of Brazil to estimate gene 31 flow, assess the importance of sexual reproduction, and compare the genetic structures of 32Pygt populations infecting wheat and nearby grasses. Our results suggest a mixed 33 reproductive system that includes sexual recombination as well as high levels of gene flow 34 among regions, including evidence for higher gene flow from grass-infecting populations and 35 into wheat-infecting populations than vice versa. The most common virulence groups were 36 shared between the grass-and wheat-infecting Pygt populations, providing additional 37 evidence for movement of Pygt between wheat fields and nearby grasses. Analyses of 38 fruiting body formation found that proto-perithecia and perithecia developed on senescing 39 stems of wheat and other grass hosts, suggesting that sexual reproduction occurs mainly 40 during the saprotrophic phase of the disease cycle on dead residues. Phalaris canariensis 41 (canarygrass) supported the fullest development of perithecia, suggesting it is a promising 42 candidate for identifying the teleomorph in the field. Based on these findings, we formulated 43 a more detailed disease cycle for wheat blast that includes an important role for grasses 44 growing near wheat fields. Our findings strongly suggest that widely grown pasture grasses 45 function as a major reservoir of wheat blast inoculum and provide a temporal and spatial 46 bridge that connects wheat fields across Brazil. 47. CC-BY-NC-ND 4.0 International license It is made available under a (which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint . http://dx.doi.org/10.1101/203455 doi: bioRxiv preprint first posted online Oct. 16, 2017; 3 Author summary (200 words) 48 After the first wheat blast epidemic occurred in 1985 in Paraná, Brazil, the disease 49 spread to Bolivia, Argentina, and Paraguay, and was introduced into Bangladesh in 2016 50 followed by India in 2017. Wheat blast is caused by Pyricularia graminis-tritici (Pygt), a 51 highly diverse pathogen species related to the rice blast fungus P. oryzae, but with an 52 independent origin and a broader host range. We conducted a large scale contemporary 53 sampling of Pygt from symptomatic wheat and other grass species across Brazil and analyzed 54 the genetic structure of Pygt populations. Pygt populations on both wheat and other grasses 55 had high genotypic and virulence diversity, a genetic structure consistent with a ...

-The objectives of this work were to estimate the genetic and phenotypic parameters and to predict the genetic and genotypic values of the selection candidates obtained from intraspecific crosses in Panicum maximum as well as the performance of the hybrid progeny of the existing and projected crosses. Seventy-nine intraspecific hybrids obtained from artificial crosses among five apomictic and three sexual autotetraploid individuals were evaluated in a clonal test with two replications and ten plants per plot. Green matter yield, total and leaf dry matter yields and leaf percentage were evaluated in five cuts per year during three years. Genetic parameters were estimated and breeding and genotypic values were predicted using the restricted maximum likelihood/best linear unbiased prediction procedure (REML/BLUP). The dominant genetic variance was estimated by adjusting the effect of full-sib families. Low magnitude individual narrow sense heritabilities (0.02-0.05), individual broad sense heritabilities (0.14-0.20) and repeatability measured on an individual basis (0.15-0.21) were obtained. Dominance effects for all evaluated characteristics indicated that breeding strategies that explore heterosis must be adopted. Less than 5% increase in the parameter repeatability was obtained for a three-year evaluation period and may be the criterion to determine the maximum number of years of evaluation to be adopted, without compromising gain per cycle of selection. The identification of hybrid candidates for future cultivars and of those that can be incorporated into the breeding program was based on the genotypic and breeding values, respectively. The prediction of the performance of the hybrid progeny, based on the breeding values of the progenitors, permitted the identification of the best crosses and indicated the best parents to use in crosses.Index terms: guineagrass, apomixis, breeding, heritability, repeatability, selection of parents. Análise biométrica e seleção de progênies tetraplóides de Panicum maximum usando os métodos de modelos mistosResumo -Os objetivos deste trabalho foram estimar parâmetros genéticos e fenotípicos e, predizer os valores genéticos e genotípicos dos candidatos à seleção obtidos de cruzamentos intraespecíficos em Panicum maximum assim como o desempenho da progênie híbrida dos cruzamentos existentes e projetados. Setenta e nove híbridos intraespecíficos, obtidos de cruzamentos artificiais entre cinco indivíduos apomíticos e três sexuais, autotetraplóides, foram avaliados em teste clonal com duas repetições e dez plantas por parcela. Foram avaliados o rendimento de matéria verde, o rendimento de matéria seca total e de folhas além da porcentagem de folhas em cinco cortes anuais durante três anos. Os parâmetros genéticos foram estimados e os valores genéticos e genotípicos foram preditos por meio de procedimento de máxima verossimilhança restrita/melhor predição linear não viciada (REML/BLUP). A variância genética dominante foi estimada ajustando o efeito de família de irmãos germano...

Bread wheat (Triticum aestivum L.) is one of the world’s most important crops. Maintaining wheat yield gains across all of its major production areas is a key target toward underpinning global food security. Brazil is a major wheat producer in South America, generating grain yields of around 6.8 million tons per year. Here, we establish and genotype a wheat association mapping resource relevant to contemporary Brazilian wheat breeding programs. The panel of 558 wheat accessions was genotyped using an Illumina iSelect 90,000 single nucleotide polymorphism array. Following quality control, the final data matrix consisted of 470 accessions and 22,475 polymorphic genetic markers (minor allele frequency ≥5%, missing data <5%). Principal component analysis identified distinct differences between materials bred predominantly for the northern Cerrado region, compared to those bred for southern Brazilian agricultural areas. We augmented the genotypic data with 26 functional Kompetitive Allele-Specific PCR (KASP) markers to identify the allelic combinations at genes with previously known effects on agronomically important traits in the panel. This highlighted breeding targets for immediate consideration – notably, increased Fusarium head blight resistance via the Fhb1 locus. To demonstrate the panel’s likely future utility, genome-wide association scans for several phenotypic traits were undertaken. Significant (Bonferroni corrected P < 0.05) marker-trait associations were detected for Fusarium kernel damage (a proxy for type 2 Fusarium resistance), identifying previously known quantitative trait loci in the panel. This association mapping panel represents an important resource for Brazilian wheat breeding, allowing future genetic studies to analyze multiple agronomic traits within a single genetically diverse population.