Wheat blast: The last enemy of hunger fighters.

Effective strategies for disease control are crucial for sustaining world food production and ensuring food security for the population. Wheat blast, a disease caused by the pathogen Magnaporthe oryzae pathotype Triticum, has been a concern for cereal producers and researchers due to its aggressiveness and rapid expansion. To solve this problem, the development of resistant varieties with durable resistance is an effective, economical and sustainable way to control the disease. Conventional breeding can be aided by several molecular tools to facilitate the mining of many sources of resistance, such as R genes and QTLs. The identification of new sources of resistance, whether in the wheat crop or in other cereals are an opportunity for efficient wheat breeding through the application of different techniques. Since this disease is still poorly studied in wheat, knowledge of the rice Magnaporthe pathotype may be adapted to control wheat blast. Thus, genetic mapping, molecular markers, transgenic approaches, and genomic editing are valuable technologies to fight wheat blast. This review aimed to compile the biotechnological alternatives available to accelerate the development of improved cultivars for resistance to wheat blast.

Evaluation of the effect of phenolic pigments on rice germination under low temperature conditions / Avaliação do efeito de pigmentos fenólicos na germinação de arroz sob condições de baixa temperatura

In Rio Grande do Sul, the main rice producer State in Brazil, low temperatures can occur during germination and seedling establishment, and in some cases, during the reproductive stage. When low temperatures occur in the early developmental stages cause delay in germination, resulting in a non-homogeneous growing. In reproductive stage, low temperatures cause spikelet sterility, directly interfering with plant yield. Researchers have shown that some phenolic compounds such as proanthocyanidins and anthocyanin are associated with low temperature tolerance in plants due to their antioxidant capacity. The red and black color in the seeds of some rice genotypes is conferred by the phenolic compounds proanthocyanidins and anthocyanin, respectively. Therefore, tis study aimed to verify whether rice genotypes with red or black seeds are more tolerant to low temperatures during germination. In this study, five rice genotypes were tested, two present seeds without pigmentation and with contrasting response to low temperature tolerance (BRS Bojuru - tolerant and BRS Pampeira - sensitive), two genotypes with red seeds (BRS 902, SCS 119 Rubi) and one black seed genotype (SCS 120 Ônix). As expected, the genotypes with pigmented seeds had a greater total phenolic compounds content. However, under low temperature conditions, the genotypes with pigmented seed showed a similar response to the sensitive genotype. Therefore, the presence of proanthocyanidins and anthocyanin in the seed of the studied genotypes does not provide tolerance to low temperatures during germination.(AU)

No Rio Grande do Sul, principal estado produtor de arroz do Brasil, baixas temperaturas podem ocorrer durante a germinação e estabelecimento de plântulas, e em alguns casos, durante o estádio reprodutivo. Quando baixas temperaturas ocorrem no estádio inicial de desenvolvimento causam atraso da germinação, resultando em um crescimento não homogêneo. No estádio reprodutivo, baixas temperaturas podem ocasionar esterilidade das espiguetas, interferindo diretamente na produtividade da planta. Pesquisas têm mostrado que alguns compostos fenólicos como as proantocianidinas e antocianinas estão associadas com tolerância a baixa temperatura em plantas devido sua capacidade antioxidante. A coloração vermelha e preta nas sementes de alguns genótipos de arroz é conferida pelos compostos fenólicos proantocianidinas e antocianinas, respectivamente. Portanto, o objetivo desse estudo foi verificar se os genótipos de arroz com sementes vermelhas ou pretas são mais tolerantes a baixas temperaturas durante a germinação. Neste trabalho, cinco genótipos foram testados, dois com sementes sem pigmentação e com resposta contrastante para tolerância a baixa temperatura (BRS Bojuru - tolerante e BRS Pampeira - sensível), dois genótipos com sementes vermelhas (BRS 902, SCS 119 Rubi) e um genótipo com sementes pretas (SCS 120 Ônix). Como esperado, os genótipos com sementes pigmentadas têm maior conteúdo de compostos fenólicos totais. Entretanto, sob condições de baixa temperatura, os genótipos com semente pigmentada mostraram resposta similar ao genótipo sensível. Dessa forma, a presença de proantocianidinas e antocianinas nas sementes dos genótipos estudados não confere tolerância a baixas temperaturas durante a germinação.(AU)

Use of microstructural characteristics of pollen and pistil to identify olive cultivars in Southern Brazil

The olive crop has a large diversity in cultivars around the world, whose identification have been based on leaf, stem or fruit traits. However, these traits may be influenced by the environment, which has led to the misidentification of cultivars. The variability of the pistil and pollen structure under electron scanning and light microscopy were studied using the cultivars 'Arbequina', 'Arbosana', 'Frantoio', 'Koroneiki', 'Manzanilla de Sevilla' and 'Picual', cultivated in Southern Brazil. The aim was to find unique patterns for their identification. This type of study has not been carried out in the conditions of Southern Brazil, where the identification of commercial cultivars sometimes is complex and confusing. There were significant differences in the variables, showing uniformity within each cultivar in different locations. The principal component analysis indicated a separation of cultivars according to similarities or micromorphological differences in the pollen wall, area of the lumen and the structural elements of the tectum. For the analysis of the pistil, the separation was even clearer, each cultivar individually forming a cluster, using as characters the length of the style in contrast to the length, width and area of the stigma. This evidenced little variation among individuals within the same cultivar. The information provided can contribute to the individual identification of very close olive tree cultivars in the conditions of Southern Brazil.(AU)

Genetic changes in the genus Vitis and the domestication of vine.

The genus Vitis belongs to the Vitaceae family and is divided into two subgenera: Muscadinia and Vitis, the main difference between these subgenera being the number of chromosomes. There are many hypotheses about the origin of the genus, which have been formed with archaeological studies and lately with molecular analyses. Even though there is no consensus on the place of origin, these studies have shown that grapes have been used by man since ancient times, starting later on its domestication. Most studies point to the Near East and Greece as the beginning of domestication, current research suggests it took place in parallel in different sites, but in all cases Vitis vinifera (L.) subsp. sylvestris [Vitis vinifera (L.) subsp. sylvestris (Gmelin) Hagi] seems to be the species chosen by our ancestors to give rise to the now known Vitis vinifera (L.) subsp. vinifera [=sativa (Hegi)= caucasica (Vavilov)]. Its evolution and expansion into other territories followed the formation of new empires and their expansion, and this is where the historical importance of this crop lies. In this process, plants with hermaphrodite flowers were preferentially selected, with firmer, sweeter, larger fruits of different colors, thus favoring the selection of genes associated with these traits, also resulting in a change in seed morphology. Currently, genetic improvement programs have made use of wild species for the introgression of disease resistance genes and tolerance to diverse soil and climate environments. In addition, the mapping of genes of interest, both linked to agronomic and fruit quality traits, has allowed the use of molecular markers for assisted selection. Information on the domestication process and genetic resources help to understand the gene pool available for the development of cultivars that respond to producer and consumer requirements.

An empirical analysis of mtSSRs: could microsatellite distribution patterns explain the evolution of mitogenomes in plants?

Microsatellites (SSRs) are tandem repeat sequences in eukaryote genomes, including plant cytoplasmic genomes. The mitochondrial genome (mtDNA) has been shown to vary in size, number, and distribution of SSRs among different plant groups. Thus, SSRs contribute with genomic diversity in mtDNAs. However, the abundance, distribution, and evolutionary significance of SSRs in mtDNA from a wide range of algae and plants have not been explored. In this study, the mtDNAs of 204 plant and algal species were investigated related to the presence of SSRs. The number of SSRs was positively correlated with genome size. Its distribution is dependent on plant and algal groups analyzed, although the cluster analysis indicates the conservation of some common motifs in algal and terrestrial plants that reflect common ancestry of groups. Many SSRs in coding and non-coding regions can be useful for molecular markers. Moreover, mitochondrial SSRs are highly abundant, representing an important source for natural or induced genetic variation, i.e., for biotechnological approaches that can modulate mtDNA gene regulation. Thus, this comparative study increases the understanding of the plant and algal SSR evolution and brings perspectives for further studies.

Characterization of rice genotypes used in Brazil regarding salinity tolerance at the seedling stage / Caracterização de genótipos de arroz utilizados no Brasil quanto à tolerância à salinidade no estádio de plântula

Rice production (Oryza sativa L.) is among the most economically important activities in the world. However, soil and salinity coming from irrigation water reduce rice yield. Therefore, the identification and/or development of salt-tolerant rice genotypes is a strategy to minimize this problem. The development of new genotypes depends on the presence of genetic diversity, and understanding the heritability of a desired trait can help in the selection process. Thus, this study aimed to identify superior genotypes, analyze the genetic diversity and estimate the heritability for salinity tolerance at the seedling stage in rice genotypes used in Brazil. For this, seedlings of 69 genotypes were kept in hydroponic solution with 40mM NaCl (4 dSm-1) for seven days. Shoot length, root length, shoot dry weight, and root dry weight) were evaluated and the results were converted into relative performance. Tolerant and moderately salt-tolerant genotypes were identified at the seedling stage, which can be used in breeding programs and can be cultivated in high salinity areas. Principal component analysis showed the presence of genetic diversity for salinity response. Finally, it was shown that most of the observed variation is of genetic origin, which can make the breeding process less difficult.

O arroz (Oryza sativa L.) é uma espécie com grande importância econômica no mundo. A salinidade do solo ou da água reduz a produtividade da cultura. Por isso, a identificação e/ou desenvolvimento de genótipos de arroz com tolerância à salinidade é uma estratégia para minimizar esse problema. O desenvolvimento de novos genótipos depende da presença de variabilidade genética, e o conhecimento da herdabilidade da característica de interesse pode auxiliar no processo de seleção. Dessa forma, esse estudo teve como objetivo identificar genótipos superiores, analisar a variabilidade genética e estimar a herdabilidade para tolerância a salinidade no estádio de plântula em genótipos de arroz utilizados no Brasil. Para isso, plântulas de 69 genótipos foram mantidas em solução hidropônica acrescida de 40 mM de NaCl (4 dSm-1) durante sete dias. Foram avaliados comprimento de parte aérea, comprimento de raiz, peso seco de parte aérea, e peso seco de raiz e os resultados foram convertidos em desempenho relativo. Foram identificados genótipos tolerantes e moderadamente tolerantes à salinidade no estádio de plântula, os quais podem ser utilizados em programas de melhoramento e cultivados em áreas com ocorrência desse estresse. A análise de componentes principais mostrou a presença de variabilidade genética para resposta à salinidade. Finalmente, foi demonstrado que a maior parte da variação observada nos caracteres é de origem genética, o que pode tornar o processo de melhoramento menos difícil.

Characterization of rice genotypes used in Brazil regarding salinity tolerance at the seedling stage / Caracterização de genótipos de arroz utilizados no Brasil quanto à tolerância à salinidade no estádio de plântula

Rice production (Oryza sativa L.) is among the most economically important activities in the world. However, soil and salinity coming from irrigation water reduce rice yield. Therefore, the identification and/or development of salt-tolerant rice genotypes is a strategy to minimize this problem. The development of new genotypes depends on the presence of genetic diversity, and understanding the heritability of a desired trait can help in the selection process. Thus, this study aimed to identify superior genotypes, analyze the genetic diversity and estimate the heritability for salinity tolerance at the seedling stage in rice genotypes used in Brazil. For this, seedlings of 69 genotypes were kept in hydroponic solution with 40 mM NaCl (4 dSm-1) for seven days. Shoot length, root length, shoot dry weight, and root dry weight) were evaluated and the results were converted into relative performance. Tolerant and moderately salt-tolerant genotypes were identified at the seedling stage, which can be used in breeding programs and can be cultivated in high salinity areas. Principal component analysis showed the presence of genetic diversity for salinity response. Finally, it was shown that most of the observed variation is of genetic origin, which can make the breeding process less difficult.

O arroz (Oryza sativa L.) é uma espécie com grande importância econômica no mundo. A salinidade do solo ou da água reduz a produtividade da cultura. Por isso, a identificação e/ou desenvolvimento de genótipos de arroz com tolerância à salinidade é uma estratégia para minimizar esse problema. O desenvolvimento de novos genótipos depende da presença de variabilidade genética, e o conhecimento da herdabilidade da característica de interesse pode auxiliar no processo de seleção. Dessa forma, esse estudo teve como objetivo identificar genótipos superiores, analisar a variabilidade genética e estimar a herdabilidade para tolerância a salinidade no estádio de plântula em genótipos de arroz utilizados no Brasil. Para isso, plântulas de 69 genótipos foram mantidas em solução hidropônica acrescida de 40mM de NaCl (4 dSm-1) durante sete dias. Foram avaliados comprimento de parte aérea, comprimento de raiz, peso seco de parte aérea, e peso seco de raiz e os resultados foram convertidos em desempenho relativo.  Foram identificados genótipos tolerantes e moderadamente tolerantes à salinidade no estádio de plântula, os quais podem ser utilizados em programas de melhoramento e cultivados em áreas com ocorrência desse estresse. A análise de componentes principais mostrou a presença de variabilidade genética para resposta à salinidade. Finalmente, foi demonstrado que a maior parte da variação ob

Evaluation of the effect of phenolic pigments on rice germination under low temperature conditions / Avaliação do efeito de pigmentos fenólicos na germinação de arroz sob condições de baixa temperatura

In Rio Grande do Sul, the main rice producer State in Brazil, low temperatures can occur during germination and seedling establishment, and in some cases, during the reproductive stage. When low temperatures occur in the early developmental stages cause delay in germination, resulting in a non-homogeneous growing. In reproductive stage, low temperatures cause spikelet sterility, directly interfering with plant yield. Researchers have shown that some phenolic compounds such as proanthocyanidins and anthocyanin are associated with low temperature tolerance in plants due to their antioxidant capacity. The red and black color in the seeds of some rice genotypes is conferred by the phenolic compounds proanthocyanidins and anthocyanin, respectively. Therefore, tis study aimed to verify whether rice genotypes with red or black seeds are more tolerant to low temperatures during germination. In this study, five rice genotypes were tested, two present seeds without pigmentation and with contrasting response to low temperature tolerance (BRS Bojuru - tolerant and BRS Pampeira - sensitive), two genotypes with red seeds (BRS 902, SCS 119 Rubi) and one black seed genotype (SCS 120 Ônix). As expected, the genotypes with pigmented seeds had a greater total phenolic compounds content. However, under low temperature conditions, the genotypes with pigmented seed showed a similar response to the s

No Rio Grande do Sul, principal estado produtor de arroz do Brasil, baixas temperaturas podem ocorrer durante a germinação e estabelecimento de plântulas, e em alguns casos, durante o estádio reprodutivo. Quando baixas temperaturas ocorrem no estádio inicial de desenvolvimento causam atraso da germinação, resultando em um crescimento não homogêneo. No estádio reprodutivo, baixas temperaturas podem ocasionar esterilidade das espiguetas, interferindo diretamente na produtividade da planta. Pesquisas têm mostrado que alguns compostos fenólicos como as proantocianidinas e antocianinas estão associadas com tolerância a baixa temperatura em plantas devido sua capacidade antioxidante. A coloração vermelha e preta nas sementes de alguns genótipos de arroz é conferida pelos compostos fenólicos proantocianidinas e antocianinas, respectivamente. Portanto, o objetivo desse estudo foi verificar se os genótipos de arroz com sementes vermelhas ou pretas são mais tolerantes a baixas temperaturas durante a germinação. Neste trabalho, cinco genótipos foram testados, dois com sementes sem pigmentação e com resposta contrastante para tolerância a baixa temperatura (BRS Bojuru - tolerante e BRS Pampeira - sensível), dois genótipos com sementes vermelhas (BRS 902, SCS 119 Rubi) e um genótipo com sementes pretas (SCS 120 Ônix). Como esperado, os genótipos com sementes pigmentadas têm maior conteúdo d

Meta-Analysis of the QTLome of Fusarium Head Blight Resistance in Bread Wheat: Refining the Current Puzzle.

Background: Fusarium Head Blight (FHB) is a worldwide devastating disease of bread wheat (Triticum aestivum L.). Genetic resistance is the most effective way to control FHB and many QTL related to this trait have been mapped on the wheat genetic map. This information, however, must be refined to be more efficiently used in breeding programs and for the advance of the basic research. The objective of the present study was to in-depth analyze the QTLome of FHB resistance in bread wheat, further integrating genetic, genomic, and transcriptomic data, aiming to find candidate genes. Methods: An exhaustive bibliographic review on 76 scientific papers was carried out collecting information about QTL related to FHB resistance mapped on bread wheat. A dense genetic consensus map with 572,862 loci was generated for QTL projection. Meta-analysis could be performed on 323 QTL. Candidate gene mining was carried out within the most refined loci, containing genes that were cross-validated with publicly available transcriptional expression data of wheat under Fusarium infection. Most highlighted genes were investigated for protein evidence. Results: A total of 556 QTL were found in the literature, distributed on all sub-genomes and chromosomes of wheat. Meta-analysis generated 65 meta-QTL, and this refinement allows one to find markers more tightly linked to these regions. Candidate gene mining within the most refined meta-QTL, meta-QTL 1/chr. 3B, harvested 324 genes and transcriptional data cross-validated 10 of these genes, as responsive to FHB. One is of these genes encodes a Glycosiltransferase and the other encodes for a Cytochrome P450, and these such proteins have already been verified as being responsible for FHB resistance, but the remaining eight genes still have to be further studied, as promising loci for breeding. Conclusions: The QTLome of FHB resistance in wheat was successfully assembled and a refinement in terms of number and length of loci was obtained. The integration of the QTLome with genomic and transcriptomic data has allowed for the discovery of promising candidate genes for use in breeding programs.

Iron tolerance in rice: an efficient method for performing quick early genotype screening.

OBJECTIVES: This study was conducted to establish a method for early, quick and cheap screening of iron excess tolerance in rice (Oryza sativa L.) cultivars. RESULTS: Based on the experiments, iron excess leads to reduction in shoot length (SL) and this can be a useful characteristic for adequate screening of tolerant genotypes. The sensitive genotypes Nipponbare and BR-IRGA 409 indicated higher accumulation of iron in their tissues while BRS-Agrisul and Epagri 108 also accumulated iron, but at lower concentrations. BR-IRGA 410 displayed an intermediate phenotype regarding iron accumulation. No changes in shoot Cu content can be observed when comparing treatments. On the other hand, an increase was seen for Zn and Mn when shoots are subjected to Fe2+ excess. Fe stress at a lower concentration than 7 mM increased Zn but decreased Mn contents in shoots of BR-IRGA 409. Strong positive correlations were found here for Fe × Zn (0.93); Fe × Mn (0.97) and Zn × Mn (0.92), probably due to the Fe-induced activation of bivalent cation transporters. Results show that genotypes scored as sensitive present higher concentration of Fe in shoots and this is an efficient method to characterize rice cultivars regarding iron response.

Genetic diversity, linkage disequilibrium, and population structure in a panel of Brazilian rice accessions.

Narrowing of genetic diversity and the quantitative nature of most agronomic traits is a challenge for rice breeding. Genome-wide association studies have a great potential to identify important variation in loci underlying quantitative and complex traits; however, before performing the analysis, it is important to assess parameters of the genotypic data and population under study, to improve the accuracy of the genotype-phenotype associations. The aim of this study was to access the genetic diversity, linkage disequilibrium, and population structure of a working panel of Brazilian and several introduced rice accessions, which are currently being phenotyped for a vast number of traits to undergo association mapping. Ninety-four accessions were genotyped with 7098 SNPs, and after filtering for higher call rates and removing rare variants, 93 accessions and 4973 high-quality SNPs remained for subsequent analyses and association studies. The overall mean of the polymorphic information content, heterozygosity, and gene diversity of the SNPs was comparable to other rice panels. The r2 measure of linkage disequilibrium decayed to 0.25 in approximately 150 kb, a slow decay, explained by the autogamous nature of rice and the small size of the panel. Regarding population structure, eight groups were formed according to Bayesian clustering. Principle components and neighbor-joining analyses were able to distinguish part of the groups formed, mainly regarding the sub-species indica and japonica. Our results demonstrate that the population and SNPs are of high quality for association mapping.

Can WRKY transcription factors help plants to overcome environmental challenges?

WRKY transcription factors (TFs) are responsible for the regulation of genes responsive to many plant growth and developmental cues, as well as to biotic and abiotic stresses. The modulation of gene expression by WRKY proteins primarily occurs by DNA binding at specific cis-regulatory elements, the W-box elements, which are short sequences located in the promoter region of certain genes. In addition, their action can occur through interaction with other TFs and the cellular transcription machinery. The current genome sequences available reveal a relatively large number of WRKY genes, reaching hundreds of copies. Recently, functional genomics studies in model plants have enabled the identification of function and mechanism of action of several WRKY TFs in plants. This review addresses the more recent studies in plants regarding the function of WRKY TFs in both model and crop plants for coping with environmental challenges, including a wide variety of abiotic and biotic stresses.

Activation of rice WRKY transcription factors: an army of stress fighting soldiers?

Rice WRKYs comprise a large family of transcription factors and present remarkable structure features and a unique DNA binding site. Their importance in plants goes beyond the response to stressful stimuli, since they participate in hormonal pathways and developmental processes. Indeed, the majority of WRKYs present an independent activation since they are able to perform self-transcriptional regulation. However, some WRKY activation depends on epigenetic and transcript regulation by micro RNAs. Their protein function depends, almost always, on the posttranslational changes. Taking to account its properties of auto-activation, all these regulators process are extremely important for complete WRKY regulation. In this sense, here we provide an overview of transcriptional activation and posttranscriptional and posttranslational regulation of rice WRKY genes under stresses.

Molecular responses to recurrent drought in two contrasting rice genotypes.

MAIN CONCLUSION: The set of variables analyzed as integrated by multivariate analysis of principal components consistently showed a memory effect induced by the drought pre-treatment in AN Cambará plants. The effects of drought can vary ddepending on many factors. Among these the occurrence of a previous water stress may leave a residual effect (memory), influencing the future performance of a plant in response to a new drought event. This study tested the hypothesis that plants experiencing recurrent drought would show more active mechanisms of water deficit tolerance, mainly plants of the genotype that is cultivated often experiencing water shortages periods. Additionally, all the plants subjected to water deficit were rehydrated by 24 h and the expression of transcription factors related to drought responses was re-evaluated. To this end, the water status of two rice genotypes, BRS Querência (flooded) and AN Cambará (dryland), was evaluated to identify molecular alterations likely underpinning drought-memory. In growth stage V5, some plants were exposed to water stress (10% VWC soil moisture-pre-treatment). Thereafter, the pots were rehydrated at the same level as the control pots and maintained under this condition until drought was reapplied (10% VWC) at the reproductive stage (R1-R2). Then, the plants were rehydrated and maintained at pot capacity for 24 h. Overall, the set of variables analyzed integrally by multivariate analysis of principal components consistently showed a memory effect induced by the drought pre-treatment in AN Cambará plants (the dryland genotype). This conclusion, based on data of the biochemical and molecular analyses, was supported by the greater capacity of maintenance of the water status by stomatal regulation of the pre-treated and rehydrated plants after the second drought stimulus.

Stay-green character and its contribution in Brazilian wheats / Caráter stay-green e sua contribuição em trigos brasileiros

The stay-green character has been related to greater stress tolerance and yield through longer activity of the photosynthetic apparatus. Association of this character with grain yield may be linked to a network of features other than the grain mass. This study aimed to shed light on the actual contribution of stay-green character in Brazilian wheats and the associations between grain yield components in different environmental conditions. The experiment was conducted in a randomized block design with three replications in the years 2003, 2004 and 2005. Sibling lines with and without the stay-green character were evaluated analyzing the phenotypic correlation and path analysis separately by year and maturity group. Under favorable growing conditions, the contribution of stay-green character in wheat is obtained by the increased ear fertility and number of grains. In a more restrictive scenario, it favors an increase in grain mass by longer filling time at the end of the cycle.(AU)

O caráter stay-green tem sido relacionado à maior tolerância a estresses e a produtividade pela manutenção mais prolongada do aparato fotossintético. A relação deste caráter com a produtividade de grãos talvez esteja associada a uma rede de características que não somente a massa de grãos. O objetivo do estudo é trazer à luz a real contribuição do caráter stay-green em trigos brasileiros, na relação entre os caracteres definidores da produtividade de grãos, em diferentes condições de ambiente. O experimento foi conduzido em delineamento experimental de blocos casualizados com três repetições, nos anos de 2003, 2004 e 2005. Foram avaliadas linhagens-irmãs com presença e ausência do caráter stay-green, analisando a correlação fenotípica e trilha separadamente por ano e grupo de maturação. Em condições favoráveis de cultivo, a contribuição do caráter stay-green em trigo se dá pelo aumento da fertilidade de espiga, incrementando o número de grãos. Num cenário mais restritivo, favorece a massa de grãos pelo maior tempo de enchimento no final do ciclo.(AU)

Stay-green character and its contribution in Brazilian wheats / Caráter stay-green e sua contribuição em trigos brasileiros

The stay-green character has been related to greater stress tolerance and yield through longer activity of the photosynthetic apparatus. Association of this character with grain yield may be linked to a network of features other than the grain mass. This study aimed to shed light on the actual contribution of stay-green character in Brazilian wheats and the associations between grain yield components in different environmental conditions. The experiment was conducted in a randomized block design with three replications in the years 2003, 2004 and 2005. Sibling lines with and without the stay-green character were evaluated analyzing the phenotypic correlation and path analysis separately by year and maturity group. Under favorable growing conditions, the contribution of stay-green character in wheat is obtained by the increased ear fertility and number of grains. In a more restrictive scenario, it favors an increase in grain mass by longer filling time at the end of the cycle.

O caráter stay-green tem sido relacionado à maior tolerância a estresses e a produtividade pela manutenção mais prolongada do aparato fotossintético. A relação deste caráter com a produtividade de grãos talvez esteja associada a uma rede de características que não somente a massa de grãos. O objetivo do estudo é trazer à luz a real contribuição do caráter stay-green em trigos brasileiros, na relação entre os caracteres definidores da produtividade de grãos, em diferentes condições de ambiente. O experimento foi conduzido em delineamento experimental de blocos casualizados com três repetições, nos anos de 2003, 2004 e 2005. Foram avaliadas linhagens-irmãs com presença e ausência do caráter stay-green, analisando a correlação fenotípica e trilha separadamente por ano e grupo de maturação. Em condições favoráveis de cultivo, a contribuição do caráter stay-green em trigo se dá pelo aumento da fertilidade de espiga, incrementando o número de grãos. Num cenário mais restritivo, favorece a massa de grãos pelo maior tempo de enchimento no final do ciclo.

Evaluation of stability and validation of reference genes for RT-qPCR expression studies in rice plants under water deficit.

Many studies use strategies that allow for the identification of a large number of genes expressed in response to different stress conditions to which the plant is subjected throughout its cycle. In order to obtain accurate and reliable results in gene expression studies, it is necessary to use reference genes, which must have uniform expression in the majority of cells in the organism studied. RNA isolation of leaves and expression analysis in real-time quantitative polymerase chain reaction (RT-qPCR) were carried out. In this study, nine candidate reference genes were tested, actin 11 (ACT11), ubiquitin conjugated to E2 enzyme (UBC-E2), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), beta tubulin (ß-tubulin), eukaryotic initiation factor 4α (eIF-4α), ubiquitin 10 (UBQ10), ubiquitin 5 (UBQ5), aquaporin TIP41 (TIP41-Like) and cyclophilin, in two genotypes of rice, AN Cambará and BRS Querência, with different levels of soil moisture (20%, 10% and recovery) in the vegetative (V5) and reproductive stages (period preceding flowering). Currently, there are different softwares that perform stability analyses and define the most suitable reference genes for a particular study. In this study, we used five different methods: geNorm, BestKeeper, ΔCt method, NormFinder and RefFinder. The results indicate that UBC-E2 and UBQ5 can be used as reference genes in all samples and softwares evaluated. The genes ß-tubulin and eIF-4α, traditionally used as reference genes, along with GAPDH, presented lower stability values. The gene expression of basic leucine zipper (bZIP23 and bZIP72) was used to validate the selected reference genes, demonstrating that the use of an inappropriate reference can induce erroneous results.

Comparative transcriptomics of rice plants under cold, iron, and salt stresses.

Abiotic stresses such as salinity, iron toxicity, and low temperatures are the main limiting factors of rice (Oryza sativa L.) yield. The elucidation of the genes involved in responses to these stresses is extremely important to understand the mechanisms that confer tolerance, as well as for the development of cultivars adapted to these conditions. In this study, the RNA-seq technique was used to compare the transcriptional profile of rice leaves (cv. BRS Querência) in stage V3, exposed to cold, iron, and salt stresses for 24 h. A range of 41 to 51 million reads was aligned, in which a total range of 88.47 to 89.21 % was mapped in the reference genome. For cold stress, 7905 differentially expressed genes (DEGs) were observed, 2092 for salt and 681 for iron stress; 370 of these were common to the three DEG stresses. Functional annotation by software MapMan demonstrated that cold stress usually promoted the greatest changes in the overall metabolism, and an enrichment analysis of overrepresented gene ontology (GO) terms showed that most of them are contained in plastids, ribosome, and chloroplasts. Saline stress induced a more complex interaction network of upregulated overrepresented GO terms with a relatively low number of genes compared with cold stress. Our study demonstrated a high number of differentially expressed genes under cold stress and a greater relationship between salt and iron stress levels. The physiological process most affected at the molecular level by the three stresses seems to be photosynthesis.

Heterosis and genetic parameters for grain quality in oat segregating populations

Improvement of quality-related traits of grains is a constant concern in white oat breeding programs, which challenges breeders to understand their dynamics. The performance of different genetic combinations must be thoroughly evaluated to make high nutritional quality cultivars available. This study aimed to estimate the heterosis on F1 and F2 generations, vigor loss, due to inbreeding, and correlation between the grain chemical components to understand the dynamics of these traits, considering two segregating oat progenies. The populations Albasul × UPF 15 (population 1) and IAC 7 × UFRGS 19 (population 2) were developed. Both populations showed transgressive segregant individuals. The combination Albasul × UPF 15 provided significant heterosis for traits -glucan total and soluble fiber contents, while the population obtained by crossing IAC 7 × UFRGS 19 generated significant gain by heterosis for total fiber, insoluble fibers and non-structural carbohydrate contents. Considering the F2 average for each population, one can observe that population 1 presents higher -glucan and lipid contents than population 2. On the other hand, population 2 has higher protein content than population 1. In both populations, the non-structural carbohydrate content is strongly and negatively correlated whith protein, total and insoluble fibers. Correlations between total fibers and lipids and between total fibers and insoluble fibers were both positive and high in both populations.

Heterosis and genetic parameters for grain quality in oat segregating populations

Improvement of quality-related traits of grains is a constant concern in white oat breeding programs, which challenges breeders to understand their dynamics. The performance of different genetic combinations must be thoroughly evaluated to make high nutritional quality cultivars available. This study aimed to estimate the heterosis on F1 and F2 generations, vigor loss, due to inbreeding, and correlation between the grain chemical components to understand the dynamics of these traits, considering two segregating oat progenies. The populations Albasul × UPF 15 (population 1) and IAC 7 × UFRGS 19 (population 2) were developed. Both populations showed transgressive segregant individuals. The combination Albasul × UPF 15 provided significant heterosis for traits -glucan total and soluble fiber contents, while the population obtained by crossing IAC 7 × UFRGS 19 generated significant gain by heterosis for total fiber, insoluble fibers and non-structural carbohydrate contents. Considering the F2 average for each population, one can observe that population 1 presents higher -glucan and lipid contents than population 2. On the other hand, population 2 has higher protein content than population 1. In both populations, the non-structural carbohydrate content is strongly and negatively correlated whith protein, total and insoluble fibers. Correlations between total fibers and lipids and between total fibers and insoluble fibers were both positive and high in both populations.(AU)