Soybean [Glycine max (L.) Merril], one of the most important crop species in the world, is very susceptible to abiotic and biotic stress. Soybean plants have developed a variety of molecular mechanisms that help them survive stressful conditions. Hybrid proline-rich proteins (HyPRPs) constitute a family of cell-wall proteins with a variable N-terminal domain and conserved C-terminal domain that is phylogenetically related to non-specific lipid transfer proteins. Members of the HyPRP family are involved in basic cellular processes and their expression and activity are modulated by environmental factors. In this study, microarray analysis and real time RT-qPCR were used to identify putative HyPRP genes in the soybean genome and to assess their expression in different plant tissues. Some of the genes were also analyzed by time-course real time RT-qPCR in response to infection by Phakopsora pachyrhizi, the causal agent of Asian soybean rust disease. Our findings indicate that the time of induction of a defense pathway is crucial in triggering the soybean resistance response to P. pachyrhizi. This is the first study to identify the soybean HyPRP group B family and to analyze disease-responsive GmHyPRP during infection by P. pachyrhizi.

A tolerância ao frio nos estádios iniciais de desenvolvimento do arroz (Oryza sativa L.) é uma característica altamente desejável para incorporar em cultivares do Rio Grande do Sul (RS), porém a seleção para esta característica deve ser feita sob condições de temperatura controlada, o que limita o número de linhas que pode ser avaliada. O conhecimento da herança desta característica é importante para definir estratégias de melhoramento genético, assim o objetivo do presente trabalho é estudar a base genética da tolerância ao frio no estádio vegetativo do arroz. Seis genótipos com reações contrastantes de tolerância ao frio foram cruzados num esquema dialélico sem os recíprocos. Os genitores e as gerações F1 e F2 foram cultivados em casa-de-vegetação até o estádio V4, quando foram submetidos a 10°C por dez dias e avaliados quanto à sobrevivência de plantas após sete dias de recuperação sob temperatura normal. Os resultados obtidos pela análise dialélica da geração F1 indicaram significância tanto dos efeitos aditivos quanto não-aditivos, mas a capacidade geral de combinação foi mais importante. A avaliação da geração F2 revelou uma herança oligogênica com um ou dois alelos dominantes responsáveis pela tolerância ao frio nos genitores tolerantes e dois genes complementares com alelos recessivos segregando nos cruzamentos envolvendo genótipos sensíveis e intermediários.

Rice (Oryza sativa L.) cold tolerance at the initial stages of development is a highly desirable trait to be incorporated into the state of Rio Grande do Sul, Brazil, cultivars, but selection for this trait must be performed under controlled temperature conditions, which limits the number of lines that can be evaluated. Knowledge of the inheritance of this trait is important to define breeding strategies. So the aim of this paper was to study the genetic basis of rice cold tolerance at the vegetative stage. Six genotypes with constrasting cold tolerance reactions were crossed in a diallel scheme without the reciprocals. The parents and the F1 and F2 generations were cultivated in a greenhouse until the V4 stage, when they were submitted to 10°C for ten days and evaluated for plant survival after seven days of recovery under normal temperature. The results obtained by the diallel analysis of the F1 generation indicated significance of both additive and non-additive effects, but the general combining ability was more important. The evaluation of the F2 generation revealed oligogenic inheritance with one or two dominant alleles responsible for cold tolerance in the cold tolerant parents and two complementary genes with recessive alleles segregating in the crosses involving sensitive and intermediate genotypes.

Rice is a tropical plant, so cold temperature may be detrimental to its development, depending on the genotype and environmental conditions. Degree of lipid unsaturation has been related to cold tolerance due to its effect on membrane stability. So, the aim of this study was to characterize the fatty acid composition and its alterations due to cold temperature in rice genotypes of diversified origin. Forty-four rice genotypes at the V4 stage were submitted to two temperature conditions: 10°C and 28°C for two days and after this they had their leaves collected for lipid extraction and quantification. Control plants were allowed to regrow until presenting four leaves fully expanded and then were subjected to 10°C for ten days for cold tolerance evaluation. Plant survival was measured seven days after recovery at 28°C and the genotypes were grouped in three cold tolerance classes: tolerant, intermediate and sensitive. These classes differed for total saturated and unsaturated fatty acids only under the cold temperature treatment. Further analysis of the more abundant fatty acids: linoleic, linolenic and palmitic, showed that the two last ones differed between tolerant and sensitive genotypes. Linolenic acid increased after cold exposure in cold tolerant genotypes while palmitic acid decreased, and an opposite behavior was found in the cold sensitive genotypes. These evidences indicate that these fatty acids are potential molecular markers useful for breeding programs as well as for future basic studies on cold tolerance in rice.