Herbaspirillum seropedicae promotes maize growth but fails to control the maize leaf anthracnose.

Herbaspirillum seropedicae is an endophytic diazotrophic bacterium and a plant growth promoting bacteria. Colletotrichum graminicola causes the anthracnose, one of the most destructive maize diseases worldwide. The main objective of this work was to evaluate the effects of H. seropedicae SmR1 strain on the plant growth and leaf anthracnose of maize plants grown in substrate amended or not amended with humic substances. In the first assay, plants were pre-treated with H. seropedicae and inoculated with C. graminicola at 7, 14 and 21 days after treatment (DAT). In the second assay, plants were treated with H. seropedicae, grown in substrate amended with humic substances and inoculated at 3 and 7 DAT. The anthracnose severity was assessed by measurement of necrotic and chlorotic leaf area, and bacteria were quantified in leaves by quantitative PCR. H. seropedicae did not affect the disease severity in maize leaves, although it efficiently colonized the leaf tissues and it promoted maize leaf growth. Humic substances improved H. seropedicae colonization in maize.

Real-time PCR quantification of the plant growth promoting bacteria Herbaspirillum seropedicae strain SmR1 in maize roots.

The plant growth promoting bacteria Herbaspirillum seropedicae SmR1 is an endophytic diazotroph found in several economically important crops. Considering that methods to monitor the plant-bacteria interaction are required, our objective was to develop a real-time PCR method for quantification of PGPB H. seropedicae in the rhizosphere of maize seedlings. Primer pairs were designed, and their specificity was verified using DNA from 12 different bacterial species. Ten standard curves of qPCR assay using HERBAS1 primers and tenfold serial dilutions of H. seropedicae SmR1 DNA were performed, and PCR efficiency of 91 % and correlation coefficient of 0.99 were obtained. H. seropedicae SmR1 limit of detection was 10(1) copies (corresponding to 60.3 fg of bacterial DNA). qPCR assay using HERBAS1 was used to detect and quantify H. seropedicae strain SmR1 in inoculated maize roots, cultivated in vitro and in pots, harvested 1, 4, 7, and 10 days after inoculation. The estimated bacterial DNA copy number per gram of root was in the range 10(7)-10(9) for plants grown in vitro and it was around 10(6) for plants grown in pots. Primer pair HERBAS1 was able to quantify H. seropedicae SmR1, and this assay can be useful for monitoring plant-bacteria interaction.

Existe variabilidade para o caráter tempo de cocção em feijão? depende do erro! / IS there variability for the character of beans cooking time? depends of the error!

O reduzido tempo para a cocção de feijão é uma característica almejada pelos programas de melhoramento. Assim, a técnica empregada para a mensuração do tempo de cozimento deve ser precisa e discriminar os genótipos pelo seu potencial genético. Neste aspecto, este estudo teve como objetivo verificar a existência de variação no método utilizado para determinação do tempo de cocção em feijão. O experimento foi desenvolvido na Universidade do Estado de Santa Catarina, nas dependências do Instituto de Melhoramento e Genética Molecular da UDESC (IMEGEM), no ano de 2009/10. Grãos oriundos de 36 populações mutantes de feijão foram submetidos ao teste de cocção por meio do aparelho cozedor de Mattson, com duas repetições por unidade experimental. Os dados foram analisados considerando três modelos estatísticos: i) especificando informações referentes ao erro experimental; ii) ao erro de amostragem e; iii) considerando as repetições como um fator de variação. Foram empregados três tipos de resíduos nas análises, sendo, o erro total, o erro experimental e o erro de amostragem. Para o mesmo conjunto de dados, resultados discrepantes foram gerados com a utilização de diferentes resíduos, evidenciando a necessidade de rigor nas especificações dos modelos estatísticos e na escolha do resíduo apropriado para testar as hipóteses. A técnica empregada para a avaliação do tempo de cocção apresentou variação intrínseca ao método, sendo necessária a utilização de repetições dentro da unidade experimental para estimar o erro de amostragem e purificar o erro experimental.

The lower cooking time for common bean is a characteristic desired by breeding programs. Thus, the technique used to measure the cooking time must be precise and efficient for the differentiation of genotypes for their genetic potential. The objective of this study was to verify the existence of variation in the method used to determination the bean cooking time. The experiment was developed in Universidade do Estado de Santa Catarina - UDESC (Santa Catarina State University - Brazil), in the premises of Instituto de Melhoramento e Genética Molecular (IMEGEM) - Molecular Genetics and Breeding Institute, in 2009/10. The grains from thirty six mutant common bean populations were subjected to the cooking test using the Mattson cooker apparatus, with two replications each experimental unit. The data were analyzed using three statistics models: i) specifying information related to experimental error; ii) to the sampling error and; iii) considering the replications as a variation factor. Three types of error were used in the statistics analysis (total error, experimental error and sampling error). Different results were obtained with use of three types of error for the same data set, shown the need of criterion about specification of statistics models and choice of appropriate error for testing the hypotheses. The technique used to evaluation of the bean cooking time showed intrinsic variation, being necessary to use the replications within the experimental unit to estimate the sampling error and purify the experimental error.