A role for root morphology and related candidate genes in P acquisition efficiency in maize.

Phosphorus (P) is an essential nutrient for plants and is acquired from the rhizosphere solution as inorganic phosphate. P is one of the least available mineral nutrients, particularly in highly weathered, tropical soils, and can substantially limit plant growth. The aim of this work was to study a possible effect of root morphology and the expression pattern of related candidate genes on P efficiency in maize. Our field phenotyping results under low and high P conditions enabled us to identify two contrasting genotypes for P acquisition efficiency that were used for the root traits studies. Root morphology was assessed in a paper pouch system to investigate root traits that could be involved in P acquisition efficiency. The genes, Rtcs, Bk2 and Rth3, which are known to be involved in root morphology, showed higher expression in the P efficient line relative to the P inefficient line. Overall, root traits showed high heritability and a low coefficient of variation. Principal component analysis revealed that out of the 24 root traits analysed, only four root traits were needed to adequately represent the diversity among genotypes. The information generated by this study will be useful for establishing early selection strategies for P efficiency in maize, which are needed to support subsequent molecular and physiological studies.

Development of genetic maps of the citrus varieties 'Murcott' tangor and 'Pera' sweet orange by using fluorescent AFLP markers.

The progeny of 87 BC(1) hybrids of 'Murcott' tangor and 'Pera' sweet orange, genotyped with fluorescent amplified fragment length polymorphism (fAFLP) markers, was used for the construction of genetic maps for both citrus varieties. Mapping strategies, considering the progeny as a result of backcrossing and cross-pollination, were exploited in Mapmaker 2.0 (LOD score >or= 3.0 and or= 3.0 and theta

Efeitos de diferentes técnicas de despendoamento na produção de milho

In order to study the effects of various detasseling practices on seed development and seed production of maize plants, a trial was carried during three growing seasons. This work included five types of detasseling (manual, male-sterile, whorl pull-off, mechanical and control) and three genotypes in their fertile and sterile versions (lines A,B and the hybrid CMS 355). These treatments were combined in a 5x3 factorial design with four replications in a randomized block design. The variables evaluated right after the imposition of the treatments were: plant height, foliar area, and total dry matter. At harvest time ear height, ear index and seed production were evaluated. The results showed that, for field hybrid corn seed production, the use of manual detasseling or sterile-male are the recommended practices. Whorl pull-off and mechanical detasseling negatively affected seed production of maize plants.

Com o objetivo de verificar os efeitos de diferentes tipos de despendoamento no desenvolvimento de plantas e produção de sementes de milho, foi conduzido, um ensaio durante três anos agrícolas. Esse trabalho consistiu de cinco tipos de despendoamento (manual, macho-estéril, arranquio do cartucho, mecânico e testemunha) e três genótipos (linhagens A e B e o híbrido CMS 355), em suas versões férteis e estéreis. Esses tratamentos foram combinados num fatorial 5x3 com quatro repetições, num delineamento experimental de blocos ao acaso. As variáveis avaliadas, após a imposição dos tratamentos foram: altura da planta, área foliar e peso da matéria seca total. Na colheita, foram avaliados: altura de inserção de espiga, índice de espiga e produção de sementes. Os resultados revelaram que num campo de produção de sementes híbridas o despendoamento manual ou o uso de macho-esterilidade são as técnicas recomendadas. Arranquio do cartucho e despendoamento mecânico afetam negativamente a produção de sementes.

EFEITOS DE DIFERENTES TÉCNICAS DE DESPENDOAMENTO NA PRODUÇÃO DE MILHO

In order to study the effects of various detasseling practices on seed development and seed production of maize plants, a trial was carried during three growing seasons. This work included five types of detasseling (manual, male-sterile, whorl pull-off, mechanical and control) and three genotypes in their fertile and sterile versions (lines A,B and the hybrid CMS 355). These treatments were combined in a 5x3 factorial design with four replications in a randomized block design. The variables evaluated right after the imposition of the treatments were: plant height, foliar area, and total dry matter. At harvest time ear height, ear index and seed production were evaluated. The results showed that, for field hybrid corn seed production, the use of manual detasseling or sterile-male are the recommended practices. Whorl pull-off and mechanical detasseling negatively affected seed production of maize plants.

Com o objetivo de verificar os efeitos de diferentes tipos de despendoamento no desenvolvimento de plantas e produção de sementes de milho, foi conduzido, um ensaio durante três anos agrícolas. Esse trabalho consistiu de cinco tipos de despendoamento (manual, macho-estéril, arranquio do cartucho, mecânico e testemunha) e três genótipos (linhagens A e B e o híbrido CMS 355), em suas versões férteis e estéreis. Esses tratamentos foram combinados num fatorial 5x3 com quatro repetições, num delineamento experimental de blocos ao acaso. As variáveis avaliadas, após a imposição dos tratamentos foram: altura da planta, área foliar e peso da matéria seca total. Na colheita, foram avaliados: altura de inserção de espiga, índice de espiga e produção de sementes. Os resultados revelaram que num campo de produção de sementes híbridas o despendoamento manual ou o uso de macho-esterilidade são as técnicas recomendadas. Arranquio do cartucho e despendoamento mecânico afetam negativamente a produção de sementes.