Adaptaciones morfologicas y fisiologicas en plantas de maiz sometidas a deficiencia de oxigeno en el suelo.

El maiz en el Brasil se cultiva normalmente en el verano, cuando lluvias intensas son comunes y la saturacion o encharcamiento del perfil del suelo suele ocurrir. En condiciones de areas bajo riego, despues de la cosecha del arroz, el cultivo del maiz puede sufrir los efectos del encharcamiento por la elevacion del nivel freatico, por lluvias ocasionales y por la infiltracion de los canales de riego. En estas circunstancias, los cultivares que presentan tolerancia al "stress" de oxigeno tienen mayores posibilidades de resistir, minimizando los riesgos de perdidas. El cultivo del maiz ha sido poco estudiado en estas circunstancias y las experiencias actuales muestran que, a pesar de importantes, los trabajos conducidos en el campo con el objetivo de evaluar tolerancia son de dificil ejecucion dado que muchos factores no pueden ser controlados adecuadamente. Considerando la inmensa area del territorio brasileno, potencialmente utilizable para el cultivo del maiz que esta sujeta a deficiencias acasionales de oxigeno, el Centro Nacional de Investigacion de Maiz y Sorgo de la Empresa Brasilena de Investigacion Agropecuaria (CNPMS/EMBRAPA), viene desarrollando trabajos para detectar, cuantificar y manipular adaptaciones morfologicas y fisiologicas en las plantas de maiz sometidas a deficiencia de oxigeno. El presente trabajo tiene por objetivo reunir informaciones basicas sobre sistemas de suelo bajo condiciones de ausencia de oxigeno (anoxia) y, ademas, estudiar la reaccion de las plantas sometidas a esta condicion

Influência do parcelamento de diferentes fontes de nitrogênio no teor de proteína em milho QPM e normal.

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Implications on the introduction of transgenics in Brazilian maize breeding programs.

Transgenic maize was approved in Brazil in 2008/2009. In 2012, it occupied 73% of the country maize growing area. This high adoption rate confirms studies indicating that technology use has been the major driving force in Brazilian agriculture. Maize seed market in the world has been a concentrated sector. Although, when this sector is associated with transgenesis, this concentration increases sharply. In one side, there is the idea that companies can benefit from gains of scale and complementarities to maximize their efficiency in research and development (R&D). On the other side, this concentration may allow the exercise of “market power” by dominant companies. The objective of this study is to analyze the impacts of the adoption of transgenic technology in the arrangements of maize breeding programs and seed production sector in Brazil. A critical analysis of the situation of the breeding programs that do not have this technology is made

A search for RFLP markers to identify genes for aluminum tolerance in maize.

The objective of this study was to identify restriction fragment length polymorphism (RFLP) markers linked to QTLs that control aluminum (Al) tolerance in maize. The strategy used was bulked segregation analysis (BSA) and the genetic material utilized was an F2 population derived from a cross between the Al-susceptible inbred line L53 and Al-tolerant inbred line L1327. Both lines were developed at the National Maize and Sorghum Research Center - CNPMS/EMBRAPA. The F2 population of 1554 individuals was evaluated in a nutrient solution containing a toxic concentration of Al and relative seminal root length (RSRL) was used as a phenotype measured tolerance. The RSRL frequency distribution was continuous, but skewed towards Al-susceptible individuals. Seedlings of the F2 population which scored the highest and the lowest RSRL values were transplanted to the field and subsequently selfed to obtain F3 families. Thirty F3 families (15 Al-susceptible and 15 Al-tolerant) were evaluated in nutrient solution, using an incomplete block design, to identify those with the smallest variances for aluminum tolerance and susceptibility. Six Al-susceptible and five Al-tolerant F3 families were chosen to construct one pool of Al-susceptible individuals, and another of Al-tolerant, herein refered as "bulks", based on average values of RSRL and genetic variance. One hundred and thirteen probes were selected, with an average interval of 30 cM, covering the 10 maize chromosomes. These were tested for their ability to discriminate the parental lines. Fifty-four of these probes were polymorphic, with 46 showing codominance. These probes were hybridized with DNA from the two contrasting bulks. Three RFLPs on chromosome 8 distinguished the bulks on the basis of band intensity. DNA of individuals from the bulks was hybridized with these probes and showed the presence of heterozygous individuals in each bulk. These results suggest that in maize there is a region related to aliminum tolerance on chromosome 8

Avaliação dos conceitos de quantidade e intensidade de mineralização de nitrogenio para trinta solos do Rio Grande do Sul.

Visando testar aplicabilidade do modelo de mineralizacao de N, sugerido por Stanford & Smith, a alguns solos brasileiros, foram utilizados os dados de incubacao por trinta semanas obtidos por Pottker & Tedescoem trinta solos do Rio Grande do Sul. O modelo matematico utilizado parte da premissa de que apenas uma fracao do N total do solo e potencialmente mineralizavel e que esse fenomeno segue uma cinetica de primeira ordem, ou seja: dN/dt=-kN, onde N = N0 e k para os grandes grupos de solos estudados foram avaliados, sendo tecidas consideracoes sobre ambos os fatores. O modelo de mineralizacao ajustou-se perfeitamente aos solos estudados (r2 >0,99). Mesmo dentro dos grandes grupos de solos, a variacao dos valores de N0 e k e grande. A meia-vida da mineralizacao de N a 24 0c foi de 11,6 semanas. Para estimar N0 por meio de regressoes, e vantajoso trabalhar com os grandes grupos de solos isoladamente