RESUMO
The biggest challenge for the reproduction of flood-irrigated rice is to identify superior genotypes that present development of high-yielding varieties with specific grain qualities, resistance to abiotic and biotic stresses in addition to superior adaptation to the target environment. Thus, the objectives of this study were to propose a multi-trait and multi-environment Bayesian model to estimate genetic parameters for the flood-irrigated rice crop. To this end, twenty-five rice genotypes belonging to the flood-irrigated rice breeding program were evaluated. Grain yield and flowering were evaluated in the agricultural year 2017/2018. The experimental design used in all experiments was a randomized block design with three replications. The Markov Chain Monte Carlo algorithm was used to estimate genetic parameters and genetic values. The flowering is highly heritable by the Bayesian credibility interval: h2 = 0.039-0.80, and 0.02-0.91, environment 1 and 2, respectively. The genetic correlation between traits was significantly different from zero in the two environments (environment 1: -0.80 to 0.74; environment 2: -0.82 to 0.86. The relationship of CVe and CVg higher for flowering in the reduced model (CVg/CVe = 5.83 and 13.98, environments 1 and 2, respectively). For the complete model, this trait presented an estimate of the relative variation index of: CVe = 4.28 and 4.21, environments 1 and 2, respectively. In summary, the multi-trait and multi-environment Bayesian model allowed a reliable estimate of the genetic parameter of flood-irrigated rice. Bayesian analyzes provide robust inference of genetic parameters. Therefore, we recommend this model for genetic evaluation of flood-irrigated rice genotypes, and their generalization, in other crops. Precise estimates of genetic parameters bring new perspectives on the application of Bayesian methods to solve modeling problems in the genetic improvement of flood-irrigated rice.
Assuntos
Oryza , Teorema de Bayes , Grão Comestível , Inundações , Genótipo , Oryza/genética , Fenótipo , Melhoramento Vegetal/métodosRESUMO
Objetivou-se com este trabalho comparar o desempenho de cultivares e linhagens de arroz de terras altas sob plantio direto e convencional. Para tanto, foi conduzido em Lavras-MG um experimento constituído de dois ensaios: um no sistema plantio direto e outro no sistema convencional, nos anos agrícolas 2003/2004 e 2004/2005. Foram testadas 13 cultivares e linhagens de arroz de terras altas. Utilizou-se o delineamento experimental de blocos ao acaso, com três repetições. As variáveis analisadas foram: produtividade de grãos, altura de planta, floração e incidência de doenças. As cultivares e linhagens têm comportamento semelhante para produtividade de grãos nos dois sistemas de cultivo. No sistema plantio direto, há uma tendência de redução na altura de plantas e alongamento do ciclo da cultura, comparado ao sistema convencional. Concluiu-se que, além do sistema convencional, o sistema plantio direto também constitui alternativa viável para a cultura do arroz de terras altas.
This study aimed to compare the performance of upland rice cultivars and rice lineages under no tillage (no-till) and conventional planting system, and to verify the existence of differentiated responses to both tillage systems. Thus, an experiment constituted of two essays, no-till and conventional tillage system was conducted in Lavras, MG, in 2003/2004 and 2004/2005 growing seasons. Thirteen upland rice cultivars and lineages were tested. A randomized block design and three replicates were used. Grain yield, plant height, flowering and disease incidence were analyzed. Rice cultivars and lineages presented similar yield in grains in both tillage systems. In no-till system there was a reduction tendency in plant height, disease incidance and cycle prolongation, as compared to conventional system. Therefore, no-till system is a viable alternative for upland rice crop.
RESUMO
Foram estudados os efeitos de doses e épocas de aplicação de Nitrogênio em arroz de terras altas no sistema de plantio direto sobre a ocorrência de brusone no campo, produção e qualidade sanitária das sementes. O trabalho foi conduzido no ano agrícola de 2001/2002 na fazenda experimental da EPAMIG em Lavras-MG (FELA/CTSM). Pelos resultados obtidos pode-se observar que para a brusone da folha e do fungo Dreschslera oryzae nas sementes houve efeito significativo da interação entre as doses e as épocas de aplicação do N. A brusone do pescoço da panícula foi influenciada pelo parcelamento das aplicações de N, a maior dose de N aplicada na diferenciação do primórdio floral provocou maior severidade da doença. As doses crescentes de N favoreceram a incidência de P. grisea nas sementes e também a produtividade. Para o arroz de terras altas, em caso de parcelamento, deve-se concentrar a maior quantidade de N próximo a diferenciação do primórdio floral, onde o aproveitamento desse elemento é mais eficiente.
Time and rate of nitrogen application on upland rice were studied under no-till systems upon field blast (Pyricularia grisea) occurrence, grain yield and seed sanitary quality. The study was conducted in 2001/2002 at Agriculture and Livestock Research Institute (EPAMIG) Experiment Station at Lavras MG, Brazil. There were significant interactions of leaf blast and Dreschslera oryzae fungi with rate and time of the nitrogen application. Split application of nitrogen affected the panicle neck blast, and the higher the rate of nitrogen applied on primary flower differentiation the greater disease severity. Increased N rates favored seed P.grisea incidence and rice yield. By splitining nitrogen application on upland rice, higher rates should be concentrate next to primary flower differentiation, when the use of this element is more efficient.