Moacil Alves de Souza

Doses e formas de aplicação de nitrogênio no desenvolvimento e produção da cultura do trigo

Objetivou-se avaliar o efeito de doses e formas de aplicacao de nitrogenio sobre o desempenho e producao de duas cultivares de trigo. O experimento, conduzido em Vicosa-MG, de maio a setembro de 2005, foi instalado segundo um esquema fatorial 2x2x5 no delineamento de blocos casualizados, com quatro repeticoes. Os tratamentos avaliados consistiram da combinacao das cultivares de trigo, BRS 210 e Pioneiro, duas formas de aplicacao de adubo nitrogenado (dose total aplicada por ocasiao da semeadura ou 20 kg ha-1 na semeadura e o restante em cobertura no inicio da fase de perfilhamento) e cinco doses de nitrogenio (40, 60, 80, 100 e 120 kg ha-1) tendo como fonte o sulfato de amonio. A cultivar Pioneiro apresentou maior potencial produtivo que a cultivar BRS 210, mas foi menos resistente ao acamamento. O parcelamento da adubacao nitrogenada proporcionou maior acamamento e nao trouxe beneficios a produtividade dos graos. As doses de N promoveram resposta quadratica da produtividade dos graos, com ponto de maxima estimado na dose de 96,8 kg ha-1 e, aumento linear do acamamento de plantas da cultivar Pioneiro.

Controle genético e tolerância ao estresse de calor em populações híbridas e em cultivares de trigo

n†The objective of this work was to get information about the genetic control of the grain yield under heat stress conditions, the tolerance of cultivar and the identification of promising segrega- tion populations for selections of lines adapted to the conditions of the central region of Brazil. Thir- teen parents and 40 populations in F1 and F2 generations derived by partial diallel crosses were evalu- ated. The experiments were conducted under field conditions in Lavras and Patos de Minas, MG, Brazil, sowing the seeds in the summertime (February) and in the winter (May). There was difference of heat tolerance among parents and hybrid populations for grain yield character, and both additive and non-additive effects were important in the genetic control of grain yield character in the presence or absence of heat. In†spite of the occurrence of populations x sowing time interactions, the high repeat- ability of the effects of the general combining ability suggests the possibility of the selection in the summertime and winter facilitating to advance the breeding programs in the region.

Tamanho de parcelas em experimentos com trigo irrigado sob plantio direto e convencional

Abstract – The objective of this work was to estimate plot size for evaluation of the grain yields of wheat, underirrigated conditions, in no-tillage system and conventional tillage. Each experiment was formed by 30 rows of30 m of length, with spacing of 20 cm among rows and density of 380 seeds/m 2 . The harvest was made in basicunits (bu) of a row meter (0.2 m 2 ), being harvested, in each assay, the central 12-meter of the 24 central rows,totaling 288 bu. The plot size was estimated using the methods of maximum curvature, modified maximum curvature,comparison of variances and method of Hatheway. The plot sizes presented great variation because of themethod used in its estimation. Smaller plots, with larger number of replications, were more efficient in the use ofthe experimental area than larger plots with smaller number of replications. Plots size varying between 1.6 and2.4 m 2 of useful area promoted appropriate evaluation of the grain yields in the different studied conditions. Index terms:

Progresso genético obtido pelo melhoramento do arroz de sequeiro em 21 anos de pesquisa em Minas Gerais

This work aimed to estimate the genetic gain obtained by the upland rice (Oryza sativa L.) breeding program developed in Minas Gerais State, Brazil, in cooperation with Empresa de Pesquisa Agropecuaria de Minas Gerais (Epamig), Embrapa-Centro Nacional de Pesquisa de Arroz e Feijao (CNPAF), Universidade Federal de Lavras (UFLA) and Universidade Federal de Vicosa (UFV), from 1974/75 to 1994/95. Results of the comparative trials of upland rice cultivars and lines conducted over the above quoted period were utilized. Because of irregular rainfall distribuition and the distinctive response of different cycles to climatic conditions, the option was to divide them into two groups, one encompassing the early genotypes and the other those of medium cycle. The achieved result showed that an average genetic gain of 1.26% and 3.37% for the early group and medium cycle, respectively, occurred. In addition, it was found that the early group statistically outyielded (P £0.01) as to grains the medium cycle group, denoting that in Minas Gerais the short cycle cultivars should be preferred.

Genetic and environmental contributions to increased wheat yield in Minas Gerais, Brazil

Producers need wheat cultivars adapted to the predominant climate conditions of the end of the rainy period. Having this in mind, EPAMIG (Agriculture and Livestock Research Institute of Minas Gerais) has been developing a wheat genetic improvement program since 1976, and the estimates of the genetic improvement established by the breeding programs could be useful to quantify their efficiency. This study focused on the quantification of the genetic progress achieved by these improvement programs of dryland wheat in the Brazilian-savanna between 1976 and 2005. The efficiency of these programs was evaluated based on grain yield data of VCU (Value for Cultivation and Use) trials conducted at ten locations in the Minas Gerais State, Brazil. The mean estimated genetic progress for mean grain yield between 1976 and 2005 was 37 kg ha-1 year-1. The genetic yield gain in the study period indicates that the improvement programs of dryland wheat in the Brazilian-savanna are effective. Besides the marked contribution of genetic gain, the environmental and technological improvements were also relevant for the yield, accounting for 47.4% of the total progress in the period. The improvement programs of dryland wheat resulted in a genotype renovation rate of 35% over the years.

Eficiência de fungicidas no controle da brusone em trigo

Wheat blast, caused by the fungus Pyricularia grisea, constitutes one of the major obstacles to the expansion of wheat production in Central Brazil. The aim of this study was to evaluate the efficiency of fungicides in the control of wheat blast. Three fungicides with different active ingredients and combined with four wheat genotypes were used. Two applications of the commercial product were performed in stages 45 and 65 of the scale of Zadoks et al. Artificial inoculation with P. grisea spores was done in stages 58-60 of the above-mentioned scale. The area under the disease progress curve (AUDPC), the severity on flag leaves (SEVFL) and the severity on spikes (SEVEsp) were determined, and grain yield (GY) was quantified. At the end of the experiment, different analyzed parameters were subjected to Pearsons correlation analysis. The fungicides epoxiconazole+pyraclostrobin and tebuconazole+trifloxystrobin provided the lowest AUDPC for the genotypes VI 03061, VI 07505 and BRS 254. There was no difference for SEVFL among genotypes in the presence of fungicides. The genotypes VI 98053 and VI 07505 showed the lowest SEVFL in the absence of fungicide. Tebuconazole+trifloxystrobin provided higher GY and lower SEVEsp. The disease severity on the ears was greater than on flag leaves. Control of wheat blast by means of fungicide application was effective for flag leaves but not for ears.

Estimação de parâmetros genéticos e predição de valor genético aditivo de trigo utilizando modelos mistos

The objective of this work was to estimate the genetic parameters and to predict the genotypic value of populations and individuals from wheat segregating populations, using the methodology of mixed models (restricted maximum likelihood/best linear unbiased prediction, REML/BLUP). Thirty-six wheat segregating populations and four controls were evaluated in the F3 generation, in a randomized complete block design, with individual information taken from within the plots. The evaluated traits were: grain yield, harvest index, number of tillers, and plant height. Genetic variability between populations was observed for all evaluated traits. The mean heritability varied from 39.15 to 92.78%, and accuracy varied from 62.57 to 96.32% in the selection of populations. The narrow-sense individual heritability was low within populations for all traits. The accuracy for individual selection had a moderate value for plant height, and low values for the other traits. Individual heritability contributes to a greater gain for the traits plant height and harvest index with the use of individual BLUP, in comparison to population BLUP. The segregating populations Embrapa22/BRS207, Embrapa22/VI98053, Embrapa22/IVI01041, BRS254/BRS207, BRS254/VI98053, BRS254/UFVT1Pioneiro, and BRS264/BRS207 stand out with high additive genetic value, for two or more traits.

Desempenho de genitores e populações segregantes de trigo sob estresse de calor

A expansao da triticultura para areas com temperaturas mais elevadas, como o Brasil-Central, constitui-se uma das principais medidas para diminuir a importacao de trigo. Assim, genotipos tolerantes ao calor serao de extrema importância para elevar a produtividade desta cultura. Objetivou-se com este trabalho detectar variabilidade genetica para tolerância ao calor, identificar populacoes e genitores mais tolerantes e quantificar o efeito de altas temperaturas sobre estes genotipos de trigo. Foram realizados dois experimentos em Vicosa (MG), utilizando-se o delineamento latice quadrado 16x16 com duas repeticoes, composto por 240 familias oriundas de oito populacoes segregantes mais 16 genitores. No primeiro experimento, semeado em fevereiro de 2007 (verao), foram avaliadas familias F2:4 e no segundo, em junho de 2007 (inverno), familias F2:5. Avaliaram-se os caracteres floracao, altura de planta, producao de graos e massa de mil graos. Diferencas de temperatura da emergencia ao florescimento foram determinantes na resposta dos genotipos entre os ambientes. Detectou-se variabilidade genetica para tolerância ao calor entre genitores e populacoes segregantes de trigo. Todos os caracteres avaliados tiveram reducao sob altas temperaturas, sendo a producao de graos o carater mais afetado, seguido da altura, floracao e massa de mil graos. Os genotipos mais tolerantes ao calor foram os genitores BR 24, Alianca e EP 93541 e as populacoes segregantes BH1146/BR24// Alianca/EP93541, BR24/Alianca//EP93541/CPAC9662 e Alianca/EP93541// CPAC9662/Pioneiro.

Rates of urea with or without urease inhibitor for topdressing wheat

The urease inhibitor NBPT(N-(n-butyl) thiophosphoric triamide) is a management alternative to increase urea efficiency in topdressing because it reduces NH3 volatilization. The objective of this study was to evaluate N recovery and yield performance of wheat ( Triticum aestivum L.) ‘BRS 254’ fertilized with different urea or urea + NBPT rates in topdressing. The experiment was conducted from May to September 2007 in Vicosa, Minas Gerais, Brazil. Treatments followed a 5 × 2 + 1 factorial design consisting of five N fertilizer rates (30, 60, 90, 120, and 150 kg ha-1) as urea or urea + NBPT (Agrotain® ) applied as topdressing and a control without N. The experiment was a randomized complete block design with four replicates. Adding NBPT to urea resulted in better N utilization by wheat plants. The 100 kg N ha-1 topdressing rate provided the best apparent N recovery by wheat plants, whereas 90 kg ha-1 provided the best N use efficiency.

Rates of nitrogen and growth retardant trinexapac-ethyl on wheat

The objective in this study was to evaluate the effects of nitrogen rates in association with rates of the growth retardant trinexapac-ethyl on wheat. The experiment was conducted in Vicosa, MG and arranged in a 5×4 factorial, randomized block design, with four repetitions. A combination of five nitrogen rates (30, 60, 90, 120 and 150kg ha-1) with four rates of trinexapac-ethyl (0, 62.5, 125 and 187.5g ha-1) were tested. Trinexapac-ethyl promotes reduction of soot dry mass and grain yield at the lowest N rates, but at the highest N rates there is increase in these characteristics. The combination between N and trinexapac-ethyl rates that promotes higher shoot dry mass is 150kg ha-1 and 187g ha-1 but that promotes higher grain yield is 100kg ha-1 and 120g ha-1, respectively.