José Airton Rodrigues Nunes

Inclusion of genetic relationship information in the pedigree selection method using mixed models

We used a mixed model approach and computer simulation to evaluate the inclusion of parentage information as determined by the genealogy established in the pedigree method. The simulations were based on a purely additive genetic model for one quantitative trait of 20 unlinked segregating loci with equal effects and an allelic frequency of 0.5 for heritability values of 10%, 25%, 50% and 75% for selection based on an F4:5 progeny mean. We simulated 1000 experiments for each heritability value, corresponding to the evaluation of 256 F4:5 progenies. The phenotypic values of the progenies were analyzed according to two models, one ignoring and one considering the additive genetic parentage among the progenies. The additive relationship coefficients among F4:5 progenies ranged from 0.0 to 1.75. The evaluated selection procedures were the phenotypic progeny mean (M) and the best linear unbiased predictor including parentage (BLUPA). The inclusion of parentage among progenies using the BLUPA procedure resulted in higher selection gains than when the relationship information was ignored, which possibly recompenses the additional work invested to obtain these records, above all in the case of low - heritability traits.

Estimation of genetic parameters and selection of Brachiaria humidicola progenies using a selection index

Objetivou-se obter parâmetros geneticos para caracteres agronomicos e de valor nutritivo da folha e do colmo de progenies de Brachiaria humidicola e comparar a selecao das melhores por um indice de selecao aditivo considerando-se apenas os caracteres agronomicos e em conjunto com os principais de valor nutritivo. Avaliaram-se 50 progenies do cruzamento cv. BRS Tupi x H31. O delineamento foi em blocos ao acaso com oito repeticoes. Foram realizados sete cortes em intervalos de 30 a 35 dias no periodo de chuvas e dois com intervalos de 60 dias no periodo seco. Observou-se variabilidade genetica entre progenies para os caracteres. As herdabilidades medias de progenies variaram de 49,14% a 75,56% para caracteres agronomicos e de 19,59% a 71,11%, para os de valor nutritivo. Houve coincidencia de nove das dez melhores progenies quando se usou o indice para somente os caracteres agronomicos ou conjuntamente com os principais caracteres de valor nutritivo.

Diversidade genética entre acessos de espécies cultivadas de pimentas

The knowledge of the genetic diversity among the accessions in germplasm banks it is important for the conservation of genetic resources and the use in breeding programs. This study aimed to evaluate the genetic divergence of 23 accessions of the genus Capsicum, and was based in seven quantitative and nineteen qualitative multicategorical descriptors and using multivariate techniques. The analyses of variance revealed significant difference (P<0.05) among the accessions of peppers for all quantitative descriptors. The coefficient variation ranged from 8,97% (LF) to 30,91% (NFA). The Tocher optimization method detected eight clusters for quantitative descriptors and also in as well as qualitative multicategoric descriptors. The UPGMA method detected three clusters for quantitative descriptors and four clusters within qualitative multicategoricdescriptors. There is genetic diversity inter and intraspecific in germplasm bank of Capsicum coming from The Federal University of Piaui, and these results indicate that there are not duplicated accessions.

Perspectives for the Use of Quantitative Genetics in Breeding of Autogamous Plants

With the increased demand for food, the use of methods and alternatives that increase efficiency in selection of inbred lines is necessary. The use of quantitative genetics plays an important role in this respect, especially when the pedigree method is used in autogamous plants. This study proposes the inclusion of relationship information among progenies using the best linear unbiased predictor (BLUP) to obtain the breeding values of greater accuracy and, consequently, increase genetic gains from the selection. A strategy is proposed that aims to accelerate the program of obtaining perennial plant inbreds and use the greatest amount of information possible in selection so as to attain maximum accuracy. In that way, it would be possible to make inbreds available which are better than the existing ones, with greater frequency, meeting the agribusiness demand involved in production of perennial plants.

Índices de seleção no aprimoramento simultâneo dos componentes da produção de frutos em açaizeiro

The objective of this work was to determine the most appropriate strategy to simultaneously increase fruit production components of assai palm (Euterpe oleracea). An experiment with 25 half-sib progenies was carried out in the county of Santa Isabel, PA, Brazil, using a randomized complete block design with four replicates and five plants per plot. The Smith & Hazel, Williams, and Mulamba & Mocks selection indexes were applied in three selective strategies. The coefficients of genetic variation, heritability, the ratio between the genetic correlation of the trait under selection and fruit yield, and the sum of all genetic correlations between the traits that comprise the index and fruit yield were used as economic weights. Weighting of the correlation ratio allowed the selection indexes to discriminate the best progenies in the different selection strategies evaluated. Simultaneous selection by the Mulamba & Mock index, as to the number of fruiting months, number of bunches harvested, fruit yield, and number of rachilles per bunch, robustly estimates genetic gains.

Estimation of genetic progress after eight cycles of recurrent selection for common bean grain yield

The objective of this study was to estimate the genetic progress of eight cycles of recurrent selection for common bean lines with high yield. The base population was obtained from 10 parents differing in several characters. To date, eight selection cycles have been performed. In each cycle the selection process continues after recombination, until lines are established, which are then evaluated more extensively in the experiment of evaluation of elite lines together with lines of other programs. The genetic progress was estimated based on the data of evaluations of these lines in each cycle over the years. The estimated genetic progress of 3.3 % per cycle allows the conclusion that recurrent selection for grain yield is efficient.

Potencial genético de progênies de feijão-caupi segregantes quanto ao tipo da inflorescência

The objective of this work was to evaluate the genetic yield potential of segregating cowpea progenies regarding inflorescence type. Sixty-eight F4 progenies obtained from the backcrosses (TV x 5058-09C x Curly-purple) x TV x 5058-09C, and (AU94-MOB-816 x Curly-purple) x AU94-MOB-816, with parents, were evaluated. Two experiments were carried out in a randomized complete block design with 17 progenies and four replicates, in a split-plot arrangement regarding inflorescence: simple and composite. The statistical analysis was carried out by mixed models via REML/BLUP procedure. The estimates of genetic variance were significant for all evaluated traits. The traits peduncle length, average number of pods per peduncle, and initial flowering showed high variability and expression of the composite inflorescence genetic component. Progenies with simple inflorescence show similar genetic yield potential to the progenies with composite inflorescence. The progenies resulting from the backcrosses (AU94-MOB-816 x Curly-purple) x AU94-MOB-816 are promising as a strategy to increase the current levels of grain yield in cowpea.

Correlações genéticas e análise de trilha para componentes da produção de frutos de açaizeiro

O conhecimento das correlacoes geneticas entre os principais caracteres utilizados no melhoramento de plantas serve de base para delinear estrategias otimizadas de selecao. O procedimento da analise de trilha permite refinar essas correlacoes, desdobrando-as em efeitos diretos e indiretos sobre o carater principal. O objetivo deste trabalho foi desdobrar as correlacoes geneticas de caracteres relativos ao cacho e a producao de frutos em progenies de meios-irmaos de acaizeiro em efeitos diretos e indiretos sobre a producao total de frutos, a fim de verificar a melhor estrategia de selecao para obtencao de progenies mais produtivas. Foi instalado um experimento com 25 progenies de meios-irmaos em blocos ao acaso, com quatro repeticoes e parcela de cinco plantas. Os dados dos anos agricolas de 2005, 2006 e 2007 foram analisados pelo enfoque de modelos mistos, e as correlacoes geneticas, submetidas a analise de trilha. A producao de frutos correlacionou-se ao numero de meses em producao, numero total de cacho, peso de frutos por cacho e ao numero de raquilas por cacho. No entanto, pela analise de trilha, apenas o peso de frutos por cacho, o numero de cachos e o numero de raquilas por cacho mostram-se como os principais determinantes na variacao da producao de frutos de acaizeiro. Dentre esses caracteres, o numero de raquilas por cacho e o menos influenciado pelo ambiente e, portanto, mais promissor para obter ganhos indiretos na producao total de frutos.

Phenotypic correlations between combining abilities of F2 cowpea populations

Cowpea is a crop that has become socio-economically relevant, mainly in developing countries. Correlation studies are important to determine the association between quantitative traits and yield to guide the selection, i.e., choose direct or indirect selection. The objective was to estimate the correlations between six agronomic traits in cowpea as well as the correlations between the estimates of combining abilities of parents. Genotypes with high pod weight and pod length, 100-grain weight, and number of beans per pod should be used to improve grain yield in cowpea. The breeder should preferably insert plants into his group of crosses that have a high combining ability for pod length, number of grains per pod and yield per plot.

Stratified mass selection of promising Spondias mombin clones in a commercial crop

This study aimed to estimate genetic parameters and identify promising clones of Spondias mombin in ungrafted commercial crop by stratified mass selection, based on the average of two harvests, using mixed models. The base population growing on a private farm in Teresina/PI comprised 82 plants, which were evaluated in the growing seasons 2008 and 2009. Total titratable acidity (TTA), total soluble solids (Brix), Brix/TTA, fruit weight (FW), seed weight (SW), pulp yield (PuY), and processing yield (PrY) were measured. Significant genetic variation among plants was detected for all traits. The coefficients of repeatability were 0.97 (TTA), 0.39 (Brix), 0.86 (Brix/TTA), 0.84 (FW), 0.82 (SW), 0.35 (PuY), and 0.39 (PrY). The chemical were generally not correlated with the physical fruit traits. Ranking by predicted phenotypic values associated with PrY and Brix/TTA identified nine promising plants (PrY>6.9% and Brix/TTA>10).