Presence Of Genetic Variability Research Articles

Heterosis Studies in Bitter Gourd

ABSTRACTImprovement in yield quantity and quality of bitter gourd, Momordica charantia L., cannot be accomplished through traditional methods. Heterosis breeding may be used to achieve this goal. A partial diallel mating design was used to evaluate standard heterosis to increase yield and quality by identification of a unique cross combination with desirable heterosis in bitter gourd. Five parents and 16 hybrids were evaluated from Oct. 2009 to Mar. 2010. Heterotic vigor was present for earliness, yield, and quality characters among hybrids. Significant differences for all characters indicated presence of genetic variability. The heterosis was negative for days to first harvest, fruit length and diameter, and single fruit weight and positive for number of fruit/plant and fruit yield/plant. Average fruit weight ranged from 115 to 249 g; the heaviest fruit were from hybrids from the crosses P1 × P3, P2 × P3, P3 × P1, P3 × P5, and P5 × P2; hybrids from the crosses P3 × P4, P4 × P3, and P5 × P4 had the smallest fruit. The longest fruit were from hybrids from the crosses P3 × P1, P2 × P3, and P1 × P3; the shortest fruit were from hybrids from the crosses P4 × P3, P4 × P2, and P3 × P4. The highest yield was from the hybrid from the cross P3 × P5 followed by hybrids from the crosses P4 × P1 and P4 × P3. Hybrids from crosses P5 × P4, P3 × P5, and P2 × P5 had 102%, 82.6%, and 82.4% higher heterosis over the better parent, respectively, for fruit yield/plant. Based on yield contributing characters and heterotic performance hybrids from crosses P5 × P4, P3 × P5, and P2 × P5 can be used to exploit develop improved commercial lines.

<b>Adaptability and stability of strawberry cultivars using a mixed model

Although strawberry crops have a strong socio-economic impact on the agricultural sector of Espirito Santo State, there are few studies on the performance of strawberry cultivars in different locations and years under a low tunnel management system (LT). Therefore, this study aimed to estimate the parameters of adaptability and stability of strawberry cultivars under LT-protected cultivation using the harmonic mean of the relative performance of genetically predicted values. Seven strawberry cultivars were assessed (‘Dover’, ‘Camino Real’, ‘Ventana’, ‘Camarosa’, ‘Seascape’, ‘Diamante’ and ‘Aromas’) in the agricultural years 2006/7, 2007/8 and 2008/9 in three locations in the mountainous region of Espirito Santo State. The experiment was arranged in a randomized block design, with 3 replications and 15 plants per plot. The analysis of deviance for the yield (ton. ha -1 ) demonstrated that only the effects of genotype and the triple interaction genotype x location x year were significant, which indicates the presence of genetic variability among the cultivars and the inconsistency of the position among the genotypes for combinations of year and location. Considering the selection for yield, adaptability and stability, in LT-protected cultivation, cultivars Camarosa and Aromas are highlighted for expressing average values that were 22% higher than the overall mean of the cultivars (24.55 ton. ha -1 ) in the environments assessed.

20EVALUATION OF YIELD AND ITS COMPONENTS FOR SIXTEEN FLAX GENOTYPES UNDER NORMAL AND SANDY SOIL CONDITIONS

The present investigation was conducted using sixteen flax genotypes, thirteen local lines and three commercial varieties (Giza 8, Sakha 1 and Sakha 3) as check. These sixteen genotypes were evaluated in two successive seasons (2012/2013 and 2013/14) at two locations viz: Giza Exp. Station, Giza Governorate (normal soil) and Ismailia Exp. Station, Ismailia Governorate (sandy soil). The experimental design was randomized complete block with three replications per each of the four environments (combination of locations x years). Mean squares due to genotypes (G) showed highly significant for all characters, indicating the presence of genetic variability among the tested genotypes for all traits under study. Mean squares due to locations (L) differed highly significantly for all traits except no. of seeds per capsule, indicating a wide range of variation between the two locations under study. Mean squares due to GL interaction were comparable in magnitude to those of GY for straw, long fiber yields per fad, plant height, technical stem length, seed yield per fad, oil yield per fad, 1000-seed weight and no. of capsules per plant, indicating that location had the major effect on the relative genotypic potential of these treats. This means that for reliable evaluation of the previous traits it would certainly be necessary to test genotypes in more than multi-location testing. Interaction components variances (σ2gl, σ2gy and σ2gly) were less than the genotypic variance (σ2g) for all characters. This means that genotypes differ in their genetic potential for these traits. This was reflected in high heritability in broad sense and low discrepancy between phenotypic and genotypic coefficients of variability specially for long fiber percentage, plant height, technical stem length, 1000-seed weight, no. of capsules per plant and oil percentage. These results indicating the possibility of using both of plant height and technical stem length as selection indices for improving straw weight per plant and using both of 1000-seed weight and no. of capsules per plant for improving seed weight per plant. S.541-D/10 and S.541-C/3 proved maximum mean performance for straw, long fiber yields per fed, plant height and technical stem length as well as long fiber percentage when compared with the three check varieties, Giza 8, Sakha 1 and Sakha 3. Also, S.541-C/3 and S.541-D/10 exhibited high tolerance to sandy soil conditions for both straw yield per fed and fiber yield per fad. Therefore the two promising lines, S.541-C/3 and S.541-D/10 may be consider good substitutes for the low yielding ones, Giza 8, Sakha 1 and Sakha 3 in future as a new Egyptian flax cultivars for both straw and fiber yields. Also, S.541-C/3, S.541-D/10 and Sakha1 exhibited highest values for seed yield per fad, oil yield per fad, seed weight per plant and 1000-seed weight than other genotypes. It can be concluded that, S.541-D/10 gave high yielding ability for seed yield/fad, oil yield per fad, seed weight per plant and oil percentage with moderate tolerant to drought. Although, the promising flax line S.541-C/3 gave high mean performance for seed yield per fad, oil yield per fad, seed weight per plant and oil percentage but exhibited low tolerant to sandy soil conditions.

Heterosis and General Combining Ability Study on Heat Tolerant Tomato (Lycopersicon esculentum Mill)

A study was carried out to estimate heterosis and general combining ability on heat tolerant tomato ( Lycopersicon escullentum Mill). The experiment was conducted at the Teaching and Research Farm of Department of Crop Production and Horticulture Modibbo Adama University of Technology, Yola. (latitude 9o18′N) gene action governing inheritance of characters in tomato ( Lycopersicon escullentum Mill) under high temperature stress. The experiment was conducted at the Teaching and Research Farm of Department of Crop Production and Horticulture Modibbo Adama University of Technology, Yola. (latitude 9o 18'N and long 12o 15'E) and the Teaching and Research Farm of Adamawa State University, Mubi (latitude 10o 03'N and long. 13o 07'E) all in Adamawa state of Nigeria. Fourteen entries consisting of six parents and eight crosses developed by crossing two males (testers) and four females (lines) following line x tester design were evaluated in three replications in a Randomized Complete Block Design (RCBD) in two locations. Ten plants where randomly sampled for recorded observation. Data were collected from the following characters; trichome count, plant height at 60DAT, number of leaves per plant at 60DAT, number of fruits per plant, weight of fruits per plant % damaged fruits and number of days to final harvest. Data were subjected to biometrical analysis. Result of the analysis of variance indicated highly significant difference for all characters among entries except weight of fruits per plant. The result suggested the presence of genetic variability among the tomato genotypes under study. Significant difference were observed in the combining ability analysis of variance in all the agronomic characters under study except for trichome count suggesting both additive and non-additive genetic effects were important in governing this characters under study with more preponderance of additive effects. The cultivars, Cherry, Currant, UC28B and RomaVF were identified as the best general combiners and the best yielders in terms of number of fruits per plant with appreciable tolerance to heat damage. N and long 12o 15′E) and the Teaching and Research Farm of Adamawa State University, Mubi (latitude 10o 03′N and long. 13o 07′E) all in Adamawa state of Nigeria. Fourteen entries consisting of six parents and eight crosses developed by crossing two males (testers) and four females (lines) following line x tester design were evaluated in a Randomized Complete Block Design (RCBD) with three replications. Ten plants where randomly sampled for recorded observation. Data were collected on Trichome count, plant height at 60DAT, number of leaves per plant at 60DAT, number of fruits per plant, weight of fruits per plant % damaged fruits and number of days to final harvest. Data were subjected to biometrical analysis. Result of the analysis of variance indicated highly significant difference for all characters among entries except weight of fruits per plant. The result suggested the presence of genetic variability among the tomato genotypes under study. Significant difference were observed in the combining ability analysis of variance in all the agronomic characters under study except for trichome count suggesting both additive and non-additive genetic effects were important in governing this characters under study with more preponderance of additive effects. The cultivars, Cherry, Currant, UC28B, and RomaVF were identified as the best general combiners and the best yielders in terms of number of fruits per plant with appreciable tolerance to heat damage. However, Currant x Roma vf and Cherry x Golden roma exhibited some level of heterosis in number of leaves, number of flower clusters, number of fruits per plant and plant height. Cherry and Currant, though identified as having highest performance in all characters under study are not commercially acceptable but could be utilized in breeding programs for improvement of tomatoes with required agronomic characteristics. However, UC28B, Roma vf and Golden roma are genotypes that have shown greater performances in all the agronomic characters which could be used for commercial cultivation. Furthermore, Currant x Roma vf and Cherry x Golden roma are desirable segregates that can be used to develop improved tomatoes with required agronomic characteristics through recurrent selection by backcrossing.

Studies on variability, heritability and genetic advance for quantitative traits in black gram [Vigna mungo(L.) Hepper

The present investigation was carried out with 57 genotypes including 42 F1 hybrids and their 17 parents (14 lines and 3 testers) for 14 quantitative characters at Hayathnagar Research Farm, CRIDA Hyderabad during Rabi 2013 to assess the variability, heritability and genetic advance in black gram (Vigna mungo (L.) Hepper). The analysis of variance revealed highly significant differences for all the 14 characters indicating presence of genetic variability among lines, testers and hybrids. The highest GCV and PCV were recorded for pod weight followed by pods per plant, seeds per plant, seed yield and plant height. The high heritability along with high genetic advance recorded for plant height, pod weight, seed yield and total biomass. The above traits can be used as selection criteria in black gram breeding programme to improve yield in blackgram.

Multivariate Analysis of Vegetative and Physiological Traits in Oil Palm (Elaies guineensis Jacq) Germplasm

Multivariate Analysis of Vegetative and Physiological Traits in Oil Palm (Elaies guineensis Jacq) Germplasm Germplasm materials provide an opportunity for tapping advantages of natural diversity for improvement. Adequate characterization for agronomic and morphological traits is necessary to ease utilization of germplasm materials by breeders. Genetic variability among 44 oil palm germplasm populations located at the Malaysian Palm Oil Board was studied based on 18 morpho-physiological traits. Data collected on the morphp-physiological traits were subjected to two multivariate analyses viz principal component analysis and clustering analysis. The result from the analysis showed that the first three PCs with Eigenvalue greater than one (>1) accounted for 90.79% of the total variation with morphological traits being the most important characters on PC 1. Distribution pattern of the germplasm materials into three clusters using Ward’s method indicated the presence of genetic variability for most of the traits studied. The mean values of characters dominant on PC 1 was highest in cluster 1 while cluster 3 had the least mean values for these traits. The selection of these traits and palms with the desired traits could enhance oil palm improvement. Furthermore, there was lack of relationship between genetic distance and geographical origin among the oil palm germplasm..

Assessment of immature embryo culture to select for drought tolerance in bread wheat

In order to evaluate the response of bread wheat genotypes to callus induction and in vitro drought stress, an investigation was carried out as a factorial experiment with a completely randomized design and five replications. The results of analysis of variance indicated significant differences between the entries and stress levels for callus relative growth (CRG), callus relative growth rate (CRGR), callus growth rate (CGR), percentage of callus chlorosis (PCCH) and percentage of callus water content (PCWC) indicating the presence of genetic variability, different responses of genotypes to different drought intensities and invitro selection of droughttolerant genotypes. Mean comparisons between genotypes revealed that maximum CRG, CGR, CRGR, PCWG, PCCH and INTOL were attributed to genotypes 5, 16, 17, 2, 3 and 20 (drought tolerant), respectively. Graphic observation exhibited that indices of drought tolerance decreased with increase of PEG concentrations. Cluster analysis of genotypes (Ward’s method) based on CRG, CGR, CRGR, PCWG, PCCH and INTOL and subsequent discriminant analysis for confirming the number of clusters, grouped the genotypes into four different clusters. The first group included genotypes 1, 3, 6, 7, 12, 13 and 18, the second group included genotypes 2, 4, 8, 9, 10 and 11 and the third group consisted of genotypes 14, 16, 17, 19 and 20, while the genotype 15 formed the fourth group. Superior genotypes 2, 5 and 16 showed drought tolerance at the callus culture level together with their high potential for callus induction leaded us to the conclusion that a hybridization breeding program using these superior plant materials supplemented with in vitro selection for drought tolerance might be beneficial for improvement drought tolerance in bread wheat.

Dissimilaridade genética em variedades de Artemisia annua L. embasada em caracteres agronômicos, fisiológicos e fitoquímicos

O presente estudo objetivou estimar a variabilidade genética existente entre caracteres agronômicos, fisiológicos e fitoquímicos em variedades de A. annua. O delineamento experimental foi inteiramente casualizado e os tratamentos foram as variedades Artemis, 2/39x5x3M, e 2/39x1V de A. annua, submetidas a avaliações agronômicas, fisiológicas e fitoquímicas. Para a realização das estimativas de distância genética foram geradas matrizes de dissimilaridade utilizando a distância Euclidiana e os métodos de agrupamento de Tocher e UPGMA. Além disso, avaliou-se a importância relativa dos caracteres para divergência genética pelo método de Singh. As análises foram realizadas pelo software Genes e os dendrogramas obtidos pelo NTSYS. A presença de variabilidade genética dentro das variedades permitiu a identificação de acessos dissimilares e com média elevada para as características estudadas. O número de ramificações, concentração intracelular de CO2, e o rendimento de óleo essencial foram os caracteres que mais contribuíram para a dissimilaridade genética de A. annua. Os acessos B24, C5 e C32 foram os mais promissores dentro das variedades e devem ser conservados para futuras hibridações, sendo que as hibridações mais promissoras na obtenção de populações segregantes desejadas são B24 x C5, B24 x C32 e C5 x C32.

Caracterização morfológica e molecular de genótipos de mangaba

O objetivo do trabalho foi verificar a divergência genética entre 25 genótipos de mangaba da região de Iramaia-Chapada Diamantina-Bahia, utilizando os marcadores morfológicos e os marcadores RAPD. As seguintes aferições foram realizadas nos frutos maduros: diâmetro longitudinal (DL) e transversal (DT), massas do fruto (MF), da semente (MS) e da polpa (MP), rendimento de polpa (%P) e a contagem do número de sementes (NS). Os caracteres químicos avaliados no fruto maduro foram: pH, acidez (Ac), sólidos solúveis totais (SST), ácido ascórbico (AA), açúcar total (ACT) açúcar redutor (ACR), açúcar não redutor (ACNR) e relação sólidos solúveis totais: acidez (SST/Ac). Para a amplificação, foram testados 51 random primers. Os resultados médios das aferições foram: DL (37,03 mm), DT (34,34 mm), MF (24,45 g), MS (2,42 g), MP (22,03 g), e NS (11,14). Para as avaliações químicas, foram verificados os resultados médios: %P (88,44%), AA (80,23 mg 100 g-1), Ac (0,96%), pH (3,67), SST (14,15 ºBrix), ACT (9,26 mg 100 g-1), ACR (5,13 mg 100 g-1), ACNR (4,13 mg 100g-1) e SST/Ac (14,56 mg 100g-1). Oito random primers foram selecionados por apresentarem bandas mais intensas, e seis (OPA 08, OPB 12, OPB 19, OPH 15, OPH 18 e OPH 19) geraram 28 regiões de bandas polimórficas. Dentre os marcadores morfológicos, MF e MP foram os que mais efetivamente contribuíram para a divergência genética. A formação de seis e sete grupos para os marcadores moleculares e morfológicos, respectivamente, indicou a presença de variabilidade genética na população avaliada.

Repeatability of drought tolerance indices in chickpea genotypes over stress and non-stress environments

To evaluate the repeatability of yield-based drought tolerance indices over years, twenty chickpea genotypes were evaluated using a randomized complete block design with three replications for four cropping seasons (2008–2012) in the experimental field of Razi University. The result of combined analysis of variance for seed yield showed significant differences for location (L) (rain-fed and irrigated), genotype (G), and LY and GL interactions, indicating the presence of genetic variability and the possibility of selection for stable, drought-tolerant genotypes. Principal component analysis (PCA) based on the Spearman's rank correlation matrix was used to visualize the relationships between different drought tolerance indices. Due to their positive significant correlation with seed yield under both conditions over four cropping seasons, the stress tolerance index (STI) and geometric mean productivity (GMP) were identified as desirable criteria for the selection of drought-tolerant genotypes under severe stress conditions. The selection of drought-tolerant chickpea genotypes using these indices in a one-year trial will mirror the results of multiple cropping season trials. According to the Spearman's rank correlation coefficients between single vs. single years and single vs. the mean of multiple years, the tolerance index (TOL), mean productivity (MP), abiotic tolerance index (ATI), stress susceptibility percentage index (SSPI) and modified stress tolerance index (K1STI) were identified as repeatable indices under severe drought conditions.

Caracterização e divergência genética de acessos de Passiflora edulis e P. cincinnata com base em características físicas e químicas de frutos

A caracterização tem sido efetuada em Coleções de Germoplasma, gerando informações sobre a descrição e a classificação do material conservado, para subsidiar programas de melhoramento genético, por identificar indivíduos desejáveis e quantificar a diversidade disponível. Neste trabalho, objetivou-se caracterizar e quantificar a divergência genética de acessos de Passiflora edulis e P. cincinnata com base em características físicas e químicas de fruto. O material genético utilizado constou de seis acessos provenientes do Banco de Germoplasma da Universidade Estadual Paulista, Câmpus de Jaboticabal-SP. Os frutos foram avaliados com relação às características físicas: peso, tamanho e diâmetro do fruto, espessura da casca, número de sementes e rendimento de suco; e químicas: teor de sólidos solúveis e acidez total titulável. Os seis acessos diferiram com relação a todos os caracteres avaliados, indicando a presença de variabilidade genética e, consequentemente, a possibilidade de obtenção de ganhos genéticos com a seleção de genótipos superiores. A divergência genética entre os acessos foi analisada pelo método de agrupamento de Tocher, com o emprego da distância de Mahalanobis, como medida de dissimilaridade, formando-se dois grupos. As estimativas das correlações genéticas positivas mais elevadas, associadas ao rendimento de suco, foram com número de sementes/fruto, diâmetro do fruto, comprimento do fruto e peso do fruto. O método de Singh, utilizado para estimar a contribuição relativa de cada caráter na expressão da divergência genética entre os seis acessos, mostrou que o tamanho do fruto e o rendimento de suco foram as características que mais contribuíram, e que acidez total titulável apresentou menor contribuição.

Genetic divergence among soybean cultivars in irrigated lowland in the State of Tocantins

In order to evaluate the genetic divergence among soybean cultivars, an assay was carried out at Formoso do Araguaia, TO, Brazil, in off-season of 2007, in irrigated lowland conditions. The experimental design were randomized blocks with 12 treatments and three replications. Genetic divergence was evaluated by multivariate procedures: Mahalanobis distance, Tocher clustering method's and nearest neighbor method. It was observed the formation of two distinct groups by the dendrogram of genetic dissimilarity, which were identical to those groups formed by Tocher's method. The Tocher optimization method and the nearest neighbor agreed among themselves. The traits number of days to maturity, plant height and weight of 100 seed were the ones that most contributed for genetic dissimilarity. The presence of genetic variability allowed the identification of dissimilar cultivars with high average for the evaluated traits. The hybridations 'DOKO' x 'CONQUEST' and 'DOKO' x 'FT-2000' are promising to obtain segregating populations with high variability

Genetic variability among soybean cultivars, under different edaphoclimatic conditions, in center south region of the state of Tocantins

In order to evaluate the genetic divergence between twelve soybean cultivars, the essays were carried out at Formoso do Araguaia, TO, in the inter-cropping 2007. The soybean cultivars studied were DM Vitoria, MG/BR 46 (Conquista), Suprema, BRS Pintado, DM 247, BRS MG 68, BRS MG Lideranca, BRS MG Seguranca, DM 339, BRS MG Garantia, A 7002 e DM 309. Genetic divergence was evaluated by multivariate procedures: generalized Mahalanobis distance, the grouping optimization method of Tocher, nearest neighbor and the technique of canonical variables. It was evaluated the following characteristics: grain production per plant, number of seeds per pod, number of pods per plant, number of days for blooming; number of days for maturation, plant height and height of first pod insertion. The methods of optimization of Tocher, nearest neighbor and graphic dispersion of the canonical variables were consistent with each other. The characteristics number of days for the maturation (39.49%), weigh of 100 seeds (26.56%) and number of days for flowering (13.59%) were the ones that more contributed to the genetic dissimilarity among the twelve cultivate tested. The presence of genetic variability allowed the identification of dissimilar cultivars and with high average for the studied characteristics. The hybrids BRSMG Garantia x DM 339 and BRSMG Garantia x MG/BR 46 (Conquista) are promising for obtaining segregating populations with superior variability.

Common bean lines as potential differential cultivars for race 65 of Colletorichum lindemuthianum.

Colletotrichum lindemuthianum, which is known for its wide diversity in virulence, is the causal agent of anthracnose of common bean (Phaseolus vulgaris). Studies of race characterization using the standard set of 12 differential cultivars have shown the predominance of race 65 in Minas Gerais state (Brazil). However, the presence of genetic variability within race 65 has complicated the development of a durable resistant bean cultivar. Therefore, the objective of this study was to identify common bean lines able to differentiate the variation within race 65 to complement the results of the standard set of differential cultivars. A total of 12 common bean lines adapted to Brazilian conditions and 12 fungal isolates classified as race 65 were used. We now propose a new nomenclature to identify the pathogenic variability of race 65 isolates. Using this methodology, five different reaction patterns were observed, allowing the differentiation of regionally important races that could not be discriminated using the standard set of differential cultivars. Furthermore, our approach makes it possible the identification of new genes and sources of resistance to anthracnose.

Divergência genética entre linhagens de melão pele de Sapo

The objective of this work was to study the genetic divergence among lines of Pele de Sapo melon evaluated in Mossoro-RN, Brazil. Twenty lines were evaluated in a randomized block design with three replications. The genetic divergence was evaluated by multivariate procedures: generalized distance of Mahalanobis, methods of grouping optimization of Tocher and UPGMA. The traits assessed were: The traits evaluated were: total number of fruits, productivity, average weight of fruits, transversal diameter, diameter longitudinal, format index, internal cavity, pulp thickness, pulp firmness, soluble solids content, concentration of harvesting and weight loss. There was partial concordance regarding the composition of the groups formed by the methods of optimizing Tocher and UPGMA. The traits that most contributed to the divergence have been pulp firmness (20.69%) and soluble solids (10.94%). The presence of genetic variability allowed the identification of cultivars dissimilar and with a mean high for the traits studied. The crosses suggested in the study of genetics divergence were: SA-13 x TH-03, SA-13 x TH-04, SA-13 x TH-05, SA-13 x TH-07, SA-13 x TH-09, SA-13 x SA-17, TH-05 x TH-04, TH-05 x SA-10, TH-05 x SA-12, TH-05 x SA-14 and TH-05 x SA-14.

Prediction of genetic gains from selection in Arabica coffee progenies

Gains from selection for yield were estimated in Arabica coffee progenies carrying rust-resistance genes. The experiment in augmented block design was installed in Três Pontas, state of Minas Gerais. Three blocks were established with six plants per plot, spaced 3.50 x 0.90 m, in 96 regular (F2 progenies) and two control treatments. The plant response to rust was evaluated on a grade scale in 2008. Yield (bags per hectare) was estimated in the growing seasons 2005 to 2008. Significant differences between treatments for yield were observed in all harvests, except 2005. The presence of genetic variability among progenies allowed significant gain from selection for yield. Under the experimental conditions of this study, selection for yield can be performed in the first high-yield year, without major losses compared to genetic gain from selection for yield when based on the mean of four harvests.

Predição de ganhos genéticos utilizando o Delineamento I em população de maracujazeiro

This study aimed to evaluate the potential population of passion for agronomic traits and to estimate genetic parameters for prediction of earnings. And still evaluating responses to selection and the earnings from the alternative selection. Were studied in this work, alternative selection of Design I in passion fruit: selection among males, females and males (all males) among females (independent of males), females and males selected, and combined selection. This disclosed the presence of genetic variability in the population, which is quite favorable to the improvement in that the genetic heterogeneity possible to obtain gains through selection. In all production characteristics evaluated, the combined selection (CS) was the one that gave greater selection gains.

Tamanho de grão comercial em cultivares de feijoeiro

Os objetivos do trabalho foram avaliar e indicar parâmetros de seleção para classificação de grãos de feijão que atendam as exigências do mercado consumidor. Foram instalados experimentos contendo 19 genótipos de feijoeiro em nove ambientes, no Estado de São Paulo. A produção de grãos foi estratificada em peneiras de classificação 10 (10/64" pol.) a 15 (15/64" pol.) e avaliada a produção relativa de grãos em peneiras 13 e 14, rendimento de peneira, massa de 1.000 grãos, tamanho de grãos e para os índices J=perfil e H=forma do grão. A produção relativa de grãos, rendimento de peneira, forma e perfil foram as características que apresentaram diferenças estatísticas significativas, indicando presença de variabilidade genética. Por meio da comparação dos resultados com testemunhas de feijoeiro já recomendadas para o setor produtivo, conclui-se que uma cultivar de feijoeiro deve apresentar alta massa de 1.000 grãos (251 a 300g), produção relativa de grãos em peneiras 13 e 14 com valores acima de sete, rendimento de peneira acima de 70,0% e também sementes elípticas e perfil semiachatado.

Germplasm evaluation and enhancement for the development of cowpea (Vigna unguiculata (L.) Walp) dual-purpose F2 genotypes.

Cowpea is an important grain legume as well as fodder crop, especially in the dry regions of South Africa. The production of this crop has been below average because of low genetic variation and cultivation of poor-yielding varieties which have not been improved. The potentials of cowpea F2 generation arising from crosses made from 55 exotic parental lines, introduced into South Africa were determined. F1 lines derived from the crosses were advanced to F2 lines in the glass-house, and the segregating F2 families were further evaluated in the field with their parental lines. The following data were collected from the progeny: number of pods per plant, 100 seed-weights, fodder yield, grain yield and harvest index. Results showed that F2 lines exhibited significant differences on all the parameters studied thus indicating the presence of genetic variability among the segregating progeny. Number of pods per plant, 100 seed-weight and harvest index showed higher significant differences. The F2 lines obtained a significant increase in number of pods per plant as compared to their parents, thus indicating the potentials of progeny for higher pod production. Harvest index for F2 lines varied between 0.16 and 0.60 (dual-purpose type), and are mostly medium cowpea types with dual purpose characteristics for producing grain for human consumption and fodder for livestock. These parameters should therefore receive highest priority in developing high yielding dual-purpose varieties. There are several promising F2 progenies which performed exceedingly well over the parents, so further screening is essential until their full potential is attained. Key words: Vigna unguiculata, germplasm, harvest index, dual-purpose, 100 seed-weights, segregating population.

Predicting the genetic gain in the Brazilian white maize landrace

The objectives of this research were to evaluate the genetic variability and predict genetic gain in the white maize landrace rescued in Barbacena, Minas Gerais, Brazil. The Brazilian maize landraces have economic and social importance for certain areas in Brazil, and research on this germplasm is very important for local food security. Three experiments were carried out with 100 half-sib progenies, in Campos dos Goytacazes, RJ, Coimbra and Barbacena, Minas Gerais, Brazil. These sites were chosen for their soil and climatic differences. An analysis of variance was significant among the progeny for all characters, indicating the presence of genetic variability between the three populations. In Campos dos Goytacazes and Coimbra, the genetic variation of the white maize landrace was responsible for most of the phenotypic variance in grain yield and can be used in selection cycles. There was no significant genetic variance in grain yield in Barbacena. For the white maize landrace it was concluded that: the characters of the component of productivity such as plant density and number of plants with kernels can produce indirect genetic gain for grain yield and are suitable for breeding; prebreeding of the maize landrace is necessary before being used directly in the elite germplasm; the population contains high genetic variability and opportunities for genetic gain; the average agronomic traits are suitable only for traditional production systems with few inputs, and polyculture; the difference between environments produces specific responses in the progeny i.e. there is a progeny x environment interaction.