Importance and correlations of characters for cowpea diversity in traditional varieties¹

Importância e correlações de caracteres para diversidade do feijão-caupi em variedades tradicionais

ABSTRACT

Cowpea is a legume with ample plasticity, versatility and nutritional potential. It is a species widely used as a source of income and subsistence for small farmers in several Brazilian states, among them Acre. Due to the different varieties found in the State, it is the target of studies aiming at its genetic improvement. Thus, as one of the first stages of its improvement, it was aimed to determine the importance and correlations of characters for diversity and selection in traditional varieties of cowpea. The experiment was carried in completely randomized design, with plots consisting of four vase with capacity to 15.7 L, with one plant each and two replicates. The characteristics evaluated were: days for emergence, flowering (days), plant vigor (note), number of main stem nodes, apical leaflet length (mm), apical leaflet width (mm), length of pod (cm) and width of the pod (cm). The correlation coefficients (phenotypic, genotypic and environmental) were obtained, and the principal components analysis and the importance of the characters by the method proposed by Singh were carried out. The Singh method and principal components analysis were partially concordant in the distinction of the evaluated characters. The days for emergence, width of the apical leaflet, flowering and length of the apical leaflet were the main determinants for quantification of the genotypes and those that contributed the most to the variability of cowpea. The least discriminant characteristic by principal component analysis and recommended for discarding was plant vigor.

Key words:
Vigna unguiculata. Phenotypic; genotypic and environmental correlations. Principal components

RESUMO

O feijão-caupi é uma leguminosa com ampla plasticidade, versatilidade e potencial nutritivo. Trata-se de uma espécie bastante utilizada como fonte de renda e subsistência para pequenos agricultores em vários estados brasileiros, entre estes, o do Acre. Devido as diferentes variedades encontradas no Estado, é alvo de estudos visando o seu melhoramento genético. Assim, como uma das primeiras etapas do seu melhoramento, objetivou-se determinar a importância e correlações de caracteres para a diversidade e seleção em variedades tradicionais de feijão-caupi. O experimento foi realizado em delineamento inteiramente casualizado, com parcelas constituídas por quatro vasos de volume igual a 15,7 L, com uma planta cada e duas repetições. As características avaliadas foram: dias para emergência, florescimento (dias), vigor da planta (nota), número de nós do caule principal, comprimento do folíolo apical (mm), largura do folíolo apical (mm), comprimento da vagem (cm) e largura da vagem (cm). Foram obtidos os coeficientes de correlações (fenotípicas, genotípicas e ambientais), realizada a análise de componentes principais e a importância dos caracteres pelo método proposto por Singh. O método de Singh e componentes principais foram parcialmente concordantes na distinção dos caracteres avaliados. Os caracteres dias para a emergência, largura do folíolo apical, florescimento e comprimento do folíolo apical foram os principais determinantes para quantificação dos genótipos, e os que mais contribuíram significativamente para a variabilidade de feijão-caupi. A característica menos discriminante pela análise de componentes principais e recomendada para descarte foi o vigor da planta.

Palavras-chaves:
Vigna unguiculata. Correlações fenotípicas; genotípicos e ambientais. Componentes principais

INTRODUCTION

Cowpea (Vigna unguiculata (L.) Walp.) is among the main legumes grown in Brazil, with great economic and socio-cultural importance. It is a rustic, versatile and nutritious species among the cultivated ones, besides being an important staple food accessible to the population and a fundamental component in the production systems, since it presents a wide flexibility in relation to the forms of use and consumption (TEÓFILO et al., 2008).

In the state of Acre, the plantation of cowpea is an important source of viable alternative income for traditional populations and family farmers. Recognized as a subsistence crop, it integrates an important part of the local productive system, due to its high plasticity to edaphoclimatic conditions. The cultivars used in the region are of Creole basis and mixed with seeds distributed by governments long ago. Therefore, knowledge of the characteristics of this crop is important and desirable to identify and select genotypes favorable to the specific environment where it is grown (CARMO; PAULINO; RAGAGNIN, 2013) and with potential for genetic improvement based on local diversity.

The understanding of this genetic potential provides a premise for the identification of divergent individuals, aiding in the selection of favorable and promising combinations, allowing to obtain superior genotypes. In this sense, the improvement has contributed to aggregation of value and conquest of new markets (FREIRE FILHO et al., 2011).

The clarity of the association between the main components of the plant, obtained by the phenotypic, genotypic and environmental correlations, is important because it indicates how selection for one character influences the expression of other characters, which can be associated in different directions and magnitudes (SILVA; NEVES, 2011).

Other resources used for the study of variability have been the techniques of multivariate analysis, which are based on multiple information. According to Moreira et al. (2009), the use of these techniques is feasible since it allows multiple combinations of information through the discrimination of the genotype relative to a complex variable with analysis of the discriminatory power and their contribution together. The principal components technique has the advantage of allowing the evaluation of the importance of each character studied on the total variation available among the evaluated genotypes, allowing the discarding of characters that contribute least to the differentiation of the genotypes. The use of these techniques also allows quantifying the contribution of each character, as proposed by Singh (1981), which measures the contribution of the variables of greater and less importance in the study of diversity.

The estimates obtained are used by the breeder to define the appropriate strategies to obtain superior genotypes based on the most important characters. In this way, the selection of a certain characteristic has its efficiency increased as one obtains knowledge about the correlations of characters, which contributed to help the breeder and increase the success of the genetic improvement in this crop. In this context, correlations and methods of principal components and Singh are important because they are plant selection indicators, allowing to diagnose superior genotypes to be inserted in the local productive system (CARPENTIERI-PÍPOLO et al., 2012) or base for crossing and generation of variability.

Given the need to increase knowledge about this species, it is essential to acquire knowledge about the genetic base referring to the characteristics of cowpea, associating the interaction of the plant characters. Thus, the objective was to determine the importance and correlations of characters for diversity and selection in traditional varieties of cowpea in Acre.

MATERIAL AND METHODS

The experiment was carried out in 2014, under greenhouse conditions, at the Federal University of Acre, Rio Branco, AC. The climate of the region is classified according to Köppen as Am2 (hot and humid with an annual dry period of 3 months) (COSTA et al., 2012). Average temperatures, maximum and minimum temperatures of 31.7 ºC and 21.4 ºC, respectively, mean relative humidity of 84.3% and mean annual rainfall of 2,018 mm, according to the average of the years 2005 to 2015 (INMET, 2017).

The 11 traditional varieties of cowpea cultivated in Acre were obtained from producers and in the local market (Table 1), and evaluated in a completely randomized design, two replicates and plots consisted of four vessels with a volume equal to 15.7 L, with one plant each.

Table 1
Identification of cowpea genotypes (Vigna unguiculata (L.) Walp.) collected in different municipalities of Acre and used in the present study

Genotypes	Origin
Baiano	Sena Madureira - SM (09º03' S and 68º39' W)
Corujinha	Sena Madureira - SM (09º03' S and 68º39' W)
Caupi Roxo	Sena Madureira - SM (09º03' S and 68º39' W)
Quarentão	Cruzeiro do Sul - CZS (07º37' S and 72º40' W)
Quarentão	Mâncio Lima - ML (07º36' S and 72º53' W)
Quarentão Praia Grande	Cruzeiro do Sul - CZS (07º37'S and 72º40' W)
Barrigudinho	Sena Madureira - SM (09º03' S and 68º39' W)
Manteigão	Sena Madureira - SM (09º03' S and 68º39' W)
Manteiguinha	Cruzeiro do Sul - CZS (07º37' S and 72º40' W)
Manteiguinha	Rodrigues Alves - RA (07º44' S and 72º38' W)
Caupi Preto	Cruzeiro do Sul - CZS (07º37' S and 72º40' W)

The evaluated characteristics were: days for emergence - DPE, obtained from the count of the days elapsed between the planting and the emergence of the cotyledons; flowering - FLOR, with the number of days comprised between emergence up to 50% of flowering plants; plant vigor - VP, based on the width and height of the plant between 3-4 weeks, assigning the following graduation: 3 not vigorous (height less than 37 cm and width less than 75 cm), 5 intermediate (height greater than 37 cm or width less than 75 cm), 7 vigorous (height greater than 37 cm and width greater than 75 cm) and 9 very vigorous (height greater than 50 cm and width greater than 100 cm); number of main stem nodes - NNCP, obtained by the average number of nodes present in the main stem between 3-4 weeks of planting; length of apical leaflet - CFA (mm), referring to the distance between the base and the apex of the apical leaflet; width of the apical leaflet - LFA (mm), from the distance between the lateral ends of the apical leaflet; pod length - COMPV (cm), referring to the average length of ten mature pods taken at random, using a ruler graduated in centimeters; and pod width - LV (cm), from the average of ten mature pods taken at random, using a ruler graduated in centimeters.

The averages, phenotypic (rF), genotypic (rG) and environmental (rE) correlation coefficients were calculated for all characteristics evaluated. The principal components of standardized data technique was used, where the eigenvalues ​​(variance associated with each main component) were estimated by the characteristic roots of covariance, and the eigenvectors (set of weighting coefficients of the principal components) were estimated by the corresponding characteristic vector elements. The feasibility of its interpretation was considered with the concentration of variability among the first variables above 80% (CRUZ; REGAZZI; CARNEIRO, 2012). The relative contribution of the characters was quantified using the criterion proposed by Singh (1981). Statistical analyzes were performed with the aid of Genes software (CRUZ, 2013).

RESULTS AND DISCUSSION

The results were of good concordance of the signs, with some discrepancy of intensity between phenotypic (rF) and genotypic (rG) correlations with environmental (rE) correlations. It can be observed that genotypic correlations presented higher values ​​than their corresponding phenotypic and environmental correlations (Table 2), which is desirable by the breeder, since this will be inherited. However, it is important to emphasize that for a practical value of selection, it is necessary for the variables to be genotypically (OLIVEIRA et al., 2011) and phenotypically correlated, since the selection is made based on the phenotype (FERREIRA et al., 2007).

Table 2
Estimates of the phenotypic (rF), genotypic (rG) and environmental (rE) correlation coefficients of 11 traditional varieties of cowpea (Vigna unguiculata (L.) Walp.) in the state of Acre

Characters		FLOR	VP	NNCP	CFA	LFA	COMPV	LV
DPE	rF	-0.049	0.101	0.454	0.535	0.644*	0.332	0.317
	rG	0.151	0.234	0.995++	0.921+	0.964++	0.457	0.507
	rE	-0.334	-0.382	-0.649+	-0.092	-0.034	0.065	0.124
FLOR	rF		-0.851**	-0.537	-0.394	-0.031	-0.117	-0.169
	rG		-0.995++	-0.893	-0.568	-0.104	-0.146	-0.420
	rE		-0.071	-0.142	-0.043	0.115	-0.036	0.133
VP	rF			0.645*	0.641*	0.311	0.373	0.548
	rG			0.806	0.712	0.352	0.437	0.751
	rE			0.664++	0.453	0.178	-0.321	0.273
NNCP	rF				0.562	0.375	0.191	0.501
	rG				0.782	0.588	0.335	0.897
	rE				0.305	0.111	-0.082	0.167
CFA	rF					0.842	0.696*	0.418
	rG					0.889	0.953+	0.462
	rE					0.729++	-0.355	0.386
LFA	rF						0.428	0.262
	rG						0.638	0.216
	rE						-0.448	0.350
COMPV	rF							0.599*
	rG							0.941+
	rE							-0.044

• Days for emergence - DPE, flowering - FLOR (days), plant vigor - VP (note), number of main stem nodes - NNCP, apical leaflet length - CFA (mm), apical leaflet width - LFA mm), length of the pod - COMPV (cm), width of the pod - LV (cm); *, **: significant at 5% and 1%, respectively, by the t test; ++ + : significant at 1 and 5%, respectively, by the bootstrap method with 5000 simulations

There were significant and high magnitude phenotypic (rF) and genotypic (rG) correlations between the pairs of characters (Table 2): DPE x LFA, DPE x NNCP, VP x NNCP, VP x CFA, VP x LV, CFA x LFA, CFA x COMPV, NNCP x CFA, NNCP x LV, LFA x COMPV, and COMPV x LV. According to Andrade et al. (2010), high phenotypic (rF) correlations present a high genetic component in their phenotypic expressions and lead to gains via visual selection when it is accompanied by the genotype correlation also high and in the same direction. Cruz, Regazzi and Carneiro (2012) and Hallauer, Carena and Miranda Filho (2010) emphasize the importance of distinguishing and quantifying the degree of genetic and environmental association among the evaluated characteristics, since the genetic causes of correlation are inheritable and can assist in guiding the breeding program from the indirect selection of characters that present difficulties due to low heritability and / or obtaining problems.

The highest genotypic estimates (Table 2) were between DPE x NNCP (0.995), DPE x LFA (0.964) and FLOR x VP (-0.995); all of them considered to be high, with emphasis on the last one that was negative, showing that the genotypes that showed the most time for flowering had the lowest plant vigor, since the negative correlations indicate that the magnitudes of the characters correlate inversely. This latter correlation is not normally expected and may have been caused by the pot in which the plants were grown, which eventually limited vegetative growth.

The pod length characteristic (COMPV) presented a high, positive and significant correlation with pod width (LV) and a positive and significant correlation with the apical leaflet length (CFA). In general, the pod length (COMPV) is related to production variables as found by Romanus, Hussein and Mashela (2008), who obtained values ​​of positive and significant correlation with the number of seeds per pod, grain yield and days to flowering, when evaluating seven lines of cowpea of the Department of Crop Science at the University of Nigeria, Nsukka.

The results on the genetic basis and correlations between the characters studied in this study suggest that, although relatively complex, apical leaflet length (CFA), apical leaflet width (LFA), pod length (COMPV), pod width (LV), number of main stem nodes (NNCP) and flowering (FLOR) should be considered in the selection of the parents, aiming the generation of variability to obtain new cultivars with higher grain yield, plant architecture (facilitating manual or mechanized harvesting) and genotypes with greater precocity. However, it is necessary to deepen these studies, correlating them with the grain or pod yield (according to purpose) for better use of these variables in the breeding stages of the species.

The knowledge of the correlations between the variables facilitates the decisions to be made in the selection of the genotypes of interest. Matos Filho et al. (2009), evaluating progenies of cowpea with erect plant architecture in the city of Teresina-PI, in 2004, verified that plants with the highest number of main stem nodes are the most productive, despite the low magnitude value, that would be a problem in the selection if the objective is the obtaining of plants for the mechanized harvest, since the greater number of nodes usually leads to the greater length (height) of the main branch. Nogueira et al. (2012), conducting track analysis and correlations between characters in soybean cultivated at two sowing times also found that the number of main stem nodes is correlated with higher productivity. Machado et al. (2008), seeking out select genotypes of precocious cowpea in Teresina-PI, found a high and positive correlation between flowering and grain yield, which may hinder selection, aiming at precocity and high productivity.

Some environmental correlations between the characters showed differences in magnitude and sign in relation to the respective genotypic correlations and revealed that the environment favored one character to the detriment of the other, and that the causes of genetic and environmental variation present different physiological mechanisms, making selection difficult (ALMEIDA; PELUZIO; AFFERRI, 2010).

The coefficient of genetic variation (CV_g) was 3.25 (FLOR) and 34.24% (VP) (Table 3). The highest estimates for the CV_g were presented by the characters of plant vigor (34.24%), pod width (12.91%), pod length (12.57%) and days for emergence (11.80%), indicating that among all the characters studied, these showed greater variability, making possible the selection in these variables. The lowest estimates of CV_g were for the characters of flowering (3.25%), apical leaflet length (6.49%), number of main stem nodes (7.20%) and apical leaflet width (8.23), showing less variability among the genotypes for these characters.

Table 3
Estimates of the coefficient of genetic variation (CV_g) and heritabilities (H²), coefficient of experimental variation (CV_e) and CV_g/CV_e ratio referring to the characters days for emergence (DPE), flowering (FLOR), plant vigor (VP), number of main stem nodes (NNCP), length of apical leaflet (CFA), width of apical leaflet (LFA), pod length (COMPV) and pod width (LV) of 11 varieties of cowpea (Vigna unguiculata (L.) Walp.) in the state of Acre

Characters	CVg (%)	H2 (%)	CVe(%)	CVg/CVe RATIO
DPE	11.80	54.02	15.4	0.76
FLOR	3.25	63.00	3.5	0.92
VP	34.24	93.59	12.6	2.70
NNCP	7.20	44.52	11.3	0.63
CFA	6.49	70.80	5.9	1.10
LFA	8.23	70.66	7.5	1.09
COMPV	12.57	89.41	6.1	2.05
LV	12.91	46.92	19.4	0.66

The low value of CV_g found in days for flowering (3.25%) was also obtained by Bemvindo et al. (2010) with a value of 1.62%, when evaluating seventeen lineages and three semi-prostrate cowpea cultivars in relation to grain yield potential and components related to the cycle and the plant architecture in rainfed and irrigated cultivation, in Teresina-PI. These results can be explained by the work of Matos Filho et al. (2009) that by evaluating the potential of progenies of cowpea with erect plant architecture, estimated coefficient of genotypic determination of 25.29% for the character days for flowering, evidencing strong presence of environmental effects in the expression of this character.

The heritabilities were of medium to high magnitudes (44.52% and 93.59%) (Table 3), being considered adequate according to the nature of the characters evaluated, indicating good possibilities for the selection of these variables. Machado et al. (2008) found values of 94% ​​for flowering and 79% for number of nodes of main branch, values ​​much higher than those found in this work, 63 and 44%, respectively.

The coefficients of experimental variation (Table 3) were within acceptable values (good experimental precision) with higher value for pod width (LV), which presented 19.4%, indicating good experimental quality. By analyzing the values of the CV_g/CV_e ratio, the characters plant vigor (VP), apical leaflet length (CFA), apical leaflet width (LFA) and pod length (COMPV) presented values above 1, indicating high variability and favorable situation for selection.

The relative contribution of the characters evaluated for diversity (Sj) and their percentage values, which are the measure of the relative importance of variable j for the study of genetic diversity, are presented in Table 4, where it is verified that the number of nodes of the main stem (9.60%) and pod width (9.70%) presented the smallest contribution and are recommended for disposal. However, the characters that presented the greatest relative contribution to dissimilarity were: days for emergence (DPE), flowering (FLOR), apical leaflet width (LFA) and plant vigor (VP), responsible for 56.83% of variation existing among the evaluated genotypes, indicating that these characteristics need to be taken into account in the diversity studies, helping in the selection of divergent genotypes for crosses with greater possibility of variability generation.

Table 4
Relative eight-character contribution for genetic divergence in 11 varieties of cowpea (Vigna unguiculata (L.) Walp.) in the state of Acre, according to Singh (1981) criterion

Variables	Sj	Value %
Days for emergence - DPE	13.87	16.17
Apical leaflet width - LFA	12.14	14.16
Flowering - FLOR	11.67	13.61
Plant Vigor - VP	11.06	12.89
Apical leaflet length - CFA	10.64	12.41
Length of the pod - COMPV	9.79	11.42
Width of the pod - LV	8.32	9.7
Number of main stem nodes - NNCP	8.23	9.6

The relative contribution values found in the literature are quite varied and dependent on the characteristics and the group of evaluated genotypes. Bertini, Teófilo and Dias (2009) verified that pod length was the variable that contributed the most to the genetic diversity of accessions of the germplasm bank of cowpea of the Federal University of Ceará with 69.04%, while, in this work, it was the third that contributed least. Considering only the morphological characters, Passos et al. (2007) also found pod length (36.64% for prostrate genotypes and 28.56 for erect) with higher contribution.

By analysis of principal components, it was verified that the first three components (CP₁, CP₂ and CP₃), concerning the eight agronomic characters considered, explained practically all the existing variability 83.39% (Table 5).

Table 5
Variance of each main component and its importance in relation to the total variance of eight characters evaluated in 11 traditional varieties of cowpea (Vigna unguiculata (L.) Walp.) in the state of Acre

Component	Variance	Variance (%)	Cumulative Variance (%)
CP1	4.0720	50.9011	50.9011
CP2	1.6276	20.3451	71.2463
CP3	0.9716	12.1454	83.3917

Among the variables of greater weight in these components, we can mention the number of main stem nodes (NNCP), days for emergence (DPE), pod width (LV), pod length (COMPV), flowering (FLOR) and apical leaflet length (CFA). These characters contributed significantly to the variability, being the most important characters for the selection (Table 6). It is identified that the character of the apical leaflet length (CFA) was the most influential in the formation of the first component. The least discriminant characteristic, and therefore likely to be discarded by this analysis, was plant vigor (VP), which is contrary to Singh’s method and the value of CV_g.

Table 6
Principal components (CP), Eigenvalues (Av1) and Eigenvectors (Av₂) of the characters days for emergence (DPE), flowering (FLOR), plant vigor (VP), number of main stem nodes (NNCP), length of apical leaflet (CFA), width of apical leaflet (LFA), pod length (COMPV) and pod width (LV) of 11 varieties of cowpea (Vigna unguiculata (L.) Walp.) in the state of Acre

Variable	CP1		CP2		CP3
	Av1	Av2	Av1	Av2	Av1	Av2
DAE	-0.5947	-0.2947	0.5480	-0.3929	-0.7927	-0.374
FLOR.	0.5244	0.411	0.7472	0.5856	-0.5654	-0.4432
VP	-0.3543	-0.3595	0.1968	0.1997	0.0581	0.059
NNCP	0.3187	0.3746	0.1702	0.2001	-0.1235	-0.1452
CFA	0.3599	0.5967	-0.2561	-0.4247	-0.0911	-0.151
LFA	-0.1188	-0.2508	0.0734	0.1549	-0.1496	-0.3158
COMPV	-0.0236	-0.1933	-0.0504	-0.4134	-0.0445	-0.3649
LV	-0.0054	-0.1355	-0.0143	-0.3579	-0.0242	-0.6074

The use of principal component analysis (NOGUEIRA et al., 2012; VIANNA et al., 2013) has been successfully used to identify variables of greater influence on the differentiation and grouping of genotypes. This technique has gained space even in different areas of genetic improvement, such as the work of Barbosa et al. (2013), which concluded that the principal components technique is an efficient tool to discriminate batches of soybean seeds.

CONCLUSIONS

1. Genotypic correlations have higher values in relation to phenotypic correlations;

2. The method proposed by Singh and principal components are partially concordant in the distinction of the evaluated characters;

3. The characters days for emergence (DPE), apical leaflet width (LFA), flowering (FLOR) and apical leaflet length (CFA) are the main determinants for differentiation and those that contribute most significantly to variability of cowpea, being indicated as selection criterion for crossing.

• 1
  Projeto de pesquisa financiado pelo CNPq

REFERENCES

• ALMEIDA, R. D. de; PELUZIO, J. M.; AFFERRI, F. S. Correlações fenotípicas, genotípicas e ambientais em soja cultivada sob condições várzea irrigada, sul do Tocantins. Bioscience Journal, v. 26, n. 1, p. 95-99, 2010.
• ANDRADE, F. N. et al. Estimativas de parâmetros genéticos em genótipos de feijão-caupi avaliados para feijão fresco. Revista Ciência Agronômica, v. 41, n. 2, p. 253-258, 2010.
• BARBOSA, R. M. et al Discrimination of soybean seed lots by multivariate exploratory techniques. Journal of Seed Science, v. 35, n. 3, p. 302-310, 2013.
• BENVINDO, R. N. et al Avaliação de genótipos de feijão-caupi de porte semi-prostrado em cultivo de sequeiro e irrigado. Comunicata Scientiae, v. 1, n. 1, p. 23-28, 2010.
• BERTINI, C. H. C. de M.; TEÓFILO, E. M.; DIAS, F. T. C. Divergência genética entre acessos de feijão-caupi do banco de germoplasmas da UFC. Revista Ciência Agronômica, v. 40, n. 1, p. 99-105, 2009.
• CARMO, P. S.; PAULINO, H. B.; RAGAGNIN, V. A. Avaliação de cultivares de feijão no sudoeste goiano. Global Science and Technology, v. 6, n. 3, p. 23-34, 2013
• CARPENTIERI-PÍPOLO, V. et al Correlações entre caracteres quantitativos em milho pipoca. Horticultura Brasileira, v. 20, n. 4, p. 551-554, 2012.
• COSTA, F. de S. et al. Inventário de emissões antrópicas e sumidouros de gases de efeito estuda do estado do Acre: ano-base 2010. Rio Branco: Embrapa Acre, 2012. 114 p.
• CRUZ, C. D. Genes: a software package for analysis in experimental statistics and quantitative genetics. Acta Scientiarum. Agronomy, v. 35, n. 3, p. 271-276, 2013.
• CRUZ, C. D.; REGAZZI, A. J.; CARNEIRO, P. C. S. Modelos biométricos aplicados ao melhoramento genético 4. ed. Viçosa: UFV, 2012. v. 1, 514 p.
• FERREIRA, F. M. et al Relações fenotípicas e genotípicas entre componentes de produção em cana-de-açúcar. Bragantia, v. 66, n. 4, p. 605-610, 2007.
• FREIRE FILHO, F. R. et al. Feijão-caupi no Brasil: produção, melhoramento genético, avanços e desafios. Teresina, 2011. 84 p.
• HALLAUER, A. R.; CARENA, M. J.; MIRANDA FILHO, J. B. Quantitative genetics in maize breeding New York: Springer, 2010. 580 p.
• INMET - INSTITUTO NACIONAL DE METEOROLOGIA. Ministério da Agricultura, Pecuária e Abastecimento. Banco de dados meteorológicos para ensino e pesquisa do Instituto Nacional de Meteorologia Disponível em: <http://www.inmet.gov.br/projetos/rede/pesquisa/>. Acesso em: 13 abr. 2017.
  » http://www.inmet.gov.br/projetos/rede/pesquisa/
• MACHADO, C. de F. et al Identificação de genótipos de feijão-caupi quanto à precocidade, arquitetura da planta e produtividade de grãos. Revista Ciência Agronômica, v. 39, n. 1, p. 114-123, 2008.
• MATOS FILHO, C. H. A. et al Potencial de produtivos de progênies de feijão-caupi com arquitetura ereta de planta. Ciência Rural, v. 39, n. 2, p. 348-345, 2009.
• MOREIRA, R. M. P. et al Potencial agronômico e divergência genética entre genótipos de feijão-vagem de crescimento determinado. Revista de Ciências Agrárias, v. 30, n. 1, p. 1051-1060, 2009.
• NOGUEIRA, A. P. O. et al Análise de trilha e correlações entre caracteres em soja cultivada em duas épocas de semeadura. Bioscience Journal, v. 28, n. 6, p. 877-888, 2012.
• OLIVEIRA, E. J. de et al. Estimativas de correlações genotípicas e fenotípicas em germoplasma de maracujazeiro. Bragantia, v. 70, n. 2, p. 255-261, 2011.
• PASSOS, A. R. et al. Divergência genética em feijão-caupi. Bragantia, v. 66, n. 4, p. 579-586, 2007.
• ROMANUS, K. G; HUSSEIN, S; MASHELA, W. P. Combining ability analysis and association of yield and yield components among selected cowpea lines. Euphytica, v. 162, n. 2, p. 205-210, 2008.
• SILVA, J. A. L.; NEVES, J. A. Componentes de produção e suas correlações em genótipos de feijão-caupi em cultivo de sequeiro e irrigado. Revista Ciência Agronômica, v. 42, n. 3, p. 702-713, 2011.
• SINGH, D. The relative importance of characters affecting genetic divergence. Indian Journal of Genetics, v. 41, n. 2, p. 237-245, 1981.
• TEÓFILO, E. M. et al Potencial fisiológicos de sementes de feijão caupi produzidas em duas regiões do estado do Ceará. Revista Ciência Agronômica, v. 39, n. 3, p. 443-448, 2008.
• VIANNA, V. F. et al The multivariate approach and influence of characters in selecting superior soybean genotypes. African Journal of Agricultural Research, v. 8, n. 30, p. 4162-4169, 2013.

Publication Dates

• Publication in this collection
  Apr-Jun 2018

History

• Received
  05 Sept 2016
• Accepted
  28 Apr 2017