Correlations and Path Analysis in Segregating Cowpea Generations Regarding Biological Nitrogen Fixation

Adeneide Candido Galdino Saraiva,Ismael Gaião Da Costa,José Nildo Tabosa,Kevison Romulo Da Silva França,Antonio Francisco De Mendonça Júnior,Antonio Félix Da Costa,Mario De Andrade Lira Junior,Gheysa Coelho Silva,José Wilson Da Siiva,Cybelle Souza De Oliveira

doi:10.5539/jas.v14n2p79

Abstract

The objective of this research was to evaluate the correlations between variables related to the biological nitrogen fixation (BNF) in segregating generations of cowpea and to unfold these correlations in direct and indirect effects, through path analysis. An outdoor bench experiment was conducted at Carpina Experimental Sugarcane Station of, located at the Zona da Mata region of the State of the Pernambuco, Northeast of Brazil (Federal Rural University of Pernambuco), between March and April 2016. The seeds were planted in 20 cm &times; 30 cm polyethylene bags, using a substrate composed of a mixture of vermiculite and sand washed in a ratio of 1:1. Bradyrhizobium references, recommended for culture, were used as a mixture of two strains. Parental and F2, F3 and F4 generations were evaluated in a randomized block design with four replicates. Data collection was performed 45 days after the emergency (DAE). Phenotypic correlations and path analysis of the number of nodules per plant (NN), nodules dry mass (NDM), dry roots mass (DRM), dry mass of aerial part (DMAP), nodulation efficiency (NODE) and nitrogen accumulated in the aerial part (NAAP). The phenotypic correlations between the variables related to the BNF showed high magnitudes, demonstrating that there is a great influence of each of the variables on the others, furthermore the path analysis of the coefficients indicated that all the primary components (NN, NDM, DRM, DMAP and NODE) must be considered when it is desired to increase the NAAP in segregating generations of cowpea.

Highlights

The results found that the primary components are directly related to the basic variable nitrogen accumulated in the aerial part (NAAP), they show negative correlation with the variable nodulation efficiency (NODE)
The nodules per plant (NN) character contributed most directly to explain nitrogen accumulated in the aerial part (NAAP), as it showed a total effect of medium magnitude (0.4 < r < 0.7) with a direct effect of 0.6313, offsetting the negative indirect effects that occurred via MRD (-0.1554) and NODE (-0.3004), through the positive indirect effects via nodules dry mass (NDM) (0.2639) and dry mass of aerial part (DMAP) (0.1562), resulting in a positive correlation coefficient estimate (0.9396)
The phenotypic correlations between the biological nitrogen fixation (BNF)-related variables show that there is a strong influence of each variable on the others

Summary

Introduction

Walp.) is a legume consumed as green and dry grains that has a high protein content, short cycle for maturity and drought tolerance. It is a dicotyledonous species of African origin, known in several regions of Brazil as feijão-de-corda, feijão-macássar, feijão-de-praia e feijão-miúdo. Brazil is the world’s third largest producer of cowpea, after Nigeria and Niger. These three countries together represent 82.46% of the harvested area and 81.92% of world production (FAO, 2017; CONAB, 2017)

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