Inheritance of genetic resistance to fusarium wilt in cowpea

Abstract

Information on the inheritance of cowpea resistance to Fusarium oxysporum f. sp. tracheiphilum infections are relatively unknown. The goal of the present work was to determine the inheritance of cowpea resistance (denoted by MNCO1-649F-2-1 genotype) to Fusarium wilt and to recommend the best method to incorporate this resistance in susceptible genotypes. Two parent genotypes MNCO1-649F-2-1 (resistant) and cultivar BR-17 Gurguéia (susceptible) were crossed in a greenhouse. The hybridization between susceptible and resistant parents was performed to obtain F1 plants, which were crossed among themselves to obtain F2 plants. All plants presenting the first pair of developed leaves were inoculated with a conidial suspension of F. oxysporum f. sp. tracheiphilum (106 conidia/mL) by conidia root-immersion methodology. The assessment of fusarium wilt intensity was performed at 21 days after inoculation, with the aid of a descriptive scale. According to chi-square (χ2) test, the segregating ratios of 1:0 (resistant:susceptible) was accepted for F1 generation, and the ratio of 3:1 (resistant:susceptible) was accepted in F2 generation, assuming a dominant monogenic character, supported with results in the backcrosses. Maximum-likelihood methods confirm that resistance is attributed only to genes with major effects, and the analysis with means values and variance of populations also presented a monogenic inheritance. Our results make it possible to recommend backcrossing to introduce resistance in susceptible genotypes.