ABSTRACT Cowpea [Vigna unguiculata (L.) Walp.] is an important socioeconomic crop in Brazil, mainly in the Northeast and more recently in the Midwest of Brazil. Charcoal rot caused by Macrophomina phaseolina (Tassi) Goid, is an important disease in semiarid regions, where edaphoclimatic conditions are favorable to the development of disease. The aim of this study was to evaluate the response of 100 cowpea lines to two isolates of M. phaseolina. The experiments were conducted in a completely randomized design, with five replications (two plants per pot). The main variables evaluated were lesion length and relative growth compared to control (RGCC). Among the evaluated accessions, 15% of the lines were resistant to isolate 59 and 11% of the lines were resistant to isolate CMM 2106 of M. phaseolina. Therefore, these accessions can be used as a source of resistance to M. phaseolina by farmers directly as new cultivars or in future hybridizations of cowpea genetic breeding programs.

ABSTRACT Given the lack of information on the use of spontaneous plants from the Caatinga biome as green manure to produce green grains, the present work aimed to agronomically and economically optimize cowpea production for green grains and their components when fertilized with equitable biomass amounts of hairy woodrose (Merremia aegyptia L.) and roostertree (Calotropis procera Ait.) in two cropping seasons in a semi-arid environment. The experiment used a randomized complete block design, with five treatments and five replicates. The treatments consisted of equitable amounts of dry M. aegyptia and C. procera biomass of 16, 29, 42, 55 and 68 t ha-1. In each experiment, an additional treatment was planted with cowpea without fertilizer (absolute control), and another was fertilized with mineral fertilizer for the purpose of comparison with the treatment of maximum physical or economic efficiency. The maximum optimized physical (agronomic) efficiencies of cowpea green pods and grain production were reached in the productivity of green pods at 3.90 t ha-1 and green grains at 4.06 t ha-1, with incorporation into the soil of 45.07 and 50.48 t ha-1 of green manure, respectively. The maximum economic efficiency of cowpea green grain production was reached at a net income of R$5826.12 ha-1 and at a rate of return of 1.29 reals for each real invested with application to the soil of 38.74 and 37.85 t ha-1 of the tested green manure biomass.