Differential Tolerance of Cowpea Cultivars to Osmotic Stress in Germinative Phase: A Multivariate Approach

Studies on germination and initial development of plants emerge as a promising approach that might provide relevant information for identifying tolerance to abiotic stresses, such as water deficit. Thus, this study aimed to characterize the behavior of different cultivars of Vigna unguiculata L. Walp. to water deficit, from germination and vigor parameters. The experiment was conducted at the Seed Analysis Laboratory of the Federal University of Ceará, located in Fortaleza, Ceará, Brazil. The experimental design used was completely randomized (CRD), in a 14x4 factorial arrangement, with fourteen cultivars (BRS-Pujante, BRS-Guariba, BRS-Potengi, BR 17-Gurgueia, BRS-Tumucumaque, BRS-Pajeú, BRS-Rouxinol, BRS-Novaera, BRS-Xiquexique, BRS-Milênio, BRS-Acauã, Patativa, BR 3-Tracuateua, and BRS-Aracê) and four levels of osmotic potential (0, -0.1, -0.2 and -0.4 MPa) of the germination solution, with four repetitions. The variables analyzed were final percentage of germination, germination speed index, average germination time, root and aerial part lengths, root dry mass and dry mass of the aerial part and the relationship between them. Data were analyzed through exploratory principal component analysis (PCA) using the R software. The BRS-Milênio, BRS-Acauã and BRS-Aracê cultivars presented difficulties in tolerating the stresses of -0.1 and -0.2 MPa, especially the BRS-Milênio cultivar at the level -0.2 MPa. Whereas BRS-Novaera and BRS-Pajeú cultivars were characterized with possible tolerance at both the -0.1 and -0.2 MPa levels. The study pointed to the BRS-Pujante cultivar as the most sensitive to the -0.4 MPa level. The multivariate technique used allowed for a satisfactory characterization of the treatments adopted.