Research Article Genetic diversity in cowpea landraces analyzed by ISSR markers

Abstract

The cowpea, Vigna unguiculata (Fabeaceae) is widely cultivated in semi-arid regions, such as northeast Brazil. Due to the low crop yields in this region, it would be useful to develop cultivars adapted to these climate conditions. Landraces are seen as an important source of germplasm to be used in breeding programs of this species due to their good adaptation to the environment, but for this strategy to be viable, their genetic variability must be studied. To this end, we evaluated the genetic diversity, using ISSR molecular markers, of 52 samples of cowpea landraces collected mostly from small producers from all over the state of Ceará, Brazil. The DNA of the genotypes was extracted and analyzed using 25 primers. Based on the electrophoresis profiles of the bands, a genetic dissimilarity matrix was prepared, and a cluster analysis made using the UPGMA and modified Tocher methods. Fourteen primers amplified 80 bands, of which 61 were polymorphic, generating a polymorphism rate of 76%. The selected markers were efficient in identifying genetic variability among the varieties under evaluation, providing a large amount of information. The polymorphic information content varied from 0.13 to 0.66 and the band frequency ranged from 0.01 to 1.00. The two clustering methods agreed in the number of groups formed (n = 6), with the genetic distances ranging from 0.05 to 0.31, values considered low, suggesting a narrow genetic base for the landraces of this species in Ceará state.

Relationships between Hybrid Performance and Genetic Distance Revealed by Morphological and Molecular Markers in Cowpea (Vignaunguiculata (L.) Walp)

“…These results are in agreement with Igwe et al (2017) who studied the genetic diversity among cowpea genotypes using SCoT and ISSR markers, they found that both marker types demonstrated high values for total number of alleles, genetic parameters (PIC, MI and RP), genetic diversity and total number of polymorphic bands. Dias et al (2015) and Araújo et al (2019) found 76% polymorphism, a high value and similar to that was found in our study; also Ghalmi et al (2010) studied the genetic diversity among 20 cultivars of cowpea using RAPD and ISSR markers, revealed relatively high levels of diversity which were similar to our results. Mahfouz (2015) studied the genetic diversity among cowpea genotypes and revealed that the high polymorphism attained by ISSR markers show their coverage of the genome.…”

Genetic diversity and structure analysis ofVigna unguiculataL. (Walp.) landraces from southeastern Mexico using ISSR markers

“…The ISSR markers used in this study successfully assessed the genetic diversity of cowpea landraces, showing high values of % P and PIC. The high levels of polymorphism detected by ISSR primers reflect their coverage of the genome, since microsatellites, besides being abundant, are well distributed (Araújo et al ., 2019). It has been shown that high polymorphism identifiable by molecular markers in cowpea hinged on the presence of repeated sequences of AC, CA, AG and GA, as adopted in this study (Igwe et al ., 2017).…”

“…It has been shown that high polymorphism identifiable by molecular markers in cowpea hinged on the presence of repeated sequences of AC, CA, AG and GA, as adopted in this study (Igwe et al ., 2017). The mean PIC value observed here (0.35) was similar with previously reported values in cowpea (Chen et al ., 2017; Araújo et al ., 2019). PIC value, as measured by Botstein et al .…”

“…Twelve ISSR primers, previously used in cowpea genetic diversity studies (Ghalmi et al ., 2010; Gajera et al ., 2014; Igwe et al ., 2017; Araújo et al ., 2019), were tested for their ability to detect polymorphisms in Mexican cowpea landraces. After a preliminary test, 10 primers that yielded good amplification and high levels of polymorphism were selected for ISSR analysis (Table 2).…”

“…Nevertheless, farmers use the same names across similar landraces. This suggests either repeating genotypes or misclassification (Araújo et al ., 2019). Few efforts have been made to characterize the genetic diversity and conservation status of cowpea germplasm in Mexico (Lagunes-Espinoza et al ., 2007; Morales-Morales et al ., 2019).…”