Seed Phenotyping and Genetic Diversity Assessment of Cowpea (V. unguiculata) Germplasm Collection

Abstract

Cowpea is a nutrient-rich staple legume and climate-resilient crop for vulnerable agroecosystems. However, the crop still remains underutilized, mainly due to its narrow genetic base, and the production is often ravaged by aphid infestation outbreaks. Thus, genetic diversity assessment and the detection of defense-related alleles are fundamental to germplasm management and utilization in breeding strategies to support food safety in climate change times. A germplasm collection of 87 cowpea landraces sourced from Greece was subjected to seed phenotyping, SSR genotyping and to screening for the presence of aphid-resistance-conferring alleles. Significant diversity in the species’ local germplasm was revealed. The landraces were grouped in metapopulations based on their broader geographical origin. High amounts of variation and statistically significant differences were detected among the landraces regarding the seed morphological traits, the seed color and eye color according to MANOVA (Wilk’s λ = 0.2, p < 0.01) and significant correlations were revealed among these features according to Pearson’s test (p < 0.05). High levels of genetic polymorphism were detected for the metapopulations, ranging from 59% (VuPop3) to 82% (VuPop4). The AMOVA revealed that 93% of the molecular diversity was distributed among the landraces of each metapopulation. Further population structure analysis presumed the existence of two inferred populations, where in population A, 79% of the landraces have a cream/cream-brown seed coat, whereas in population B, 94% of the landraces are brown-ochre to black-seeded. Molecular screening for alleles conferring aphid resistance revealed the correspondence of 12 landraces to the resistant genotype of TVu-2876. The study highlights the importance of cowpea germplasm collection genetic diversity, as a source of important agronomic traits, to support breeding efforts and expand cowpea cultivation to foster food security and agriculture sustainability and diversification in climate change.

Cowpea Constraints and Breeding in Europe

“…Today, cowpea is cultivated in areas of Southern Europe such as Greece, Italy, Spain, Cyprus, Croatia, Portugal and Serbia, Bosnia and Herzegovina, and North Macedonia [ 54 , 55 , 56 , 57 , 58 , 59 ], but is less widespread in Central Europe [ 52 ]. Cultivated areas for cowpea dry beans production are also reported in Slovenia and Hungary [ 58 ].…”

“…Worth mentioning is that work has also been done in India for biotic stresses resistance [ 250 ]. A corresponding investigation has not yet taken place for cowpea genetic material of European origin, however the potential of twelve Greek cowpea landraces to Aphis craccivora was highlighted, as they were found to possess the allele CP-171-172 indicative for aphid resistance of the TVu-2876 genotype [ 59 ].…”

Dissecting the Genetic Diversity of USDA Cowpea Germplasm Collection Using Kompetitive Allele Specific PCR-Single Nucleotide Polymorphism Markers

“…Currently, the International Institute of Tropical Agriculture (IITA) and the United States Department of Agriculture-Genetic Resources Information Network (USDA-GRIN) maintain over 20,000 cowpea accessions, including wild cowpea relatives, available to breeders and geneticists worldwide [ 5 ]. Studies evaluating seed morphology and color, along with genetic assessment, provide a more comprehensive understanding of cowpea diversity [ 6 ]. This is important for identifying desirable traits and supporting breeding efforts.…”

“…Exploring untapped diversity could enhance food security. Utilizing local, underexploited germplasm can broaden cowpea’s genetic base, which could lead to more robust varieties [ 6 ]. Analyzing genomes from multiple cowpea subpopulations helps to identify both core (conserved) and non-core (variable) genes potentially important for adaptation and breeding goals [ 8 ].…”

“…This is important for identifying desirable traits and supporting breeding efforts. Research highlights cowpea's potential in vulnerable agroecosystems as a climatesmart protein source [6,7]. Exploring untapped diversity could enhance food security.…”