Iberian Peninsula cowpea diversity: chloroplast, microsatellite and morpho-agronomic variability

Abstract

Cowpea (Vigna unguiculata (L.) Walp.) is an important legume crop in Southern Europe and a valuable source of proteins, minerals, and vitamins. Moreover, cowpea has additional interest stemming from drought tolerance and high biological nitrogen fixation. In this research, the genetic diversity of cowpea landraces from Southern European countries was evaluated using molecular and morpho-agronomical approaches, with the objective of enhancing legumes diversity grown through sustainable cropping. A set of 10 chloroplast microsatellite primer pairs (cpSSRs) was used to evaluate genetic diversity and phylogenetic relationships among 113 Vigna accessions including Vigna unguiculata subsp. unguiculata, subsp. alba, subsp. pubescens, subsp. tenuis and var. spontanea and accessions from other Vigna species, as V. mungo, V. radiata and V. racemosa. This set of primers successfully established ten haplotypes, with the most frequent being shared by the V. unguiculata subsp. unguiculata cultigroups unguiculata and sesquipedalis and var. spontanea. Eight loci were polymorphic; nevertheless, a low level of polymorphism was verified within the cultivated cowpeas. Additionally, 10 agronomic traits were evaluated on cowpea landraces of the cultigroup unguiculata, mainly from Portugal. PCA clustered the landraces into three main groups, each one containing Portuguese landraces. Total seed weight per plant revealed the highest coefficient of variation, and 100 seed weight the highest heritability. The performed study shows the wide agro-morphological diversity still existing in cowpea in Iberian Peninsula and other Southern European countries, despite the low polymorphism detected in its chloroplast genome. The high variability detected in the collection of cowpea analysed and the sharing of haplotypes by cultivated and wild material is of great importance for breeding programs of this species.

Key words:

• agro-morphological diversity
• cpSSR
• germplasm
• haplotype
• Iberian gene pool
• landraces
• legumes
• molecular markers

Acknowledgments

The authors wish to thank the curators of the germplasm seed banks, namely, the National Institute for Agrarian and Veterinarian Research (INIAV, Elvas, Portugal), the National Plant Genetic Resources Centre-National Institute for Agricultural and Food Technology Research (CRF-INIA, Alcalá de Henares, Spain), the Germplasm Bank of Horticultural Species of the Center for Agro-Food Research and Technology (BGHZ-CITA, Zaragoza, Spain); the Agricultural University of Athens (AUA, Greece); the Institute of Biosciences and Bioresources of the Italian National Research Council (IBBR-CNR, Bari, Italy); the Botanic Garden Meise (Belgium); the Leibniz Institute of Plant Genetics and Crop Plant Research (IPK, Gatersleben, Germany) and the Brazilian Agricultural Research Corporation (EMBRAPA, Brazil). The authors acknowledge the the anonymous reviewers which helped to increase the quality and value of this study.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplemental data

Supplemental data for this article can be accessed here: https://doi.org/doi/10.1080/14772000.2020.1832155.

Associate Editor: Oscar Pérez-Escobar

Additional information

Funding

This work was supported by the European Union’s Seventh Framework Programme for research, technological development and demonstration under the project EUROLEGUME grant agreement number 613781 and by National Funds by FCT - Portuguese Foundation for Science and Technology, under the project UIDB/04033/2020.