Variability of morphological and phenological traits in Vigna unguiculata (L.) Walp. accessions contrasting by growth type in different ecological and geographical conditions

Background . Cowpea ( Vigna unguiculata (L.) Walp.) is a thermophilic crop that occupies the third place in the world in terms of cultivation area among leguminous crops. Vegetable cowpea cultivars are successfully cultivated in the open ground in Russia, in its southern regions and the south of the Far East. The creation of new cultivars adapted to cultivation in different regions and suitable for widespread industrial production, is extremely relevant. Materials and methods. The variability of 20 morphological and three phenological traits of six cowpea accessions with different growth habit types and architectonics was assessed in various ecological and geographical conditions at VIR experiment stations (in Astrakhan Province, Primorye Territory and Krasnodar Territory) in 2019-2022. The variability and interrelationships of the traits were estimated using basic and multivariate statistical methods. Results. The analysis revealed a significant influence of the factor complex (genotype/accession, research location) on the variability of traits. Phenological traits, the length of internodes and leaflets depended most strongly on the research location. The range of variation in the number of nodes, branches, peduncles and pods per plant, stem thickness and pod size were determined by the genotype to a larger extent. The range of stem length variability was significantly influenced by the research location and the genotype, though the genotype had a stronger influence. The genotypes responded differently to changes in growing conditions. For most of the studied accessions, an increase in the main stem length was noted in the monsoon climate conditions of the Primorye Territory, for some of them the type of growth habit changed from determinant to indeterminate. In our research, the plant length was positively correlated with the amount of precipitation and with the average relative humidity. Excessive humidity and precipitation had minimal effect only on the cultivar ‘Lyanchihe’, whose plants retained dwarfness and compact architectonics. Factor analysis (principal factors analysis) revealed four factors responsible for the main part of the variance of the analyzed traits. The characteristics of the leaf were combined in the first factor, those of architectonics and time of plant development in the second, traits of the seedling and the juvenile stage in the third, and those of the pod in the fourth factor. These complexes of traits (factors) determined the variability of cowpea in our research. Conclusion . The performed analysis of morphological and phenological traits revealed a significant increase of stem length and changes in plant architectonics under conditions of high relative humidity and a large amount of precipitation. In some cases, even the type of growth habit was changed. The further research on the studied characters variability involving more accessions and the determination of molecular mechanisms that control stability of the growth habit type and length of the stem will allow us to proceed to a more efficient and rapid creation of new cultivars suitable for mechanized cultivation. This is extremely important for the development of new areas by cultivating species, the demand in which as a source of food and feed is increasing in the Russian Federation.