Evaluation of Productivity and Morphological Variability of Asparagus Cowpea Cultivars Intended for Vegetable Production

Despite the high nutritional value of cowpea and its potential for sustainable farming, its cultivation is limited by the lack of vegetable varieties adapted to different soil and climatic conditions, which complicates the fight against food insecurity in many countries. Therefore, this study aims to conduct a comprehensive evaluation of cowpea (Vigna unguiculata (L.) Walp. subsp. sesquipedalis (L.) Verdc.) varieties with the aim of identifying genotypes with high productivity potential and resistance to the main adverse environmental factors of the Right-Bank Forest-Steppe of Ukraine. The experimental study was carried out in a three-year period (2014–2016). Depending on the variant of the experiment, cowpea germination was observed from 25 May to 30 May. The shortest sowing–shoot period (10 days) was observed in the variety ‘U-Tya-Kontou’ (China), with the longest (13 days) in the varieties ‘Kafedralna’ (Ukraine) and ‘American Improved’ (USA). In the control variant, shoots were obtained on 28 May. Flowering started from 9 July to 16 July; technical maturity (unripe (green) beans) started from 27 July to 2 July; and biological maturity of the seeds started from 30 August to 5 September. For the variety ‘American Improved’, the shortest period of seedling–technical maturity (unripe (green) beans) (58 days) and seedling–biological maturity (92 days) was recorded. By cultivar, the maximum plant height was achieved with varieties ‘Groik’ (Israel) at 100.5 cm and ‘Gasson’ (Vietnam) at 61.8 cm, which are 52 cm and 13.3 cm more than the control height. They differ by the quick growth of the main and side shoots, which allows them to be grown on supports. The highest yield of green beans was recorded in the cowpea variety ‘Gasson’ at 14.4 t∙ha[sup.−1], which is 38.5% higher than the control. In the variety ‘Groik’, the yield of green beans (11.4 t∙ha[sup.−1]) did not differ significantly from the control (‘Kafedralna’—10.4 t∙ha[sup.−1]). The varieties ‘U-Tya-Kontou’ and ‘American Improved’ were characterized by the lowest yield of green beans, which reached 5.8 and 4.2 t∙ha[sup.−1], respectively, which is 44.2 and 59.6% less than the control. As a result of statistical analysis of cowpea yields, the limits of its fluctuation were established as follows: fluctuations in the sum of effective temperatures by 10 °C (>10 °C) contributed to a deviation in green bean yields from 20.0 to 24.7 kg (ha)[sup.−1], and fluctuations in precipitation by 10 mm contributed to a d