Tuber Development and Tuber Yield Potential of Winged Bean (Psophocarpus tetragonolobus (L.) DC.), an Alternative Crop for Animal Feed

The winged bean is only one of the members of the leguminous species that has the potential for duo-purpose for its pod and tuber yields. The protein and nutritional content in the tuber can be used as alternative crops for animal feed. Previous studies identified the winged bean varieties as having high potential for tuber production, although their tuber development remains unclear. This study aims to elucidate the development of winged bean tubers based on their size and weight during eight months of growth. Tuber yields of high-potential winged bean varieties (W018 and W099) were compared to commercial varieties (Ratchaburi) under field conditions over two years. The experiments were laid out in randomized complete block design with three replications in the 2021–2022 and 2022–2023 growing seasons. The tuber formation of winged bean exhibited a significant increase in tuber weight and size in the fourth month of growth in all varieties, with a gradual change from fibrous roots to tubers. Particularly in the W018 and W099 varieties, tuber development persisted up to eight months after transplanting. On the other hand, the Ratchaburi variety had small tuber size, resulting in the tubers weighing less than in the W018 and W099 varieties. The results indicated that winged bean varieties had different tuber development, with the W018 and W099 varieties being suitable for tuber harvesting at eight months. The large tuber size can be an appropriate alternative to animal feed materials. At the same time, the Ratchaburi variety requires only five months since it is cultivated primarily for tuber consumption, which is concerned with size and shape. Moreover, the yields of the W018 and W099 varieties were significantly higher compared to Ratchaburi at 22.4, 19.3, and 7.423 T/ha in the 2021–2022 growing season and 8.4, 7.9, and 5.6 T/ha in the growing season of 2022–2023, respectively. The protein content in the winged bean tubers increased to 13.00% at eight months. The years (Y) and genotypes (G) differed considerably for tuber formation. The variation in both Y and G and the shoot/root ratio are also discussed in this study.