The Genetic Driving Force for the Grain-Vegetable Cowpea Diversification: A Focus on the Pod Length

The formation/loss of characterized traits in a given cultivated species is strongly affected by long-term artificial selection. Cowpea (V. unguiculata L. Walp.) is an important legume crop for many residences in the tropics and subtropics of the world, being consumed as either a grain, fodder or vegetable crop depending on local cultivation and consumption habits. Cowpea is believed to have originated from African and be brought to India and East Asia later [1]. Nowadays, cultivated cowpea has well diverged into two main subspecies, which is the ssp. sesquipedialis, known as yard-long bean or asparagus bean, and the ssp. unguiculata well known as common cowpea or African cowpea [2]. The ssp. unguiculata has undergone through intensive selection for seed characteristics, including particularly high protein content and grain yield, in addition to the ‘bush’-type plant architecture and short (20-30 cm in length) and crisp pods usually with a high fiber content [3,4]. On the contrary, the ssp. sesquipedialis was most often consumed as a vegetable [5]. This subspecies is characterized by long (30-90 cm in length) succulent pods that tastes tender and crisp. The pods are often harvested when immature, and are stewed, fried or preserved for eating. When grown in the field, the ssp. sesquipedialis develops characteristic climbing and twining stems.