Breeding Drought Tolerant Cowpea Varieties for Southern USA.

Cowpea came to the Americas from Africa through Jamaica in about 1700 and by early 1900s it spread to several states in the USA primarily in the central and southern parts as a fodder, cover and food crop. Since then it has become a prestigious food crop in Texas and California  in particular and throughout the southern USA in general with a long tradition of eating black eye pea on the New Year’s day for good luck. Commercial production in the US extends as far north as 40 ° latitude. The State of Texas was the largest producer of black-eyed peas in the US from the 1930's until the 1970's, with more than one million acres planted. However, its cultivation has declined over time due to many production constraints including reduced rainfall, declining ground water table and frequent drought. Therefore, a systematic breeding program has been initiated to develop a range of improved cowpea varieties with drought tolerance. A total of 40 cowpea lines from Africa and USA were screened for drought tolerance using the shallow box screening method. Extreme varietal differences were observed for shoot dehydration tolerance. IT99K-241-2 was the most tolerant cowpea variety closely followed by TX2028-1-3-1, CB-27 and Dan Ila. Other US varieties including CB-46 were highly susceptible. Appropriate crosses have been made to study the inheritance and to develop breeding populations for incorporating this trait into improved varieties. Studies are also underway to elucidate the physiological mechanisms for drought tolerance. Details will be presented and discussed.