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A. Graves Gillaspie Jr. and Robert L. Jarret

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Ricardo Goenaga, Adolfo Quiles and A. Graves Gillaspie

Cowpea or Southernpea [Vigna unguiculata (L.) Walp.] is an important grain legume in many parts of the tropics. However, viral diseases, particularly Cucumber mosaic virus (CMV) and Blackeye cowpea mosaic virus (BlCMV), can be a limiting factor in cowpea production. We evaluated in replicated field plots and under virus pressure nine PIs (441919, 441925, 441917, 147071, 146618, 180014, 180355, 194208, 612607) and three commercial cultivars (Coronet, KnuckleHull-VNR, Pinkeye Purplehull), some of which had shown absence of symptoms for CMV and BlCMV in unreplicated, seed regeneration plots of the U.S. cowpea collection. Only 3% of all plots had plants infected with both CMV and BlCMV in 2003 and 2004. This percentage increased to 47% in 2005. The accession PI 441917 had the highest 3-year mean for grain yield. However, PI 147071, PI 180014, and ‘KnuckleHull-VNR’ had higher seed protein concentration than other genotypes, but their grain yield was significantly lower than that of PI 441917. The cultivar Coronet and PI 180355 attained midbloom and maturity earlier than the other genotypes. Overall, PI 441917 outperformed all other genotypes for grain yield, including virus-resistant PI 612607 and the cultivar KnuckleHull-VNR. This accession is in the process of being released as a virus-tolerant genotype and should be useful in cowpea breeding programs to help control yield losses by CMV and BlCMV.

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Ricardo Goenaga, A. Graves Gillaspie Jr and Adolfo Quiles

Cowpea or Southernpea [Vigna unguiculata (L.) Walp.] is an important legume crop used as a feed for livestock, as a green vegetable, and for consumption of its dry beans, which provide 22% to 25% protein. The crop is very sensitive to alkaline soil conditions. When grown at soil pH of 7.5 or higher, cowpea develops severe leaf chlorosis caused by deficiencies of iron (Fe), zinc (Zn), and manganese (Mn) resulting in stunted plant growth and yield reduction. We evaluated in replicated field experiments at St. Croix, U.S. Virgin Islands, and Juana Díaz, Puerto Rico, 24 PIs and two commercial cultivars, some of which have shown some tolerance to alkaline soils in unreplicated, seed regeneration plots of the U.S. cowpea collection. Alkaline soil conditions at St. Croix were too severe resulting in average yield of genotypes at this location being significantly lower and 77% less than that at Juana Díaz. Nevertheless, some genotypes performed well at both locations. For example, PIs 222756, 214354, 163142, 582605, 582840, 255766, 582610, 582614, 582576, 582809, and 349674 yielded in the upper half of the group at both locations. Accession PI 163142 ranked third in grain yield production at both locations and outyielded the iron-chlorosis-resistant controls at St. Croix. These genotypes deserve further attention as potential sources of alkaline soil tolerance.