Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: February 12, 2009
Publication Date: August 1, 2009
Citation: Harrison Jr, H.F., Fery, R.L., Thies, J.A., Smith, J.P. 2009. Evaluation of Cowpea Germplasm Lines Adapted for Use as a Cover Crop in the Southeastern US. HortScience. 44(5):1511. Technical Abstract: Cowpeas (Vigna unguiculata) are desirable as a cover crop, because they are tolerant of heat, drought and poor soils, grow vigorously and compete well against weeds, and provide nitrogen for rotational crops. Cowpeas were grown extensively as a forage and green manure crop in the southeastern U.S. prior to the onset of modern agricultural practices. Most of the old forage cultivars are no longer available; however, ‘Iron Clay’, which may have originated from two forage varieties, is widely grown as a cover crop. Modern southernpea cultivars have a compact growth habit and are determinate; thus, they are inferior to the forage varieties for use as a cover crop. This study was conducted to identify cowpea genotypes that are suitable for use as a cover crop. A preliminary screening experiment was conducted to evaluate a collection 47 cowpea populations. Eleven populations were selected for further testing based on their vigorous growth and weed suppressing ability. In a field experiment repeated over four years, the selected genotypes were not different from the cover crop ‘Iron Clay’ in biomass production; vigor ratings, vine growth ratings, and canopy widths of some genotypes exceeded those of ‘Iron Clay’. A strong year x population interaction indicated that the relative performance of the populations was not consistent across environments. Vigor ratings and canopy measurements were efficient selection criteria that could be useful for developing cover crop cowpea cultivars. All except one selection were highly resistant to southern root knot nematode [Meloidogyne incognita], and the selections varied in seed size, photoperiod, and susceptibility to foliar diseases. Seven of the populations were selected for further evaluation. A pure-line selection procedure was executed, i.e., a single plant was selected from each of seven populations. All of the selected plants were progeny tested in 2007, and did not segregate for important characteristics. In a subsequent experiment, the growth of individual plants, grown without competition from adjacent plants, was measured at two week intervals to determine the growth potential of the lines. Several lines grew more rapidly than ‘Iron Clay’ or had shorter photoperiods which allowed them to remain vegetative later in the growing season.