Abstract

Field trials were conducted between 2008/09 and 2009/10 seasons to evaluate four new cowpea lines, selected in preliminary studies, for yield, adaptation and resistance to the parasitic weed Alectra vogelii in Malawi. The design was randomised complete block design with 4 replicates at research stations and 5 at on-farm sites. For on-farm, villages were the sites and each farmer hosted one replicate. The trial sites were Lisasadzi, Mngwangwa, Bunda College, Chitedze Research Station, Rivirivi and Mpokwa in 2008/09 season and in 2009/10 the sites at Chitedze and Mpokwa were replaced by Mkwinda and Chitala Research Station. Four promising cowpea lines, IT98K-503-1, IT97K-825-15, IT99K-7-21-2-2-1 and IT99K-494-6, all originally from IITA and selected for resistance to parasitic weed Alectra vogelii in screen house studies, were compared with released varieties Sudan 1, IT82E-16 and a farmers local entry. The following parameters were evaluated: cowpea grain yield, plants/m², seeds/pod, seed weight (g/100 seeds), days to mid-flower, days to maturity, disease scores (scale 1 [clean] – 9 [most severe]) and A. vogelii emergence (plants/m²). The line IT99K-494-6 was found to have comparable or better agronomic traits as compared to control varieties and was eventually released in Malawi in January 2011. The line which is medium maturing has brown grain texture with yield potential of 1-2.0 t/ha. Such a resistant variety is important in A. vogelii hot spots to reduce build up in soil seed bank and a viable option for farmers to rotate with cowpeas in order to manage other pests such as Striga asiatica, an important parasitic weed, or improve soil fertility through the nitrogen fixation of cowpeas.

Key words: Legumes, witchweeds, parasitic weeds, cowpea, Alectra vogelii, Vigna unguiculata.