Screening legumes for integrated management of witchweeds (Alectra vogelii and Striga asiatica) in Malawi

Abstract

In Malawi the parasitic weeds (witchweeds) for cereals and legumes exist simultaneously. The predominant species for cereals is Striga asiatica, while for legumes it is Alectra vogelii, which causes damage in groundnuts (Arachis hypogea L.), cowpeas (Vigna unguiculata) and soybeans (Glycine max.). Growing legumes is a control measure for S. asiatica in cereal crops. Studies were initiated in 2000/2001 at Chitedze Research Station to screen amongst several entries of groundnuts, pigeon peas (Cajanus cajan), sunhemp (Crotalaria spp.), soybeans, velvet beans (Mucuna spp) for resistance to A. vogelii. In 2002/2003 a similar experiment was repeated, utilizing the promising entries. In 2003/2004 a screen house pot study was conducted at Bunda College to evaluate soybean lines with and without A. vogelii infection. Results from the 2000/2001 screening study indicated that amongst the crops soybean are the most susceptible to Alectra. Within soybeans, Bossier, Ocepara-4 and 501/6/12 were the least susceptible, with < 1.0 plant m -2 , compared to 5.0 plants m -2 with 427/5/7. All pigeon peas and green manure entries had no Alectra emerging on them. Similar results were obtained when the study was repeated with a few entries in 2002/2003. In a screen house study of 2003/2004, soybean varieties Bossier and Ocepara-4 had the least Alectra on them (<0.33 plants pot -1 ), while other entries such as