Screening of Cowpea Genotypes for Their Reactions to Alectra Vogelii (Benth.) in the Southern Guinea Savanna of Nigeria

Abstract

Field experiments were conducted at Garkawa, Plateau State, Nigeria (08^o52’N; 09^o34’E) during the rainy seasons of 2011 and 2012 to evaluate the reactions of cowpea genotypes to Alectrra infestations. The treatments consisted of eleven cowpea genotypes laid out in a Randomized Complete Block Design with three replications. Five varieties (IT97K-499-35, IT98K573-1-1, IT03K-338-1, IT98K-205-8 and UAM 11D, 24-55-3) were confirmed resistant to Alectra in the study area.  The Gazum local variety, Banjar, Borno brown, and TVX3236 were found to be very susceptible to Alectra; while IT84S-246-4 and IT98KD-391 recorded moderate infestation of Alectra.  The combined year effect on days to Alectra emergence showed that Gazum local, TVX3236, Banjar and Borno brown supported significantly the earliest emergence of Alectra; while the genotypes IT89KD-373-1-1 and IT84S-246-4 delayed the emergence of Alectra by 6 and 4 days , respectively. Gazum local recorded the highest number of crop plants infested with Alectra. Similarly, Alectra shoot counts were highest in Gazum local and TVX 3236.  Apart from IT84S-246-4 in 2011, pod number, pod weight and 1000 seed weights were significantly higher in the Alectra free genotypes against lower values in the Alectra infested genotypes. Also, the Alectra infested genotypes recorded significantly more crop damaged syndrome score compared with the resistant genotypes which were healthier.   It may be concluded from this investigation that IT97K-499-35, IT98K-573-1-1, IT03K-338-1, IT98K-205-8 and UAM 11D-24-55-3 that were found to be resistant to Alectra infestation which gave relatively higher grain yields are recommended for cultivation by farmers in the study area.

Keywords: key words, Cowpea genotypes,  Alectra  vogelii, Resistance/ Tolerance, Guinea Savannah.