Abstract:
Production of cowpea is severely hampered by different races of the parasitic
weed, Striga gesnerioides. Cultivation of Striga-resistant cowpea is the most
reliable protocol to effectively combat the parasite. The current study reported
the identification of genetic markers associated with multi-race-Striga
resistance and seed size across the genome of cowpea RIL populations. The
landrace GH3684 from Ghana was tested for resistance against all known
races of Striga gesnerioides in West Africa. Pot experiments were used to test
for resistance in each line against Striga populations collected from Northern
Ghana (GH) and Nigeria (SG3). Seed size was measured in field trials. SSR
and SNP markers were identified and used for phylogenetic analysis and
genetic mapping. A genetic linkage map was constructed with QTL
IciMapping. Segregation of SSR-1 marker with known association with the
Striga resistance gene rsg3 was 100 % consistent with the cowpea phenotypes
in SG3. This study indicated that the SG3 resistance gene is located at 12.60
cM away from that of the GH race. On the whole, 70 % of the inbred lines of
cowpea were resistant to Striga in Ghana and the lines designated UCC-11,
UCC-24, UCC-32, UCC-122, UCC-221, UCC-241, UCC-328 (best RIL
candidates for release) and GH3684 were immune to all 7 known races of
Striga in West Africa. SARC-LO2 had resistance to four races of Striga (SG2,
SG4z, SG5 and SG6). The low genetic diversity and polymorphism
information content suggest close genetic relatedness within the RIL
population. One and five SNP marker(s) were found to be associated with
cowpea seed size and Striga resistance respectively.
