Molecular genetics of race‐specific resistance of cowpea to Striga gesnerioides (Willd.)

Abstract

Cowpea, Vigna unguiculata (L.) Walp., is an important warm-season legume grown primarily in the semi-arid tropics. The majority of cowpea is grown by subsistence farmers in West and Central sub-Saharan Africa, where its grain and leaves are valued as human food and its stover is used for animal forage. Like all crop plants, cowpea is subject to yield losses resulting from a variety of biotic and abiotic stresses. Among the important biotic constraints to cowpea production is parasitism by the root hemiparasitic weeds Striga gesnerioides (Willd.) [witchweed] and Alectra vogelii (Benth.). At least seven races of S. gesnerioides have been identified within the cowpea-growing regions of West Africa, based on host differential response and genetic diversity analysis. Several race-specific resistance genes have been identified and located to one of two linkage groups (LG1 and LG6) of the current cowpea genetic map. Molecular markers associated with race-specific resistance genes have been identified, and several sequence-confirmed amplified regions (SCARs) have been developed for use in marker-assisted selection and breeding strategies for rapid cowpea improvement. The mechanism of race-specific resistance in the cowpea-Striga interaction has also been examined, with several genes involved in phytohormone and general disease resistance signaling transduction observed to be differentially expressed in resistant and susceptible phenotypes. Results suggest that PR5 expression may be a useful marker of Striga infection, and that salicylic acid signaling appears to play a role in the cowpea-Striga interaction.

Significance of Cuscutain, a cysteine protease from Cuscuta reflexa, in host-parasite interactions

“…The use of herbicides on infected plants with an established host parasite interaction only appears to be successful and not harmful to the host plant if the host is herbicide resistant [2,3]. Due to difficulties with conventional breeding techniques, molecular biology genomic research on parasites is needed to develop new control strategies [4-8]. Research on host reactions to parasitic plant infection in model plants such as Arabidopsis thaliana , Medicago truncatula and crops like tomato or tobacco have already generated promising results [9-12].…”

Molecular, Genetic and Agronomic Approaches to Utilizing Pulses as Cover Crops and Green Manure into Cropping Systems

“…Currently, sequence confirmed amplified region (SCAR) markers were found suitable for identifying most of the major race specific resistance genes to S. gesnerioides and they were utilized in MAS breeding [88,89]. Besides Striga , an restriction fragment length polymorphism (RFLP) marker was found to be associated with the rust caused by Uromyces vignae and it was converted to a SCAR marker [90].…”

Variation for host range within and among populations of the parasitic plant Striga hermonthica

“…Most studies of the molecular genetics of host-parasite specificity within the Striga-cereal host-parasite system have been carried out on S. gesnerioides, which is a naturally inbreeding species and infects a range of dicotyledenous hosts such as cowpea (for a review see Li et al, 2009). In this host-parasite interaction, there is clear evidence of host species-parasite population specificity.…”

“…In this host-parasite interaction, there is clear evidence of host species-parasite population specificity. Recently, the first resistance gene conferring resistance to S. gesnerioides has been identified and cloned from cowpea and shown to exhibit a gene for gene interaction with a specific race (SG3) of the parasite (Li et al, 2009). The situation is much less clear for the outbreeding species S. hermonthica, in which greater genetic variation is likely to be maintained within populations from generation to generation (Bharatha et al, 1990).…”