GENETIC DIVERSITY OF STRIGA AND IMPLICATIONS FOR CONTROL AND MODELING FUTURE DISTRIBUTIONS

Abstract

The current knowledge of genetic diversity of Striga asiatica, S. hermonthica, and S. gesnerioides is reviewed. The genetic variability of these species has not been sufficiently evaluated relative to their wide distributions. Genetic diversity is a result of hybridization, clinal variation, local adaptation, and frequent colonization events. Colonization events of autogamous species formed genetically uniform populations. There is a general correlation between geographic distance and genetic distance and evidence of host specific Striga populations. The genetic diversity inherent in Striga is extremely important for modeling its future dispersal in light of global climate change. Under present day climate conditions, ecological niche models predict Striga species as serious agronomic threats to tropical and subtropical regions including the Western Hemisphere. Future climate change scenarios may result in an overall reduction in spread of Striga species in tropical and subtropical habitats with modest expansion in temperate regions.

Genetic Diversity ofStriga hermonthicaPopulations in Ethiopia: Evaluating the Role of Geography and Host Specificity in Shaping Population Structure

“…Limited studies on witchweed genetic diversity have been conducted, especially considering its wide range (Mohamed et al 2007). Striga hermonthica is an obligate outbreeder (Safa et al 1984), and its hybridization with Striga aspera has caused some taxonomic confusion (Aigbokhan et al 2000).…”

Assessment of Reaction Patterns of Hybrids to Striga hermonthica (Del.) Benth. under Artificial Infestation in Kenya and Nigeria

“…Mohamed et al (2007) have listed geographic isolation as a significant evolutionary force shaping the genetic structure of S. hermonthica populations. Some diversity assessment studies using allozymes and random amplified polymorphic DNA demonstrated that geographic distance played a major role in determining the genetic differentiation in S. hermonthica populations collected from different countries in the various regions of Africa (Bharathalakshmi et al, 1990; Kuiper et al, 1996; Koyama, 2000).…”

The parasitic weeds scourge in northern Zimbabwe: effects of soil degradation, hosts and food security implications to rural farmers

“…The observation confirms the findings by Press and Phoenix (2005) that most parasitic plants can potentially attack a large number of differently occurring species hence they have been called 'generalists' although there are exceptions to that assertion. Mohamed et al (2007) also reported that Striga spp have been found parasitizing cereals crops and wild plants. The implications of this observation is that rotation can no longer be effective as the parasite can still depend on the weed for survival until seed production.…”