Review: Arbuscular Mycorrhizal Fungi and Phosphorus Solubilizing Bacteria: Plausible Candidates or Striga hermonthica Management in Sorghum

Striga spp. root hemi parasitic weeds on major staple food crops including sorghum maize, pearl millet and rice, have been reported to threaten food security in sub-Saharan Africa. Among Striga spp., S. hermonthica is the most important and most prevalent in the region and thrives best under low soil fertility. Striga germinates in response to stimulants exuded by host roots. Following germination the parasite attaches, penetrates the host roots, establishes connection with the host xylem, grows parasitically and remains subterranean for 6-8 weeks. During the subterranean phase the parasite inflicts most of its damage. Several control tactics including cultural, chemical and biological methods have been released for combating the parasite. However, adoption rate of available control technologies remains minimal. Low adoption rate of the released technologies is attributable, mainly, to the mismatch of the technologies and the prevalent low-input subsistent farming system. The need for simple, inexpensively environmentally benign methods of control that affect the parasite at early stages of development is imperative. In nature, the Striga germination stimulants, collectively named strigolactones, are the hyphal branching factors of arbuscular mycorrhiza fungi (AMF) and their production and release from host roots are promoted by low soil fertility. The link between low soil fertility, Striga infection and mycorrhization promoted research on AMF as Striga antagonists with positive effects. However, AMF colonization was influenced by a multitude of variables including plant species, genotypes, drought, cultural practices, pesticides, initial soil fertility and the rhizospheric microbes, particularly phosphorus-solublizing bacteria and growth-promoting Rhizobacteria, where both synergistic and antagonistic interactions were reported.