A Review on the Biology and Resource Acquisition of Striga, and the Defense Responses of Host Plants - Abstract
Striga is an herbaceous hemiparasitic angiosperm that belongs to the Orobanchaceae family of root parasites. It is an annual and very rarely
perennial parasite. It is one of the most destructive crop pests in Africa, India, and Southeast Asia. Particularly in the Sahel region, it is the most
significant invasive species of sorghum, maize, pearl millet, upland rice, and sugarcane. In sub-Saharan Africa, more than 50 million hectares of
arable land covered with cereals and legumes are infested with one or more of these species. Consequently, annual crop losses are estimated at $75
million, $87 million, and $1.2 billion, in Ethiopia, Mali and Nigeria, respectively. In general, it causes over US $10 billion annual yield losses across
the world.
From the total 42 Striga species, 11 of them are identified to infest crops. Except Striga gesnerioides that can infect some dicotyledonous crops
all the others are parasites of monocotyledons. Among the parasitic members, Striga hermonthica and Striga asiatica are the most economically
important species. Soon after the germination, Striga uses chemical exudates from the host’s root to develop a special organ called the haustorium.
The haustorium dissolves and invades the host plant’s roots in a matter of hours, forming vascular connections that allow it to successfully siphon all
the resources required for growth. Following the parasite’s attachment, the host plant recognizes it as an alien and tries to defend itself by deploying
a variety of defensive mechanisms against the parasite’s attacks at various locations along the root.
Striga’s life cycle is extremely complex. Through a variety of mechanisms, it can easily hijack the defensive responses of a compatible host and
could result in yield losses ranging from a few percent to total crop failure. Because of this and other reasons, this study concluded that integrated
management approaches have a higher potential of reducing Striga infestation than do single control measures. Therefore, care should be taken to
test and identify effective control methods by integrating cultivars resistant to Striga.