Resistance to Striga hermonthica (Del.) Benth. in sorghum
Abstract
Striga hermonthica is a serious agronomic pest in the semi-arid savannas of Africa. It is the most destructive weed occurring in African sorghum fields and, excluding bird predation, may be the single most important sorghum yield loss factor. Because heavy infestations may lead in certain years to total crop failure, it is imperative that Striga populations be controlled so that they remain below the economic threshold. Varietal resistance may be the single most promising economic control measure. This study was undertaken to: (1) examine the adaptation and resistance to S. hermonthica of six sorghum lines in Niger, West Africa; (2) investigate the inheritance of resistance in three of these lines; and (3) evaluate an integrated method for control of Striga in the fields of subsistence farmers in Niger. Cultivators SRN39 and IS9830 were found to possess superior yield stability to local checks. SRN39 showed excellent field resistance in both years whereas IS9830, although more susceptible to Striga attack, was prone to escape to escape the effects of infestation due to its short life cycle. The inheritance study was conducted outdoors in artificially-infested pots in the 1987 crop season. Resistance of SRN39 was maintained in pot culture and subsequent analysis indicated that reduced infestation is a simply-inherited trait, possibly under the control of a single recessive gene. Although Framida is less adapted to the dry Nigerien climate, the pot study confirmed earlier reports that it may be a useful source of resistance. The effects of varietal resistance, urea application and mode of tillage prior to sowing on Striga infestation were investigated during two growing seasons. Varietal resistance was the most effective treatment independent of other inputs. Striga emergence and flowering were delayed and infestation was reduced on SRN39 compared to Framida and a local check. Early season application of urea (100 kg N ha$\sp{-1}$) delayed Striga emergence and flowering and reduced infestation as well as increasing sorghum growth and yield. Plowing with oxen improved water infiltration in a dry year (1987) but resulted in increased Striga infestation in a year with above-average rainfall (1986).
Degree
Ph.D.
Advisors
Ejeta, Purdue University.
Subject Area
Genetics|Agronomy
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.