Abstract:
Sorghum is the second most important cereal food crop after maize in Ethiopia. However, the
parasitic weed Striga hermonthica severely constraints its production, and causes considerable
crop damage in the semi-arid tropics. The use of Striga resistant sorghum varieties is one of the
most feasible ways of managing the Striga problem. Precise and reliable screening techniques are
indispensable in order to select Striga resistant lines through breeding. Field and bioassay
experiments were carried out to 1) assess the field reaction of selected advanced lines under Striga
hermonthica infestation condition; and 2) validate the reaction of these lines for low germination
stimuli using bioassay in the laboratory. Twenty-two (22)sorghum genotypes with two resistant
and one susceptible check were evaluated under Striga hot spot area at Fadis Agricultural
Research Center in 2016 season using 5x5 triple lattice design. The bioassay experiment was
conducted using the same genotypes in a completely randomized design (CRD) with three
replications at National Agricultural Biotechnology Research Center of Holetta. During the field
experiment, 11 parameters were measured among which Striga count emerged on each genotype
was the indicator of resistance genotypes. Genotypes differed significantly in all measured
parameters and in their reactions to Striga. Maximum germination distance (MGD), germination
rate near the host roots, germination index, and haustorial initiation percentage were recorded
and significant differences were observed among the genotypes tested. Germination rate of Striga
around the host root and maximum germination distance from the host root was also used as the
index of resistance. Sorghum genotypes 2006 MW 6044, ETSC 300080, ETSC 300081, 05 MW
6019, ETSC 300086, 2006 MW 6123, ETSC 300003, ETSC 300082, and 05 MW 6028 induced less
Striga seed germination and lower maximum germination distance, which was not significantly
different from the resistant checks Gobiye and SRN-39. Out of the 22 genotypes, eight had a
maximum germination distance of less than 10 mm (MGD<10). 2006 MW 6044, ETSC 300003,
ETSC 300081, 05 MW 6019, and ETSC 300080 showed Striga resistance in the field and low
germination stimulant in bioassay test. Thus, these genotypes were the most promising sources of
resistance to the obligate root parasite Striga hermonthica. From field and bioassay experiments, it
could be suggested that genetic variability for resistance and tolerance is available in a range of
genotypes, which could be used for future breeding and production in Striga infested areas.
