FIELD AND BIOASSAY BASED SCREENING OF SORGHUM [Sorghum bicolor(L.) Moench] INBRED LINES FOR RESISTANCE TO STRIGA [Striga hermonthica (Del.)] IN EAST HARARGHE, ETHIOPIA

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.