Evaluation of Mechanisms of Barley Genotypes Tolerance and Antixenosis Schizaphis graminum (Rondani)

Schizaphis graminum (Rondani) (Hem.: Aphididae) is one of the seriously injurious pests of cereals particularly of barley. The population of the pest has beenon the increase in recent years. Besides chemical control، another practically suitable method of controlling the pest is the use of resistant barley genotypes. In this research، 47 advanced lines along with 13 cultivars were screened in their seedling stages in greenhouse conditions (25±2ºC، 55±10% relative humidity and 16:8 photophase) while testing basis two mechanisms of antixenosis and tolerance on them. Screening was made on the basis of mean number of aphids (14 days after infection with the aphid). Rhaihan، Nosrat cultivars as well as line 20 (Mall-4-3094-2//Alpha/Cum/3/Victoria/… ICB01-1368-0AP)، carrying the least، while line 13 (Legia/CWB117-5-9-5)، line 44 (Sls/Bda//Sararood-1) and Zarjo cultivar attracting the most mean number of aphids، were selected for antixenosis and for tolerance tests. Antixenosis experiment was carried out as based upon the number of attracted aphids to different cultivars within 24، 48، and 72 hours following insect release. Results indicated that Zarjo and Raihan cultivars bore the weakest vs the strongest antixenosis، respectively، as observed within all the three experimental times. Tolerance experiment was judged by the effect of aphid feeding on host plant height wise. Raihan cultivar had the most increase in its secondary height (compared with control) and the least percentage of decrease in its main height (%2. 09). Conversely، Zarjo cultivar exhibited the least increase in its secondary height (compared with control) and the greatest percentage of decrease in its main height (%65. 96)، suggesting a least level of tolerance.