Resistance of different sorghum breeding lines to some insect pests

Twenty four promissing sorghum breeding lines, whithin the continued breeding program of the Rain fed Crop Research Centre (RCRC), were evalluated for possible resistance to some pests. Experiments were conducted at University of Gezira Experimental farm, Wad Medani, Sudan (14"-24" N, 33"- 39" E, 407m above the sea level ) on an irrigated crop (March - May 2002 season I) and on a rainfed crop (August-October 2002 season II). A wide array of insect pests were encountered, most of which existed in negliable densities or inflict very minor damage. The most serious and abundant groups which were considered in this study included, the stem borers (Chilo partellus and/or Sesamia cretica) being the most serious occurring during both seasons, dura aphid (Melanaphis sacchari), and the shedder bug (Creontiades pallidus) which appeared only during the second season. Significant differences were recorded between the different breeding lines in their response to the different pests during both growth stage. Percent infestation by stem borers during the first season ranged between 2.4 - 46.3and 2.2 - 45on the vegetative and flowering stages respectively. During the second season the damage was between 3.3 - 46.3for vegetative and 1.8 - 22.5on the flowering stage. Line 3 continuously being the most resistance line to pests. Damage by the dura aphid and shedder bugs during the second season seem to have little effect on the performance of the tested lines. However, line 3 also showed high resistance to their attack. Compensation potential in response to stem borers attack through production of productive tillers also vary between different breeding lines tested. The most effective line in tiller production are those that responded during early vegetative stage. Observations showed that tender and juicy stems are the most characteristics attracting stem borers, while aphid and shedder bugs are more attracted to plants that are leafy, stunted and with over-lapped leaves