Plant Resistance in Sorghums to the Sugarcane Aphid (Hemiptera: Aphididae)

Ten sorghum, Sorghum bicolor (L.) Moench, lines near or in commercial release were evaluated with the intent of identifying the phenotypic expression of host-plant resistance to the sugarcane aphid Melanaphis sacchari (Zehnter) (Hemiptera: Aphididae). Two of the 10 entries (OL2042 and SP7715) expressed a high degree of resistance to the sugarcane aphid, with damage ratings <3.0 (damage rating scale of 1.0 to 9.0, with 1.0 being no damage and 9.0 a dead plant) and were not significantly different than the known resistant Tx2783. Screening the four other entries (OL0029, SP74C40, SP78M30, and SP73B12) resulted in having very good expression of resistance scoring between <3.0 and >4.0 and were statistically lower than the susceptible check Tx7000. Chlorophyll loss and damage ratings exhibited a linear relationship (R-2 = 0.87), followed by a slight improvement (R-2 = 0.89) in the regression models when the difference in plant height was added as a second independent variable. The relationship helps explain the degree of tolerance when sorghum is challenged with high sugarcane aphid densities. These results provide sorghum producers with options for planting sorghums resistant to sugarcane aphid while allowing for more time to find and develop new sources of resistance.