Influence of sugarcane aphid (Melanaphis sacchari) infestation on the resistance of sweet stem sorghum (Sorghum bicolor) to Meloidogyne species under field conditions

Nematode resistant sweet stem sorghum cultivar ‘Ndendane-X1’ has high degrees Brix for ethanol production. However, the cultivar is highly susceptible to sugarcane aphid. The study was conducted to determine the effects of aphid infestation on resistance of cv. ‘Ndendane-X1’ to a mixture of root-knot (Meloidogyne species) nematodes under field conditions. Seeds were sown at 0.3 m x 0.3 m spacing and irrigated using drip irrigation. Soon after emergence, plants were randomly selected, with one set having nematode alone, whereas the other was infested with 20 M. sacchari adults to form a nematode-aphid treatment. The nematode alone treatment was regularly sprayed under cover for aphid management, thereby ensuring that drifts were being prevented from landing on the nematode + aphid treatments. At 150 days after infestation, relative to nematode alone, nematode-aphid had reduced sucrose from 13 to 61 %, but had increased fecundity of Meloidogyne species from 59 to 199 %, with reduced plant growth variables from 35 to 55 %, along with reduced mineral nutrient elements in leaf tissues from 33 to 73 %. In conclusion, the successful use of nematode resistance in sweet stem sorghum cv. ‘Ndendane-X1’ in areas with high population densities of Meloidogyne species would depend upon the effective management of the sugarcane aphid population densities.