Comparative Life Histories of Greenbugs and Sugarcane Aphids (Hemiptera: Aphididae) Coinfesting Susceptible and Resistant Sorghums

Abstract

Host-plant resistance has been a fundamental component of aphid management in cereal crops. Over decades, various sources of resistance to greenbug, Schizaphis graminum (Rondani), were bred into cultivars of sorghum, Sorghum bicolor (L.) Moench, to counter recurring virulent greenbug biotypes. The recent invasion of sugarcane aphid, Melanaphis sacchari (Zehntner), raised questions about plant-mediated interactions between the two aphids and the possibility of using greenbug antibiosis against sugarcane aphid. The present work was undertaken to characterize the impact of PI 550610 resistance to 'biotype I' greenbug, expressed in seed parental line KS 116B, on aphid life histories and to observe plant-mediated interactions between aphid species in its presence and absence. At 23°C, sugarcane aphid nymphs matured 1.5 d faster than greenbug nymphs on susceptible hybrid P8500, but at similar rates on the resistant line, which delayed maturity by 1-1.5 d in both species and increased juvenile mortality by three- to fourfold. Sugarcane aphid reproductive rate was double that of greenbug on susceptible sorghum (4.45 vs. 2.30 nymphs per female per day), but not significantly different on the resistant one (3.09 vs. 2.27). Thus, PI 550610 expresses antibiosis, not tolerance, to these aphids. Coinfestation of P8500 had a positive effect on greenbug intrinsic rate of increase (rm), which changed to negative on KS 116B, whereas the rm of sugarcane aphid was unaffected by coinfestation with greenbug on either cultivar. The results indicate that KS 116B will be useful for producing sugarcane aphid-resistant hybrids, and that PI 550610 antibiosis changes the sugarcane aphid-greenbug interspecific relationship from commensalism to amensalism.

Influence of Sorghum Cultivar, Phenological Stage, and Fertilization on Development and Reproduction of Melanaphis sacchari (Hemiptera: Aphididae)

“…The rates of development, fecundity, and population increase observed in our study are consistent with previous life table studies with M. sacchari on susceptible sorghums (Bayoumy et al 2016;. However, greater rates of population growth were documented on other susceptible sorghums (Bayoumy et al 2016;.…”

“…The rates of development, fecundity, and population increase observed in our study are consistent with previous life table studies with M. sacchari on susceptible sorghums (Bayoumy et al 2016;. However, greater rates of population growth were documented on other susceptible sorghums (Bayoumy et al 2016;. These studies highlight the remarkable reproductive potential of this pest, and support the need for frequent pest scouting (Brewer et al 2017) throughout the growing season.…”

“…(Maia et al 2000). Our study adds to a growing body of evidence that resistant cultivars can and do play a key role in integrated pest management programs for M. sacchari (Armstrong et al 2015;Bayoumy et al 2016;Brewer et al 2017;Szczepaniec 2018). Several resistant germplasms now have been identified, including cultivars with cross resistance to greenbug, Schizaphis graminum (Rondani) (Hemiptera: Aphididae) (Armstrong et al 2015).…”

“…Sorghum cultivar exerted the greatest influence on M. sacchari biology because no aphids survived to reproductive adults on resistant cultivar DKS 37-07. This effect is considerably greater than impacts of resistant cultivar KS 116B which reduced the intrinsic rate of increase by approximately 60% in life table studies (Bayoumy et al 2016), suggesting DKS 37-07 possesses higher levels of resistance than other resistant cultivars. Although mechanisms of resistance were not examined in this study, the lower nitrogen content in leaves of DKS 37-07 relative to DKS 38-88 suggests resistance may be related to nutritional content.…”

Sugarcane Aphid Resistance in Pearl Millet

“…Besides causing direct feeding damage on susceptible cultivars, SCA can also increase the plant's susceptibility to other aphids such as greenbug, (Schizaphis graminum (Rondani)) (Michaud et al, 2017) and bird cherry-oat aphid, (Rhopalosiphum padi L). (Bayoumy et al, 2016). This probably occurs via elicitation of higher nitrogen content in the phloem, a factor which is usually limiting for aphid growth and reproduction.…”