Antibiosis to SCA in Pl 550610 and SCA-Greenbug Interactions

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Antibiosis to SCA in PI 550610and SCA-Greenbug InteractionsJ.P. MichaudKansas State UniversitySorghum Sugarcane Aphid Research Exchange MeetingNew Orleans, LAJanuary 7 8, 2016

IntroductionAggressive aphids such as SCA and greenbug (GB) subvert plant physiologyAntibiotic traits prevent such aphids from hijacking plant metabolic processesHost plants also mediate interactionsbetween aphids in mixed coloniesMost such interactions are negative andasymmetric (one aphid hurts the other)However, top down benefits of aggregationtend to be more important

Materials & MethodsWe reared SCA and GB, alone and together,on susceptible and resistant sorghumsEither: 10 GB, 10 SCA, or 5 GB + 5 SCA- all 1st instars (< 12 h old)P8500 (susceptible) and KS116B (resistant)Last aphid to molt to adult left to reproduceon the same plantAll life history data recorded daily - survival, developmental time, reproductionLife tables constructed (rm, lx, mx, DT etc.)

Survival (%)SusceptibleResistantSorghum cultivarKS116B (with 550610 res) reduces nymphalsurvival (birth to adult) of both aphid speciesabaa

Developmental time (birth adult molt) of GB vs SCAon susceptible and resistant sorghums (23 C)abaaSusceptibleResistantResistance slows development of both aphid species and eliminatesthe developmental rate advantage of SCA over GB

Nymphs / femaleTime (days)Relative reproductive rates of SCA vs GB at (23 C) on susceptible sorghum

Relative reproductive rates of SCA vs GB at (23 C)on resistant sorghum Time (days)

Population doubling times (in days) at 23 C (73 F)Greenbug Sugarcane AphidSusceptibleResistant2.171.542.773.3090 F daytime high, followed by 56 F overnight low = 73 F daily average

PI 550610 resistance changes commensalism into amensalism(facilitation turns into interference)

Strange things happen to aphid life tableswhen SCA and GB co-infest plants (GB+ and SCA+)


...and then there are new aphids on sorghum...Rusty plum aphid, Hysteroneura setariae

Other aphids co-infesting sorghum with SCA:Sipha maydisRhopalosiphum padi

These aphids cannot colonize sorghum by themselves

Key LearningsResistance from PI 550610 is effective against both greenbug and SCAAggressive aphids such as SCA can either improve or diminish plant suitability for other aphid species, depending on the cv.Both bottom-up and top-down effects can favor co-infestation by multiple aphid spp.Rhopalosiphum padi is able to colonize susceptible sorghums infested with SCANew aphid species being found on sorghum with SCA, e.g., rusty plum aphid, hedgehog grain aphid.


CultivarP8500 (susceptible) KS-116B (resistant)


GT (d) 9 8 7 7109910

Proportional survival 0.85 0.90 0.743 0.800 0.370.260.240.28

Nymphs / female / day 2.30 2.64 4.45 4.20 2.272.443.093.00


rm 0.32 0.37 0.45 0.45

1.34 1.45 1.57 1.57

Doubling time (d) 2.17 1.87 1.54 1.54 2.773.653.303.30

Co-infestation effect on rm0.160-0.240