antibiosis to sca in pl 550610 and sca-greenbug interactions
TRANSCRIPT
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Antibiosis to SCA in PI 550610and SCA-Greenbug Interactions
J.P. MichaudKansas State University
Sorghum – Sugarcane Aphid Research Exchange Meeting
New Orleans, LAJanuary 7 – 8, 2016
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Introduction
• ‘Aggressive’ aphids such as SCA and greenbug (GB) subvert plant physiology
• Antibiotic traits prevent such aphids from ‘hijacking’ plant metabolic processes
• Host plants also mediate interactionsbetween aphids in mixed colonies
• Most such interactions are negative andasymmetric (one aphid hurts the other)
• However, ‘top down’ benefits of aggregationtend to be more important
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Materials & Methods
• We reared SCA and GB, alone and together,on susceptible and resistant sorghums
• Either: 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 reproduce
on the same plant• All life history data recorded daily - survival, developmental time, reproduction• Life tables constructed (rm, lx, mx, DT etc.)
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GB SCA0
20
40
60
80
100
Surv
ival
(%)
Susceptible
GB SCA0
20
40
60
80
100
Resistant
Sorghum cultivar
KS116B (with 550610 res) reduces nymphalsurvival (birth to adult) of both aphid species
ab
aa
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GB SCA0
2
4
6
8
10
GB SCA0
2
4
6
8
10
Developmental time (birth – adult molt) of GB vs SCAon susceptible and resistant sorghums (23 °C)
a
b
aa
Susceptible ResistantResistance slows development of both aphid species and eliminates
the developmental rate advantage of SCA over GB
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 280
2
4
6
8
GB
SCA
Nym
phs /
fem
ale
Time (days)
Relative reproductive rates of SCA vs GB at (23 °C) on susceptible sorghum
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 280
2
4
6
8
GB
SCA
Relative reproductive rates of SCA vs GB at (23 °C)on resistant sorghum
Time (days)
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Population doubling times (in days) at 23 °C (73 °F)
Greenbug Sugarcane Aphid
Susceptible
Resistant
2.17 1.54
2.77 3.30
90 °F daytime high, followed by 56 °F overnight low = 73 °F daily average
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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+)
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...and then there are ‘new’ aphids on sorghum...
Rusty plum aphid, Hysteroneura setariae
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Other aphids co-infesting sorghum with SCA:
Sipha maydis Rhopalosiphum padi
These aphids cannot colonize sorghum by themselves
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Key Learnings• Resistance from PI 550610 is effective
against both greenbug and SCA• Aggressive 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 SCA
• ‘New’ aphid species being found on sorghum with SCA, e.g., rusty plum aphid, hedgehog grain aphid.
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Discussion