The influence of The influence of Banana bunchy top virus Banana bunchy top virus infection infection on the morphology and growth ofon the morphology and growth of bananabanana

researchedresearched

byby

C. RC. R22 Hooks, M.G. Wright, D.S. Hooks, M.G. Wright, D.S. KabasawaKabasawa, , R. R. ManandharManandhar, & R.P.P. Almeida, & R.P.P. Almeida

University of Hawaii at Manoa Department of Plant & University of Hawaii at Manoa Department of Plant & Environmental Protection SciencesEnvironmental Protection Sciences

OutlineOutline

•• IntroductionIntroduction•• BBTV factsBBTV facts•• Field ExperimentsField Experiments

–– ObjectivesObjectives–– Experimental protocolExperimental protocol–– ResultsResults–– SummarySummary

•• Ending remarksEnding remarks•• AcknowledgementsAcknowledgements

Brief introductionBrief introduction

•• Banana bunchy top disease (BBTD) is 1 of the most Banana bunchy top disease (BBTD) is 1 of the most important disease of bananas in many producing regionsimportant disease of bananas in many producing regions

•• Virus can be spread by:Virus can be spread by:–– infected plant suckersinfected plant suckers–– infected plant tissues used in banana microinfected plant tissues used in banana micro--

propagationpropagation–– Aphid vectors, Aphid vectors, PentaloniaPentalonia nigronervosanigronervosa

•• Lots of misconceptions or inaccuracies regarding BBTDLots of misconceptions or inaccuracies regarding BBTD

BBTV facts BBTV facts -- what type of virus is what type of virus is BBTVBBTV??

NonNon--persistent viruspersistent virus

•• xx--mittedmitted by several aphid by several aphid speciesspecies

•• brief period of probing brief period of probing ((secssecs to to minsmins))

•• short retention time in short retention time in vectorvector

Persistent virusPersistent virus

•• xx--mittedmitted specifically by 1 specifically by 1 or a few aphid speciesor a few aphid species

•• lengthy feeding period lengthy feeding period (hours)(hours)

•• virus is retained in the virus is retained in the vector for many daysvector for many days

SemiSemi--persistent viruspersistent virus –– shares some properties of both typesshares some properties of both types

BBTV is a persistent virusBBTV is a persistent virus

BBTV factsBBTV facts

•• Cannot be spread mechanically (e.g., knives, Cannot be spread mechanically (e.g., knives, tools, etc.)tools, etc.)

•• One aphid is capable of spreading the virus.One aphid is capable of spreading the virus.

•• Aphids that have not fed on a BBTV infected Aphids that have not fed on a BBTV infected plant cannot spread the virus.plant cannot spread the virus.

•• Concentration of BBTV is higher in younger Concentration of BBTV is higher in younger leaves & decrease with increasing leaf age.leaves & decrease with increasing leaf age.

BBTV factsBBTV facts

•• Several strains of BBTV have been reported. Several strains of BBTV have been reported.

•• Once the virus enters any part of the banana Once the virus enters any part of the banana mat, the entire mat should be assumed mat, the entire mat should be assumed infected. infected.

•• Apple (e.g., dwarf Brazilian) & Williams may Apple (e.g., dwarf Brazilian) & Williams may be similarly susceptible to BBTV.be similarly susceptible to BBTV.

Current management strategy for BBTVCurrent management strategy for BBTV

•• Insecticides (e.g., Insecticides (e.g., ProvadoProvado 1.6 F)1.6 F)

•• Identifying and removing virusIdentifying and removing virus--infected infected plants as plants as early early as possibleas possible

•• Replace with known Replace with known virusvirus--freefree plantsplants

ObjectivesObjectives

1)1) Determine the incubation period of BBTDDetermine the incubation period of BBTD

2)2) Determine what aspects of banana growth, Determine what aspects of banana growth, morphology, and physiology differed between morphology, and physiology differed between infected and healthy plantsinfected and healthy plants

3)3) Investigate whether the growth of banana Investigate whether the growth of banana plants are impacted by the presence of clean plants are impacted by the presence of clean banana aphidsbanana aphids

Experimental treatments Experimental treatments

1.1. Virus (sick aphids)Virus (sick aphids)

2.2. clean (healthy aphids)clean (healthy aphids)

3.3. check ( )check ( )

BBTV

MrMr NigronervosaNigronervosa,,your test came your test came back back negneg for BBTV.for BBTV.

Experimental proceduresExperimental procedures

Source plant (e.g., symptomatic & clean)Source plant (e.g., symptomatic & clean)

Inoculated plant

BBTV plot # 3

Chlorophyll samplingChlorophyll sampling

Cork borer sm

p

SPAD

Leaf area

Leaf production

Canopy

Height

Psuedostem diam.

Petiole morphologyPetiole morphology

•• Petiole widthPetiole width

•• Petiole lengthPetiole length

•• Petiole distantPetiole distant

caliper

ResultsResults

ResultsResults

Results

88 banana plants88 banana plantswere inoculated with were inoculated with ““sicksick”” aphids and 38 aphids and 38 became sick. Hum,became sick. Hum,that's 43.2% (PCR that's 43.2% (PCR confirmed).confirmed).

% % of infected plantsof infected plants

Days after inoculation0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90

No.

of s

ympt

omat

ic p

lant

s

0

2

4

6

8

10

12Fig. 1

Days after inoculation

10 20 30 40 50 60 70 80 90

Chl

orop

hyll

leve

ls (S

PA

D)

20

25

30

35

40

45ControlVirus

Fig. 2

Days after inoculation10 20 30 40 50 60 70 80 90

Can

opy

size

(cm

)

40

60

80

100

120

140

160

180CheckVirus Fig. 3

Days after inoculation10 20 30 40 50 60 70 80 90

Leaf

are

a (c

m2 )

0

1000

2000

3000

4000

5000CheckVirus

Fig. 4

Days after inoculation10 20 30 40 50 60 70 80 90

Leaf

pro

duct

ion

0.0

0.5

1.0

1.5

2.0

2.5CheckVirus

Fig. 5

SummarySummary

•• Clean & virusClean & virus--free aphid control plants showed free aphid control plants showed similar growth.similar growth.

•• ChlChl levels (tot levels (tot ChlChl, , ChlChl a & b) > in clean a & b) > in clean vsvs. . infected plantsinfected plants

•• Infected plants show reduction in petiole Infected plants show reduction in petiole morphology, plant canopy & height, leaf area, morphology, plant canopy & height, leaf area, pseudostem diameterpseudostem diameter

•• Most of these differences were initially observed Most of these differences were initially observed 40 to 50 DAI.40 to 50 DAI.

SummarySummary

•• Petiole width & lf prod were similar w/ clean & Petiole width & lf prod were similar w/ clean & infected plants.infected plants.

•• Incubation period of BBTV in HI ranged from 30 Incubation period of BBTV in HI ranged from 30 to 85 days. (Australia 19 to 125 d)to 85 days. (Australia 19 to 125 d)

•• At least 6 leaves need to appear after virus At least 6 leaves need to appear after virus inoculation before the appearance of symptoms.inoculation before the appearance of symptoms.

•• Most plants showed symptoms between 30 Most plants showed symptoms between 30 -- 50 50 DAI (71%).DAI (71%).

•• PCR could detect diseased plant 5 to 10 d prior PCR could detect diseased plant 5 to 10 d prior to the appearance of visual symptoms.to the appearance of visual symptoms.

Ending remarksEnding remarks

•• Using growth features for early detection signs Using growth features for early detection signs of of BBTVBBTV for disease for disease mgntmgnt., may not be feasible ., may not be feasible ––not obvious for rapid field diagnosis.not obvious for rapid field diagnosis.

•• Appearance of pale leaf margin was the most Appearance of pale leaf margin was the most betimes feature for diagnosing infected plants.betimes feature for diagnosing infected plants.

•• A strict monitoring program (e.g., young plants) A strict monitoring program (e.g., young plants) for early virus detection would require that fields for early virus detection would require that fields be be ed a minimum of every 5 days.ed a minimum of every 5 days.

•• Individuals growing bananas should use known Individuals growing bananas should use known virusvirus--free stock as planting material.free stock as planting material.

AcknowledgementsAcknowledgements

•• The crew at the University of Hawaii at Manoa The crew at the University of Hawaii at Manoa Poamoho Research Station Poamoho Research Station

•• Jacquelyn Robson & Mandy Jacquelyn Robson & Mandy AnhaltAnhalt for supplying for supplying micromicro--propagated banana plants propagated banana plants

•• PCR team PCR team -- Simone Simone PradoPrado, Tatiana Almeida , Tatiana Almeida & Amy & Amy HolmsteadHolmstead

•• Funding support CSREES TFunding support CSREES T--STAR, WSTAR, W--SARE & SARE & USDA PBARCUSDA PBARC

The EndThe End

Banana caretaker