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

Transcription

1 The influence of Banana bunchy top virus infection on the morphology and growth of banana researched by C. R 2 Hooks, M.G. Wright, D.S. Kabasawa, R. Manandhar,, & R.P.P. Almeida University of Hawaii at Manoa Department of Plant & Environmental Protection Sciences

2 Outline Introduction BBTV facts Field Experiments Objectives Experimental protocol Results Summary Ending remarks Acknowledgements

3 Brief introduction Banana bunchy top disease (BBTD) is 1 of the most important disease of bananas in many producing regions Virus can be spread by: infected plant suckers infected plant tissues used in banana micro- propagation Aphid vectors, Pentalonia nigronervosa Lots of misconceptions or inaccuracies regarding BBTD

4 BBTV facts - what type of virus is BBTV? Non-persistent virus x-mitted by several aphid species brief period of probing (secs to mins) short retention time in vector Persistent virus x-mitted specifically by 1 or a few aphid species lengthy feeding period (hours) virus is retained in the vector for many days Semi-persistent virus shares some properties of both types BBTV is a persistent virus

5 BBTV facts Cannot be spread mechanically (e.g., knives, tools, etc.) One aphid is capable of spreading the virus. Aphids that have not fed on a BBTV infected plant cannot spread the virus. Concentration of BBTV is higher in younger leaves & decrease with increasing leaf age.

6 BBTV facts Several strains of BBTV have been reported. Once the virus enters any part of the banana mat, the entire mat should be assumed infected. Apple (e.g., dwarf Brazilian) & Williams may be similarly susceptible to BBTV.

7 Current management strategy for BBTV Insecticides (e.g., Provado 1.6 F) Identifying and removing virus-infected infected plants as early as possible Replace with known virus-free plants

8 Objectives 1) Determine the incubation period of BBTD 2) Determine what aspects of banana growth, morphology, and physiology differed between infected and healthy plants 3) Investigate whether the growth of banana plants are impacted by the presence of clean banana aphids

9 Experimental treatments 1. Virus (sick aphids) B B T V 2. clean (healthy aphids) Mr Nigronervosa, your test came back neg for BBTV. 3. check ( )

10 Experimental procedures Source plant (e.g., symptomatic & clean)

11 Inoculated plant

12 BBTV plot # 3

13 Chlorophyll sampling Cork borer smp SPAD

14 Leaf area

15 Leaf production

16 Canopy Psuedostem diam. Height

17 Petiole morphology Petiole width Petiole length Petiole distant caliper

18 Results Results Results

19 % of infected plants 88 banana plants were inoculated with sick aphids and 38 became sick. Hum, that's 43.2% (PCR confirmed).

20 No. of symptomatic plants Fig Days after inoculation

21 Chlorophyll levels (SPAD) Control Virus Fig Days after inoculation

22 Check Virus Fig. 3 Canopy size (cm) Days after inoculation

23 Check Virus Fig. 4 Leaf area (cm 2 ) Days after inoculation

24 Fig. 5 Check Virus Leaf production Days after inoculation

25 Summary Clean & virus-free aphid control plants showed similar growth. Chl levels (tot Chl, Chl a & b) > in clean vs. infected plants Infected plants show reduction in petiole morphology, plant canopy & height, leaf area, pseudostem diameter Most of these differences were initially observed 40 to 50 DAI.

26 Summary Petiole width & lf prod were similar w/ clean & infected plants. Incubation period of BBTV in HI ranged from 30 to 85 days. (Australia 19 to 125 d) At least 6 leaves need to appear after virus inoculation before the appearance of symptoms. Most plants showed symptoms between DAI (71%). PCR could detect diseased plant 5 to 10 d prior to the appearance of visual symptoms.

27 Ending remarks Using growth features for early detection signs of BBTV for disease mgnt., may not be feasible not obvious for rapid field diagnosis. Appearance of pale leaf margin was the most betimes feature for diagnosing infected plants. A strict monitoring program (e.g., young plants) for early virus detection would require that fields be ed a minimum of every 5 days. Individuals growing bananas should use known virus-free stock as planting material.

28 Acknowledgements The crew at the University of Hawaii at Manoa Poamoho Research Station Jacquelyn Robson & Mandy Anhalt for supplying micro-propagated banana plants PCR team - Simone Prado,, Tatiana Almeida & Amy Holmstead Funding support CSREES T-STAR, T W-SARE W & USDA PBARC

29 The End Banana caretaker