management of post harvest diseases of sub-tropical and tropical fruit using their natural...

8/3/2019 Management of Post Harvest Diseases of Sub-tropical and Tropical Fruit Using Their Natural Resistance Mechanisms

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Management of postharvest diseases of

sub-tropical and tropical fruit using their

natural resistance mechanisms

Project Leader

Dr Lindy Coates

Email

[email protected]

Fax

0738462387

Phone

0732554353

Project Country

Philippines [1]

Inactive project countries

Sri Lanka

Project Coordinator Phone

(02) 6217 0553

Project Outcomes

The project team tested activators that were known resistance-inducing agents, includingacibenzolar-S-methyl (Bion), and elicitors derived from fungal pathogens (in banana). In anothercomponent they characterised some key biochemical defences contributing to the resistance,and identified treatments, varietal properties or other agronomic practices which may influence


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their relative concentrations.Mango was the common crop studied in Australia, Sri Lanka and the Philippines. In field trials,Bion was the consistently effective activator of resistance to anthracnose disease, when appliedas a foliar spray or as a soil drench 3-5 times throughout the fruiting period. There is clearly thepotential for reducing the number of fungicides applied in a given season if Bion is applied.Ultraviolet (UV-C) treatment to harvested mango activated biochemical defences and reducedanthracnose. Another key finding from field trials in Australia (cv. Keitt) and Sri Lanka (cv.Karuthacolomban) was that increasing nitrogen fertilisation enhances anthracnose levels in fruit,

which was correlated with high skin nitrogen and lower levels of preformed alk(en)ylresorcinolsin skin tissue. (The capacity to analyse the alk(en)ylresorcinol compounds was made possibleafter establishing collaboration with an expert in Poland.)Some mango cultivars (and rootstocks) consistently showed high levels of resistance toanthracnose, e.g. 'Keitt' in Australia and 'Gira' and 'Karuthacolomban' in Sri Lanka. There wassome correlation between resistance amongst varieties and levels of constitutive defences. In SriLanka the galloyltannin class of compounds was identified as a major component contributing toantifungal activity in mango peel extracts.All banana work was conducted in Sri Lanka. The existence and partial characterisation ofseveral phenylphenalone-type phytoalexins accumulating in response to infection withPhyllosticta musarum, the pathogen causing freckle disease, was confirmed. Freckle infection

also induced other biochemical defences, like pathogenesis-related proteins, phenolics andother structural defences. A banana leaf bioassay system was developed for assessingresistance-inducing capacity of elicitors derived from the banana freckle and anthracnosepathogens.In field trials, preharvest treatment with Bion and salicylic acid reduced anthracnose and crownrot, and stalk-end rot was also reduced by salicylic acid. Fertiliser field trials demonstrated thatincreased nitrogen enhances anthracnose, while application of potassium reduced anthracnoseand finger-end rot, particularly in soils with low initial levels of potassium. As with mango,cultivar differences in the resistance (or susceptibility) to anthracnose were demonstrated.It is recommended that further field trials focus on the incorporation of Bion into field diseasemanagement programs, but its registration and adoption remains the decision of Syngenta.

Other defence activators should be assessed as they become available. Postharvest UV-Ctreatment should be assessed under commercial packing-line conditions, and it is hoped thatthis will have application to disease management in mango in the near future.The information on nitrogen fertilisation in banana and mango could have immediate impact ifmade widely available to growers and other agricultural/extension staff. The short-term impact ofthe variety work is that growers/industry could choose more disease-resistant varieties. In thelonger term, the selection and adoption of more resistant rootstocks (mango) is feasible and thework on biochemical defences could lead to assays for screening germplasm for resistance aspart of a breeding program.The global knowledge of natural plant defence and what affects it has been significantlyenhanced in this project, and the capacity of all project teams to conduct such research hasbeen elevated. Some information is available immediately to industry and has beendisseminated via workshops and field days.

Project ID:

HORT/1997/094

Start Date


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01/07/2002

Project Coordinator Fax

(02) 6217 0501

Reference Number

BR-972706-35395

Project Type

Bilateral

Project Status

Concluded

Final Progress Report

Tropical and subtropical fruit crops are particularly susceptible to deterioration by postharvestdisease, and significant losses are incurred in all production areas. Current control measuresrely heavily on the use of fungicides, both before and after harvest. However, for many reasonswe can expect that the use of these fungicides will become increasingly limiting. It is thusimperative that alternative or complementary strategies are sought.

The project was undertaken to evaluate the prospect of utilising inherent plant defencemechanisms in the management of postharvest diseases focusing on mango (Australia, SriLanka and The Philippines) and banana (Sri Lanka). The key diseases were anthracnose in

mango and banana, caused by Colletotrichum gloeosporioides and C. musae, respectively, andstem-end rot in mango, caused by Botryosphaeria spp. A significant component was to identifyand evaluate activators of plant defences under field conditions. The activators were knownresistance-inducing agents, including acibenzolar-S-methyl (Bion), and elicitors derived fromfungal pathogens (in banana). Another component was to characterise some of the keybiochemical defences contributing to the resistance, and to identify treatments, varietalproperties or other agronomic practices which may influence their relative concentrations. Thefinal key objective was to enhance the capacity of project teams to conduct plant defenceresearch, and provide information to respective industries via workshops and field days.

Mango was the crop common to project activities in Australia, Sri Lanka and The Philippines. In

field trials, Bion was the most consistently effective activator of resistance to anthracnosedisease, when applied as a foliar spray or as a soil drench 3-5 times throughout the fruitingperiod. There is clearly the potential for reducing the number of fungicides applied in a givenseason if Bion is applied. UV-C treatment to harvested mango activated biochemical defencesand reduced anthracnose. Another key finding from field trials in Australia (cv. Keitt) and SriLanka (cv. Karuthacolomban) was that increasing nitrogen fertilisation enhances anthracnoselevels in fruit, which was correlated with high skin nitrogen and lower levels of preformedalk(en)ylresorcinols in skin tissue. Some mango cultivars (and rootstocks) consistently showedhigh levels of resistance to anthracnose, eg. 'Keitt' in Australia and 'Gira' and 'Karuthacolomban'in Sri Lanka. There was some correlation between resistance amongst varieties and levels of


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constitutive defences. In Sri Lanka the galloyltannin class of compounds was identified to be amajor component contributing to antifungal activity in mango peel extracts. The capacity toanalyse the alk(en)ylresorcinol compounds was made possible after establishing collaborationwith an expert in Poland.

All banana work was conducted in Sri Lanka. The existence and partial characterisation ofseveral phenylphenalone-type phytoalexins accumulating in response to infection withPhyllosticta musarum, the pathogen causing freckle disease, was confirmed. Freckle infection

also induced other biochemical defences, like PR proteins, phenolics and other structuraldefences. A banana leaf bioassay system was developed for assessing resistance-inducingcapacity of elicitors derived from the banana freckle and anthracnose (Colletotrichum musae)pathogens, and the active components were identified as 5-C polysaccharides (with a proteincomponent for the C. musae elicitor). In field trials, preharvest treatment with Bion and salicylicacid reduced anthracnose and crown rot, and stalk-end rot was also reduced by salicylic acid.Fertiliser field trials demonstrated that increased nitrogen enhances anthracnose, whileapplication of potassium reduced anthracnose and finger-end rot, particularly in soils with lowinitial levels of potassium. As with mango, cultivar differences in the resistance (or susceptibility)to anthracnose were demonstrated.

It is recommended that further field trials focus on the incorporation of Bion into field diseasemanagement programs, but its registration and adoption remains the decision of Syngenta.Other defence activators should be assessed as they become available. Postharvest UV-Ctreatment should be assessed under commercial packingline conditions, and it is hoped thatthis will have application to disease management in mango in the near future. The informationon nitrogen fertilisation in banana and mango could have immediate impact if made widelyavailable to growers and other agricultural/extension staff. The short term impact of the varietywork is that growers/industry could choose more disease resistant varieties. In the longer term,the selection and adoption of more resistant rootstocks (mango) is feasible and the work onbiochemical defences could lead to the development of assays for screening germplasm forresistance as part of a breeding program. The global knowledge of natural plant defence and

what affects it has been significantly enhanced in this project, and the capacity of all projectteams to conduct such research has been elevated. Some information is available immediatelyto industry and has been disseminated via workshops and field days.

Finish Date

31/12/2005

Extension Start Date

01/01/2006

Commissioned Organisation:

Queensland Department of Primary Industries and Fisheries, Australia

dockey

ACIA-6SEW2R


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Project Coordinator Email

[email protected]

Commissioned Organisation

Queensland Department of Primary Industries and Fisheries, Queensland Horticulture Institute,

Australia

Extension Finish Date

30/06/2007

Overview Collaborators

Department of Agriculture, Sri LankaUniversity of Peradeniya, Sri LankaPhilippine Council for Agriculture, Forestry and Natural Resources Research and

Development, PhilippinesUniversity of the Philippines at Los Banos, Philippines

ACIAR Research Program Manager

Mr Les Baxter

Progress Reports (Year 1, 2, 3 etc)

Year1:

Subproject/objective 1. Host defence mechanisms in mango and avocado fruit. >>>

Within a five week period from December 2002 to January 2003 mango and avocado peel wasextracted with appropriate organic solvents and the crude extracts partially purified by column(flash) chromatography. Many resulting fractions demonstrated antifungal activity as determinedby TLC plate bioassay, and were analysed by 1HNMR and ESMS. Some of the active fractionswere found to contain combinations of fatty acids (palmitic, oleic, linoleic and linolenic acids)and also B-sitosterol. Another promising bioactive fraction could not be satisfactorily identified.The major antifungal compound known in avocado, (Z,Z)-2-hydroxy-4-oxohenicosa-12,15-dien-1-yl acetate (or diene) was identified. This work is continuing.

In Sri Lanka bioactive compounds in mango are also being characterised. Crude analyses ofpulp tissue suggest that two antifungal compounds (yet to be identified) may be present athigher concentrations than in the peel. Another significant result obtained within the first yeardemonstrated that if mango fruits were de-sapped (stalks cut and sap drained out) soon afterharvest, the postharvest anthracnose disease was more severe compared to fruits that were notde-sapped (stalks left on). This implies a major role for sap, and its antifungal components, inthe resistance of mango to postharvest disease. This work will be repeated and extended toinclude investigation of Australian cultivars, and also characterisation of the antifungal agentsinvolved.


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Field trials in mango cv. Keitt have demonstrated that postharvest anthracnose disease is moresevere following applications of high levels of nitrogenous fertiliser through the fruiting period,corroborating previous work. Future work will determine whether levels of antifungal compoundsare affected by the high N treatments, and whether the stage of application of N fertiliser affectspostharvest disease.

Preliminary field trials have also demonstrated that preharvest treatment of fruit with a knownresistance "activator", acibenzolar-S-methyl, may reduce the severity and delay the onset of

postharvest anthracnose disease. Mango peel samples from these preliminary experiments havebeen stored at -80C for future determination of the effect of ASM treatments on levels ofantifungal compounds.

Subproject/objective 2. Freckle-induced resistance in banana fruit.

Peel of immature banana fruits cv. `Embul' did not contain detectable levels of preformedantifungal compounds. However, the fruit peel tissues responded to freckle infection byPhyllosticta musarum, with several induced defences, most notably by accumulation ofphytoalexins. Freckle-infected fruits are resistant to anthracnose disease caused byColletotrichum musae. Infection by C. musae elicits only traces of the same phytoalexins.

Further experiments indicate that there are differences in types and relative abundance ofpreformed antifungal compounds as well as phytoalexins among cultivars. The phytoalexins arebeing purified prior to their characterisation. Additionally, the pH of the peel in freckle-infected cvEmbul is maintained at a higher level and is more resistant to anthracnose than cv. Kolikuttu.Further experiments will be carried out to investigate the significance of increased peel pHfollowing freckle infection, in the resistance of fruits to anthracnose.

Subproject/objective 3. Research capacity enhancement

A project commencement workshop was held at Indooroopilly 10-14 February 2003. It wasattended by all Australian researchers associated with the project (DPI and UQ), and the project

leader and three project scientists from Sri Lanka. The workshop was also attended byadditional Israeli and Australian scientists with significant expertise in related fields of study. Allparticipants benefited from the interactions and discussions on research plans, methodologiesetc. A workshop handbook was produced and is a valuable resource.

The Australian project leader visited Sri Lanka in July 2002 to hold discussions with projectteams at the University of Peradeniya and Department of Agriculture. An Australian teammember visited Sri Lanka in June 2003 and was able to collaborate with the Department ofAgriculture team in the mango nutrition trial. He also presented 2 seminars on Australian mangoproduction, breeding and nutrition research, assisted students with sourcing of referencematerials and held discussions with staff regarding project activities.

The facilities for plant defence research at the University of Peradeniya have been significantlyenhanced in the first year by the purchase of capital equipment, ie. an electrophoresis kit andaccessories, a stereo microscope and camera, a freeze dryer, ultrasonic homogeniser and pHmeter. These items were purchased in Australia by project staff and then consigned to SriLanka.

Year2:

Year 2 (01/07/2003-30/06/2004)1. Host defence mechanisms in mango and avocado fruit (Sri Lanka and Australia) .>>>


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In Sri Lanka, one antifungal fraction of mango peel extract has been tentatively identified as amixture of galloyl tannins with glycosidic linkages. Galloyl tannins have previously been isolatedfrom other plant species and have been shown to possess antifungal activity.In both Australia and Sri Lanka, differences were found in the resistance of several mangocultivars to anthracnose. Peel and sap samples have been taken from the different cultivars foranalysis of antifungal resorcinols. In both countries it was also found that non-de-sappedmango fruit had lower levels of postharvest disease (anthracnose and stem-end rot) thande-sapped fruit, suggesting that sap plays a role in mango disease resistance.

Withholding nitrogen fertiliser or delaying application until late in fruit development resulted inlower anthracnose levels in Keitt mango fruit, compared to fruit from trees receiving earlierapplications of nitrogen. Peel samples from this trial are currently awaiting analysis for resorcinollevels.Preharvest applications of acibenzolar-S-methyl (Bion) did not significantly reduce anthracnoselevels in Kensington Pride mango fruit. However, there was a trend showing less anthracnose inacibenzolar-S-methyl treated fruit compared to control fruit.In preliminary studies, rootstock choice was shown to influence the susceptibility of KensingtonPride mangoes to anthracnose.In avocado, peel samples were taken from Hass fruitlets sampled at several different stages offruit development. These are to be analysed for antifungal diene levels in the coming months.

Attempts will be made to correlate this data with differences in the susceptibility of avocado fruitto infection by C. gloeosporioides (the anthracnose and pepper spot pathogen) at differentstages of fruit maturity.2. Freckle-induced resistance in banana fruit (Sri Lanka). >>Local banana cultivars exhibited differential susceptibility to freckle disease and anthracnose inSri Lankan studies. The cultivar "Puvalu", which is highly susceptible to freckle, was found toaccumulate high levels of phytoalexins following severe infection by the freckle fungus. As aresult, this cultivar is highly resistant to anthracnose. The cultivar Seeni, however, which isresistant to both freckle and anthracnose, was found to contain a preformed antifungalsubstance that was not detected in any other cultivars tested. Chemical analysis of thephytoalexins induced by freckle infection is underway.

Freckle infection was also shown to delay the respiratory climacteric peak and ripening of fruitcompared to non-freckled fruit, as well as significantly increasing pH of the fruit peel in allcommercial cultivars tested.Harvested banana fruit cultivars of Embul, were sprayed with different concentrations of thedefence activators salicylic acid (SA) or acibenzolar-S-methyl (Bion), and inoculated 72 hourslater with Colletotrichum musae. SA (1000 mg/l) and Bion (400 mg/l) treatments significantlyreduced anthracnose development compared with controls.3. Research capacity enhancement. >>>Three research students from the University of Peradeniya (Sri Lanka) visited DPI&F(Indooroopilly and Mareeba) in January 2004 to undergo research training. One of the QDPIFteam visited the University of Peradeniya in June 2004 and provided research methodologytraining to the Peradeniya group, particularly in pathogen isolation, identification and field trials.A two day workshop was presented at the Postgraduate Institute of Science (University ofPeradeniya) on Postharvest handling and disease control in fruit to project collaborators as wellas participants from industry and other institutions.

Year3:

Australia-Sri Lanka component. >>

Subproject/objective 1. >> Host defence mechanisms in mango and avocado fruit. >>>


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In Australian research, mango peel and sap extracts have been analysed by HPLC forquantification of constitutive antifungal compounds 5-n-heptadecenylresorcinol (C17:1) and5-n-pentadecylresorcinol (C15:0). The analyses were performed at UQ, Gatton and also by acollaborator in Poland. The analyses confirm that the heptadecenyl resorcinol is most abundantin mango. Pentadecyl resorcinol is also present in lower amounts. The abundance of thecompounds varies among cultivars, eg. Kensington Pride>Keitt=Celebration>Kent=R2E2=NamDoc Mai=Calypso=Honey Gold=Brooks (peel extracts) and Keitt> KensingtonPride=R2E2>Calypso=Celebration> Honey Gold>Nam Doc Mai (sap extracts). These findings

are broadly in line with comparative reaction to inoculation with Colletotrichum gloeosporioides,the anthracnose pathogen, ie. from most tolerant or resistant to most susceptible,Keitt>Kensington Pride>Calypso>Honey Gold>R2E2>Nam Doc Mai. Similar varietal responsesto anthracnose have been reported in Sri Lankan cultivars: Twelve Sri Lankan mango cultivarswere screened for anthracnose development and the initial studies indicated that the cultivars,'Petti'and 'Walu' were highly susceptible to anthracnose while cvs. 'Gira', 'KC' , 'Peterpassand',and 'Pol' were the most resistant. 'Kohu' 'Malwan', 'Rata', 'Neelum', 'Wal' and 'Seylum' weremoderately susceptible. Antifungal activity levels in the cultivars are being evaluated.

A second season's field trial in Australia has demonstrated that maintaining 2-3 cm stalks atharvest could reduce the severity of postharvest anthracnose and stem-end rot diseases.

Further analyses demonstrated a strong relationship between resorcinol compounds, skinnitrogen and amount of nitrogen fertiliser applied to mango trees. As skin N increases,resorcinol levels decrease. These studies imply a major role for constitutive resorcinolcompounds in the defence response of mango to these pathogens.

In other Australian field studies, pre-harvest treatment with the plant defence activatoracibenzolar-S-methyl (ASM, Bion) again significantly enhanced resistance to postharvestanthracnose in mango. Another product, soluble potassium silicate, which may function similarlyto ASM, was also trialled, and shown to enhance resistance to anthracnose. Treatments wereeffective when applied three times through the fruiting period as a fruit dip, or soil drench. Fieldspray treatments with salicylic acid also reduced severity of anthracnose.

There was evidence from laboratory tests in Australia and Sri Lanka that postharvest exposureof mango fruit to ultra violet-C radiation, or treatment with ASM or salicylic acid (SA) could alsodecrease the severity of anthracnose. The apparent induction of resistance by these field andlab treatments was often accompanied by increases in activities of pathogenesis-relatedproteins, chitinase and B-1-3-glucanase.

In mango fertiliser trials conducted in Sri Lanka, high potassium levels were shown to reduceanthracnose severity in fruit whereas high nitrogen levels increased anthracnose. Sri Lankanfield trials also showed that high potassium levels reduce anthracnose severity in banana fruit.

Project staff in Australia have experienced ongoing difficulties in establishing suitable extractionand HPLC techniques for quantifying diene compounds in avocado peel extracts. We havenegotiated access to an HPLC machine in the Forestry building at the QDPIF IndooroopillyResearch Centre, but due to time constraints and unexpected inconsistencies in thechromatography, it has not yet been possible to establish a reliable HPLC method that wouldserve for routine analysis of samples. Recently a project staff member has undertaken trainingin HPLC theory and practice, and we hope to optimise the analyses with assistance from a newtechnical officer based at Forestry in the near future.

Subproject/objective 2. >>> Freckle-induced resistance in banana fruit. >>>In Sri lanka, polyacrylamide gel electrophoresis of extracts from banana infected with the freckle


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pathogen, Phyllosticta musarum, showed presence of at least 6 proteins or peptides that wereabsent or less intense in non-infected banana. Chitinase activity and total phenolic compoundswere also enhanced in infected banana.

A polysaccharide fraction from pycnidia of the freckle fungus has been partially purified. It isparticularly effective at eliciting phytoalexin accumulation and phenolic-associated browningwhen applied to banana petiole segments. It is being further purified by gel filtrationchromatography.

Subproject/objective 3. >>> Research capacity enhancement. >>>

The Sri Lankan project leader visited project staff at DPI&F, Indooroopilly and Mareeba inOctober 2004 where project matters were discussed and visits made to the fields andlaboratories. Research capacity at Peradeniya was further enhanced through the purchase of anorbital shaker, magnetic stirrer, research microscope and ammonia meter.

Project members are now able to routinely analyse and quantify antifungal resorcinolcompounds by HPLC technique after receiving some standard compounds and technicalassistance from a Polish collaborator.

Australia - Philippines component. >>>

This project was extended to the Philippines during this reporting period, with co-funding fromAusAID for the Philippines-Australia component The first annual report for the Philippinescomponent is not due until 31 December 2005. In August 2004, the Philippines project leaderand partners from the University of the Philippines at Los Baos and Mindanao Provincialagencies visited Australia. The team met colleagues at DPI&F Indooroopilly and Nambour, andwere briefed on the activities of the Sri Lankan component of the project. They participated in anundergraduate student session lead by the University of Queensland Gatton supervisor ofstudents who are involved in the project. They then held discussions with their Australiancounterparts on project extension matters and jointly developed a tentative work plans for the2004/2005 and 2005/2006 seasons.

In the 2004-2005 Australian mango season, preliminary investigations of effects of activators andother products on diseases in mango were made at trial sites in north Queensland and SEQueensland. The following activators were identified for use in the field trials: a silicon-basedproduct, acibenzolar-S-methyl, Pentra bark (R) surfactant (Agrichem product), and a kaolin andcopper base product. The efficacy of these activators in spray and/or drench field applicationsfor the control of postharvest rots of mangoes was investigated singly and in combination withsome fungicides. This was compared with an industry fungicide standard program that includedazoxystrobin.

Preliminary results from the DPI&F Ayr Research Station site and on two mango cultivars,Kensington Pride and R2E2, suggests that none of the activators gave satisfactory control onanthracnose and stem end rots, the two main postharvest diseases of concern, when comparedwith the standard fungicide program. The use of the activators in combination with two fungicidesprays, however, gave good disease control, comparable to results with five sprays in thestandard fungicide spray program. At one orchard, two trunk injections with the silicon productsignificantly decreased the severity of postharvest anthracnose. The above findings were takeninto consideration in revising the 2005-2006 work plans for the Philippines and Australia. Otherfactors that could have impeded on a response from the activators have been identified and willalso be investigated during the 2005 season.


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Dr Chrys Akem, DPI&F, Ayr (Australian research leader of the Philippine component), visited thePhilippines in April 2005. He participated in a project initiation workshop (held in tandem withanother new project PHT/2003/071 mango IPM/Supply chain improvement), visited potentialfield sites with Filipino partners, assisted in development of a revised work-plan and delivered alecture to the staff of PCARRD, UPLB and the Crop Protection Institute, focusing on theAustralian mango industry and current strategies for the management of field and postharvestdiseases.

Year4:

Objective 1. Host defence mechanisms in mango fruit (Sri Lanka, the Philippines and Australia).

Field trials to evaluate the efficacy of defence activators for postharvest disease control inmango were conducted in Australia (North and South Queensland) and the Philippines. In NorthQueensland, KasilR (potassium silicate) applied as a soil drench and BionR (acibenzolar-S-methyl) applied as a foliar spray significantly reduced the incidence of stem-end rot and totalpostharvest disease in 'R2E2' mango fruit. Reductions in anthracnose by these treatments werenot statistically significant this season. There were also no significant reductions in postharvestdisease levels in 'Kensington Pride' (KP) mangoes by defence activator treatments at both the

North and South Queensland field sites, although there was an encouraging trend of reducedanthracnose by two silicon treatments at one field site in south Queensland. Variability in theresponse of mango to defence activator treatments may be related to timing and method ofapplication, soil type and regularity of flowering/fruit set. In the Philippines where trials were conducted on 'Carabao' mango at two field sites (Site 1:Davao del Sur, relatively dry mango production area and, Site 2: Davao del Norte, relatively wetmango production area), BionR significantly reduced postharvest anthracnose, blossom blightand scab at site 2. Scab was also reduced by BionR at site 1. KasilR and rice hull ash (a mulchcontaining over 60% silica) reduced anthracnose and blossom blight under certain conditions atsite 2. Follow-up trials are planned for Australia, the Philippines and Sri Lanka for the nextmango season.

In Sri Lanka, desapping mango fruit significantly reduced both anthracnose and stem-end rot intwo local cultivars, confirming results from last season. Desapping 'KP' mangoes in Australiahowever did not reduce disease, which contrasts with results obtained in Australia last year.Fruit in the current season were very mature with low volumes of sap, which may account for thedifferent result. A further trial to investigate the effect of maturity and desapping on postharvestdisease in 'KP' mango is planned for the 06/07 mango season in Australia.

A selection of Sri Lankan mango cultivars of differing susceptibility to postharvest disease(anthracnose and stem-end rot) were analysed for chitinase activity in sap, sap volumes andgalloyl tannin levels in peel. Peel samples have also been extracted for resorcinol analysis.

Results obtained to date indicate some correlation between galloyl tannin levels andanthracnose resistance, although one highly susceptible cultivar did have high levels of galloyltannin. Results of resorcinol analyses will provide more information when they becomeavailable.

Objective 2. Host defence mechanisms in banana fruit (Sri Lanka).

Higher levels of total soluble phenolic acids, free phenolic acids, glycosidically-bound phenolicacids, ester-bound phenolic acids and cell wall-bound phenolic acids were found in freckle-infected banana peel compared to non-freckled peel. PR-proteins (chitinase and -1,


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3-glucanase) were also higher in freckled peel.

Elicitors were separated from cell wall extracts of Phyllosticta musarum (freckle pathogen) andColletotrichum musae (anthracnose pathogen) using gel filtration chromatography and resultingfractions were screened using a banana petiole bioassay. Fractions eliciting the strongestdefence responses were then identified for further investigation. The elicitor of C. musae wasfound to be a protein whereas that of P. musarum contained glycoproteins. Further purificationand characterisation of these are continuing.

Anthracnose development was lower in banana cultivars which had relatively low peel pH (ie.below 5.5) during ripening. In liquid culture C. musae increased pH levels of the growth mediumby secreting ammonia. The data suggests that in certain cultivars mechanisms may exist tocounter pathogen-induced pH changes.

A field trial was conducted to evaluate the defence activators BionR, salicylic acid and K2HPO4.While results are still being analysed, there are promising indications that treatments reducedanthracnose and crown rot.

Objective 3. Research capacity enhancement (Sri Lanka and Australia).

Two industry training workshops were held in Sri Lanka in October 2005. The 2-day workshopswere designed to instruct participants and improve postharvest handling capacity in Sri Lanka.The topics covered included production issues, numerous aspects of postharvest handling,quality and supply chain management. Field visits were also included to see vegetableproduction and harvest first hand. The first workshop, 'Postharvest Handling of Fruits andVegetables' was held at the Postgraduate Institute of Science, University of Peradeniya. Thetarget group was researchers, academics, industry personnel and others possessing sufficientbackground knowledge. The second workshop, 'Postharvest Handling of Cut Flowers andVegetables' was held in Nuwara Eliya and was attended by growers, sellers, researchers andindustry personnel. Both workshops were highly successful and well attended.

Year5:

Final report received 17/09/2007

Project Background and Objectives

Sri Lanka, the Philippines and Australia are significant producers of tropical fruit with goodprospects for market development. However with current control measures, field andpostharvest disease losses can affect productivity and hamper market access. The shelf-life ofmost tropical and subtropical fruit crops is limited by their high susceptibility to postharvest

diseases caused by fungi - examples are the diseases anthracnose and stem-end rot - withlosses of 20 per cent common. In mango, anthracnose also blights flowers and can causecomplete crop loss before harvest, particularly if rain occurs at flowering. Field application offungicides (e.g. copper compounds, mancozeb), and postharvest treatment with hot water andfungicides, currently form the basis for control of such pathogens, however due to theinadequacy of current options for field and postharvest disease control, alternative strategiesneed to be developed.Until recently, little attention has been given to the fact that plants have evolved their ownpowerful defence mechanisms to limit and prevent disease on developing fruit. These includebiochemical (e.g. pathogenesis-related proteins, phytoalexins) and physical (e.g. lignification)


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barriers to pathogen invasion, and may be constitutive (preformed) or inducible in nature. Thechemical defences, involving preformed or induced chemicals, cause infections to remainlocalised and quiescent (with colonisation restricted). As climacteric fruit ripen, the defencemechanisms begin to break down (antifungal compound levels drop) and disease begins todevelop. Some cultivars have naturally higher levels of the constitutive antifungals (for examplethe cultivar Hass avocado) and so disease development in ripening fruit is delayed, allowingmore fruit to be marketed and consumed before disease develops. Furthermore, constitutivemechanisms may be up-regulated (induced) by a range of elicitors, to enhance host defences

(and delay disease development).

Collaborating Institutions

Department of Agriculture, Sri LankaUniversity of Peradeniya, Sri LankaPhilippine Council for Agriculture, Forestry and Natural Resources Research and Development,PhilippinesUniversity of the Philippines at Los Banos, Philippines

Program Areas

Horticulture [2]

Overview Methodologies

This project characterised natural disease resistance mechanisms in selected commerciallyimportant fruit crops from Sri Lanka (mango, banana), and Australia (mango, avocado).Strategies were developed for their enhancement, using defence-boosting treatments andimproved grower practice, to reduce field losses and suppress postharvest disease development(Sri Lanka and the Philippines - mango; Australia - mango and avocado).

The Sri Lanka-Australia component of the project undertook a more detailed understanding ofthe nature and composition of natural defence responses of mango, banana and avocado fruitto pathogen invasion during fruit development and postharvest storage. The Sri Lankan andAustralian teams sought to define the physicochemical nature of these host defence systems interms of genotypic (species, variety or cultivar) and phenotypic (growth rate, productionenvironment) influences.Because harvested fruit becomes less able to suppress pathogen invasion as it ripens,relationships between levels of natural defence systems and fruit physiology (maturity andripening-related changes in composition) were also examined. The impact of cultural practiceson defence systems was also studied as part of formulating recommendations for the fieldmanagement of postharvest diseases.

In other studies the research team investigated the physicochemical host defence systems oreach of the host-pathogen systems under study, their induction and maintenance for naturaldefence. As well, the effectiveness of chemical (e.g. salicylic acid) and/or biological (e.g.non-pathogenic mutant) treatments was studied against the background knowledge of genotypeand phenotype influences on host defence systems and their interaction with fruit physiology.The success of the initial work on defence boosting treatments for mango (1/7/2002-30/5/2004)in the Sri Lankan-Australian collaboration led to the expansion of this component to thePhilippines.The Philippine-Australian component sought to evaluate and demonstrate sustainablealternative approaches to improve control of field and postharvest diseases of mangoes. This


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entailed participatory evaluation of superior treatments at farmer field sites and research stationsat several locations.

Overview Objectives

The project aimed to improve control options for diseases of tropical fruit, both in the field andpostharvest, by exploring the powerful defence mechanisms that plants have evolved to limitand prevent disease on developing fruit. By so doing, the project also aimed to reduce relianceon synthetic fungicides.

Project Budget

$991912.00Philippines [1]

Grant Report Value

$1091103.00

Grant Report Recipient

Queensland Department of Primary Industries and Fisheries

Grant Report Recipient Post Code

4068

Grant Report Finish Date

30/06/2007

Grant Report Start Date

25/01/2002

Related publications

Postharvest handling of tropical fruit [3]

Source URL: http://aciar.gov.au/project/HORT/1997/094

Links:

[1] http://aciar.gov.au/country/Philippines[2] http://aciar.gov.au/programarea/Horticulture[3] http://aciar.gov.au/publication/pr050

management of post harvest diseases of sub-tropical and tropical fruit using their natural...

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