Nut rots of chestnut: a significant problem · 1 Nut rots of chestnut: a significant problem Danti R., Turchetti T. CNR - Institute for Sustainable Plant Protection Istituto per la

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Nut rots of chestnut: a significant problem

Danti R., Turchetti T.

CNR - Institute for Sustainable Plant Protection

Istituto per la Protezione Sostenibile delle Piante - CNR

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World production of chestnut fruits in 2010

Volumes expressed in tons (source FAOSTAT)

China 1,620,000 Turkey 59,171

South Korea 82,300 Italy 42,700

Japan 23,500 Portugal 22,400

North Korea 10,700 Spain 18,600

Greece 11,000

France 9,536

Albania 5,500

Total Asia 1,736,500 Total Europe 169,417

Istituto per la Protezione

Sostenibile delle Piante - CNR

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.

Trend of European chestnut productions from 1961 to 2010



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Different factors involved in the decrease in the

production of Italian chestnuts, such as:

• Social and economic reasons;

• Environmental and climate change;

• Diseases of chestnut and fruits caused by insects

and fungi;

• Interactions between all these constraints.



5Istituto per la Protezione delle Piante - CNR

Some data on Italian production of chestnut in 2008Source ISTAT

Region Surface (ha) Volumes (tons)

Campania 13,300 19,600

Calabria 10,700 9,600

Piedmont 5,400 5,800

Tuscany 7,800 5,400

Latium 5,200 7,000

Emila Romagna 1,600 1,050

Others 0,500

Total 46,200 50,850

Production in Italy (source ISTAT)



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FUNGI (infect nuts on the trees or on

the ground, or in post-harvest)

Greenish moulds: Penicilllium

expansum, Penicillum sp.

Black rot: Ciboria batschiana (syn.

Sclerotinia pseudotuberosa);

brown rot, mummification:

Gnomoniopsis sp.; G. pascoe; G.

castanea; G. smithogilvyi (Australia);

Phoma endogena, Phomopsis

endogena. Same fungus?

Pests and fungi causing damage to chestnut fruits

INSECTS (attack the fruits while still on

trees)

Chestnut moths

Pammene fasciana: larvae feed on

leaves then enter unripe burrs

penetrating the developing nuts;

Cydia splendana: larvae feed on

leaves then attack the unripe burrs

penetrating the developing fruits;

Cydia fagiglandana: eggs are laid on

burrs; larvae penetrate the nuts

and feed the endosperm.

Chestnut weevil

Curculio elephas: females bore the

burr and the pericarp laying a

single egg in the nut; larvae tunnel

the endosperm for feeding.

General character: fungal diseases

are often not visible externally.

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The main fungal diseases of chestnut fruits

Greenish mould: Penicillium spp.

Infections are common when chestnuts are not

properly stored (fruits not dry, cold chambers

adjusted incorrectly);

Penicillia have a brief life-cycle and are able to

sporulate abundantly;

Hot water treatment may enhance infections;

Penicillium expansum can grow at 2°C and also

in the storage cold chambers.



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Black rot from Ciboria batschiana (syn. Sclerotinia

pseudotuberosa)



Sporulation occurs on

colonized chestnuts 1-year

later. Ascomata are

apothecial and stipitate.

Frequent in cool and humid

sites.

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• C. batschiana colonizes the nuts on plants and on the ground;

• The infection starts through the hilum and the torch or galleries caused by insects;

• It has been reported also as an endophyte of fruits on trees;

• Symptoms are not visible from outside;

• Infections are more frequent in humid sites and rainy season which favour sporulation;

• Mycelium survives for 4 years in the affected fruits;

• In not proper storage, the fungus can infect the adjacent healthy nuts.


Black rot



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Brown rot from Gnomoniopsis sp.

Mummification: nuts turn chalky, whyte and sponge-like.

• Increased incidence in the last 10 years

in correspondance with ACGW invasion;

• prevailing rotting agent of chestnuts;

• strictly associated to necrotic galls;

• pycnidia formed on necrotic and

overwintering galls favour its spread.



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Brown rot from Gnomoniopsis sp.

• reported as an endophyte in 1- and 2-

years-old twigs and unripe nuts;

• It’s able to colonize easily gall tissue

and nuts still in burrs;

• produces pycnidia inside the burrs in

autumn and the fruits are infected

through the hylum and the torch;

• Infected fruits show a brownish colour

and then are mummified;

• The optimal temperature for its growth

is 25°C, the mycelium is viable even at

35°C;

• It is favored by hot summers and it

could be able to cause severe damage

as consequence of climatic change.

Spread of brown rot could be

favoured by a weakening of chestnut

trees due to frequent drought periods

and to recurrent gall wasp attacks.



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Recent morphological and molecular

assays (ITS4 and ITS 5 sequences)

supported the homology of

Gnomoniopsis sp. and G. castanea, G.

pascoe, G. smithogilvyi (Maresi et al.,

2013)

Close correspondence between

symptoms due to Gnomoniopsis sp. and

to Phoma endogena, Phomopsis

endogena reported as early as 1879 and

1951, respectively, in northern Italy.



Gnomoniopsis sp.

from chestnut

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Rot from Colletotrichum acutatum

C. acutatum was reported in necrotized galls and from dead insects inside galls

of Chinese wasp (Gaffuri et al., 2015)

Isolated also from chestnut twigs and from rotting fruits in two different

Provinces of Tuscany (Florence and Arezzo) and near Turin in Piedmont

(Turchetti unpublished data).

Described as an endophyte, its spread could be again favoured by stress

conditions (ACGW and drought) which make chestnut trees more susceptible to

latent pathogens. Its possible ecological role in chestnut-ACGW is yet to be

defined.



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ControlTo prevent damage by insects and fungi and preserve quality of fruits.

1. Farm: harvest and post-harvest (cold water treatments and

drying);

2. Industrial processing: harvest, post-harvest (warm water

treatment) followed by other processes .



storage (during 3 months at ± 0°C), industrial peeling and freezing

(tunnel with a CO2 flow at – 65°C during 15 – 20 minutes).

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Farm treatments: cold water curing

Phases

• Immersion in cold water (ratio

nuts/water 1:2) at 18 ± 1°C for 9

days;

• Fruits are dried in open air for 1 day.

Preservation may result from:

• a light fermentation of soluble sugars in

the fruits due to lactic bacteria;

• increased permeability of pericarp and

consequent solubilisation of phenolic

compounds in the fruit.



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Farm treatments: cold water curing

Migliorini et al, 2010: Chemical and physical characteristics of tap water and

curing water

Tap Water

control

Days of curing

3 6 9

pH 7.7a 5.87 c 5.96 c 6.32 b

Phenolic compound content

(mg gallic acid L-¹)

< 1.0 d 124.8 c 308.34 b 436.40 a

Phenolic index at 280 nm <0.01c 3.35 b 7.29 a 8.91 a



Nuts were stored in a cold room at 15 ± 1°C for 90 days to evaluate the

effectiveness of cold water treatment for fruit preservation (Migliorini et

al., 2010).

Inhibiting effect of treatment on fruit degradation:

•after 90 days of storage treated fruits had: a higher moisture content; a

higher sucrose, starch and phenolics content; the presence of insect larvae,

outer and inner moulds (fungi) resulted significantly reduced in treated fruits.

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Industrial post-harvest treatments: hot water

curing.

Cooling in tap water 15-

18 °C for 45 minDraining off

Draining

off



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Cold water curing

•No special equipment required;

•weight of fruits is maximized;

•fruits damaged by insects are

rapidly separated from the

healthy ones;

•fruits are immobilized for 10-11

days.

Hot water curing

•Complete control of insects

larvae;

•high degree of sweetness;

•infrastructure is required and

very work intensive.



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1) Water temperature and duration of treatment

Temperature Minutes

50°C 30

55°C 15

60°C 5

Improvements

2) Biological products added to hot water treatment.

Both the culture filtrate of T. harzianum T22 and fatty acids

additioned were effective in increasing the percentage of

healthy chestnuts and their shelf-life compared to the

control obtained following the normal company protocol

(Ruocco et al., in print)

3) Lactobacillus pentosus strains added to cold water curing process

improved the effect of the treatment and reduced the microbial

complexity of curing water (Blaiotta et al. 2014).



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Other treatments

Gamma radiationInhibition of post- harvest rotting fungi in chestnuts has been reviewed by Thomas

(1988);

• insects and fungi as Aspergillus sp. were efficently controlled;

• biological, physical, chemical and nutrional characteristics of chestnuts were not

affected and antioxidant activities were favoured (Antonio et al. 2011, 2012).

• further investigations on other rotting fungi (Ciboria batschiana, Gnomoniopsis sp.

and Colletotrichum acutatum) are desirable;

Ionizing radiationsrecently proposed (Chestnutrad project) for preservation of chestnuts: evaluation

of the adequate doses is in course in relation to the physical, chemical and

microbiological characteristics during storage (Albino Bento 2014).

Modified atmosphere technologyFresh chestnuts were stored for a maximum period of 120 days at 1 ± 1°C and 90-

95% RH using M.A. technology. Nuts were stored into pallet bags in CO2 - enriched

(80%). Quality of stored fruits was evaluated. The treated nuts were considered

marketable for up to 60-120 days (Peano et al.2014).



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Things to do (and conclusions)

Monitoring the spread of the emerging chestnut fungal rot agents;

and evaluate their role in relation to environmental factors and

other biotic stress agents;

Special attention is needed towards Gnomoniopsis sp. brown rot

and Colletotricum rot strictly associated to ACGW infestation;

Set up control techniques based on the use of biological products

to increase the marketability of nuts, reducing the environmental

impact of the traditional procedures;

Evaluate more deeply the use new alternative methods for the

preservation of chestnut fruits;

Evaluate the presence of mycotoxins in chestnuts infected by

rotting fungi.

Istituto per la Protezione Sostenibile delle Piante - CNR

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Thank you!

Documents

Nut rots of chestnut: a significant problem · 1 Nut rots of chestnut: a significant problem Danti R., Turchetti T. CNR - Institute for Sustainable Plant Protection Istituto per la