Nut rots of chestnut: a significant problem

Transcription

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

2 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 2

3 Trend of European chestnut productions from 1961 to

4 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. 4

5 Some data on Italian production of chestnut in 2008 Source ISTAT Production in Italy (source 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 delle Piante - CNR 5

6 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. 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? 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. 6

7 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. 7

8 The main fungal diseases of chestnut fruits Black rot from Ciboria batschiana (syn. Sclerotinia pseudotuberosa) Frequent in cool and humid sites. Sporulation occurs on colonized chestnuts 1-year later. Ascomata are apothecial and stipitate. 8

9 The main fungal diseases of chestnut fruits Black rot 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. 9

10 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. 10

11 The main fungal diseases of chestnut fruits Brown rot from Gnomoniopsis sp. Spread of brown rot could be favoured by a weakening of chestnut trees due to frequent drought periods and to recurrent gall wasp attacks. 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. 11

12 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) Gnomoniopsis sp. from chestnut 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. 12

13 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. 13

14 The main fungal diseases of chestnut fruits Control To 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 CO 2 flow at 65 C during minutes). 14

15 The main fungal diseases of chestnut fruits 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. 15

16 The main fungal diseases of chestnut fruits Farm treatments: cold water curing 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). Migliorini et al, 2010: Chemical and physical characteristics of tap water and curing water Tap Water control Days of curing ph 7.7a 5.87 c 5.96 c 6.32 b Phenolic compound content (mg gallic acid L-¹) < 1.0 d c b a Phenolic index at 280 nm <0.01c 3.35 b 7.29 a 8.91 a 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. 16

17 The main fungal diseases of chestnut fruits Industrial post-harvest treatments: hot water curing. Draining off Draining off Cooling in tap water C for 45 min 17

18 Cold water curing Hot water curing No special equipment required; weight of fruits is maximized; fruits damaged by insects are rapidly separated from the healthy ones; Complete control of insects larvae; high degree of sweetness; infrastructure is required and very work intensive. fruits are immobilized for days. 18

19 The main fungal diseases of chestnut fruits Improvements 1) Water temperature and duration of treatment Temperature Minutes 50 C C C 5 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). 19

20 The main fungal diseases of chestnut fruits Other treatments Gamma radiation Inhibition 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 radiations recently 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 technology Fresh 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 days (Peano et al.2014). 20

21 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. 21

22 Thank you! 22