chestnut blight disease in portugal

CHESTNUT BLIGHT DISEASE IN PORTUGAL

Helena BragançaInstituto Nacional de Recursos Biológicos – INRB, I.P.

Quinta do Marquês 2784-505 Oeiras, [email protected]

Chestnut blight disease caused by Cryphonectria parasitica (Murr) Barr.

• Cryphonectria parasitica (Murr.) Barr. [Syn. Endothiaparasitica (Murril) P. J. Anderson & H. W. Anderson] (anamorph: Endothiella) is the causal agent of chestnut blight disease which infects tree species in the Castanea and Quercus genera.

• Taxonomically, C. parasitica is included in Ascomycotaphylum, Ascomycetes class, Sordariomycetidaesubclass, Diaporthales order, Valsaceae family and Cryphonectria genus (Kirk et al. 2001). Recently a new family Cryphonectriaceae was proposed in the Diaporthales by Gryzenhout et al. (2006a) including Cryphonectria

Chestnut blight disease – Spread, symptoms and signs

•Symptoms: foliage yellowing, wilting and dieback (caused by the girdling of attacked branches). Smooth bark of young branches becomes reddish and sunken. Cankers with longitudinal bark fissures appears. Some symptoms are visible from a distance during the growing season of the tree, since dry leaves remain in the twigs and copious epicormic shoots are produced by the plant below the cankers.

•Signs: presence of the reproductive structures of the parasite - pycnidia and perithecia – in yellowish to orange stromataemerging from branches or the main stem. Fungus proliferates in the cambium and in the bark tissue forming pale brown mycelial fans. Yellow tendrils of conidia (cirrhi) extrude from the stromata can be observed in wet weather.

•Long distance transportation of ascospores and mycelialparticles can be achieved by animal vectors such as birds and insects and also be carried by wind. Conidia dissemination is made by insects, birds, snails, mammals and by rain

The mechanisms of C. parasitica diffusion are not fully understood, mainly because it is not known (with seldom exceptions) the processes conducing to the dissemination phase in the biological life-cycle of the fungus at different environmental conditions.

C. parasitica wounding parasite that infects branches and stems.

Chestnut blight disease in world

• 1904 - The disease was first identified in the beginning of the 20st Century and caused the almost complete destruction of the American Chestnut population, Castanea dentata [Marsh.] Borkh.

• 1938 – First report in Europe: identification of the disease in European Chestnut stands, Castanea sativa Mill., in northern Italy.

• NowadaysEurope: all the European chestnut stands with the exception of the coppice stands in the southern UK and the scattered chestnut stands in the Netherlands Asia: China, Georgia, India (Uttar Pradesh), Japan(Honshu), Korea Democratic People's Republic, KoreaRepublic, Taiwan, Turkey. Africa: Tunisia. NorthAmerica: Canada (British Columbia, Ontario), USA (widespread).

Chestnut blight disease in Portugal

• 1929 - C. parasitica was first described by Câmara (1929), on bark samples collected on branches from young plants of Castanea crenata Sieb. & Zucc, in the Beira Baixa Province, near the village of Alcaide, Fundão.

• 1989 - Two disease foci were found on C. sativa in the Trás-os-Montes province (Carrazedo de Montenegro, Valpaços and in Parada, Bragança).

• 1990 - The disease was recognised by governmental ordinance (“Portaria847/90, 18 Setembro”) but no financial support was allocated to the control.

• 1998 – Establishment of an eradication program with financial support (“Despacho Conjunto 117/98, 18 Fevereiro”) which included logging and incineration of diseased branches or the entire tree.

Chestnut distribution in Portugal by NUT II division (data from DGRF National Forest Inventory, INE 2007)


NUT II a 1995 2005 chestnut (103ha) Norte 33.7 24.5 Centro 6.2 3.2 Lisboa e Vale do Tejo 0.2 0.0 Alentejo 0.1 0.5 Algarve 0.2 0.0 Açoresb 0.0 0.0 Madeirab 1.0 1.0 Total 41.4 29.2

b Estimated value


To assess the distribution of chestnut blight and the variability of C. parasitica across Portugal it was crucial to put into action a Nationwide monitoring program comprising all chestnut growing regions in Portugal

The selection of the sites to be monitored for the presence of chestnut blight sought to cover all the area of chestnut in Portugal with the inclusion of the highest number possible of sites previously known to present the disease. Considering the information given by the Agriculture and Forest Services and the map of chestnut distribution area in the country (DGRF map) sample sites were selected according to that information


SURVEY AND GEOGRAPHIC DISTRIBUTION

In each of the regions an assessment of all chestnut sites (by district parish – “freguesia”) with an area >0.5 ha was done. Subsequently, these areas were monitored for the presence of C. parasitica. In each district parish, as a rule, sites with previously reported presence of chestnut blight were always monitored. For the remaining areas selected, monitoring sites were randomly selected and then inspected for the presence of symptoms and/or signs of the blight.

Each sampling site was at least 1 km apart from other sites. One canker per tree was sampled for a maximum of ten different trees per site

Distinct data from the sites (e.g., signs and symptoms of disease, stand characterization, environmental conditions, etc.) and individual tree descriptions were gathered in order to find correlations with the disease.

Experimental design

district parish with chestnut


Long-term storage of C. parasitica strains

Isolation and identification of strains in laboratory

Other diseases observed- McCartney bottles with PDA stored at 6ºC- Cryo-vials tubes with glycerol stored at -80ºC

Bark samples were removed from the cankers and brought to the laboratory. Small pieces were surface-disinfected, placed on PDA plates and incubated at 25ºC in the dark. One isolate per canker was used for further analysis.

Bark samples with signs of other diseases: slide preparations for microscopic observation/ identification to the genus level


Chestnut blight disease in Portugal - Results

311MadeiraMadeira Island

1618S. Miguel

1214Terceira

26Pico

Azores Islands

02Algarve*

725 (2 FS)Alentejo

010 (8 FS)Ribatejo e Oeste*

06 ( 2 FS)Beira Litoral

623( 14 FS)Beira Interior

5873Trás-os-Montes e Alto Douro

44(FS)Entre Douro e Minho

Portugal(Mainland)

No. of Sites with C. parasitica isolates

No. of Sites prospectedRegional Agriculture Department

FS - forest stands


* Includes sites with signs and symptoms of chestnut blight

SURVEY AND GEOGRAPHIC DISTRIBUTION


Monitoring sites


Monitoring sitesDistrict parish

A total of 191 chestnut stands were surveyed across the entire country.

A total of 617 C. parasitica isolates were obtained from 108 sites (56.5% of the sampling sites ) across the four mainland provinces (Minho, Trás-Montes, Beira Interior, Alentejo), the Azores Islands (S. Miguel, Terceira, Pico), and the Madeira Island.

A collection of C. parasitica strains has been established



Genetic diversity of c. parasitica - vegetative compatibility type (vctypes).

EU -66

EU-66

EU -66

EU -66

EU -66

EU -66

EU -66

EU -11

EU -1EU -12

EU -28

EU -33

Isolates were initially paired with previously selected Portuguese vc type testers. Isolates incompatible with these testers were paired in all possible combinations, in order to identify new Portuguese vc types. The Portuguese vc types identified were then paired with European vc type testers EU-1 to EU-74.

Vegetative compability is controlled by allelic interactions in which two individuals are compatible only if they share the same alleles at all vic loci


80,2%

7,1%

0,8%

1,9%6,6%

0,2%

0,2%

1,0%1,9%

EU-1EU-2EU-11EU-12EU-28EU-33EU-66P-7P-9

Percentage of vegetative compatability types (CV) in a total of 617 Portuguese differentiateisolates

Distribution of C. parasitica VC types

Azores archipelago

Madeira archipelago

Terceira

S. Miguel

Pico

Madeira

Alentejo

Beira Interior

Trás-os-Montese Alto Douro

Entre Douro e Minho

EU-1EU-2EU-11EU-12EU-28EU-33EU-66P-7P-9

Chestnut distribution


Regional Department of AgricultureArea

VC types

81%

4% 15%

75%

25%

85%

5% 5% 5%

80%

9% 9%1%

0.2%

94%

6%

97%

3%

Distribution of C. parasitica VC types by region


PCR amplification products of mating type alleles M1 (MAT-1) and M2 (MAT-2).

a b c d e f g h i j kM 1 M 2 M 1 M 2 M 1 M 2 M 1 M 2 M 1 M 2 M 1 M 2 M 1 M 2 M 1 M 2 M 1 M 2 M 1 M 2

20001650

bp

a b c d e f g h i j kM 1 M 2M 1 M 2 M 1 M 2M 1 M 2 M 1 M 2M 1 M 2 M 1 M 2M 1 M 2 M 1 M 2M 1 M 2 M 1 M 2M 1 M 2 M 1 M 2M 1 M 2 M 1 M 2M 1 M 2 M 1 M 2M 1 M 2 M 1 M 2M 1 M 2

20001650

bp

A sample of 152 isolates selected from all Portuguese provinces was assayed for mating type using PCR amplification with the primers M1-GS1 and M1-GS2-rev for MAT-1 and the primers M2-GS2 and InvA5n for MAT-2

Dominant mode of reproduction (sexual vs. asexual) of the pathogen by mating type determination (Mat-1 and Mat-2) and presence of perithecia


M a t i n g t y p e b C a n k e r s w i t h p e r i t h e c i a c

S u b p o p u l a t i o n

No.

of s

ites

No.

of i

sola

tes

MAT

-1

MAT

-2 n

( % )

T r á s - o s - M o n t e s e A l t o D o u r o

1 - S e r a p i c o s / S . R . A l h a r i s 9 5 0 0 3 4 1 1 7

2 – S . J . C o r v e i r a / P a d r e l a a 1 7 1 1 9 4 1 6 8 4 1 2

3 – C o r v e i r a / A r g e m i l a 4 9 0 8 2 0 9 0 2 7

4 – C a r r a z e d o M o n t e n e g r o a 6 2 8 9 1 1 3 9 3 6

5 - C h a v e s 2 1 3 - - 7 2 9

6 – C u r o u p o s 1 0 4 3 8 0 - -

7 – E s p i n h o s o 5 3 9 0 2 - -

8 - B r a g a n ç a 1 4 0 4 2 - -

9 - T a r o u c a 3 1 2 0 1 - -

1 0 - P e n e d o n o 1 2 - - - -

1 1 - M i n h o a 4 1 9 3 3 2 9 3 1

1 2 - B e i r a I n t e r i o r 6 3 5 3 1 - -

1 3 - A l e n t e j o 7 3 0 5 1 - -

1 4 - S . M i g u e l a 1 6 3 8 1 3 9 4 7 5 3

1 5 - T e r c e i r a a 1 2 4 0 2 1 1 3 6 3 5 4

1 6 - P i c o 2 3 1 2 2 5 0

1 7 - M a d e i r a a 3 1 6 6 1 1 2 1 7

T o t a l

1 0 8 6 1 7 8 5 8 5 4 1 4 3 1

a Includes cases where both mating types were present within a same site.b A subsample of isolates in each populations was assessed for mating types.cPercent of cankers with sexual structures (perithecia).n - number of canker samples examined. (-) No data available for these subpopulations.


Occurrence of healing canker, culture morphology and dsRNA screening to confirm hypovirus in C. parasitica

A sample of 87 isolates, that showed reduced levels of pigmentation and sporulation was screened for dsRNA, i.e. the genome of the hypovirus. Among the 87 isolates, 56 were from Trás-os-Montes e Alto Douro, 24 from the Azores Islands, five from Alentejo, one from Madeira Island, and one from Minho.

Healing canker in Serra da PadrelaTrás-os-Montes


C. parasitica culture morphology on Difco Potato Dextrose Agar: virulent isolate presenting the characteristic high levels of sporulation and orange pigmentation (left) and hypovirulent isolate presenting reduced levels of sporulation and pigmentation

Pairs of virulent (orange) and hypovirulent (white) isolates of C. parasitica, belonging to different vc types, on Difco Potato Dextrose Agar. No conversion of the virulent isolate to a hypovirulent

isolate (left); Successful conversion of the virulent isolate to a hypovirulent isolate as indicated by a sector of white converted mycelium (right).

CHESTNUT BLIGHT DISEASE IN PORTUGAL - RESULTS

•Chestnut blight has spread into most of the chestnut growing area of Portugal

• Low diversity of C. parasitica was found. The dominant and most widespread vc type was EU-11, which comprised 80.2% of all the isolates

•Sexual reproduction of C. parasitica is common in Portugal

•dsDNA hypovirus of C. parasitica was found in Trás-os-Montes

•Hypovirulent strains found in Portugal belongs to the dominant vc type in country (EU-11).

CHESTNUT BLIGHT DISEASE IN PORTUGAL - CONCLUSIONS

•The present low diversity of C. parasitica, associated with the existence of hypovirulent strains of the fungus, may contribute to the natural control of the disease in Portugal.

•The dsDNA hypovirus of C. parasitica are transmitted preferentially between vegetative self compatible individuals, hence, the fact that hypovirulent strains found in Portugal belongs to the dominant vc type in country will promote natural dissemination of hypovirulence.

•However, if low vc type diversity will favor hypovirus invasion of C. parasiticapopulations, conversely, the frequent sexual reproduction observed could pose a major obstacle to the spread of the hypovirus due to the potential increase of vctype diversity through sexual recombination and the production of hypovirus-free ascospores.

CHESTNUT BLIGHT DISEASE IN PORTUGAL - CONCLUSIONS

Biological control in Portugal?

•The implementation of biological control should not increase the potential for recombination in the local population.

•The hypovirulent strains should always belong to a vc type existing in the area, preferentially, the prevailing natural occurring vc type in the region.

•The introduction of hypovirulent strains in restricted areas should only be justified if asexual reproduction prevails, since the hypovirus is only transmitted through this type of reproduction.

• For the safe utilization of this technique in an ecological and environmental large scale, a robust scientific know-how is required, which is at present time economically unviable in the context of the Portuguese economy.

•The implementation of good cultural practices may be of fundamental importance to prevent further dissemination and fight the chestnut blight.


Serviços Florestais e de Agricultura, Parques Naturais e propriedades do estado

Açores•Terceira - Eng.ª Fátima Amorim, Eng.º Jorge Oliveira Martins•S. Miguel - Eng.ª Aida Medeiros, Pico: Tiago Freitas (estudante)Madeira•Eng.º Manuel Pita, Eng.º Adriano Maia, Eng.º Duarte Sardinha, Eng.º Ferdinando Abreu, Eng.ª Natália Nunes e Guarda Florestal ShoneContinente•DGRF - Eng.ª Isabel Saraiva, Eng.º Rui Natário, Eng.º Campos Andrade•DRAEDM - Eng.ª Gisela Chicau e Eng.ª Isabel Moreira da Silva•DRATM – Eng.ª Dulce Anastácio, Eng.ª M. Manuel Mesquita, Eng.º Dinis Ponteira, Eng.º Luís Sá e Eng.º Manuel Trigo.•DRABI – Eng.º Machado e Eng.ª Isabel Mata•DRABL – Eng.º Virgílio Cunha•DRARO – Eng.ª Gisela Cid•DRAAL – Eng.º Caria•DRAALG – Eng.ª Célia Torrado•ICN/PNSSM – Eng.º Luís Grilo•ICN/“Parques de Sintra, Monte da Lua” - Eng.º Jaime Ferreira e Eng.º Manuel Cavalleri•IFADAP - Eng.º Rui Melo, Eng.º Jorge Guerreiro, Eng.ª Helena Ramos e Eng.ª Natália Cordeiro•Tapada Nacional de Mafra - Eng.º Rui Feio e Eng.º José Salvado•Tapada Militar de Mafra - Tenente Coronel Portela Ribeiro e Eng.º Manuel Oliveira

Proprietários•Luís Cancela de Abreu (Belmonte - Beira Interior), Luís Brum (Biscoitos - Terceira), Hermano Mota (Gorreana – S. Miguel).

Instituições de Investigação e Universidades)•EAN / INRB – Dra. Cristina Lopes•ESAB – Prof. Eugénia Gouveia, Prof. Maria do Loreto•ESACB - Prof. João Pedro Luz e Engº José Marcelino.•FCUL/ICAT – Prof. Lélia Chambel, Dr. Abdou, Dr. Gonçalo Bernardo, Dr. Mário Gadanho, Dra. Isabel Zilhão, Dra Tania Tenreiro•ISA – Prof. Margarida Tomé e Prof. Nuno Cortês•UA – Prof. David Horta Lopes•UTAD – Prof. Carlos Abreu e Prof. Luís Martins


This research was supported by PIDDAC 204 - EFN (Supervisor N. Santos), AGRO 219 –EFN (Supervisor H. Bragança)/DRATM (Supervisor Dulce Anastácio)/ESAB (Supervisor Eugénia Gouveia) and PIDDAC 206 projects (Supervisor Helena Bragança)

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chestnut blight disease in portugal

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