Mating type, mefenoxam sensitivity, and pathotype diversity in Phytophthora infestans isolates from tomato in Brazil

O objetivo deste trabalho foi caracterizar 79 isolados de Phytophthora infestans, coletados em campos de tomate (Solanum lycopersicum), quanto ao grupo de compatibilidade, à sensibilidade ao mefenoxan, e à diversidade de patótipos. Os isolados foram obtidos em coletas realizadas nos anos de 2006 e 2007, em sete Estados do Brasil e no Distrito Federal. Os isolados foram usados para determinação do grupo de compatibilidade sexual (n=79), resistência ao fungicida mefenoxam (n=79) e espectro de virulência aos genes de efeito principal Ph-1, Ph-2 e Ph-3/Ph-4 (n=62). Todos os isolados foram classificados no grupo de compatibilidade A1. Isolados insensíveis ao fungicida mefenoxam foram detectados em todos os Estados amostrados, e apresentaram frequência média superior a 50%. Não houve diferença de diversidade de patótipos entre as subpopulações coletadas em 2006 e 2007, e nem entre os isolados agrupados como resistentes ou intermediariamente sensíveis ao mefenoxam. Os genes de resistência foram suplantados em diferentes frequências: Ph-1, 88,7%; Ph-2, 64,5%; e Ph-3/Ph-4, 25,8%. Isolados complexos capazes de suplantar a resistência dos quatro genes de resistência foram encontrados em baixa frequência. Programas de melhoramento de tomate no Brasil devem evitar o desenvolvimento de cultivares com resistência baseada exclusivamente em genes de efeito principal.The objective of this work was to characterize 79 Phytophthora infestans isolates collected in tomato (Solanum lycopersicum) fields, as to mating type, mefenoxam sensitivity, and pathotype composition. The isolates were sampled in 2006 and 2007 in seven Brazilian states as well as in the Distrito Federal. They were characterised as to mating type (n=79), sensitivity to fungicide mefenoxam (n=79), and virulence to three major resistance genes Ph-1, Ph-2, and Ph-3/Ph-4 (n=62). All isolates were of the mating type A1. Resistant isolates were detected in all sampled states, and its average frequency was superior to 50%. No difference was detected in pathotype diversity, neither between subpopulations collected in 2006 and 2007 nor between isolates grouped as resistant or intermediately sensitive to mefenoxam. All major resistance genes were overcome at different frequencies: Ph-1, 88.7%; Ph-2, 64.5%; and Ph-3/Ph-4, 25.8%. Isolates with virulence genes able to overcome all major resistance genes were detected at low frequencies. Tomato breeding programs in Brazil must avoid the development of cultivars with resistance based exclusively on major genes

Search for tomato Solanum (section Lycopersicon) accessions with resistance to two races of Verticillium dahliae

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Biológicas, Departamento de Fitopatologia, 2009.O tomate (Solanum lycopersicum) é uma das hortaliças mais atacadas por doenças de diversas etiologias, sendo que os fungos causam a maior parte destas doenças. Destacam-se entre estas a murcha-de-verticílio (Verticillium dahliae) e a mancha-de-estenfílio (Stemphylium solani e S. lycopersici). A melhor forma de controle destas doenças é o plantio de cultivares resistentes. Os genes de resistência Ve e Sm conferem resistência à murcha-deverticílio e à mancha-de-estenfílio, respectivamente. O surgimento e o estabelecimento da raça 2 de V. dahliae, para a qual não existe cultivares de tomateiro resistentes, e a ocorrência de surtos epidêmicos da mancha-deestenfílio, que sugere a ausência do gene Sm em muitas cultivares utilizadas e erros de identificação e de controle do patógeno, têm causado muitos prejuízos aos produtores das principais regiões produtoras da hortaliça no Brasil. Tendo como base os problemas citados, teve-se como objetivo identificar acessos de tomateiro selvagens e domésticos disponíveis no banco de germoplasma da Embrapa Hortaliças com resistência a V. dahliae (capítulo 1) e à S. solani e a S. lycopersici (capítulo 2). Todos os experimentos foram conduzidos em casa-devegetação. No capítulo 1, 100 acessos de tomateiro foram testados quanto à resistência a um isolado de V. dahliae raça 1, sendo que a inoculação foi feita através do método de imersão de raízes. Os genótipos foram avaliados 30 dias após a inoculação, através de um corte na base do caule para a verificação de escurecimento vascular, atribuindo às plantas uma escala de notas que varia de 1 (plantas sadias) a 5 (plantas mortas). Os acessos que demonstraram resistência foram reavaliados com o mesmo isolado para confirmação de resistência e mais outros quatro, pertencentes às raças 1 e 2 e de diferentes localidades, considerando-se também nessa etapa os parâmetros epidemiológicos período de incubação (PI) e índice de doença (ID). Verificou-se que houve reação diferencial dos genótipos aos isolados de cada raça (resistente à raça 1, suscetível a raça 2 e vice-versa), verificando-se também uma maior freqüência de acessos resistentes à raça 1 do patógeno. Alguns genótipos apresentaram resistência do tipo “vertical” a todos os isolados inoculados. A maior parte dos genótipos resistentes pertencia a acessos da espécie S. lycopersicum. No capítulo 2, 109 acessos de tomateiro foram testados quanto à resistência a um isolado de S. solani e a outro de S. lycopersici, através de pulverização da suspensão do inóculo em folíolos de tomate até o escorrimento. Aos 15 dias após a inoculação as plantas eram avaliadas através da visualização de sintomas foliares, sendo que as plantas resistentes apresentaram folhas sadias ou com pequenas pontuações necróticas, caracterizando reação de hipersensibilidade. Os genótipos considerados resistentes foram reavaliados com os mesmos isolados para confirmação da resistência, considerando-se os padrões epidemiológicos PI, área abaixo da curva de progresso da doença (AACPD) e ID. A maior parte dos genótipos confirmou a resistência verificada na pré-seleção. Alguns demonstraram suscetibilidade na seleção definitiva, sendo que a “resistência” inicial ocorreu devido a escapes, ou resistência do tipo “horizontal”. Verificou-se resistência aos patógenos em acessos das espécies S. lycopersicum, S. pimpinellifolium (provavelmente portadores do gene Sm), S. habrochaites e S. peruvianum (provavelmente portadores de novos alelos/genes de resistência). Os genótipos resistentes a ambas as doenças podem ser utilizados em programas de melhoramento genético e manejo integrado da doença. Para a confirmação da presença dos alelos/genes de resistência à V. dahliae e à Stemphylium nas fontes promissoras identificadas, é necessária a caracterização genética, além do teste em condições de campo sob diferentes intensidades das doenças. _________________________________________________________________________________ ABSTRACTTomato (Solanum lycopersicum) is one of the vegetables most affected by diseases of different etiologies, and the fungi cause most of these diseases, as Verticillium wilt (Verticillium dahliae) and gray leaf spot (Stemphylium solani and S. lycopersici). The best way to control these diseases is to use resistant cultivars. The Ve and Sm genes confer resistance to Verticillium wilt and gray leaf spot, respectively. The emergence and establishment of race 2 of V. dahliae, for which there is no resistant cultivars of tomato, and the occurrence of epidemic outbreaks of gray leaf spot, which suggests the absence of Sm gene in many cultivars used and errors in identification and control of the pathogen, have caused damage to many producers of the main vegetable producing regions of Brazil. Based on these problems, the main objective was to identify Solanum (section Lycopersicon) accessions of wild and domestic tomatoes available in the germplasm bank of Embrapa Vegetables with resistance to V. dahliae (Chapter 1) and S. solani and S. lycopersici (Chapter 2). All experiments were conducted in greenhouse. In Chapter 1, 100 accessions of tomato were tested for resistance to an isolate of V. dahliae race 1, and the inoculation was made by the root dipping method. Disease assessment was done 30 days after inoculation through a cut in the base of the stem to verify vascular browning, giving the plants a scale of grades ranging from 1 (healthy plant) to 5 (dead plants). A second assessment was done with the same isolate for confirmation of resistance and another four, belonging to races 1 and 2 and in different locations, based upon the epidemiological parameters incubation period (IP) and disease index (DI). Sources of race-specific resistance and also with resistance to both races were identified. The most resistant accessions belonged to S. lycopersicum In Chapter 2, 109 accessions of tomato were tested for resistance to a strain of S. solani and the other from S. lycopersici, by spraying the suspension of the inoculum on tomato leaves. At 15 days after inoculation the plants were assessed by visualization of leaf symptoms, and the resistant plants had healthy leaves or with small necrotic scores, featuring a hypersensitivity reaction. The genotypes considered resistant were evaluated with the same isolates for confirmation of resistance, considering the epidemiological patterns IP, area under the disease progress curve (AUDPC) and DI. Promising sources of resistance were identified in accessions of S. lycopersicum, S. habrochaites, S. peruvianum and S. pimpinellifolium. The S. pimpinellifolium and S. lycopersicum accessions probably have the resistance gene Sm. However, S. habrochaites and S. peruvianum might be potential new sources of gene/alleles that confer resistance to both fungi. The resistant genotypes may be useful for tomato breeding programs and integrated management of disease. To confirm the presence of alleles/genes for resistance to V. dahliae and Stemphylium in these genotypes, a genetic characterization is required in addition to testing in the field under different intensities of disease

Mating type, mefenoxam sensitivity, and pathotype diversity in Phytophthora infestans isolates from tomato in Brazil Grupo de compatibilidade, sensibilidade ao mefenoxam e diversidade de patótipos de isolados de Phytophthora infestans de tomate no Brasil

The objective of this work was to characterize 79 Phytophthora infestans isolates collected in tomato (Solanum lycopersicum) fields, as to mating type, mefenoxam sensitivity, and pathotype composition. The isolates were sampled in 2006 and 2007 in seven Brazilian states as well as in the Distrito Federal. They were characterised as to mating type (n=79), sensitivity to fungicide mefenoxam (n=79), and virulence to three major resistance genes Ph-1, Ph-2, and Ph-3/Ph-4 (n=62). All isolates were of the mating type A1. Resistant isolates were detected in all sampled states, and its average frequency was superior to 50%. No difference was detected in pathotype diversity, neither between subpopulations collected in 2006 and 2007 nor between isolates grouped as resistant or intermediately sensitive to mefenoxam. All major resistance genes were overcome at different frequencies: Ph-1, 88.7%; Ph-2, 64.5%; and Ph-3/Ph-4, 25.8%. Isolates with virulence genes able to overcome all major resistance genes were detected at low frequencies. Tomato breeding programs in Brazil must avoid the development of cultivars with resistance based exclusively on major genes.O objetivo deste trabalho foi caracterizar 79 isolados de Phytophthora infestans, coletados em campos de tomate (Solanum lycopersicum), quanto ao grupo de compatibilidade, à sensibilidade ao mefenoxan, e à diversidade de patótipos. Os isolados foram obtidos em coletas realizadas nos anos de 2006 e 2007, em sete Estados do Brasil e no Distrito Federal. Os isolados foram usados para determinação do grupo de compatibilidade sexual (n=79), resistência ao fungicida mefenoxam (n=79) e espectro de virulência aos genes de efeito principal Ph-1, Ph-2 e Ph-3/Ph-4 (n=62). Todos os isolados foram classificados no grupo de compatibilidade A1. Isolados insensíveis ao fungicida mefenoxam foram detectados em todos os Estados amostrados, e apresentaram frequência média superior a 50%. Não houve diferença de diversidade de patótipos entre as subpopulações coletadas em 2006 e 2007, e nem entre os isolados agrupados como resistentes ou intermediariamente sensíveis ao mefenoxam. Os genes de resistência foram suplantados em diferentes frequências: Ph-1, 88,7%; Ph-2, 64,5%; e Ph-3/Ph-4, 25,8%. Isolados complexos capazes de suplantar a resistência dos quatro genes de resistência foram encontrados em baixa frequência. Programas de melhoramento de tomate no Brasil devem evitar o desenvolvimento de cultivares com resistência baseada exclusivamente em genes de efeito principal

Mating type, mefenoxam sensitivity, and pathotype diversity in Phytophthora infestans isolates from tomato in Brazil

The objective of this work was to characterize 79 Phytophthora infestans isolates collected in tomato (Solanum lycopersicum) fields, as to mating type, mefenoxam sensitivity, and pathotype composition. The isolates were sampled in 2006 and 2007 in seven Brazilian states as well as in the Distrito Federal. They were characterised as to mating type (n=79), sensitivity to fungicide mefenoxam (n=79), and virulence to three major resistance genes Ph-1, Ph-2, and Ph-3/Ph-4 (n=62). All isolates were of the mating type A1. Resistant isolates were detected in all sampled states, and its average frequency was superior to 50%. No difference was detected in pathotype diversity, neither between subpopulations collected in 2006 and 2007 nor between isolates grouped as resistant or intermediately sensitive to mefenoxam. All major resistance genes were overcome at different frequencies: Ph-1, 88.7%; Ph-2, 64.5%; and Ph-3/Ph-4, 25.8%. Isolates with virulence genes able to overcome all major resistance genes were detected at low frequencies. Tomato breeding programs in Brazil must avoid the development of cultivars with resistance based exclusively on major genes

Primeiro relato da ocorrência de Ditylenchus gallaeformans em Miconia albicans no Cerrado Brasileiro, no Estado de Goiás

Miconia albicans (Melastomataceae), whose common name is canela-de-velha, is a native plant of the tropical region that is abundant in the Cerrado biome. A nematode species was found parasitizing M. albicans, causing severe deformation and gall-like structures on the infected leaves and inflorescences. Morphological, morphometric and molecular characterizations identified the nematode as Ditylenchus gallaeformans. This nematode has great potential as a biocontrol agent of plants in the family Melastomataceae, which are invasive weeds in ecosystems of the Pacific Islands. This is the first report of D. gallaeformans parasitizing M. albicans in the Cerrado of the state of Goiás.Miconia albicans (Melastomataceae), nome popular: canela-de-velha, é uma espécie vegetal nativa das regiões tropicais e abundante no bioma cerrado. Uma espécie de nematoide foi encontrada parasitando M. albicans causando severas deformações e galhas em folhas e inflorescências. Caracterizações morfológicas, morfométricas e moleculares foram realizadas e o nematoide foi identificado como sendo Ditylenchus gallaeformans. Esse nematoide tem grande potencial para o uso no controle biológico de espécies vegetais da família Melastomataceae que são invasoras em ecossistemas das ilhas do Pacífico. Este é o primeiro relato de D. gallaeformans parasitando M. albicans no cerrado goiano

Sensitivity of South American tropical forests to an extreme climate anomaly

NERC Knowledge Exchange Fellowship (NE/V018760/1) to E.N.H.C.The tropical forest carbon sink is known to be drought sensitive, but it is unclear which forests are the most vulnerable to extreme events. Forests with hotter and drier baseline conditions may be protected by prior adaptation, or more vulnerable because they operate closer to physiological limits. Here we report that forests in drier South American climates experienced the greatest impacts of the 2015–2016 El Niño, indicating greater vulnerability to extreme temperatures and drought. The long-term, ground-measured tree-by-tree responses of 123 forest plots across tropical South America show that the biomass carbon sink ceased during the event with carbon balance becoming indistinguishable from zero (−0.02 ± 0.37 Mg C ha−1 per year). However, intact tropical South American forests overall were no more sensitive to the extreme 2015–2016 El Niño than to previous less intense events, remaining a key defence against climate change as long as they are protected.Publisher PDFPeer reviewe

Sensitivity of South American tropical forests to an extreme climate anomaly

Abstract: The tropical forest carbon sink is known to be drought sensitive, but it is unclear which forests are the most vulnerable to extreme events. Forests with hotter and drier baseline conditions may be protected by prior adaptation, or more vulnerable because they operate closer to physiological limits. Here we report that forests in drier South American climates experienced the greatest impacts of the 2015–2016 El Niño, indicating greater vulnerability to extreme temperatures and drought. The long-term, ground-measured tree-by-tree responses of 123 forest plots across tropical South America show that the biomass carbon sink ceased during the event with carbon balance becoming indistinguishable from zero (−0.02 ± 0.37 Mg C ha−1 per year). However, intact tropical South American forests overall were no more sensitive to the extreme 2015–2016 El Niño than to previous less intense events, remaining a key defence against climate change as long as they are protected

Sensitivity of South American tropical forests to an extreme climate anomaly

Funder: A Moore Foundation grant, Royal Society Global Challenges grant (Sensitivity of Tropical Forest Ecosystem Services to Climate Changes), CNPq grants (441282/2016-4, 403764/2012-2 and 558244/2009-2), FAPEAM grants 1600/2006, 465/2010 and PPFOR 147/2015, CNPq grants 473308/2009-6 and 558320/2009-0. European Research Council (ERC Advanced Grant 291585 – ‘T-FORCES’), the Gordon and Betty Moore Foundation (#1656 ‘RAINFOR’, and ‘MonANPeru’), the European Union’s Fifth, Sixth and Seventh Framework Programme (EVK2-CT-1999-00023 – ‘CARBONSINK-LBA’, 283080 – ‘GEOCARBON’, 282664 – ‘AMAZALERT), the Natural Environment Research Council (NE/ D005590/1 – ‘TROBIT’, NE/F005806/1 – ‘AMAZONICA’, E/M0022021/1 - ‘PPFOR’), several NERC Urgency and New Investigators Grants, the NERC/State of São Paulo Research Foundation (FAPESP) consortium grants ‘BIO-RED’ (NE/N012542/1), ‘ECOFOR’ (NE/K016431/1, 2012/51872-5, 2012/51509-8), ‘ARBOLES’ (NE/S011811/1, FAPESP 2018/15001-6), ‘SEOSAW’ (NE/P008755/1), ‘SECO’ (NE/T01279X/1), Brazilian National Research Council (PELD/CNPq 403710/2012-0), the Royal Society (University Research Fellowships and Global challenges Awards) (ICA/R1/180100 - ‘FORAMA’), the National Geographic Society, US National Science Foundation (DEB 1754647) and Colombia’s Colciencias. We thank the National Council for Science and Technology Development of Brazil (CNPq) for support to the Cerrado/Amazonia Transition Long-Term Ecology Project (PELD/441244/2016-5), the PPBio Phytogeography of Amazonia/Cerrado Transition Project (CNPq/PPBio/457602/2012-0), PELD-RAS (CNPq, Process 441659/2016-0), RESFLORA (Process 420254/2018-8), Synergize (Process 442354/2019-3), the Empresa Brasileira de Pesquisa Agropecuária – Embrapa (SEG: 02.08.06.005.00), the Fundação de Amparo à Pesquisa do Estado de São Paulo – FAPESP (2012/51509-8 and 2012/51872-5), the Goiás Research Foundation (FAPEG/PELD: 2017/10267000329) the EcoSpace Project (CNPq 459941/2014-3) and several PVE and Productivity Grants. We also thank the “Investissement d’Avenir” program (CEBA, ref. ANR-10LABX-25-01), the São Paulo Research Foundation (FAPESP 03/12595-7) and the Sustainable Landscapes Brazil Project (through Brazilian Agricultural Research Corporation (EMBRAPA), the US Forest Service, USAID, and the US Department of State) for supporting plot inventories in the Atlantic Forest sites in Sao Paulo, Brazil. L.E.O.C.A. was supported by CNPq (processes 305054/2016-3 and 442371/2019-5). We thank to the National Council for Technological and Scientific Development (CNPq) for the financial support of the PELD project (441244/2016-5, 441572/2020-0) and FAPEMAT (0346321/2021). NE/B503384/1, NE/N012542/1 - ‘BIO-RED’, ERC Advanced Grant 291585 - ‘T-FORCES’, NE/F005806/1 - ‘AMAZONICA’, NE/N004655/1 - ‘TREMOR’, NERC New Investigators Awards, the Gordon and Betty Moore Foundation (‘RAINFOR’, ‘MonANPeru’), ERC Starter Grant 758873 -‘TreeMort’, EU Framework 6, a Royal Society University Research Fellowship, and a Leverhulme Trust Research Fellowship.The tropical forest carbon sink is known to be drought sensitive, but it is unclear which forests are the most vulnerable to extreme events. Forests with hotter and drier baseline conditions may be protected by prior adaptation, or more vulnerable because they operate closer to physiological limits. Here we report that forests in drier South American climates experienced the greatest impacts of the 2015–2016 El Niño, indicating greater vulnerability to extreme temperatures and drought. The long-term, ground-measured tree-by-tree responses of 123 forest plots across tropical South America show that the biomass carbon sink ceased during the event with carbon balance becoming indistinguishable from zero (−0.02 ± 0.37 Mg C ha−1 per year). However, intact tropical South American forests overall were no more sensitive to the extreme 2015–2016 El Niño than to previous less intense events, remaining a key defence against climate change as long as they are protected