Soybean Virus Disease: The Long Course of a Rehabilitation

Transcription

1 Federal Department of Economic Affairs, Education and Research EAER Agroscope Soybean Virus Disease: The Long Course of a Rehabilitation C.A. Betrix, A. Schori, I good food, healthy environment

2 Diagnosis concept Introduction "Tourmaline Crisis in 2014 Analysis of the cycle of the disease Study of the transmission of the plant to the seed Epidemiology and agronomic impact Study of the transmission of the seed to the plant Environmental context 2

3 Diagnosis: finding the cause of a disease Disease Environment 3

4 Diagnosis: finding the cause of a disease Field Elements Distribution of symptomatic plants in the plot Host species Symptômes History of the plot etc Diagnostic Tools Hypothesis Viral species Pathogen "candidate" Immunological techniques (ELISA, LFD, IPEM... etc) Molecular characterization (Hybridization, PCR, sequencing). Biochemical characterization Particle shape Biological Identify Characteristics the cause of the symptoms Host range Biological indexing Koch's postulate (Validation) 4

5 The "Tourmaline" variety susceptible to SMV? 25 hectares affected in

6 Analysis of seed lots available in DSP 0 % 2012 Prod: AB 0.11 % 2013 Prod: FG Prod: GM Prod: CC Prod: SG 0.05 % >2.95 % >2.95 % 0.11 % 0.36 % Prod: GM % 0.11 % Prod: AT Prod: CC Prod: BT >2.95 % 2.95 % Prod: FG Presence of SMV detected at low level in all available seed lots 6

7 Analysis of the cycle of the disease SMV (Soybean Mosaic Virus) 1. Mechanical transmission 2. Transmission Plant Seed 4. Analysis of the «délavement» 3. Transmission Seed Plant 7

8 Analysis of the cycle of the disease Virus transmission SMV (Soybean Mosaic Virus) 1. Mechanical transmission Gallec 92 % Opaline 98 % Tourmaline 95 % 2. Transmission Plant Seed Gallec 8 % Opaline 20 % Tourmaline 9 % Evolution after 6 months of storage Gallec 11 % Opaline 16 % Tourmaline 11 % 3. Transmission Seed Plant Gallec 6 % Opaline 7 % Tourmaline 20 % 8

9 Analysis of the cycle of the disease Virus disease and «Délavement» % délavement Gallec 61% Opaline 68% Tourmaline 35% % SMV + Non-Délavée 3% Delavée 3% Non-Délavée 2% Delavée 8% Non-Délavée 3% Delavée 29% Transmission Seed Plant % SMV + Gallec Non-Délavée 0 % Delavée 10 % Opaline Non-Délavée 2 % Delavée 23 % Tourmaline Non-Délavée 10 % Delavée 15 % 9

10 Diagnosis: finding the cause of a disease Disease Environment 10

11 Search for reservoir plants Chenopodium sp. are a reservoir for SMV and a host for aphids 11

12 Evaluation of Vector Pressure Sitobion avenae Rhopalosiphum padi Phorodon humuli Myzus persicae Metopolophium festucae Metopolophium dirhodum Aphis fabae Brevicoryne brassicae Acyrthosiphon pisum 12

13 Conclusions of the mechanistic analysis The virus is transmitted from the plant to the seeds and vice versa Several potential vectors are present at Changins The virus is established on adventitious plants reservoirs All conditions are present for the development of the disease 13

14 Prevalence of SMV in Soybean fields at 4 sites Opaline 100% 50% 0% % 9% 76% 6% 5% 4% 38% 1% 0% 0% 4% 3% 3% 5% 0% 2% Nyon Giez Nyon Goumoens Giez Delley 3% Opaline Tourmaline Gallec Opaline Tourmaline 14

15 Notation of symptoms (1 9) Symptoms of Virus Disease vs Presence of the Virus Evaluation of leaf symptoms Lots Var. % SMV P1 Gallec 38% P2 Opaline 38% P3 Tourmaline 76% P4 Tourmaline 67% P5 Tourmaline 63% P6 Tourmaline 64% 0 P1 P2 P3 P4 P5 P6 No correlation between symptoms and infection rate (Fields and Growth chamber results) 15

16 Yields 2015 Gallec Opaline Tourmaline No correlation between yields and virus rates 16

17 Agronomic Parameters Studied Seedling emergence Density vigour Green plants at harvest Protein rate and oil content Origin of seeds No correlation between agronomic measures and virus rate 17

18 Diagnosis: finding the cause of a disease Field Components Diagnostic tools Viral Species Pathogen "candidat" Biological characteristics Koch's postulate (Validation) 18

19 Conclusions Virology Transmission by the seed Presence of vectors Presence of weeds reservoirs All conditions are present for the development of the disease Agronomy / Selection Yields of the varieties studied are not affected by SMV Strong presence of SMV in Changins = strong selection pressure on the genetic material created The initial problem is not of viral origin 19

20 Acknowledgments Merci pour votre attention Jean-Charles De Groote Olivier Schumpp Floriane Bussereau Agroscope une bonne Thomas alimentation, Steinger un environnement sain Nathalie Dubuis Justine Brodard 20

21 Thank you for your attention Olivier Schumpp Agroscope good food, healthy environment 21