Agrow Trends in the Incidence and Management of Fungicide Resistance
Published By : Agrow Published Date : 2016-09-01 Category : Food & Beverages Sub Category : Agriculture No. of Pages : 96

Agrow Trends in the Incidence and Management of Fungicide Resistance. Fungicides are critical components in the crop protection arsenal. However, there has been very little in-depth coverage about the costly and fast-growing threats from fungicidal resistance.
Fungicide resistance and increasingly stringent regulations are major threats to the commercial longevity of the majority of fungicide active ingredients.
This unique new Agrow report is based on an in-depth assessment of accessible literature and comprehensively explains what these threats are, how they arise, the science behind them, and how companies can challenge these threats in various crop varieties across the world.
Major themes explored in this report include:
• The complexities of the evolution of resistance to Demethylation Inhibitors (DMIs), especially in cereal pathogens.
• The first cases of resistance to newer Succinate Dehydro-genase Inhibitors (SDHI) fungicides, also mainly in cereal diseases.
• Multi-drug resistance primarily in Botrytis cinerea (and also in Zymoseptoria tritici), both via efflux pump mechanisms and the simultaneous acquisition of multiple target site mutations.
The risk of resistance to new and forthcoming fungicides, including biocontrol agents and ribonucleic acids (RNAs), is also discussed.
Resistance to fungicides has become a major preoccupation across the global crop protection industry and combatting resistance has taken centre stage in considering the development of new fungicides and the management of existing compounds.

About the Author 5
Disclaimer 5
Executive Summary 6
1. Definitions 7
1.1 Resistance 7
1.2 EC50 and resistance factor (RF) 7
1.3 Cross resistance (CR) 7
1.4 Fitness penalty 8
1.5 Mode of resistance (MOR) 8
1.6 Resistance risk 8
1.7 Genotypic descriptions of resistant strains 8
2. Importance of fungicides in crop protection 10
3. Impact of resistance on current crop protection. 12
4. Resistance in the field and laboratory. 13
4.1 Baited samples versus random sampling. 13
4.2 Detection of resistance when fungicide mixtures are in use. 14
4.3 Monosporic isolations methods. 14
4.4 High-throughput phenotyping. 15
4.5 Genotypic monitoring 15
4.5.1 Methods for pathogen detection and identification 16
4.5.2 Methods for pathogen differentiation and enumeration 16
4.5.3 Limitations and advantages of genotypic monitoring. 17
5. Evolutionary perspective on resistance. 18
5.1 Dose 19
5.2 Number of applications. 20
5.3 Mixtures and alternations. 20
5.4 Fitness penalties. 21
5.5 Resistance risk related to pathogen life history parameters. 21
6. New cases of fungicide resistance since 2013 23
6.1 A1 Phenylamides 28
6.2 A2 Pyrimidines 28
6.3 A3 Hymexazole and octhilinone 28
6.4 B1/2/3 MBCs, N-phenylcarbamates, benzamides and thiazole carbamates. 29
6.5 B4 Pencycuron 30
6.6 B5 Fluopicolide 30
6.7 B6 Phenamacril 31
6.8 C1 complex 1 31
6.9 C2 SDHI 32
6.9.1 Barley net-blotch Pyrenophora teres 34
6.9.2 Potato early blight Alternaria solani 34
6.9.3 Vine powdery mildew Erysiphe necator 34
6.9.4 Apple scab Venturia inaequalis 35
6.9.5 Wheat septoria tritici blotch Zymoseptoria tritici 35
6.9.6 Prospects for resistance to SDHI fungicides. 35
6.10 C3 QoI 36
6.10.1 Asian soybean rust P. pachyrhizi 38
6.10.2 Wheat blast Magnaporthe grisea 38
6.10.3 Cercospora leaf blight of soybean Cercospora kikuchii 38
6.10.4 Anthracnose leaf spot of Peach Colletotrichum siamense 39
6.10.5 New fungicides active at the QoI site. 39
6.11 C4 QiI 39
6.12 C5 Uncouplers 39
6.13 C6 Fentin 39
6.14 C7 Silthiofam 39
6.15 C8 QoSI Ametoctradin 40
6.16 D1 Anilino-pyrimidine (AP) 40
6.17 D2, D3, D4, D5 Amino acid biosynthesis 40
6.18 E1 Azanapthalene 40
6.19 E2 Phenylpyrroles 41
6.20 E3 Dicarboximides 41
6.21 F1/2/3/4 Lipid synthesis and membrane integrity 42
6.22 G1 Demethylation inhibitors. 42
6.22.1 Molecular basis for resistance 42
6.22.2 Asian soybean rust Phakopsora pachyrhizi 44
6.22.3 Barley powdery mildew Blumeria graminis f. sp hordei 44
6.22.4 Rice false smut Villosiclava virens 45
6.22.5 Oilseed rape light leaf spot pathogen Pyrenopeziza brassicae 45
6.22.6 Barley net-blotch Pyrenophora teres 45
6.22.7 Over-expression 45
6.22.8 Multiple drug resistance 45
6.22.9 Efficacy 46
6.23 G2 14 reductase and 8-7isomerase inhibitors 48
6.24 G3 3-ketoreductase inhibitors 48
6.25 H4 Polyoxin 48
6.26 H5 - CesA3 CAA 49
6.27 I 1/2/3 Melanin biosynthesis 49
6.28 P-fungicides 50
6.29 U6 Cyflufenamid 50
6.30 U8 Metrafenone 50
6.31 U27 Cymoxanil 50
6.32 U33 Fosetyl-al 50
6.33 Oxathiapiprolin 51
7. Multidrug resistance 52
7.1 Reports of MDR, species, fungicides and genes 53
7.2 Impact of MDR and resistance on resistance management. 54
8. Risk-assessment of pathogens. 55
9. Geographic spread of resistance 57
10. New fungicide groups and resistance. Can we predict risk of resistance? 60
10.1 New fungicide classes 60
10.1.1 Biologicals 60
10.1.2 RNAi 61
11. Impact of the potential withdrawal of actives on resistance management 62
12. Conclusions 65
13. Pathogen synonym table 66
14. References 69


Figures & Tables
Table 1. Percentage loss of farmgate value resulting from withdrawal of category 1 2 or 3 fungicides 10
Table 2. Fungicide resistance by class of fungicide 24
Table 3. β-Tubulin – archetype ASPENI 30
Table 4. Myosin-5 archetype GIBBZE 31
Table 5. SDH-B archetype PYRNTE 32
Table 6. SDH-C archetype PYRNTE 33
Table 7. SDH-D archetype PYRNTE 33
Table 8. Cyt-B archetype SEPPTR 37
Table 9. OS-1 archetype BOTRCI 42
Table 10. Cyp51A archetype ASPEFU 47
Table 11. Cyp51B archetype SEPPTR 47
Table 12. CesA3 archetype PHYTIN 49
Table 13. Oxysterol-binding protein (OSBP)-Related Proteins (ORP) archetype PHYTIN 51
Table 14. Reports of MDR, species, fungicides and genes. 52
Table 15. High Risk Pathogens 1 55
Table 16. High Risk Pathogens 2 56
Table 17. Geographic spread of resistance of major pathogens 57
Table 18. Fungicides at risk of withdrawn registrations; impact on resistance 63