Insect Resistance Management Predicting Insect Resistance in Bt Cotton using Modeling. K. R. Kranthi Central Institute for Cotton Research, Nagpur

Transcription

1 Insect Resistance Management Predicting Insect Resistance in Bt Cotton using Modeling K. R. Kranthi Central Institute for Cotton Research, Nagpur

2 Can bollworms develop resistance to Bt-cotton? When would bollworm develop resistance to BG-II in India? What can we do to delay resistance development?

3 Bt Cotton spread like wild fire in India Three genes (Cry1Ac, Cry2Ab & Cry1C), Six events, >1000 hybrids, and more to come Bt Cotton has taken the country by storm % area under Bt Cotton Doubled yields, halved pesticides: How well can we sustain these benefits?

4 Bollworm Resistance to Bt Cotton Year Sites IC 50 RR LC 50 RR Kranthi et al (unpublished) 2010 Resistance inhelicoverpa armigera populations can be a major concern

5 Evidence for cadherin mutation based resistance in China & India Banding pattern of three cadherin genotypes from H. armigera. Bands obtained with primers for normal sub-unitsunits in lanes 3,5 & 7. Bands obtained with primers for mutated subunit in lanes 4, 6 and 8

6 Frequency of Cry1Ac resistant allele 1. >5000 larvae from 50 sites of north, central & south India isofemale lines (single pair mating) F-1 pairs from 278 isofemale lines , F-2 larvae assayed with Cry1Ac 1 and 4 ug/ml and with MECH-184 leaves Bt-cotton field survivors were tested for the presence of R-alleles. l RESULTS Zone Allele freq. Genotype freq Number North /667 Central /440 South /400

7 Cry1Ac resistance is inherited as a semi-dominant trait in Indian strains of H. armigera Kranthi et al., 2006

8 Cross resistance studies (LC 50 ug/g) with Cry1Ac resistant H. armigera Toxin Cry1Ac-S Cry1Ac-R RR Cry1Ac 0.01( ) ) 2.9( ) 290 Cry1Ab 1.9 ( ) 66.8 (12-89) 35 Cry1Aa 0.12 ( ) 6.0 (2-12) 50 Cry1C 1.49 ( ) 45.4 (30-120) 30 Cry1Ba 1.09 ( ) 89.9 (28-154) 90 Cry2Aa 0.7 ( ) 1.10 ( ) 1 Cry1F ( ) ( ) 8 Cry1Ac resistance selected strains (R and near-isogenic) show resistance to Cry1Aa, Cry1Ab, Cry1C, Cry1Ba and Cry1F but not to Cry2Aa No cross resistance to any insecticide

9 Cross resistance Cry1Ac:Cry2Ab

10 Relative fitness of Cry1Ac resistant and y susceptible strains on Bt cotton

11 Inter-relationships of Cry toxins: Bioinformatics Cry toxins with least homology have a greater chance to be effective in gene pyramids

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13 Indian Data Cry1Ac Cry2Ab Frequency of fth the R allele l Dominance Survival of RR on Bt cotton Survival of SS on Bt cotton Emigration rate Fitness cost of R allele

14 Additional equations for twin stack modeling Bt-Adapt-II

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16 With only Cry1Ac it would have taken 12 years

17 With Bollgard and Bollgard II area as in India it would take 16 years

18 With Bollgard and Bollgard II area (+ 5% refuge in bag) it would take 18 years

19 With Bollgard and Bollgard II (+10% refugia) henceforth it would take 20 years

20 With only Bollgard II henceforth in India it would take 18 years

21 With Bollgard phased out by 2016 and Bollgard II alone later, would take 16 years

22 With Bollgard and Bollgard II (+5% Refugia in bag) it would take 19 years

23 With Bollgard and Bollgard II +5% Refugia + 50% PESTICIDE based control of larvae in BG II it would take 25 years

24 With only Bollgard it would have taken 12 years

25 With only Bollgard II it would have taken >55 years

26 With only Bollgard at 95% area all through it would take 57 years

27 With Bollgard only for 1 year and only Bollgard II later would take away 12 years advantage

28 With Bollgard only for 2 years and only Bollgard II later would take away 18 years advantage

29 With Bollgard only for 5 years and only Bollgard II later it would take away 40 years advantage

30 With Bollgard only for 3 years and only Bollgard II later it would take 26 years

31 With Bollgard 50% for 3 years and 2% later; only Bollgard II later it would take only 12 years

32 IRM Policy Recommendations for India 1. Phase out single gene products as soon as possible 2. Approve 5% Refuge in bag (same non-bt hybrid) + 5% pigeon-pea option 3. One bio-insecticide spray for bollworm control in BG-II plots 4. New GM products must be based on two or more independently acting genes in a stack

33 IRM Strategies for Bt-Cotton CottoninIndia Early duration pigeonpea variety as border rows One bio-insecticide or conventional spray at DAS Gene stacks with no cross resistance (Eg: Bollgard-II) Hand-picking of surviving larvae from Bt-cotton fields during September in North, October in Central & November in South India Destroy residual pupae by deep ploughing in Bt-cotton fields immediately after final harvest Timely crop termination & destroy stalks

34 Pink bollworm Resistance Monsanto Data Gujarat Feb 10 State District # of Type Populations Inference locations assayed Amreli 9 Cry1 Ac cotton 7 7 populations resistant 24 Cry1 Ac cotton populations resistant Junagarh 7 Cry1 Ac cotton 6 6 populations resistant 7 Cry1 Ac cotton 3 3populations resistant 1 Non-Bt 1 1 population resistant t Baruch 4 Cry1 Ac cotton Not yet assayed Total Cry1Ac cotton + 1 Non-Bt 33 Cry1Ac + 1 Non-Bt 33 populations from Cry1Ac cotton and 1 from non-bt show resistance to Cry1Ac in assays

35 Amrasca devastans Resistance to Imidacloprid 2010

36 Thank you My younger brother Naga Raj Kranthi created the software model