Genetic and phenotypic insights in the adaptation of Magnaporthe oryzae to rice
Magnaporthe oryzae is a model and a major pathogen of rice
• Worldwide distribution • 5 M T losses/year (0.8%) • 2/3 fongicide market on rice • Localy 100 % losses
But resistance breakdown common and rapid
Rice blast controlled by: fungicides
agronomic practices
resistant varieties
Rationale
Explained by:
- Gene for gene interactions
- Mutations in avirulence genes
AvrPik AvrPita
Kanzaki et al Plant J. 2012 Chuma et al Plos Path. 2011
-9 cloned avr genes corresponding to rice R genes:
ACE1, AvrPi-a, AvrPi-b, AvrCo39, AvrPi-i, AvrPi-k, AvrPi-ta, AvrPi-zt, AvrPi9
-All kinds of mutations: Deletion, duplication, point mutation, transposon insertion…
-Frequency of mutation type depending on the avr gene -Frequency of virulent strains depending on the avr gene
- Each Avr/R gene couple probably has a unique co-evolutionary history - Mo samples not always appropriate and R gene deployment info lacking to study adaptation
Two Mo genetic groups have migrated from two Mo diversity centers corresponding to rice domestication centers
Hypothesis: Mo genetic groups specialized on rice subspecies?
Saleh et al Molecular Ecology 2012; Saleh et al New Phytologist 2014
indica
~ 6500 hectares
Acuce genotype for more than 110 years Yield ~ 5-7 t/ha
Traditional varieties No chemical fertilizer
High microbial diversity in the soil No fungicide
Area close to diversity center of M. oryzae
> 30 varieties Mixtures
Glutinous (japonica)
and non-glutinous (indica)
Gao et al, 2012 mo de rn Acu ce Trad .
HPN NG XG LJG AZG Acuce CH1184 S S R R R R CH1188 S S R R R S CH1186 S S R R R R CH1192 S S R R R R CH1209 S S S S R S CH1185 S S R R S R CH1205 S S R R R R CH1190 S S R R R R CH1207 S S R R R R CH1195 S S S S R R CH1189 S S S S S S CH1378 S R S S S S CH1193 S S S S S S CH1177 S S S S S S CH1197 S S S S S S CH1368 S S S S S S CH1387 S S S S S S CH1179 S R S S S S CH1178 R R S S S S CH1173 S S S S S S CH1383 S R S S S S CH1182 S S S S S S CH1198 S S S S S S CH1176 S S S S S S CH1322 S R S S S S CH1367 S R S S S S CH1290 S R S S S S Japonica Indica
Strains from japonica form a genetic group Strains from japonica are specialists
Other strains are generalists
Japonica rice is a potential universal host
In blue : strains clollected on japonica rice
14 R-genes tested
10 R-genes different between japonica and indica
Indica rice Japonica rice
Why so few indica isolates on japonica rice? Japonica isolatesare not virulent on indica rice
R² = 0.6122 0 0,002 0,004 0,006 0 10 20 R² = 0.785 0 20 40 60 80 100 0 10 20 R² = 0.315 0 20 40 60 80 0 10 20 R² = 0.427 0 0,002 0,004 0,006 0,008 0 10 20 R² = 0.719 0 20 40 60 80 100 0 10 20 R² = 0.539 0 20 40 60 80 100 0 10 20 Huang Pi Nuo
(japonica - YuanYang) (japonica- YuanYang)Nuo Gu
Su rfa ce /le sion (c m 2 ) Pe rc en ta ge of S le sio ns S l es io ns /le af R² = 0.417 0 20 40 60 80 100 0 10 20 R² = 0.016 0 0,002 0,004 0,006 0,008 0 10 20 R² = 0.004 0 10 20 30 40 0 10 20 Number of AVR Nipponbare (japonica-Japan)
Indica rice Japonica rice
Many R genes Many Avr genes
Specialization due to unbalanced situation between japonica and indica rice
Few Avr genes Few R genes
Japonica strains
Indica strains Incompatibility
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Some perspectives
Add supplementary fitness cost evaluation (sporulation)
Study specialization at local scale in other situations
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Acknowledgements
Collaborators: YAU
JingJing Liao, Huichuan Huang
Xiaohong He, Chengyun Li, Youyong Zhu Romain Gallet
Elisabeth Fournier
Henri Adreit, Joëlle Milazzo, Christophe Tertois