Breeding for Disease Resistance Dr. Moustafa Azab Field Crops Research Institute

1. Breeding for Disease Resistance Dr. Moustafa Azab Field Crops Research Institute

2. Wheat has been the basic staple food for bread making from more than 7000 years. • Bread wheat was introduced from India in early 20th century. • Selected materials were developed over years for high yield and resistance to rusts.

3. Semidwarf genotypes from CIMMYT increased yield and resistance to rusts. • Planted area is 1.25 m.ha and total production is about 8.0 m.tons while consumption is about 14.0 m.tons (gap:6.0 m.tons). • The main biotic stresses are rust diseases.

5. Breeding for Disease Resistance : Why? Diseases cause damages to plants and plant products on which human depends for food, clothing, furniture, environment, …etc.

6. Types of damages: 1- Limit kinds of plants : - chestnut (USA): chestnut blight . - American elm (shed tree) : Dutch elm disease. 2- Reduce quality and quality of plant products: - Stored grains and seeds. - Stored fruits and vegetables. 3- Poisonous products: - Ergot in wheat. - Range diseases.

7. 4- Financial losses (~250 b$) - Coffees beens in Brazil (rust) - Wheat: USA 1940,s CWANA 1986–1996, East Africa 1990(Ug 99), CWANA 2004 – 2010. - Onion in Egypt.

8. 5- Cause famines : • Late blight of potato (phytophthora infestance) in North Europe in 1845 and 1846 epidemics. • Belgium in June , next in mid October to France, Germany, England and Ireland and extended to Italy, Spain, Poland and Scandinavian countries. • completely destroyed crop in Ireland. • Death of thousands in Europe and 0.5 million in Ireland and migration of 1.5 million people to USA.

9. Diseases Control : 1- Chemical control. 2- Cultural practices (removal of plant debris, crop rotation, soil fallow, weed control, appropriate amounts of fertilize, irrigation, sowing dates. 3- Eradication . 4- Quarantine. 5- Biological control. 6- Monitoring of the appearance and development of plant diseases epidemics (early warning). 7- Resistant varieties.

10. Knowledge needed for breeding for disease resistance: 1- Differences within host species in resistance to disease (Genetic Diversity). 2-Variations in the pathogenic capabilities of parasitic organisms . 3- Optimum environmental conditions for disease development.

11. Host Environmental Conditions Parasite

12. Sources of Genetic Resistance: 1-Recombination within species (inter-varietals variations) 2- Inter-specific variability. 3- Inter-genera variation . 4- Wild relatives

13. Genetic Resistance Genetic resistance has been recognized as the most economical and environmentally friendly control measure against plant diseases

14. Genetic Resistance • ADVANTAGES: • Eliminate the need for chemical control • Require no action by farmers after cultivar selection • DISADVANTAGES: • Resistance may become ineffective after a period • Diverts attention from breeding for yield • Requires knowledge of pathogen virulence and evolution

15. The Major Steps in Breeding Programs: • Identifying limiting factor. • Existence of genetic diversity. • Selection of genotypes with desired traits. • Incorporating desired genes to popular cultivars. • Applying the appropriate selection pressure. • Evaluation for yield potential. • Seed multiplication.

16. Genetic Diversity: • Chinese spring cultivar: genetic and cytogenetics of wheat. • Akokomugi and Daroma: semi dwarf. • PI 178383 (from Turkey): source of resistance to bunt. • Bezostaj 1: winter hardiness. • Kavkaz and Aurora: wide adaptability having 1B/1R chromosome.

17. Breeding for Disease Resistance in Wheat: Because of the dynamic nature of pathogens causing different injuries to wheat, both breeders and pathologists must work parallel in understanding pathogenecity of causal agents and breeding methodology.

18. Breeding Methods for Disease Resistance : • Pure-line and mass selection. • Backcross breeding. • Pedigree method. • Multiline and cultivar mixture.

19. 1. Pure – line and Mass Selection : • Mainly used in mixed populations. • Roughing susceptible off-types. • Single plants. • Head / row selection. • Bulk selected plants or selected rows.

20. 2. Backcross Breeding : • The most popular method in breeding for disease resistance. • Transfer resistance genes from different source to commercial cultivars. • Depends of a series of backcrosses to the main commercial cultivar with maintaining disease resistance by selection under artificial infection. • This method was used extensively to develop new high yield cultivars resistance to diseases.

21. Parent A ( BC1 ) X F1 AB Parent A ( BC4) Parent A ( BC2 ) Parent A ( BC3 ) X X X BC1 BC2 BC3 Backcross Breeding Methodology: X Parent B ( Donor of Resistance) Parent A ( Recurrent Parent) Number of backcrosses depends on homozygosity of desired characters of the recurrent parent. Lines with good agronomic characters having gene (s) for resistance

22. 3. Pedigree Method : • The main objective of this method is to combine desirable genes that are found in two or more different genotypes. • When we use this method? • When the two parents are high yielding, adaptability to environment, having genes for resistance (either one var. or both), used in pyramiding. • Methodology: crossing – F1- F2 (selection) – F3 – F4 - F5 and selection must be under artificial selection. • Molecular marker technique for pyramiding.

23. 4. Multiline Cultivars : • What is Multiline cultivar? Mixture • Why? Heterogeneous for resistance genes. • Result: buffering system against loss. - It is durable resistance prevent the development of complex pathogen races in multiline. - Number of components lines in the mixture. - Epidemiological situation. -Replacement of components new complex race would not be evolved.

24. Genetics of Resistance Specific Resistance Non- Specific Resistance VR HR Major genes Minor genes Operate on gene- for- gene basis Don’t operate on gene- for- gene basis Resistance genes act epistatically and inherited through oligo – genes. Stable resistance and controlled by several additive genes. Nelson (1975): VR & HR are not the action of different genes , they are expression of the same genes in different genetic backgrounds. Genes function vertically when separate and horizontally when together.

25. Sources of Resistance: • Within closely related material (local and foreign cultivars). • Inter-specific. • Inter-genera. • Mutations.

26. Example of sources of resistance: • Sr2 from Yaroslav (T.turgidum). • Sr24 from tall wheat grass (Thinopyrum elongatum). • Sr31 from rye (Secale cereal). • Sr36 from timopheevi (T. timopheevi). • Sr22 from T.beoticum &T.monococcum(T.turgidum). • SrR from rye (translocation 1RS/1BL).

27. Example of sources of resistance(cont.): • Lr19 from Thinopyrum sp. • Rye chromosome arm conferred Lr26, Sr31, Yr9, and Pm 8 . • Pasquini et.al 2010 in Italy: -Dasypyrum villosum = Haynaldia villosa (2n =14). - V 1 to V 7 are homeologous to wheat chromosomes. - 6 V has resistance genes to LR, SR and Pm. Breeders still need more genes for resistance

28. Sources of Resistance to viral Diseases: • Breeding for resistance to viral disease is very complex because of combinations of viruses, vectors and grass hosts. • It is very difficult to find sources of resistance to viral diseases within wheat varieties and relatives. • However, some sources were described: 1. Banks et al. (1995) described several alien translocation lines produced by homoelogous chromosomes pairing and cell culture that involved a 7Ag chromosome from Agropyron intermedium which involved exchange with wheat chromosome 7D.

29. Conclusions Race-specific resistance based onmajor geneshas been successfully used in breeding programs due to its relative easiness Race-specific resistance is of relatively short life and needs continuous pyramiding of resistance genes to enhance its durability (i.e. race-specific resistance genes should be utilized in combinations). National breeding programs are encouraged to adopt breeding strategies that give long-lasting (durable) resistance at a negligible cost in yield.

30. Sources of Resistance to Viral Diseases: Breeding for resistance to viral disease is very complex because of combinations of viruses, vectors and grass hosts. It is very difficult to find sources of resistance to viral diseases within wheat varieties and relatives.

31. However, some sources were described : • Banks et al (1995) described several alien translocation lines produced by homologous chromosome pairing and call culture that involved a 7 Ag chromosome from Agropyron intermedium which involved exchange with wheat chromosome 7 D.

32. 2) In China, Chen et al 2010 found that Haylandia villosa possesses many genes useful as source of resistance to powdery mildew, leaf rust, stem rust, eye spot and wheat streak mosaic. Triticum aestivum H. villosa translocations included different lines carrying resistant to these diseases as follow: a- T6 VS/6AL carrying genes for resistance to powdery mildew . b- T4 VS/ 4DL carrying genes for resistance to yellow mosaic virus. c- T6 AS/6VL carrying genes for resistance to stem rust.

33. 3) Friebe et al (2010) reported that there is only gene for resistance to wheat streak mosaic virus from thinopyrum intermedium by translocation of whole arm designated as T4 DL. 4JS, they also produced another translocation to this called T4 DL.4DS-4JS.

34. Finally Scientists efforts, breeders and pathologist, over long years resulted in availability of resistance to diseases in wheat and become related to wheat sustainability over decades and contributed to food security for world’s people.

35. THANK YOU