Lineaje-exclusion, a strategy for breeding rice with durable resistance to Pyricularia grisea Sacc. in Colombia
Rice blast has challenged plant breeders when they were searching for durable resistance in Colombia. Rapid resistance breakdowns were commonly observed in newly bred cultivars and they are attributed to frequent appearance of new pathotypes. Recent population studies of the rice blast pathosystem have shown that Pyricularia grisea in a given region, typically expresses a phylogenetic organization of distinct lineages (‘genetic families’ as defined by MGR-DNA fingerprinting). Each lineage exhibits a definable virulence spectrum, and the potential for developing new pathotypes appears to be constrained by lineage-specific avirulences. Lineageexclusion is a breeding strategy aimed to enlighten the choosing of genes to obtain more durable resistance in the field. Combining genes that complementary exclude fragments of virulence, will provide complete resistance to known lineages. The resistance of pyramids bearing the major resistance genes Pi-1 (t) and Pi-2 (t) was determined at three sites in a primary rice growing region in Colombia, from 1996 to 1998.The chosen R-genes are individually defeated by common lineages in Colombia, but combined, provide resistance to the complementary spectra of virulence. The pyramids were selected by screening the progeny of a cross of nearisogenic lines with the representative.The presence and homozygosity of both genes were confirmed through molecular markers. Neither single Colombian isolate, nor mixture of isolates infected the pyramids. The pyramids proved to be highly resistant in the field, and no major changes in lineage composition or virulence spectrum were observed. However, some moderately compatible isolates of lineage SRL-6 were transiently observed in the area of Santa Rosa. Resistance breakdown (vulnerability) may depend on within lineage rather than between lineage distributions of virulence.
| Main Authors: | , , |
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| Format: | article biblioteca |
| Language: | spa |
| Published: |
Corporación colombiana de investigación agropecuaria - AGROSAVIA
2003
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| Online Access: | http://revistacta.agrosavia.co/index.php/revista/article/view/9 http://hdl.handle.net/20.500.12324/35068 |
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| Summary: | Rice blast has challenged plant breeders when they were searching for durable resistance in Colombia. Rapid resistance breakdowns were commonly observed in newly bred cultivars and they are attributed to frequent appearance of new pathotypes. Recent population studies of the rice blast pathosystem have shown that Pyricularia grisea in a given region, typically expresses a phylogenetic organization of distinct lineages (‘genetic families’ as defined by MGR-DNA fingerprinting). Each lineage exhibits a definable virulence spectrum, and the potential for developing new pathotypes appears to be constrained by lineage-specific avirulences. Lineageexclusion is a breeding strategy aimed to enlighten the choosing of genes to obtain more durable resistance in the field. Combining genes that complementary exclude fragments of virulence, will provide complete resistance to known lineages. The resistance of pyramids bearing the major resistance genes Pi-1 (t) and Pi-2 (t) was determined at three sites in a primary rice growing region in Colombia, from 1996 to 1998.The chosen R-genes are individually defeated by common lineages in Colombia, but combined, provide resistance to the complementary spectra of virulence. The pyramids were selected by screening the progeny of a cross of nearisogenic lines with the representative.The presence and homozygosity of both genes were confirmed through molecular markers. Neither single Colombian isolate, nor mixture of isolates infected the pyramids. The pyramids proved to be highly resistant in the field, and no major changes in lineage composition or virulence spectrum were observed. However, some moderately compatible isolates of lineage SRL-6 were transiently observed in the area of Santa Rosa. Resistance breakdown (vulnerability) may depend on within lineage rather than between lineage distributions of virulence. |
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