Main Article Content
Application of gene discovery to varietal improvement in sugarcane
Abstract
Recent work has shown that differentially expressed
cDNA fragments identified during biotic challenge have great potential as
genetic markers for pest and disease resistance in sugarcane. Responses to the
smut fungus (Ustilago scitaminea), the stalk borer eldana (Eldana
saccharina) and Sugarcane Mosaic Virus (SCMV) have been the main functional
targets to date. Potentially useful cDNAs were identified using SSH and
cDNA-AFLP differential display. These were isolated, sequenced and assigned
putative functions by comparison with international databases. Using an RFLP
approach, fragments with identities suggesting a role in resistance mechanisms
were used as probes on a population of 78 sugarcane genotypes used in the
breeding programme and well characterised for the traits of interest.
Polymorphic markers were scored, and association with phenotype analysed using
statistical methods developed in house. A set of 51 probes used for RFLP
analysis has yielded 275 polymorphisms to date. Preliminary analyses of the
data have identified 69 polymorphisms showing correlation with eldana
resistance, 59 with smut, and 35 with SCMV. Most of the probes (76%) yielded at
least one RFLP marker associated with smut, eldana or SCMV resistance,
illustrating the efficiency of this marker generating strategy. Groups of
uncorrelated markers have been found to be associated with each of the
resistance traits under investigation, indicating the likelihood that each one
represents a different aspect or mechanism of resistance. Markers identified in
this project are already being used to devise crosses for the coordinated
assembly of resistance factors in progeny. A subset of the most significant
markers has been screened against a further collection of 53 varieties in order
to extend the capacity of marker-assisted breeding. In addition, newly
identified cDNAs are continually being investigated via RFLP screening.
South African Journal of Botany
2004, 70(1): 167–172
cDNA fragments identified during biotic challenge have great potential as
genetic markers for pest and disease resistance in sugarcane. Responses to the
smut fungus (Ustilago scitaminea), the stalk borer eldana (Eldana
saccharina) and Sugarcane Mosaic Virus (SCMV) have been the main functional
targets to date. Potentially useful cDNAs were identified using SSH and
cDNA-AFLP differential display. These were isolated, sequenced and assigned
putative functions by comparison with international databases. Using an RFLP
approach, fragments with identities suggesting a role in resistance mechanisms
were used as probes on a population of 78 sugarcane genotypes used in the
breeding programme and well characterised for the traits of interest.
Polymorphic markers were scored, and association with phenotype analysed using
statistical methods developed in house. A set of 51 probes used for RFLP
analysis has yielded 275 polymorphisms to date. Preliminary analyses of the
data have identified 69 polymorphisms showing correlation with eldana
resistance, 59 with smut, and 35 with SCMV. Most of the probes (76%) yielded at
least one RFLP marker associated with smut, eldana or SCMV resistance,
illustrating the efficiency of this marker generating strategy. Groups of
uncorrelated markers have been found to be associated with each of the
resistance traits under investigation, indicating the likelihood that each one
represents a different aspect or mechanism of resistance. Markers identified in
this project are already being used to devise crosses for the coordinated
assembly of resistance factors in progeny. A subset of the most significant
markers has been screened against a further collection of 53 varieties in order
to extend the capacity of marker-assisted breeding. In addition, newly
identified cDNAs are continually being investigated via RFLP screening.
South African Journal of Botany
2004, 70(1): 167–172
