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Design of an F1 hybrid breeding strategy for ryegrasses based on selection of self-incompatibility locus-specific alleles.

Pembleton LW, Shinozuka H, Wang J, Spangenberg GC, Forster JW, Cogan NO - Front Plant Sci (2015)

Bottom Line: This property is partially due to an inability to effectively exploit heterosis through the formation of F1 hybrids.Based on simulation of various levels of SI allele diversity restriction, the most effective scheme will generate 83.33% F1 hybrids.Results from the study, including the impact of varying flowering time, are discussed along with a proposed breeding design for commercial application.

View Article: PubMed Central - PubMed

Affiliation: Biosciences Research Division, AgriBio, La Trobe University Bundoora, VIC, Australia ; Dairy Futures Cooperative Research Centre, AgriBio, La Trobe University Bundoora, VIC, Australia ; School of Applied Systems Biology, La Trobe University Bundoora, VIC, Australia.

ABSTRACT
Relatively modest levels of genetic gain have been achieved in conventional ryegrass breeding when compared to cereal crops such as maize, current estimates indicating an annual improvement of 0.25-0.6% in dry matter production. This property is partially due to an inability to effectively exploit heterosis through the formation of F1 hybrids. Controlled crossing of ryegrass lines from geographically distant origins has demonstrated the occurrence of heterosis, which can result in increases of dry matter production in the order of 25%. Although capture of hybrid vigor offers obvious advantages for ryegrass cultivar production, to date there have been no effective and commercially suitable methods for obtaining high proportions of F1 hybrid seed. Continued advances in fine-scale genetic and physical mapping of the gametophytic self-incompatibility (SI) loci (S and Z) of ryegrasses are likely in the near future to permit the identification of closely linked genetic markers that define locus-specific haplotypes, allowing prediction of allelic variants and hence compatibility between different plant genotypes. Given the availability of such information, a strategy for efficient generation of ryegrass cultivars with a high proportion of F1 hybrid individuals has been simulated, which is suitable for commercial implementation. Through development of two parental pools with restricted diversity at the SI loci, relative crossing compatibility between pools is increased. Based on simulation of various levels of SI allele diversity restriction, the most effective scheme will generate 83.33% F1 hybrids. Results from the study, including the impact of varying flowering time, are discussed along with a proposed breeding design for commercial application.

No MeSH data available.


Overview of the F1 hybrid breeding scheme based on restriction of SI allele diversity within two defined parental pools.
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Figure 1: Overview of the F1 hybrid breeding scheme based on restriction of SI allele diversity within two defined parental pools.

Mentions: Of the four methods that have been described for F1 hybrid ryegrass production, selective restriction of SI allele diversity using predictive genetic markers offers the highest potential for cost-effective application to commercial breeding programs within the next decade. Both GM- and CMS-based approaches are limited by high costs, regulatory constraints, or a requirement to use specific genetic backgrounds, which may not be phenotypically elite in nature (Wilkins and Humphreys, 2003). Similarly, population hybrids are limited in capacity to generate high proportions of F1 hybrid seed. In contrast, the strategy described in the present study would allow breeders to exploit a broad range of germplasm (which may have already experienced multiple rounds of phenotypic selection), with no prior requirements to introgress genetic loci, or to deregulate a GM trait. Predictive markers will enable breeders to selectively restrict SI allele diversity (without self-fertilization) within two defined parental pools in order to reduce within-pool compatibility, followed by seed bulk-up in order to combine between the two pools by random intermating. The mutual restriction of SI allele diversity will ensure that between- exceeds within-pool compatibility, resulting in an increased production of F1 progeny (Figure 1). A number of potential strategies for effective use of SI linked markers for hybrid production are explored using simulation methods in order to demonstrate potential outcomes, leading to the development of a detailed breeding program design that matches the most effective strategy.


Design of an F1 hybrid breeding strategy for ryegrasses based on selection of self-incompatibility locus-specific alleles.

Pembleton LW, Shinozuka H, Wang J, Spangenberg GC, Forster JW, Cogan NO - Front Plant Sci (2015)

Overview of the F1 hybrid breeding scheme based on restriction of SI allele diversity within two defined parental pools.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4585157&req=5

Figure 1: Overview of the F1 hybrid breeding scheme based on restriction of SI allele diversity within two defined parental pools.
Mentions: Of the four methods that have been described for F1 hybrid ryegrass production, selective restriction of SI allele diversity using predictive genetic markers offers the highest potential for cost-effective application to commercial breeding programs within the next decade. Both GM- and CMS-based approaches are limited by high costs, regulatory constraints, or a requirement to use specific genetic backgrounds, which may not be phenotypically elite in nature (Wilkins and Humphreys, 2003). Similarly, population hybrids are limited in capacity to generate high proportions of F1 hybrid seed. In contrast, the strategy described in the present study would allow breeders to exploit a broad range of germplasm (which may have already experienced multiple rounds of phenotypic selection), with no prior requirements to introgress genetic loci, or to deregulate a GM trait. Predictive markers will enable breeders to selectively restrict SI allele diversity (without self-fertilization) within two defined parental pools in order to reduce within-pool compatibility, followed by seed bulk-up in order to combine between the two pools by random intermating. The mutual restriction of SI allele diversity will ensure that between- exceeds within-pool compatibility, resulting in an increased production of F1 progeny (Figure 1). A number of potential strategies for effective use of SI linked markers for hybrid production are explored using simulation methods in order to demonstrate potential outcomes, leading to the development of a detailed breeding program design that matches the most effective strategy.

Bottom Line: This property is partially due to an inability to effectively exploit heterosis through the formation of F1 hybrids.Based on simulation of various levels of SI allele diversity restriction, the most effective scheme will generate 83.33% F1 hybrids.Results from the study, including the impact of varying flowering time, are discussed along with a proposed breeding design for commercial application.

View Article: PubMed Central - PubMed

Affiliation: Biosciences Research Division, AgriBio, La Trobe University Bundoora, VIC, Australia ; Dairy Futures Cooperative Research Centre, AgriBio, La Trobe University Bundoora, VIC, Australia ; School of Applied Systems Biology, La Trobe University Bundoora, VIC, Australia.

ABSTRACT
Relatively modest levels of genetic gain have been achieved in conventional ryegrass breeding when compared to cereal crops such as maize, current estimates indicating an annual improvement of 0.25-0.6% in dry matter production. This property is partially due to an inability to effectively exploit heterosis through the formation of F1 hybrids. Controlled crossing of ryegrass lines from geographically distant origins has demonstrated the occurrence of heterosis, which can result in increases of dry matter production in the order of 25%. Although capture of hybrid vigor offers obvious advantages for ryegrass cultivar production, to date there have been no effective and commercially suitable methods for obtaining high proportions of F1 hybrid seed. Continued advances in fine-scale genetic and physical mapping of the gametophytic self-incompatibility (SI) loci (S and Z) of ryegrasses are likely in the near future to permit the identification of closely linked genetic markers that define locus-specific haplotypes, allowing prediction of allelic variants and hence compatibility between different plant genotypes. Given the availability of such information, a strategy for efficient generation of ryegrass cultivars with a high proportion of F1 hybrid individuals has been simulated, which is suitable for commercial implementation. Through development of two parental pools with restricted diversity at the SI loci, relative crossing compatibility between pools is increased. Based on simulation of various levels of SI allele diversity restriction, the most effective scheme will generate 83.33% F1 hybrids. Results from the study, including the impact of varying flowering time, are discussed along with a proposed breeding design for commercial application.

No MeSH data available.