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Two quantitative trait loci, Dw1 and Dw2, are primarily responsible for rootstock-induced dwarfing in apple.

Foster TM, Celton JM, Chagné D, Tustin DS, Gardiner SE - Hortic Res (2015)

Bottom Line: The apple dwarfing rootstock 'Malling9' ('M9') has been used worldwide both to reduce scion vigour and as a genetic source for breeding new rootstocks.A smaller-effect QTL affecting dwarfing (Dw2) was identified on LG11, and four minor-effect QTLs were found on LG6, LG9, LG10 and LG12.Phenotypic analysis indicates that the combination of Dw1 and Dw2 has the strongest influence on rootstock-induced dwarfing, and that Dw1 has a stronger effect than Dw2.

View Article: PubMed Central - PubMed

Affiliation: The New Zealand Institute for Plant & Food Research Ltd , Palmerston North Private Bag 11600, Palmerston North 4474, New Zealand.

ABSTRACT
The apple dwarfing rootstock 'Malling9' ('M9') has been used worldwide both to reduce scion vigour and as a genetic source for breeding new rootstocks. Progeny of 'M9' segregate for rootstock-induced dwarfing of the scion, indicating that this trait is controlled by one or more genetic factors. A quantitative trait locus (QTL) analysis of a rootstock population derived from the cross between 'M9' × 'Robusta5' (non-dwarfing) and grafted with 'Braeburn' scions identified a major QTL (Dw1) on linkage group (LG) 5, which exhibits a significant influence on dwarfing of the scion. A smaller-effect QTL affecting dwarfing (Dw2) was identified on LG11, and four minor-effect QTLs were found on LG6, LG9, LG10 and LG12. Phenotypic analysis indicates that the combination of Dw1 and Dw2 has the strongest influence on rootstock-induced dwarfing, and that Dw1 has a stronger effect than Dw2. Genetic markers linked to Dw1 and Dw2 were screened over 41 rootstock accessions that confer a range of effects on scion growth. The majority of the dwarfing and semi-dwarfing rootstock accessions screened carried marker alleles linked to Dw1 and Dw2. This suggests that most apple dwarfing rootstocks have been derived from the same genetic source.

No MeSH data available.


Three-year-old compound trees with ‘Braeburn’ scions grafted to sibling rootstocks from a segregating population of ‘M9’ × ‘R5’. The tree on the left is grafted to a rootstock with Dw1 and Dw2, the one on the right has a rootstock with neither. Red arrowheads indicate graft junction, 2-m measure for scale.
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fig1: Three-year-old compound trees with ‘Braeburn’ scions grafted to sibling rootstocks from a segregating population of ‘M9’ × ‘R5’. The tree on the left is grafted to a rootstock with Dw1 and Dw2, the one on the right has a rootstock with neither. Red arrowheads indicate graft junction, 2-m measure for scale.

Mentions: There was a wide variation in overall dwarfing phenotype (DW%), increase in scion TCA, primary axis height, node number and the number of flowers in the spring of year 2 (Supplementary Figure S1). Based on phenotypic assessment from year 2 to year 7, individuals were placed into one of five classes: dwarfed, semi-dwarfed, intermediate, vigorous and very vigorous. Some individuals were more dwarfed than ‘M9’, and some were more vigorous than ‘R5’ (very vigorous). While the differences in scion vigour were apparent by year 3 (Figure 1), the distinction between classes became more pronounced over successive growth cycles.


Two quantitative trait loci, Dw1 and Dw2, are primarily responsible for rootstock-induced dwarfing in apple.

Foster TM, Celton JM, Chagné D, Tustin DS, Gardiner SE - Hortic Res (2015)

Three-year-old compound trees with ‘Braeburn’ scions grafted to sibling rootstocks from a segregating population of ‘M9’ × ‘R5’. The tree on the left is grafted to a rootstock with Dw1 and Dw2, the one on the right has a rootstock with neither. Red arrowheads indicate graft junction, 2-m measure for scale.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4595989&req=5

fig1: Three-year-old compound trees with ‘Braeburn’ scions grafted to sibling rootstocks from a segregating population of ‘M9’ × ‘R5’. The tree on the left is grafted to a rootstock with Dw1 and Dw2, the one on the right has a rootstock with neither. Red arrowheads indicate graft junction, 2-m measure for scale.
Mentions: There was a wide variation in overall dwarfing phenotype (DW%), increase in scion TCA, primary axis height, node number and the number of flowers in the spring of year 2 (Supplementary Figure S1). Based on phenotypic assessment from year 2 to year 7, individuals were placed into one of five classes: dwarfed, semi-dwarfed, intermediate, vigorous and very vigorous. Some individuals were more dwarfed than ‘M9’, and some were more vigorous than ‘R5’ (very vigorous). While the differences in scion vigour were apparent by year 3 (Figure 1), the distinction between classes became more pronounced over successive growth cycles.

Bottom Line: The apple dwarfing rootstock 'Malling9' ('M9') has been used worldwide both to reduce scion vigour and as a genetic source for breeding new rootstocks.A smaller-effect QTL affecting dwarfing (Dw2) was identified on LG11, and four minor-effect QTLs were found on LG6, LG9, LG10 and LG12.Phenotypic analysis indicates that the combination of Dw1 and Dw2 has the strongest influence on rootstock-induced dwarfing, and that Dw1 has a stronger effect than Dw2.

View Article: PubMed Central - PubMed

Affiliation: The New Zealand Institute for Plant & Food Research Ltd , Palmerston North Private Bag 11600, Palmerston North 4474, New Zealand.

ABSTRACT
The apple dwarfing rootstock 'Malling9' ('M9') has been used worldwide both to reduce scion vigour and as a genetic source for breeding new rootstocks. Progeny of 'M9' segregate for rootstock-induced dwarfing of the scion, indicating that this trait is controlled by one or more genetic factors. A quantitative trait locus (QTL) analysis of a rootstock population derived from the cross between 'M9' × 'Robusta5' (non-dwarfing) and grafted with 'Braeburn' scions identified a major QTL (Dw1) on linkage group (LG) 5, which exhibits a significant influence on dwarfing of the scion. A smaller-effect QTL affecting dwarfing (Dw2) was identified on LG11, and four minor-effect QTLs were found on LG6, LG9, LG10 and LG12. Phenotypic analysis indicates that the combination of Dw1 and Dw2 has the strongest influence on rootstock-induced dwarfing, and that Dw1 has a stronger effect than Dw2. Genetic markers linked to Dw1 and Dw2 were screened over 41 rootstock accessions that confer a range of effects on scion growth. The majority of the dwarfing and semi-dwarfing rootstock accessions screened carried marker alleles linked to Dw1 and Dw2. This suggests that most apple dwarfing rootstocks have been derived from the same genetic source.

No MeSH data available.