Genetic improvement of sugar maple for high sap sugar content. I. Clone selection and seed orchard development

Abstract

A grafted seed orchard of Acersaccharum Marsh, was established in Ohio in 1957 as part of a program of genetic improvement of sugar yield. During the 3rd decade, the orchard trees averaged 4.2% sap sugar. Although environmental sources of variance in sugar concentration were large, clonal differences were evident and generally consistent over the years; the clone × year interaction was negligible. Sap sugar concentration varied from year to year, but after an increase coinciding with early crown development in the 1st decade, there was no upward or downward trend with age. Inclusion of one seedling family in the orchard made it possible to obtain an approximation of within-family variance by comparison with within-clone variance. It was estimated to be about one-third of total family variance. The clone–family comparison also suggested that about 11% of total clonal variance was a rootstock effect. Sap tests over 3 years in a plantation of seed-orchard offspring showed that an initial thinning to an average 6.3 × 6.3 m spacing would leave trees with an average 4% sap sugar concentration. At final spacing the concentration would be higher. Only a few clones in the orchard produced medium or heavy crops of male or female flowers prior to age 27, but those from which seed was collected in early years averaged at least 4% sap sugar. All clones and the seedling family flowered by age 27.

Modelling the effect of climate on maple syrup production in Québec, Canada

“…Yield of maple syrup may vary according to numerous factors including physical tree parameters (Blum, 1973), genetic characteristics (Kriebel, 1989), foliar chemistry (Leaf and Watterston, 1964), soil fertility (Watterston et al, 1963), sap extraction and conversion methods (Morrow and Gibbs, 1969), and management of the production. For example, modernization of collection systems including the use of plastic tubing and vacuum pumping has gained in popularity over the last decades with an expected positive effect on maple syrup yield Koelling et al, 1968).…”

Spatial genetic structure within three sugar maple (Acer saccharum Marsh.) stands

“…is well documented. A variation has been demonstrated in growth rates among provenances (Wendel & Gabriel, 1980), in sugar concentration among clones (Kriebel, 1989), in seed and fruit characters among and within provenances (Gabriel, 1978), and in allozyme frequencies among populations (Perry & Knowles, 1989). Ledig & Korbobo (1983) observed differentiation in physiological characteristics of progeny from stands separated by less than 0.8 km.…”

Interannual and spatial variability of maple syrup yield as related to climatic factors

“…Previous winter conditions, such as high mean January temperatures, can also be negatively correlated to yield, possibly due to the importance of cold hardiness on sap sugar content ( Rock & Spencer, 2001 ; Duchesne et al, 2009 ; Tyminski, 2011 ). Along with local climatic conditions, many other factors can affect maple syrup yield, including physical tree parameters ( Blum, 1973 ), genetic characteristics ( Kriebel, 1989 ), foliar chemistry ( Leaf & Watterston, 1964 ), soil fertility ( Watterston, Leaf & Engelken, 1963 ) and sap extraction and conversion methods ( Morrow & Gibbs, 1969 ). Although these factors can explain variations in maple syrup yield between trees or sites, climate remains the main factor affecting annual yield fluctuations, through its effect on sap flow fluxes, sugar concentration, or both ( Marvin & Erickson, 1956 ; Cool, 1957 ; Pothier, 1995 ; Duchesne et al, 2009 ).…”