Good Fruit Grower

June 1

Issue link:

Contents of this Issue


Page 29 of 47

T here is likely not a "best" apple rootstock, though the replant-tolerant Geneva rootstocks (G.41, G.214, G.935, G.210, G.30, G.890) are much better than the available standards of Budagovksy 9, Mark, Malling 9 clones, M.26 and the semidwarf rootstocks. In replant situations, it is common to have lack of vigor con- tributing to an undersized, low-yielding orchard. The most impressive trait of the replant- tolerant Geneva rootstocks is their combination of productivity and vigor. When the precocity of the replant- tolerant Geneva rootstocks is combined with the ability to grow a canopy, exceptional yields have been generated. Experience will show which scions will do better with which rootstock in a given site. It is likely that particular scion- rootstock combinations will demonstrate superior results. The best prac- tice is to plant three or four of the replant-tolerant, especially the woolly apple aphid resistant Geneva rootstocks with each scion in each site to gain experience to show which combinations are better. As the spring of 2013 demonstrated, return bloom and produc- tivity in general are better in blocks with dwarf rootstocks, and worst in blocks with seedling and vigorous semidwarf Malling or Budagovksy rootstocks. Lack of winter hardiness and suscep- tibility to fi re blight has diminished the appeal of Malling 9 in some sectors of the Washington apple industry. The M.9 clones have a place in the industry for the near future, but Geneva apple rootstocks have benefi ts that growers will fi nd advantageous. Fire blight All the commercially released Geneva rootstocks offer fire blight and phytophthora resistance. Replant tol- erance has been demonstrated in trials in Washington State with an additional benefi t of greater productivity than M.9 and Mark. Several Geneva rootstocks have demonstrated winter hardiness and woolly apple aphid resistance. In addition to the replant-tolerant Geneva rootstocks, there are a few commercially released Geneva rootstocks that offer advantages over other commercially available rootstocks. These other rootstocks offer fi re blight resistance but may have issues to be considered when ordering trees. • G.16 is hypersensitive to virus infection. Some blocks fi ve or more years old have a steady attrition of ½ to 1 percent of trees that lose vigor and become unthrifty. While resistant to several root pathogens, G.16 does not have the best replant tolerance and is not a good candidate for replacement trees. • G.202 was selected mostly for its ability to root, which makes it easier to propagate. It does not offer the crop density or the replant tolerance that other Geneva rootstocks provide, and its fruit size has been noted to be smaller than with other rootstocks. It may be suitable for highly precocious scions that tend to produce oversized fruit. • G.969 has not been trialed in the western United States. Its replant tolerance is unknown in the more severe conditions of the arid West. It is described as a precocious freestanding tree suitable for process- ing varieties. It could also be suitable for weak soils and/or weak-growing scions. The concept of "free- standing" usually indicates horticultural practices that involve heading and delay fruiting. If G.969 is managed in a tall spindle system, it will need a trellis to support the crop. • G.11 produces trees with a smaller canopy volume and lower vegetative vigor, usually smaller than M.9- T337. It is a very productive rootstock and produces good fruit size. G.11 is often more healthy than M.9 clones in replant conditions. The productivity of G.11 reduces its vegetative vigor. It is an excellent rootstock for most planting situations, though not for replacement trees in unfumigated orchard sites. 30 JUNE 2014 GOOD FRUIT GROWER The quest for better apple rootstocks. by Tom Auvil Washington Tree Fruit Research Commission Good, better, best? Bench grafts in a trial at Vantage, Washington, pictured in July of the year of planting. PHOTO COURTESY OF TOM AUVIL New Varieties

Articles in this issue

Links on this page

Archives of this issue

view archives of Good Fruit Grower - June 1