Summary of 2003 Golden Delicious Rootstock Trial Through 2009

by R. M. Crassweller & D. E. Smith

A plethora of apple rootstocks have been released in the last few years. Many are coming from eastern European countries and were not readily available before. Countries such as the Czech Republic, Germany (formerly East Germany) and Russia have released several new rootstocks. The rootstocks from the Czech Republic are designated the J-TE series; J = jablon (apple) and TE = Těchobuzice, the location of the research center. The rootstocks from Germany are designated PiAU from Pillnitz with AU = apfel-unterlage (apple rootstock). Rootstocks from Russia were named in honor of the original breeder pomologists V.J. Budagovsky located at the Michurinsk College of Agriculture. Currently the most widely used rootstock from this series is B.9. Japan has released a series of rootstocks designated JM. These rootstocks are reportedly smaller than M.9 propagate by hardwood cuttings; some have resistance to apple crown rot and most are resistant to wooly apple aphids. The regional research project, NC-140 has for years evaluated new rootstock releases in a cooperative replicated manner. The results are typically published at the end of the 5th (Marini et al., 2009) and 10th growing season. While there are numerous ongoing rootstock trials (see accompanying report) we thought a more thorough report of one planting would be more beneficial than trying to summarize many studies. The purpose of this report is to present an interim report of one such planting using Golden Delicious on 18 different rootstocks planted at the Horticulture Research Farm at Rock Springs in central Pennsylvania. The planting has been supported by the Research Committee of SHAP under the ongoing projects.

Materials & Methods

As part of the NC-140 Regional Research Project Golden Delicious (Gibson) was grafted on the 18 rootstocks listed in Table 1 and planted in the spring of 2003. The spacing was 3.5m x 5.5m with a single wire at 8 ft with conduit at each tree. The trees were trained as a vertical axe. There were 6 to 8 trees each in four blocks with two tree of each rootstock per block. Data collected yearly included trunk circumference which was converted to trunk cross sectional area (TCSA cm2). Flower clusters were counted in 2004 and 2005 but removed shortly after fruit set in 2004. In subsequent years bloom was evaluated by rating the bloom density on a 0 to 5 scale with 0 = no bloom, 3 = full crop and 5 = snowball bloom. Beginning in 2005 yields per tree (kg) and number of fruit per tree were measured at harvest. Efficiency (gm/cm2 of TCSA) was calculated as was crop load (# fruit/cm2 of TCSA). Average fruit weight (g) was calculated from taking the total yield per tree and dividing by the number of fruit. Cumulative yield was calculated by taking total yield over all the years (2005 – 2007). Cumulative efficiency was calculated by taking total yield from 2005 – 2006 and dividing by TCSA in 2006.

Results

In 2004 trees on B.62-396 had the greatest number of flowers per tree; while J-TE-G had the highest flower density (Table 2). In 2005 G.935 had the greatest number of flowers and flower density although neither was significantly better than B.62-396. In both years JM.2 had the lowest number of flowers. In 2006 through 2008 the highest bloom rating varied by rootstock (data not shown), however, JM.2 consistently had the lowest bloom rating all three years, contradicting the supposedly higher flowering capability as outlined by Wertheim (1998).

Tree height and spread was measured at the end of the 5th leaf in 2007. Trees on J-TE-G were the shortest and had the narrowest spread (Table 3). Trees on PiAU 56-83 were the tallest and had the greatest spread although they were not significantly larger than trees on JM.2, JM.8, or PiAU 51-4. At the end of 2008 tree size as measured by TCSA was greatest for JM.2 and the least for J-TE-G. Trees that had similar TCSA’s to JM.2 were PiAU 51-4 and PiAU 56-83. Trees with similar TCSA’s to J-TE-G were B.62-396, B.9, G.16, G.41, G.935 and M.9T337. Trees that were similar to JM.2 in height, spread and TCSA are larger than M.26 and would not be considered dwarfing.

Trees on PiAU 51-4 produced the greatest cumulative number of fruit and total yield during the first four producing seasons (2005 – 2008) but not significantly more so than eight other rootstocks (Table 4). Trees on J-TE-G produced the lowest number of cumulative fruit and cumulative yield. Trees on JM.2 had relatively low numbers of fruit, low yields and were the least efficient. There were no differences in average fruit weight as influenced by rootstock. Cumulative efficiency was greatest for trees on J-TE-G but not significantly better than ten other rootstocks. JM.2 had the lowest efficiency

Conclusions

The study will be continued until 2012 so the results presented here should be considered preliminary. However at this point, Geneva 41 and Geneva 935 have performed well in comparison to M.9T337. Geneva 16 has also performed well, but we are concerned in noticing a tendency for the foliage to look off color in the early fall and it may indicate a compatibility problem with this rootstock. B.62-396 has performed well and should be further tested. In other trials in Europe B.62-396 was rated better than B.9 because it was easier to propagate (Bite & Lepsis, 2004). In comparison of size, B.62-396 was significantly smaller than M.26 and similar although slightly larger than several clones of M.9 (Czynczyk et al., 2001). (Note: B.62-396 has recently been renamed B.10 (Robinson 2009)). CG.6210, although larger than we would like, has been very productive and precocious. Since this planting is supported we do not know for certain if this rootstock could be free standing. The Pilnitz rootstocks in this trial are too vigorous although they have produced large yields. JM.2 and JM.8 in this trial are too large and unproductive, especially JM.2 which was significantly larger than M.26. J-TE-G produced the smallest tree and may be too small at lower tree densities. A report from Germany (Stehr, 2007) indicated that J-TE-G is similar to M.27 in size and approximately 40% smaller than M.9, However, in the same report J-TE-H is reported to be slightly larger than M.9 (about 15%). PiAU 56-83 is 90% larger than M.9. Clearly there is much confusion over the tree size produced on many of these rootstocks.

References

Bite, A., & J. Lepsis. 2004. The results of extended duration testing of apple rootstocks in Latvia. Acta Hort. 658:115 – 118.

Czynczyk, A., P. Bielicki & B. Bartosiewicz. 2001. Testing new dwarfing apple rootstocks from Polish and foreign breeding programs. Acta Hort. 577:83-89

Marini, R., B. Black, R. Crassweller, P. Domoto, C. Hampson, S. Johnson, K. Kosola, S. McArtney, J. Masabni, R. Moran, R. Quesada, T. Robinson and C. Rom. 2009. Performance of Golden Delicious apple on 23 rootstocks at 12 locations: A five-year summary of the 2003 NC-140 dwarf rootstock trial. J. Amer. Pom. Soc. 63:115-127

Robinson, T. L. 2009. personal communication

Stehr, R. 2007. Fifteen years of experience with different dwarfing apple rootstocks in northern Germany. Acta Hort. 732:67-77.

Wertheim, S. J. 1998. Apple rootstocks in Rootstock Guide. pg 19 – 59. Fruit Research Station. Brugstraat 51, 4475 AN Wilhelminadorp, The Netherlands.

Authors’ Note: This is part of the Cultivar and Rootstock Planting at PSU Report printed elsewhere.