As some of the newest options on the market, the Russian-developed Krymsk rootstocks have created a buzz with fruit growers looking to better regulate production.

For cherry producers, Krymsk 5 and Krymsk 6 offer promising alternatives to achieve ideal output and quality, explained Oregon State University Extension professor Lynn Long.

The horticulturalist is currently testing the Russian offering, alongside several other rootstocks, with different cherry varieties to find the best growing combinations for farmers.

"What I would like to find is a rootstock that will increase the productivity for a variety such as Regina, which does not produce well, and also find rootstocks that would be precocious but not so productive that I have difficulty maintaining my leaf-to-fruit ratio and quality with high-yielding varieties such as Sweetheart," he told www.freshfruitportal.com.

Long's testing has included five types of rootstock - Mazzard, MaxMa 14, Gisela 6, Krymsk 5 and Krymsk 6 - and three cherry varieties - Bing, Regina and Sweetheart.

Paired properly, Long said the right rootstock could promote greater balance in production.

For a low-productivity variety such as Regina the ideal rootstock will boost production. Paired with a high-yielding variety such as Sweetheart, however, the same rootstock may overwhelm the plant with excess fruit.

"You put any of those highly productive rootstocks with a variety such as Sweetheart and you quickly get into a situation in which you have too much fruit on the tree and your fruit quality suffers," he said.

"It may increase the production of Regina but it will also increase the production of a highly productive variety such as Sweetheart to the point that where there are too many cherries on the tree and that affects fruit size, firmness and shipping ability."

In initial trails, Krymsk 5 has shown promise when paired with a high-yielding fruit such as Sweetheart.

"There are some good indications that Krymsk 5 seems to give you intermediate levels of productivity, good precocity and it works well with a highly productive variety such as Sweetheart. We’ve been able to maintain good fruit size, keep the quality up and get good yields without getting into a situation in which the tree is overset," he said.

"In this trial, we’re finding that the rootstocks such as Krymsk 5 and MaxMa 14 with Sweetheart give you an intermediate level of productivity, whereas Gisela 6 has a high level of productivity and Mazzard has a very low level of precocity and it takes a long time for it to come into production."

For the low-yielding Regina, Krymsk 6 may offer a needed boost.

"What we’re looking for with a variety such as Regina is something that will increase its productivity so that you can get some reasonable yields off of it. What we’ve found is that both Gisela 6 and Krymsk 6 will do that," Long said.

"Krymsk 6 actually had the highest yields all but one year of the study. Gisela 6 also did very well. We found that MaxMa 14 was not much better than Mazzard when it came to Regina. It gave you the same intermediate levels of productivity but with Regina it did not perform well as far as yields were concerned."

So far Long's testing has only been carried out in Oregon, but he expects the results to be applicable to a variety of growing regions.

"I think [Krymsk] gives growers another opportunity to obtain the precocity that they need to get early production in their orchard but also to balance their leaf-to-fruit ratios so that they can maintain good fruit quality," he said.

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