Cutting Type and Time-of-Year Affect Rooting Ability of Hardy Minnesota PrunusSpecies

Abstract

Many species within the genus Prunusare difficult to root, and most cultivated accessions are grafted for propagule production. The University of Minnesota Prunusgermplasm and cultivar releases include a variety of ornamental and edible fruit types that have received little research focus. Many accessions have never been evaluated for the ability to root, even though at least one sour cherry, P. cerasus‘Northstar’, is sold on its own root system. Two experiments were conducted to evaluate if cutting position, time of year, or auxin treatment are important for terminal and basal softwood-semi-hardwood rooting success of: I) P.× cistena(control); P. armeniaca‘Westcot’, and ‘Hardygold’; P. cerasus‘Northstar’, and ‘Meteor’; P. domestica‘Superior’, and P. spp.‘Alderman’ treated with 0.0041 M (1000 ppm) or 0.017 M (4000 ppm) indole-3-butryric acid-potassium salt (K-IBA) and II) P.× cistena(control) and P. spp.‘Alderman’ treated with 0.00033 M (80 ppm) of K-IBA and 80 ppm Indole-3-caprioc acid (ICapA). Cuttings were taken biweekly (5 June-11 Sept.. 2012) and then monthly until 4 Dec. 2012. After six weeks in the mist, cuttings were scored for callus formation, root development, and bud break (leaves, flowering). The highest frequency of rooting occurred in June and again in Oct.-Dec. for P.× cistenaand July, Sept.-Oct. for P. armeniaca‘Westcot’. All other cultivars had very low or no rooting. On average, regardless of genotypic variability, all Prunusanalyzed had ≤60% rooting, which is less than commercially acceptable. The highest mean percent rooting ranged from 1.1% ( P. spp.‘Alderman’) to 24.1% ( P. armeniaca‘Westcot’) and 40.2% ( P.× cistena), although many had 100% rooting in specific cutting harvest weeks. Unexpected leaf and/or flowering of cuttings occurred as early as early June for ‘Westcot’, ‘Superior’, ‘Alderman’, and P.× cistena(Growing Degree Days (GDD) = 837) or late June for ‘Hardygold’, ‘Meteor’, and ‘North Star’ (GDD =1070) was unprecedented. The reasons for such a quick release from dormancy, often without the accumulation of chilling units, are unknown.