Needs Assessment for Future US Pear Rootstock Research Directions Based on the Current State of Pear Production and Rootstock Research

Abstract

The area devoted to pear production in the United States (U.S.) is declining due to lack of precocity and high cost of production. The U.S. pear industry currently lacks “modern” orchard systems characterized by compact trees that produce early, high yields of large, high quality fruit. Tall, shaded canopies are not economically sustainable and are at a competitive disadvantage for attracting and sustaining a labor supply. There is broad and deep consensus in the pear industry that developing size-controlling rootstocks is imperative to remain competitive nationally and globally. Currently employed rootstocks in the U.S. are Pyrus communisseedlings and clones, none of which achieve more than about a one-third size reduction, and P. betulifoliaseedlings. Quince ( C. oblonga), used with interstems in Europe and South America, is utilized commercially (without interstems) in the U.S. only for ‘Comice’ in southern Oregon and northern California. This is due primarily to a lack of cold hardiness needed in more northern production areas, a lack of graft-compatibility with the other major scion cultivars, fire blight and iron chlorosis susceptibility, and relative lack of productivity versus other rootstocks, especially in California. Current evaluative trials rely on older U.S. and imported selections, and include the NC-140 Multistate Rootstock Research Project and several individual programs in California, New York, Oregon and Washington. A fundamental deficiency is the lack of a mature pear rootstock breeding program, despite access to the USDA-ARS National Clonal Germplasm Repository (NCGR), which holds a major worldwide collection of Pyrusand related genera. International breeding programs focus on increasing yield efficiency, but also graft compatibility, fruit quality and size, high soil pH tolerance, winter hardiness, warm climate/low chilling adaptation, drought and salt tolerance, and resistance to fire blight, pear decline, and pear scab. An intensive planning and implementation effort is needed to develop the necessary contacts, collaborations, explorations, and importation logistics to acquire the most promising clonal selections for propagation and testing. Basic research needs include effects of dwarfing rootstock on tree architecture and fruiting, the underlying mechanisms of dwarfing functional in pear, the inheritance of key traits, and selection criteria for breeding. Propagation and orchard systems have also been identified as major research needs.