CHAPTER 1: COLLECTION, MAINTENANCE, CHARACTERIZATION AND UTILIZATION OF WILD APPLES OF CENTRAL ASIA.

Authors: Forsline, Philip; ALDWINCKLE, HERB - CORNELL UNIVERSITY; DICKSON, E - UNIVERSITY OF CALGARY; LUBY, J - UNIVERSITY OF MINNESOTA; HOKANSON, STAN - UNIVERSITY OF MINNESOTA

Submitted to: Wild Apple and Fruit Trees of Central Asia
Publication Type: Other
Publication Acceptance Date: 12/1/2002
Publication Date: 2/1/2003
Citation: Forsline, P.L., Aldwinckle, H.S., Dickson, E.E., Luby, J.J., Hokanson, S. Chapter 1: Collection, Maintenance, Characterization and Utilization of Wild Apples of Central AsiaA. p. 1-61. In: J. Janick, P. Forsline, E. Dickscon, R. Way and M. Thompson (eds.) Horticultural Reviews, vol. 29. Wild Apple and Fruit Trees of Central Asia. 2003.

Interpretive Summary: Malus sieversii, considered to be the main progenitor of the commercial apple M. x domestica was collected extensively in wild habitats in Central Asia on four expeditions between 1989 and 1996. These collection trips were sponsored by the USDA, ARS National Plant Germplasm System. Collections were made across a very broad range of latitude (38oN to 48oN) and longitude (69oE to 81oE). Elevation at the 12 sites visited ranged from 600 M to 1800 M, and climatic data listed annual precipitation from 250 mm to 1300 mm. Site data were recorded on all 892 seed lots collected as well as 44 elite samples that were collected for grafting. Fruit size in these samples ranged from 25 mm to 72 mm in diameter. Partial red color was noted on 80% of the samples and 55% had acceptable flavor qualities. Of the 122,000 seeds that were collected, 31,000 have been distributed to 24 cooperators for grow-out and evaluation. The remainder of the seeds are split for storage at -20oC at PGRU and at the National Center for Genetic Resources Preservation (NCGRP) at Ft. Collins, CO. Cooperators have evaluated the resulting seedlings for traits such as horticultural properties of trees and fruits, disease and pest resistance, environmental stress tolerance, plant stature and molecular genetic diversity. The resistance to apple scab across the 12 sites ranges from 5% to 49%. Fire blight resistance is about 30% on samples that have been inoculated. Seedling populations are being grown across wide environments in North America, Norway, Germany, South Africa and New Zealand. From these grow-outs we expect to identify selections adapted to different climatic zones. The success of utilization of the M. sieversii germplasm in cooperators' breeding programs will not be known for many years. The ongoing evaluations will ensure that it is tested for critical traits in a large range of apple production regions. We anticipate that this germplasm will ultimately offer useful genetic diversity for several reasons. First, the ecological amplitude of the species in its native habitats is truly impressive. Samples were collected from diverse ecosystems ranging from lush, humid, temperate forests to sparse dry, cold northern forests to near-desert habitats. Potential ecotypes from these regions should offer environmental adaptation as rootstock or scion for most apple production regions, except for sub-tropical areas. Second, M. sieversii in its native habitat has coevolved with several organisms that are pathogenic in orchards. Apple scab and codling moth were especially noted in collection sites. Finally, some M. sieversii genotypes will be readily useful because they are already similar in phenotype to commercial cultivars for some critical horticultural traits. The elite clonal accessions and similar seedlings that will be discovered during evaluation may contribute to new cultivars without extensive back crossing.

Technical Abstract: Malus sieversii Lebed., a wild apple species native to Central Asia, has been recognized as a major progenitor of the domesticated apple, M. x domestica Borkh. In ancient times, apple seeds and trees were likely dispersed from Central Asia, east to China and west to Europe, via trade caravan routes popularly referred to as the 'Silk Road'. This flow of apple germplasm ceased over the last few centuries as overland trade through the region decreased and, in the 20th century, as Central Asia was isolated for political reasons. In the 1980s, the U.S. Department of Agriculture (USDA) National Plant Germplasm System recognized that M. sieversii, was a critical species lacking representation in its Malus collection at the Plant Genetic Resources Unit (PGRU) in Geneva, New York. The material was critical because present cultivars of the commercial apple have a narrow genetic base with most commercial production based on very few cultivars. Collection expeditions were undertaken in 1989, 1993, 1995 and 1996. The expeditions successfully introduced large quantities of seeds as well as a limited number of clonal accessions to the ex situ collection at the PGRU. Most collections were made as seeds and altogether over 122,000 seeds were collected from 892 trees. This chapter summarizes the characterization of these apple collections from data collected on-site in Kazakhstan as well as the grow-outs of the seedlings in Geneva, New York and in 24 additional research institutes that received seeds of these collections from PGRU. Characterization and evaluation have been completed on horticultural traits, disease and pest resistance, environmental stress tolerance, and molecular genetic diversity. Chapters 2 and 3 in this book are translations of books from Russian to English, written by our collaborator in Kazakhstan, Professor A. Djangaliev. These chapters were edited by the authors of chapter 1.