{ "item_title" : "In Vitro Methods for Conservation of Plant Genetic Resources", "item_author" : [" J. H. Dodds "], "item_description" : "However, the transition from primitive to 'advanced' cultivars has had the effect of narrowing the genetic base. This has happened in two distinct ways: (1) selection for relative uniformity, resulting in 'pure' lines, multi- lines, single or double hybrids, etc.; and (2) selection for closely defined objectives. Both of these processes have resulted in a marked reduction in genetic variation. At the same time, there has been a tendency to restrict the gene pool from which parental material has been drawn. This is a result of the high level of productivity achieved when breeding within a restricted but well-adapted gene pool, and of breeding methods which have made it possible to introduce specifically desired improvements, such as disease resistance and quality characteristics, into breeding stocks with a minimum of disturbance to genotypic structure. Developments in agriculture, such as intensive mechanization, the widespread application of fertilizers and the use of herbicides, fungicides and pesticides, have created a situation whereby a few, selected high- yielding cultivars may be grown over large parts of the earth, so further contributing to a decline in crop genetic diversity. This process is under way in all countries, both developed and developing, and unfortunately in- cludes some of the richest primary and secondary gene centres of several important food crops.", "item_img_path" : "https://covers1.booksamillion.com/covers/bam/0/41/233/870/041233870X_b.jpg", "price_data" : { "retail_price" : "169.99", "online_price" : "169.99", "our_price" : "169.99", "club_price" : "169.99", "savings_pct" : "0", "savings_amt" : "0.00", "club_savings_pct" : "0", "club_savings_amt" : "0.00", "discount_pct" : "10", "store_price" : "" } }

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