Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1961 Stock, scion and interstem reactions in apple trees Donald Benjamin White Iowa State University Follow this and additional works at:https://lib.dr.iastate.edu/rtd Part of theAgriculture Commons, and thePlant Sciences Commons Recommended Citation White, Donald Benjamin, "Stock, scion and interstem reactions in apple trees " (1961).Retrospective Theses and Dissertations. 2470. https://lib.dr.iastate.edu/rtd/2470 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please [email protected]. This dissertation has been 61-6171 microfilmed exactly as received WHITE, Donald Benjamin, 1930- STOCK, SCION AND INTERSTEM REACTIONS IN APPLE TREES. Iowa State University of Science and Technology Ph.D., 19B1 Agriculture, plant culture University Microfilms, Inc., Ann Arbor, Michigan STOCK, SCION AND INTERSTEM REACTIONS IN APPLE TREES by Donald Benjamin White A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of The Requirements for the Degree of DOCTOR OF PHILOSOPHY Major Subject: Horticulture Approved: Signature was redacted for privacy. In 'Charge of Major Work Signature was redacted for privacy. Head 'of Ma jor Department Signature was redacted for privacy. Dëah of Gradua Iowa State University Of Science and Technology Ames, Iowa 1961 il TABLE OF CONTENTS Page INTRODUCTION 1 REVIEW OF LITERATURE 4 MATERIALS 22 METHODS 27 RESULTS 31 DISCUSSION 164 SUMMARY - 174 BIBLIOGRAPHY 177 ACKNOWLEDGMENTS 184 1 INTRODUCTION Dwarf fruit trees have been a part of the European garden for centuries. Their planting in the American garden was limited until the recent trend towards urbanization brought into prominence an emphasis on the planting and culture of dwarf fruit trees. Early experiments in this country discouraged the com­ mercial use of this type of tree (Hall, 1915). However, the economic pressures of today's industrial economy have prompted a renewed interest in the commercial value of dwarf fruit trees in the apple producing industry. The disappearance of highly productive land into the urban expansion program, high land values, and the cost-price squeeze, demand high produc­ tion and low maintenance per unit area. This has been especially true with the tree fruit industry. Dwarf fruit trees, as a result of smaller stature, reduce pruning, spraying and harvesting costs. Earliness of bearing and increased yield per acre (Roberts, 1954, 1957» 1959; Tukey, I960; Upshall, 1959; Lorang, i960) resulting from more in­ tensive cultural practices have made this type of orchard extremely competitive. These advantages, coupled with the fact that dwarf trees are adaptable to mechanization, have created a need for the development of productive, hardy stocks for use in Canada and the northern United States. The dwarf fruit stock inventory has been widely tested 2 in Europe and eastern United States. However, many of the common dwarfing rootstocks for apple varieties are not reli­ ably hardy in the northern plains area and Canada. Many of these rootstocks perform best under cool soil conditions during the growing season (Banta, 1955; Nelson and Tukey, 1955)* Most of the dwarfing rootstocks produce poorly anchored trees when used as the root system for standard varieties. The dwarf apple rootstocks also are difficult to propagate and maintain. Regardless of the problems attendant with the use of dwarfing stocks, they appear to hold the key to the survival and growth of the commercial fruit industry. Indeed, they may be the only hope this industry has of coping with the demands of an expanding population. The selection and testing of dwarfing rootstocks has centered around the apple, Malus domestica. Borkh. Most of the dwarfing stocks have been collected, tested and identified according to the size of tree produced, by the East Mailing Research Station at Kent, England. Dwarf trees are produced either by using the selected stock as the primary root system, or by interposing a piece of the stock between a vigorous rootstock and the named variety. The latter tech­ nique, or interstem method, appears to be gaining in popularity by eliminating the problem of poor anchorage, which is charac­ teristic of many dwarfing rootstocks. Although dwarf trees have been grown for centuries, very 3 little is known about the dwarfing reaction of rootstocks and intersterns. To date the only reliable procedure for deter­ mining rootstock or interstem influences has been by grafting each variety to each stock (Shaw, 1935 )• The development of stocks and varieties is imperative if the commercial fruit grower is to keep pace with modern agriculture. Stocks must produce uniform trees of low stature. They must be easily propagated and sufficiently hardy so as to withstand the rigors of the climate in the commercial production areas. This study was designed to test a large number of the common and recently introduced rootstock and interstem apple varieties for usefulness in the production of acceptable dwarf trees. 4 REVIEW OF LITERATURE It was from motives of gain that the grafting of trees and the propagation thereby of spurious off­ spring was first devised so that the growth of the fruits even might be a thing interdicted to the poor. (Bostock and Riley, 1885) The preceding statement, written about the time of Christ by Pliny (25AD), indicates that a knowledge of the art and science of propagating fruit trees by graftage is of ancient origin. It suggests the use of stocks in that grafting, by definition, requires at least two components, a scion and a stock. By the same token it is possible that the ancients also acquired some knowledge of stock-scion relationships. Of necessity, much of this review of literature will deal with rootstock-scion relationships. A great deal of the research to date has been concerned with this problem and the effects resulting from grafting roots and scions are similar to those developing from the use of interstems. Indeed, the interstem method of propagating dwarf fruit trees was devised to accomplish the same results as those produced from the use of dwarfing rootstocks. Pliny was not the first to write about grafting as a method of producing fruit trees. It is known that the art of graftage fascinated plantsmen centuries before Pliny's time. Theophrastus 300 BC (Hort, 1916) , a contemporary of Plato, Aristotle, and Diogenes, described grafting and budding with special reference to fruits. This knowledge presupposes a 5 recognition of the techniques of propagation and compatibility. The fact that many tree fruits do not come true to type from seed necessitates asexual or vegetative propagation. This seems to have been fairly common knowledge to plantsmen of that time. Evidently the value of grafting was appreciated before the time of these early writings. Maney (19^2) noted that the use of dwarfing stocks was recorded over 2000 years ago in ancient Greek writings. Cato 200 BC (Brehaut, 1933) , wrote an excellent, detailed description of grafting and bud­ ding as a method for propagating fruit trees. Not only were the ancients proficient in the art of graftage, but they also displayed some knowledge of the factors responsible for dwarfing. In fact, some of their explanations are embodied in our present day concept of the phenomena. Some of the basic techniques involved in grafting and a recognition of incompatibility were put forth in 200B C when Cato (Harrison, 1913) wrote that extreme care should be exercised in the timing, manner of grafting and selection of the stock and scion. He observed that the scion variety to be grafted should always be of better quality than the stock and that results were always better when a cultivated stock of the same species was used, rather than a wild seedling type. It could be surmised from these observations that certain types of stocks were specifically selected for the purpose of propagation. This is not too surprising since 6 references to dwarf plant types can be found In many of the ancient writings. Cato exhibited some knowledge of the af­ finity various components had for one another, not only by recommending a cultivated stock, but in mentioning that usual­ ly apple was grafted on apple and that the pear could not be grafted upon oak, even though it could be grafted onto the apple. At that time, graftage was used primarily for the propagation of slow growing fruits and trees. According to Pliny (25 AD) a certain amount of supersti­ tion surrounded the practice of grafting at that time, for it was believed that if the hawthorn was used as a stock it would not be "easy to avoid the disastrous effects of lightning" that would be hurled against the spot. Even with the super­ stition, which probably was cultivated by the artisans to lend some mystery to their calling, many observations of that time are pertinent to the production of grafted trees. Reference is made to grafting the pear upon quince, which is the common method for propagating both standard and dwarf pears today. Pliny also refers to the stock influencing the quality of the fruit produced on a grafted plant. One of the earliest records of the interstem method of propagating fruit trees was written in 1639 by John Parkinson (Sax, 1956) who described the use of an interstem to overcome incompatibility between the nectorine and plum stock. It was not until a few years later that the principle was applied to