84 



THE CANADIAN HORTICULTURIST 



April, 1910 



The Principles of Plant Breeding^ 



Prof. Win. Lochhead, Macdonald College 



SOME persons may have doubts as to 

 the general application of Mendel's 

 results and laws. Insullicicnt time 

 has elapsed (nine years) for confirming 

 Mendel's conclusions in the crossing of 

 all plants and animals, but much test- 

 ing has been done, and it may be said 

 that the laws hold true in the majority 

 of cases where hybrids have been se- 

 cured. The following partial list will 

 give some idea of the amount of con- 

 firmatory work accomplished : Correns 

 with peas, corn, garden truck and net- 

 tle. Tschermak with peas. De Vries 

 with corn. Locke with corn. Riffen 

 with wheat and barley. Saunders with 

 sweet peas. Bateson and Saunders with 

 Lychnis, Atropa, Datura, and a large 

 variety of organisms. Bateson and 

 Gregory with primroses. Hirst with 

 rabbits and tomatoes. Experiments car- 

 ried on also with rats, guinea pigs, cats 

 and horses among animals, and with 

 oats and beans among plants, have 

 shown Mendelian inheritance in certain 

 characters in hybrids. 



It must be understood that in the 

 list just cited the Mendelian Law of In- 

 heritance was confirmed with regard to 

 but a few pairs of characters in each 

 case. The task of the future investi- 

 gator is to determine: (i) The plants 

 and animals that mendelize, (2) the dom- 

 inant and recessive characters of each 

 pair of contrasting characters, and (3) 

 the causes of the apparent exceptions to 

 mendelization ; for example, in those 

 cases of blended inheritance where the 

 character possessed by the hybrid is an 

 average or blend of the two parental 

 characters, and in cases of mosaic in- 

 heritance "where the characteristic col- 

 ors of the two parents are inherited in 

 the offspring in patches on different 

 parts of the body." 



While it is true that the majority of 

 cases that follow Mendel's Laws of In- 

 heritance have reference to hybrids be- 

 tween varieties, several cases have been 

 observed where hybrids of elementary 

 species and Linnaean species follow the 

 same laws. 



The plant breeder who attempts to 

 work along Mendelian lines must bear 

 in mind that he must breed for one char- 

 acter at a time, and that he cannot "ob- 

 tain in combination both of a pair of 

 contrasted characters." 



Burbank secures his best work by 

 crossing. Occasionally hybrids are pro- 

 duced which surpass the parents in vig- 

 or of growth or hardiness or profuse- 

 ness of bloom. His hybrid walnuts, 



•The conclusion of a series of articles that has 

 appeared at intervals in The Canadian Horticul- 

 turist, during the past year. Preceding instal- 

 ments were published in last June, September 

 and March issues. The entire article was origin- 

 ally prepared for and read at a convention of 

 the Quebec Pomological Society. 



which are exceedingly vigorous grow- 

 ers, fine grained and compact, were ob- 

 tained as hybrids by crossing the Eng- 

 lish walnut with the California black 

 walnut. His Wickson plum was pro- 

 duced by crossing his Burbank plum 

 with the Kelsey, both being derived from 

 the Japanese Prunus triflora. His Bur- 

 bank and Satsuma plums are probably 

 mutants, which he secured from phim 

 pits sent him from Japan. 



The Shasta daisy is an example of the 

 results of crossing. It is the product of 

 crossing three forms— the English, the 

 American and the Japanese daisies. It 

 has the tall, stiff stem of the English 

 daisy, the prominent white flowers of 

 the Japenese species, and the profuse- 

 ness of bloom of the American species. 



THE ASSOCIATION OF 0HARA0TEH8. 



It is probable that in man's early his- 

 tory, when he was becoming acquainted 

 with the plants that grew all about him, 

 he perceived the correlation of the quali- 

 ties of certain plants with certain physi- 

 cal characters; i. e., he early associat- 

 ed qualities with characters. Wood-lore, 

 for example, is largely the information 

 the woodsman has gathered together 

 with reference to the association of plant 

 and animal qualities with their physical 

 characters. 



It is frequently observed that a par- 

 ticular color in a flower is asso- 

 ciated with a particular taste or 

 color in the fruit or seed, or 

 a particular color with a particular 

 form. Nilsson has discovered some very 

 interesting correlations in his studies of 

 barleys, while Burbank uses intuitively 

 the principles of correlation in the large 

 amount of selection he practices, for he 

 makes the majority of his selections 

 while the plants are in the seedling 

 stage. He can "predict one quality or 

 one function from the study of others." 



This correlation of characters brings 

 forward again the idea of unit-charac- 

 ters, which we have seen, formed the 

 basis of Mendelism. The idea of cor- 

 relation forces on us the assumption 

 that the unit may express itself in many 

 ways. It may express itself in the leaf, 

 seed, fruit, stem and tissue; the "cor- 

 related external marks may be but the 

 expression of the same internal charac- 

 ter." 



The scientific study of hybridism be- 

 comes, therefore, very complex. It re- 

 quires a careful examination of all parts 

 of the plants under consideration. The 

 most trifling marks are worthy of study 

 and comparison with valuable qualities, 

 since selection may be guided by them. 



A correct and thorough knowledge of 

 the principles underlying plant breeding 

 is very important. Fruit growers are 

 sometimes carried away with the im- 



pression that the origination of new va- 

 rieties is a simple matter, and that defi- 

 nite results should be secured in a year 

 or two. They should remember that 

 while it is true that the methods which 

 have been developed during the last few- 

 years are less empirical than formerly, 

 wc are just beginning to understand 

 the rationale of plant breeding. We ar ■ 

 making such rapid progress in our study 

 of the mode of inheritance that the 

 breeder will soon be in a position to 

 move more rapidly, "more surely, and 

 with greater economy of time and of 

 material." Through a knowledge of 

 the processes of Selection, Mutation 

 and Hybridism, may we not hof>c to 

 get greatly increased yields and much 

 better products, if we can originate bet- 

 ter and more productive varieties? The 

 time is fast approaching when the gov- 

 ernment must grasp the importance of 

 this subject of plant breeding and be 

 willing to expend much more than it is 

 now expending in the establishment and 

 maintenance of high-class breeding sta- 

 tions. The future additions to the 

 wealth of the country must come main- 

 ly from an increase in the producing 

 capacity of our agricultural lands. 



Pruning the Peach 



J. L. Hilbom, LeuBingtoD, Oat. 



To follow my method of pruning 

 peaches, it is necessary to start when 

 the trees are planted. Before taking the 

 trees to the field, I have them all gone 

 over, cutting the main stem back to 

 twenty or twenty-four inches above the 

 point where the tree was in the soil. I 

 then cut any side branches back to one 

 bud from the trunk. These buds will 

 usually burst, as also such good buds as 

 are on the main stem. 



After the trees are well started, say 

 in June, I go over them and rub off all 

 but four or five, which I select to form 

 a head. An ideal head in my estimation 

 is one that has the branches fairly well 

 distributed from the top of the trunk 

 to within ten or twelve inches of the 

 ground. The first year after planting 

 and all succeeding years, I prune in pro- 

 portion to the growth that the tree has 

 made. . Branches that have only grown 

 twelve to fifteen inches, I would not dis- 

 turb unless it was to remove the ter- 

 minal bud to compel it to branch. 



Branches that have grown eighteen 

 inches and upwards, I cut back from one 

 quarter to one half the growth, — the 

 latter where the growth is three to four 

 feet,- — and always endeavor to cut back 

 to one or more side branches. Before 

 cutting back, I thin out surplus branches 

 and leave only such as have room for 

 proper development. 



Sour cherries need more moisture 

 and will thrive in heavier land than 

 sweet cherries. 



