Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1964 Selection for seed size in Lotus corniculatus L Arlen D. Draper Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Genetics Commons Recommended Citation Draper, Arlen D., "Selection for seed size in Lotus corniculatus L " (1964). Retrospective Theses and Dissertations. 2659. https://lib.dr.iastate.edu/rtd/2659 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 contact [email protected]. This dissertation has been 64—10,636 microfilmed exactly as received DRAPER, Arien D, 1930- SELECTION FOR SEED SIZE IN LOTUS CORNICULATUS L. Iowa State University of Science and Technology Ph.D., 1964 Biology-Genetic s University Microfilms, Inc., Ann Arbor, Michigan SELECTION FOR SEED SIZE IN LOTUS CORNICULATUS L. by Arien D Draper A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of The Requirements for the Degree of DOCTOR OF PHILOSOPHY Major Subject: Crop Breeding Approved: Signature was redacted for privacy. In Charge of Major Work Signature was redacted for privacy. Head of Major Department Signature was redacted for privacy. Iowa State University . Of Science and Technology Ames, Iowa 1964 ii TABLE OF CONTENTS Page INTRODUCTION 1 REVIEW OF LITERATURE 3 Introduction 3 Classification 4 History 5 Description 6 Cytology 10 Seed Size 10 Recurrent Selection 18 MATERIALS AND METHODS 23 Preliminary Seed Size Study 23 Selection of Parental Clones 24 Recurrent Selection for Seed Size 25 Progeny Seedling Vigor Studies 28 S EXPERIMENTAL RESULTS 31 Preliminary Seed Size Study 31 Selection of Parental Clones 33 Recurrent Selection for Seed Size 35 Progeny Seedling Vigor Studies 55 DISCUSSION 62 SUMMARY AND CONCLUSIONS 67 LITERATURE CITED 70 ACKNOWLEDGEMENTS 76 1 INTRODUCTION Birdsfoot trefoil, Lotus corniculatus L., is a forage legume rela­ tively new to the United States and has received less attention from agricultural workers than many other legumes. It has some desirable characteristics of interest to those wanting a long-lived pasture species. Its major weakness is a lack of seedling vigor, which has created problems in obtaining good stands. Major emphasis of research with this crop has been directed toward methods of reducing competition from other species and increasing the yield of adult plants. Forage yields, however, are dependent on stand establishment and since there will be competition from other species, perhaps the logical approach to the problem is to increase the seedling vigor of birdsfoot trefoil. A relationship between seed size and seedling vigor has been noted by investigators in many crop species. Information regarding this rela­ tionship was meager for birdsfoot trefoil. This study consisted of a preliminary seed size test, seed size evaluations of 2 varieties, 3 cycles of simple recurrent selection for seed size, and a seedling vigor evalua­ tion of open pollination progenies of some cycle 3 lines. This was done with regard to the following objectives: 1. To determine whether differences could be detected in seedling vigor of plots established from large, medium, and small seed sizes of the same variety. 2. To determine whether forage yields of adult plants from large, medium, and small seed sizes of the variety were different. 3. To determine the range in seed size of Viking and Empire varieties 2 of birdsfoot trefoil. 4. To find the plants in each variety producing the largest seed for initiation of a recurrent selection program for seed size. 5. To determine whether the mean seed size of Viking and Empire could be increased by recurrent selection procedures. 6. To determine if the larger seed produced by recurrent selection would give rise to seedlings with greater seedling vigor. 3 REVIEW OF LITERATURE Introduction Birdsfoot trefoil (Lotus corniculatus L.) is a long-lived legume which, during the past 30 years, has come into extensive use as a forage species in North America. It has been used as a forage crop in Europe for over 200 years and has been recognized for almost 300 years. How and when it was introduced into the United States is unknown. However, it received no serious attention as a potential domesticated species until the late 1930's. It has come into prominence as a desirable forage species because it appears capable of filling a niche not filled by the other forage legumes. Birdsfoot trefoil is capable of reseeding itself even under quite severe grazing and will survive in soils that are imperfectly drain­ ed. It is winter hardy, has a long life potential, and a fair yield which is distributed fairly well over the growing season. It is comparable to alfalfa in feed value, but does not cause bloat in the grazing animals. It appears that birdsfoot trefoil may provide a forage species that will serve as a supplement to the other forage legumes rather than a replacement. A recent survey (completed in January 1964) by several agencies work­ ing cooperatively, indicated that the 1963 acreage of birdsfoot trefoil in Iowa was approximately 165,000 acres. This estimate included all pastures containing birdsfoot trefoil whether seeded alone, or in mixtures with other forage species. This estimate is a little more than double a similar estimate made five years ago. This is a small acreage when compar­ ed with the other legume forages but it does indicate that birdsfoot 4 trefoil is gaining acceptance among Iowa farmers. Along with its favorable attributes, birdsfoot trefoil has a weakness which limits its wider use. Its greatest weakness is that it lacks seed­ ling vigor. It is unable to withstand severe competition from weeds, companion crops, or other forage species when seeded in mixtures., -Stand establishment often is hazardous under present cultural practices. Studies of the relationship of seed size and subsequent seedling vigor, in this species and others, have shown that, in general, large seeds have an advantage over small seeds because a seedling tends to have a growth rate in proportion to its initial seed size. The faster growing seedling has a better opportunity to cope with its environment and attain successful establishment. The present study was an effort to increase the seed size of two com­ mon agronomic varieties (Empire and Viking) of birdsfoot trefoil by a recurrent selection breeding scheme with the hope that seedling vigor also would be increased. Classification The Leguminosae, one of the largest families of the Angiosperms, contains three subfamilies: Mimosoideae, Caesalpinioideae and Papili- onoideae. To the latter subfamily belong the tribes Trifolieae and Loteae. The important genera Trifolium, Melilotus, and Medicago belong to the Trifolieae and Lotus is a member of the Loteae. Isely (1951) reported that of the approximately 150 species comprising Loteae, 100 or more belong to the genus Lotus. Also, the natural range of some of the species has been broadened by the activities of man, particularly that of Lotus 5 corniculatus, which is now present on all the continents. The classification of L. corniculatus has been extended to subspecies or varieties to include the broad-leaved and narrow-leaved forms. The narrow-leaved form is referred to by MacDonald (1946) as L. corniculatus var. tenuifolius, et tenuis, Gaudien. However, Isely (1951) used a study by Tome and Johnson (1945) as justification for considering the narrow- leaved form as a separate species, Lotus tenuis Kit. Some refer to it as L. tenuifolius; it is considered by many others as a variety or subspecies, L. corniculatus var. tenuifolius L. To treat it as a separate species seems reasonable since Dawson (1941) reported the chromosome numbers as 2n = 24 and 2n = 12 for L. corniculatus and L. tenuis respectively, even though they are morphologically similar. In the broad-leaved form of L. corniculatus, MacDonald (1946) mention­ ed two distinct types. The erect form is common in Continental Europe and is referred to as common birdsfoot trefoil, L. corniculatus var. vul­ garis, Koch. The dwarf form of the British Isles is the second type and is referred to as L. corniculatus var. arvensis Pers. Many authors choose to ignore the varietal names when writing about L. corniculatus. History MacDonald (1946) made an extensive review of literature concerning all aspects of birdsfoot trefoil and cited evidence that it has been used as an agricultural crop plant to a varied extent for only about 200 years, but was recognized as early as 1597. Isely (1951) reported that L. comi culatus now occurs throughout Europe, with the exception of the northern extremity, in much of western. Asia, North Africa, Australia, New Zealand, 6 and scattered areas of North America. Its appearance in the United States however, was rather late. McKee and Schoth (1941) suggested that birdsfoot trefoil first became naturalized in eastern New York and western Oregon and spread over a relatively large area. Specimens in herbaria show that plants of birdsfoot trefoil were collected in New Jersey as early as 1876, in North Carolina and New York in 1885, and in Alabama in 1888. Nelson (1917) first mentioned it in the northwestern United States in 1917, where it occurred as an escape plant from ballast at Linnton, Oregon. Studies investigating the potentialities of birdsfoot trefoil have been conducted at experiment stations rather extensively for the past 20-25 years. It appears to be best adapted to and used in the northcentral region, pacific northwest, and northeast regions of the United States. It appears to have gained a permanent foothold as a forage species in these areas. Its particular value seems to be in association with certain grass species in pastures which are to be maintained for a relatively long period.