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The efficiency of water use of 15 alfalfa genotypes of diverse genetic origin was studied in a growth room at three soil temperatures. The genotypes were similar in water used per unit of dry matter produced, but there was a significant temperature × genotype interaction. Genotypes of Medicago falcata L. used less water per day than genotypes of Medicago media Pers. and Medicago sativa L., but this was due to their slower growth rate. It was concluded that to develop higher yielding cultivars for optimum moisture conditions, selection should be for high rate of growth and rapid recovery and not for water use efficiency.

Twenty alfalfa varieties, representing a broad cross-section of alfalfas from different climatic zones, were grown in a greenhouse at soil temperatures of 5°, 12°, 19°, and 27 °C to determine the effect of root zone temperatures on herbage and root growth. The air temperature varied between 15° and 32 °C. The photoperiod was extended to 16 hours by supplemental lighting. There were marked varietal differences in root development at different soil temperatures. Varieties of Medicago sativa generally yielded more herbage and roots than those of Medicago falcata. However, varieties of M. falcata produced the most herbage per weight of roots. Growth of alfalfa was greatly affected by root zone temperature; the most herbage was produced at 27 °C and the most root and nodular tissue at 12 °C. Soil temperature affected the shape and color of nodular tissue. Nitrogen and phosphorus increased in herbage as the root zone temperature increased, with P increasing more than N. Time to reach the flowering stage was not appreciably affected by root zone temperature.

Summary Chromium oxide and plant pigments have been used as indicators to determine herbage digestibility, fecal output, and digestible and total herbage intake for five cows rotationally and daily strip grazing alfalfa-bromegrass ( Medicago falcata and Bromus inermis ) pasture during the grazing season of 1955. Morning and afternoon fecal samples were composited in the manner of three-day running averages to provide these estimates on a daily basis. The relationship of these variables and milk production to time has been discussed and arguments advanced to support representing time as a discontinuous arithmetic series instead of a simple arithmetic series in this and a previous experiment. Consequently, multiple correlation analyses have been recomputed for the two cows used in the previous experiment and are reported with the analyses for the five cows in this experiment. Although there was a marked linearity of decline in lactation with advancing time, daily milk production was also significantly related to variations in herbage digestibility and live weight. These were the main variables related to milk production under strip grazing. Under rotational grazing, digestible and total intake and fecal output were also significantly associated with milk production.

SynopsisCytological and limited genetic studies of tetraploid hybrids, triploid hybrids, and parental species indicated that gross homology was very high between M. sativa and M. falcata chromosomes. A chromosome pairing behavior deviating from that expected for a true autotetraploid appeared to be in existence in M. sativa.

Fifty isolates of Ascochyta imperfecta from alfalfa seed grown in Ontario, Manitoba, Saskatchewan, Alberta, and British Columbia produced varying degrees of infection on excised leaves of Medicago falcata, Medicago sativa (three strains), Melilotus alba, Melilotus officinalis, Trifolium pratense, Lotus corniculatus, Pisum sativum, and Vicia faba. F tests from analyses of variance of disease ratings showed that the differences in susceptibility between hosts and between strains of Medicago were highly significant. Among the 10 hosts and within the strains of Medicago, the interaction isolates × hosts was highly significant. Thus, specificity among the isolates was clearly demonstrated. This is interpreted to mean that parasitic strains existed among the 50 isolates.A. imperfecta was isolated from 50 to 70% of the seed samples from each province. The heaviest infestation was on seed from Manitoba, where the weather at harvest time was wet and where the crop overwintered in the field.

Many overwintering cultivated and native plants proved susceptible to the low-temperature basidiomycete which causes winter crown rot or snow mold of forage legumes and grasses in Alberta. Tests were made by inoculation in the late fall, or by planting in infested land. In the legumes, high resistance was found only in Medicago falcata and a Siberian strain of Trifolium pratense. T. hybridum, Melilotus spp., and the commonly grown varieties of alfalfa were particularly susceptible. Bromus spp. and Agropyron spp. proved highly resistant. Resistance was moderate in Elymus spp., Poa pratensis, and Festuca elatior; and slight in F. rubra and Phleum pratense. Agrostis alba, winter wheat, and winter rye were highly susceptible. In tests on horticultural plants, rhubarb and chives appeared to be immune; raspberry, peony, and columbine were resistant; and strawberry, parsnip, iris, and tulip were highly susceptible. A wide range of native plants and weeds suffered severe damage, and only Thalictrum spp. proved highly resistant. Shrubs and trees were not attacked.Following severe damage, crop rotation proved to be essential for the control of winter crown rot. The pathogen did not persist in the soil to any extent for longer than two to three years in land which was summer-fallowed or planted to annual crops or resistant grasses. Brome and other resistant grasses proved helpful in maintaining forage stands. Fertilizer treatments did not reduce the damage. Uncut tops and debris favored spread of the disease in alfalfa stands.

Alfalfa produced more herbage and more roots in a growth room when the fluorescent portion of an incandescent-fluorescent light source consisted of half gro-lux, high in blue-green-red light and half cool-white, high in blue-green-yellow-orange light than when it consisted of either alone. Protein content and degree of flowering were not affected by light source variations. Alfalfa cultivars, ranging in genetic makeup from Medicago falcata to M. media and M. sativa types, responded similarly to variations in light source. There was a definite trend for cultivars to produce less herbage and fewer roots as the proportion of M. falcata germ plasm in them increased. M. falcata flowered later than M. sativa in the growth room.

Summary The apparent dry matter digestibility of daily herbage consumption by eight dairy cows, rotationally and daily strip grazing alfalfa-bromegrass pasture ( Medicago falcata and Bromus inermis ) in 1957, was determined from fecal concentrations of plant pigments. Feces, sampled in the morning and afternoon, were composited into daily and three-day running average samples. Digestibility data obtained from the two series of samples were similar. Statistical comparison of these data revealed that the three-day samples corresponded best with the middle day represented in eaeh composite. Further statistical analysis showed significantly higher partial correlations of milk production and digestibility independent of the linear effects of time, using data from three-day rather than from daily samples. Examining the relationship of daily milk production to time, herbage digestibility, and live weight through multiple correlation analyses, it was found that milk production was significantly related to all three variables under rotational grazing. Although milk production was also related significantly to all three variables under strip grazing, the addition of digestibility did not improve the multiple correlation of milk production, time, and live weight.

An alfalfa population, consisting of progenies from crosses among 54 plants which had been selected out of a large population of Medicago falcata L. x Medicago media Pers. origin, was scored for degree of creeping-root development. These scores were statistically analysed on the basis of full-sib and half-sib groups. The estimate of Cov(FS) — Cov(HS) was 0.062, and Cov(HS) was 0.091. Therefore, it was concluded that genotypic variation was predominantly additive.Mass selection alone is predicted to be more efficient in breeding for the creeping-rooted character in alfalfa than a combination of mass selection and progeny testing. However, since other characters will usually be selected for along with the creeping-rooted character, the progeny test may have to be used. If progeny testing is used, the optimum number of progeny per parent under test should be approximately 30, provided these have been obtained from at least 8 to 10 different, unrelated, and randomly-selected mates.

Petals in three strains of M. falcata L. contain lutein 50–52%, lutein-5,6-epoxide 16–18%, chrysanthemaxanthin 9–10%, flavoxanthin 7–8%, and in smaller amounts β-carotene, ζ-carotene, a hydroxy-α-carotene-like pigment, two neoxanthins, auroxanthin and a flavoxanthin-like pigment. Almost 98% of all carotenoids were xanthophylls esterified with fatty acids. Uniformity of major carotenoid content in the three strains is consistent with their all belonging to the same species.

An analysis of scores for winter hardiness in a population of plants of alfalfa, derived from Medicago falcata L. x M. media Pers., indicated that most of the genotypic variation was non-additive. The genotypic correlation between winter hardiness and creeping root was found to be 0.38, increased winter hardiness being associated with increased creeping rootedness.

White seed in alfalfa is conditioned by a duplicate set of homozygous recessive genes for colorless and one dominant color inhibitor gene. This gene complex also inhibits anthocyanin production throughout the plant. The distribution of the offspring of a white-seeded hybrid having pure alfalfa parentage was interpreted as resulting from selective pairing of chromosomes, and that of a white-seeded hybrid, having as one parent an artificially induced autotetraploid from diploid Medicago falcata, as being the result of random chromosome pairing. These results are taken as evidence that alfalfa is of autotetraploid orfgin, and has evolved into a functional diploid.

Chromosomes from the pachytene stage of meiosis in diploid Medicago falcata L. were used to construct an idiogram showing mean chromosome lengths, arm ratios, and the number and distribution of chromomeres. The total length of the haploid chromosome complement was 277.9 microns, with the chromosomes ranging in length from 41.2 to 25.7 microns. The shortest chromosome was the nucleolus organizer chromosome. Six chromosomes had median or submedian centromeres; two were acrocentric, having arm ratios of 2.71 and 3.71. The idiogram was similar to published idiograms of diploid M. sativa L. Using the M. falcata idiogram and the published idiograms of diploid M. sativa, a description was suggested for an idiogram common to all diploid alfalfas.