No abstract

California produces more than 30% of the US alfalfa (Medicago sativa L.) seed crop. The majority of this seed is produced using honey bees (Apis mellifera) for pollination. Strength of reward, i.e. quantity and quality of nectar, is a primary factor in pollinator foraging activity. Positive correlations occur between nectar production and honey bee visitation, and honey bee visitation and seed production. Objectives of this investigation were to determine the effectiveness of phenotypic recurrent selection for increased nectar volume production and receptacle diameter and to determine the relationships among receptacle diameter, seeds/pod, seed production, and nectar volume in alfalfa. Populations of ‘CUF‐101,’ ‘Team,’ and ‘Vernal’ origin were developed by two cycles of phenotypic recurrent selection under either greenhouse conditions for nectar volume and receptacle diameter or field conditions for seeds/pod and seed production. Selection for either nectar volume or receptacle diameter resulted in a significant linear response in receptacle diameter. Nectar volume responded in a linear fashion to selection for nectar volume but did not respond when selection was for receptacle diameter. Selection for seeds/pod produced a significant linear response in nectar volume. Selection for seed production had no effect on nectar volume or receptacle diameter. Initial selection for receptacle diameter followed by nectar extraction should be an effective method of increasing nectar volume production.

No abstract

The purpose of this research was to ascertain the genetic control of reproductive tiller production in orchardgrass (Dactylis glomerata L.) and to determine whether sparse panicle production affects.forage yield and quality. We postulated that sparse‐flowering synthetic would retain forage quality longer than normal cultivars as reproductive tillers mature in late spring and early summer. In the greenhouse, up to 12 weeks of cool, short days were required before some orchardgrass plants would flower under long‐day conditions. The response of progeny from three crosses to floral induction treatments suggested that a complex interaction of genetic and environmental factors controls the onset and rate of reproductive tiller production. Reciprocal differences were not observed. Syn 2 generation of synthetics, that produced relatively few flowering tillers when grown in the northeastern USA, flowered and produced satisfactory seed yields at Prosser, Wash.In the field under a hay management cutting system, the most sparse‐flowering synthetic had slightly lower first harvest forage yield in June. than the check cultivars, possibly because dry matter was produced rapidly by the flowering culms of the cultivars. The absence of significant differences among entries for in vitro dry matter disappearance or lignin concentration suggests that the synthetics and cultivars were similar in forage quality. Thus, the experimental strains exhibited no apparent improvement in forage production or quality.

Among nearly 4,000 spaced plants in a breeding nursery of orchardgrass, Dactylis glomerata, 9 remained nonflowering near University Park, Pa., during the growing seasons of 1959, 1960, and 1961. Experiments with floral inductive treatments of 8, 10, 13, and 16 weeks of short days at 10 C or below subdivided selected clones from this nursery into three groups. Three 4‐clone synthetics with different cold inductive floral requirements were formulated. First‐generation (Syn 1) seed produced in 1963 at Prosser, Wash., of Syn A, Syn B, and Syn C, averaged, respectively, 50 g, 21 g, and 32 g per clone. The Syn 1 generation was compared with ‘Pennlate’ in solid‐seeded field plots for production of panicles and forage in the Northeast. In June 1965 Pennlate, Syn A, Syn B, and Syn C produced, respectively, 12.6, 13.1, 4.1, and 1.7 panicles per square foot in Pennsylvania and 37.2, 4.3, 1.8, and 0.6 in Vermont These data indicated a genetic basis for the nonflowering characteristic.

Subfreezing storage of seed is a comparatively new technique; therefore, few reports are available on longterm effects, particularly on retention of viability by forage crop seed lots produced under different environments. This study was based on 291 seed lots from seven forage crop species produced at three locations (Prosser, Wash., Shafter and Tehachapi, Calif.) during 1957‐1960. All seed lots were stored in a refrigerator at 5 C from year of harvest until placed in a freezer in told‐1960 for long‐term storage at ‐15 C and 60% relative humidity. All seed lots were tested for germination in the year of production and in 1971 and 1978 to determine germinability of each lot in those years. Original high seed quality was more important than location of seed production for retention of germinability although crop species did differ in germinability retention among the three production locations. Most notable was orchardgrass (Dactylis glomerata L.) seed produced at Shafter, which lost 22.5% in mean germinability in 19 years compared to 6.5% for seed grown at Prosser. Combined results for the three locations showed that birdsfoot trefoil (Lotus corniculatus L.), white clover (Trifolium repens L.), and alfalfa (Medicago sativa L.) seed retained germinability best, followed by timothy (Phleum pratense L.) and orchardgrass. Red clover (Trifolium pratense L.) and bromegrass (Bromus inermis Leyss.) suffered the greatest loss in germinability. The bromegrass seed, which had good original mean germination (90%), retained germination reasonably well until 1971 (12 years) but lost 11.8% in mean germination during the 7 additional years of storage. The original mean germination of the red clover seed lots was only 74.7% which undoubtedly contributed to the I 1% loss in germinability the first 12 years of storage. With the exception of bromegrass seed, germinability of forage crop seed can be maintained for up to 20 years if the seed was of high germination before subfreezing storage.

Honey bees (Apis mellifera L.) and alfalfa leafcutting bees (Megachile rotundata F.) collect nectar when pollinating alfalfa (Medicago sativa L.). The objectives of this study were to: (i) determine the expression of receptacle diameter (RD) and nectar volume (NE) in the field for subpopulations selected in the greenhouse, and (ii) determine if differences in either RD or NE were associated with seed yield. Bidirectional selection was practiced for RD and for NE in three cultivars. Cycle‐2 subpopulations from each source were evaluated at Five Points, CA, and at Prosser, WA for RD, NE, number of seeds/pod, 100 seed weight, number of pods/raceme, and seed yield. Large and small RD subpopulations differed (P ≤ 0.05) at both Five Points (score = 1.9 and 1.1, respectively) and Prosser (score = 3.1 and 1.3, respectively). Small RD subpopulations produced higher seed yields than large RD subpopulations. CUF 101 subpopulations selected for high and low NE differed in NE at both Five Points (15.7 vs. 6.0 μL/100 florets, P ≤ 0.05) and Prosser (62.1 vs. 44.8 μL/100 florets, P ≤ 0.10). Team and Vernal subpopulations selected for high and low NE differed (P ≤ 0.05) for the trait only at Prosser (70.1 vs. 39.8 and 68.7 vs. 32.9 μL/100 florets, respectively). The high NE subpopulation derived from CUF 101 produced more seed (P ≤ 0.05) than the corresponding low NE subpopulation (653 vs. 472 kg/ha, respectively). Greenhouse selection for RD and NE altered these traits under field conditions. Increased NE in alfalfa has the potential for increasing seed production.

No abstract