Evaluation of a lucerne germplasm collection in relation to traits conferring grazing tolerance

Summary A collection of 90 accessions of different germplasm groups from the Medicago sativa complex was evaluated at Lodi, Italy, for dry-matter yield, time to anthesis, height of regrowth, plant diameter, stem density, vegetative recovery after winter, and presence of deep-set crown and ability to spread with creeping roots or rhizomes, these latter characters possibly contributing to grazing tolerance. The germplasm groups proved rather distinct for these traits, but all included types potentially suitable for grazing. Interesting types combining deep-set crown and high yield occurred mainly in subsp. x varia and materials originated from artificial crosses involving at various extent the subspecies falcata, sativa and x varia. Though belonging to subsp. sativa, mielga wild populations from Spain had aerial traits similar to those of the long-dormant, low-yielding subsp. falcata. Deep-crowned plants had greater plant diameter than shallow-crowned plants, and could be categorised into four distinct top-growth models according to their habit and vigour. One of these models combined spreading ability with high yield. The about 150 plants selected for their combination of deep crown, wide diameter, and good yield were characterised by a branch-rooted system. There was general correspondence between top-growth and root morphology of each model. Of the four deep-crowned models, three had rhizomes, with wide range of underground development and morphology, while the fourth had creeping roots. The latter model was the most rare among the examined accessions, never appearing in either cultivated or wild subsp. sativa. The implications of the results on the development of grazing-tolerant lucerne varieties are discussed.     

Thermal dependence of glutathione reductase in one tetraploid and its near-isogenic diploid alfalfa

Summary A more thorough understanding of the biochemical basis of superior performance of one alfalfa (Medicago sativa L.) genotype compared to another would expedite improvement in agronomically useful genotypes. Information on thermal dependence of glutathione reductase (GR, E.C. 1.6.4.2) in different ploidy levels of alfalfa is lacking. Our objective was to investigate the thermal dependency of GR in two genetically comparable populations of alfalfa at diploid and tetraploid levels. Thermal stability was similar for the enzyme from both populations, whereas variation was found for: i) the minimum apparent Km (0.53 and 4.14 M NADPH), ii) the temperature at which the minimum apparent Km was observed (15 and 25° C), and iii) the thermal kinetic windows (TKW) (the temperature range over which the apparent Km is within 200% of the observed minimum Km, 5 and 20° C width) in diploid and tetraploid alfalfa, respectively. The TKW data suggest that the diploid can perform optimally under a narrower (i.e. smaller TKW) and lower range (i.e. the temperature at which the lowest Km was observed) of temperatures, whereas the tetraploid can perform optimally under a wider range (i.e. larger TKW) of temperatures. This finding is in agreement with previously published growth data on near-isogenic populations of diploid and tetraploid alfalfa.Abbreviations GR glutathione reductase - TKW thermal kinetic window - Km apparent Km This work was supported by USDA Specific Cooperative Agreement No. 58-7MN1-8-143 from the Plant Stress and Water Conservation Unit, USDA-ARS, Lubbock, Texas. Joint contribution of the Texas Tech University, USDA-ARS, Lubbock, TX and University of Wisconsin, Madison, WI. TTU Journal No. T-4-306.     

The yield stability of CIMMYT'S maize germplasm

Summary Relationships between whole-plant and germination NaCl tolerance and two in vitro measures of NaCl tolerance were evaluated in lucerne (Medicago sativa L.). No significant correlations were observed between relative NaCl tolerance of non-regenerating callus cultures, herbage regrowth, seed or pollen germination, and pollen tube growth. Simulated selection using indirect measures of NaCl tolerance produced small expected gains in relative NaCl tolerance during herbage regrowth and seed germination. These gains were less than 30% of those expected with direct selection for regrowth or germination tolerance. Selection based on the apparent NaCl tolerance of callus tissue or male gamephytes would appear unproductive. Direct selection for NaCl tolerance both at germination and during mature plant regrowth would appear to be necessary to rapidly develop lucerne populations with field-relevant levels of tolerance to NaCl stress.Approved by the Arizona Agric. Expt. Stn. as Journal Series no. 5015.     

Single plant versus clonal line performance in alfalfa

Summary Single plants and clonal lines of fifty-six alfalfa clones were compared in a field trial. The error coefficient of variation was much higher for single plants than for clonal lines. Unreplicated single-plant and clonal-line performance were inadequately related. Replicated single-plant performance approached closely the performance of unreplicated clonal lines. Correlation between yield and height was low.     

Between and within cultivar variability in salt tolerance in lucerne, (Medicago sativa L.)

Summary The response of two-week-old seedlings of 35 cultivars of lucerne (Medicago sativa L.) to increasing NaCl concentrations was assessed in solution culture under growth room conditions. Shoot length, used as the criterion for assessing salt tolerance, was found to decrease significantly with increasing NaCl concentration for all cultivars, but there was considerable variation in response between, and within cultivars. It is concluded that selection between and within cultivars should lead to increased salt tolerance in this species.     

苜蓿加工产物中未鉴定生长因子（UGF）对肉仔鸡的影响

本文研究了苜蓿加工产物中未鉴定生长因子对肉仔鸡的影响，结果表明：自制的苜蓿汁粉可以作为专用未鉴定生长因子添加剂；用苜蓿叶粉作为未鉴定生长因子来源时，应考虑其中有害成分的影响；未鉴定生长因子提高增重不是由于蛋白质存留率提高。     

Temperature influences postdispersal predation of weed seeds

Temperature is a key factor for the living organisms on earth. It influences weed management practices, either directly or indirectly. Field experiments were conducted to determine the effect of temperature on the postdispersal seed predation of four important weed species (Cuscuta compestris, Stellaria media, Taraxacum officinale and Veronica persica) in two lucerne fields in Mashhad and Chenaran, north‐eastern Iran. These two cities have the same climate: temperate and cold alpine but the temperature varies between them. Wire mesh cages were used to determine the relative importance of birds in predation and pitfall traps were used to detect the species and the activity density of invertebrate predators. The results showed that the predation preference of different weed species was significantly different between and within fields. Seed predation fluctuated widely throughout the sampling periods, matching the periodic forage harvest and regrowth cycle of lucerne. Despite the level of seed predation fluctuating, it declined toward the last sampling periods. Using wire mesh exclusion cages showed no significant effect of birds on weed seed predation in both fields. Ants, crickets and carabid beetles were the invertebrate seed predators that were caught in the pitfall traps. There were significant correlations between the mean temperature and predator activity densities and also between the predated seeds and the mean air temperature in both locations. The results of this study indicate the significant effect of temperature on postdispersal weed seed predation. Therefore, with respect to climate change and increasing global warming, it would be possible to focus on postdispersal seed predation in weed management in the future.     

Effects of grain source and marginal change in lucerne hay particle size on feed sorting,eating behaviour,chewing activity,and milk production in mid‐lactation Holstein dairy cows

This study investigated the effects of grain source and lucerne hay (LH) particle length on eating behaviour, chewing activity, and milk production of lactating dairy cows. Eight Holstein dairy cows (175 ± 21 days in milk) were used in a replicated 4 × 4 Latin square design with four 21‐days periods. The experiment was a 2 × 2 factorial arrangement of treatments with barley grain alone or equal blend of barley and maize grains combined with short (15 mm) and long (30 mm) LH. Diets were fed ad libitum as total mixed ration with a concentrate to forage ratio of 60:40. Interactions between grain source and LH particle length on feed particle distributions, sorting index, chewing activity, and milk production were minimal. Partially replacing barley grain with maize in the diet overall did not change diurnal distributions of particles retained on the sieves of Penn State Particle Separator but reduced the proportion of particles on 1.18‐sieve and increased that of particles on pan (p < 0.05). Grain source did not affect sorting index and chewing activity. However, feeding long LH increased (p < 0.01) intakes of long particles retained on 19‐ and 8‐mm of sieve, prolonged (p < 0.05) eating time, and lowered eating rate (p < 0.05). Interestingly, cows fed with long LH ate more coarse particle during critical‐early time post feeding (i. e. 1.5 h), where eating time increased and eating rate decreased (p < 0.05). Increasing particle length of dietary LH tended to increase milk fat‐to‐protein ratio (p = 0.08). The results suggested that the increased eating time and decreased eating rate as a result of marginally increasing LH particle length would be beneficial to alleviate reduction of ruminal pH and milk fat percentage following the ingestion of highly fermentable diets.     

Volatile losses of sulfur by intact alfalfa plants

An apparatus was developed for the quantitative collection of volatile sulfur compounds released by intact plants and was used to study the effects of leaf temperature and stomatal aperture on the amount and pattern of release.

An air stream sweeps volatiles released by the plants through a water‐cooled condenser system in which the air is dried prior to trapping the volatile sulfur compounds on activated carbon. Tests with ³⁵S‐labelled 1‐butanethiol gave a mean recovery of 95.8 ± 4.3%.

The yield of volatile sulfur compounds increased greatly when air flow rate increased from 1 to 2 1 min^‐1 , but was independent of flow rate over the range 2 to 6 1 min^‐1. About 93% of the trapped activity originated from plant shoots, about 1% from stem bases and roots and about 4% from culture solutions.

Release of volatile sulfur compounds from intact plants followed a diurnal pattern, maximum rates occurring around midday and minimum rates overnight. Maximum rates of release ranged from 30 to 41 ng S g dry weight of shoots^‐1 2 hr ^‐1, while minimum rates ranged from 1.5 to 2.1 ng S g dry weight of shoots^‐1 2hr^‐1. Leaf temperature rather than stomatal aperture seemed to be the major factor controlling rate of release of volatile sulfur compounds. The rate of release was almost doubled by an increase of 7–9°C in leaf temperature.