Effects of Soil pH on Reproduction of Pratylenchus penetrans and Forage Yield of Alfalfa

''Vernal'' alfalfa was grown for 30 weeks in nematode-free soil and in soil infested with Pratylenchus penetrans. Charlottetown fine sandy loam soil was used at its pH of 4.4 and at adjusted reactions of 5.2, 6.4 and 7.3. Nematode reproduction was significantly greater at pit 5.2 and 6.4 and was not related to alfalfa root production over the full pH range studied. A significant nematode infestation X soil pit interaction on forage yield was recorded. Nematode infestation significantly decreased forage yields at ptt 5.2 and 6.4 but not at pH 4.4 and 7.3.     

热带牧草种质圃资源收集、保存及分发利用研究

简述了农业部儋州热带牧草种质圃概况,介绍了热带牧草种质资源收集、保存及分发利用状况。截止到2013年底,共收集国内外热带牧草种质7760份,先后从中选育出22个牧草及饲料作物新品种通过全国牧草品审会审定。圃内无性繁殖材料活体保存草种质1552份,隶属3科68属202种,其中禾本科牧草种质有60属186种,豆科牧草资源有6属42种,莎草科有4属5种,引进种质有378份。每年向国内外相关科研院所、大专院校及企业和个人提供实物草种质材料300余份,提供种质数据信息400余条,指出了今后热带牧草种质圃在热带牧草资源收集、保存、分发利用方面的研究重点和研究方向。     

新选育饲草玉米品系饲用营养价值初步研究

对利用一年生大刍草和四倍体多年生大刍草分别与玉米杂交选育出的一年生饲草玉米(SC1)和多年生饲草玉米(SC3)生物产量和饲用营养成分进行分析,结果表明:SC1和SC3鲜草年产量分别达115 620kg/hm2、174 045kg/hm2,是普通玉米的4～6倍;SC3的粗蛋白质(CP)和无氮浸出物(NFE)含量最高,分别为17.57%、48.73%,粗纤维(CF)含量最低,为21.65%,其粗脂肪(EE)和灰分(CA)含量分别为4.30%和7.75%;SC1的营养成分含量分别为:(CP)14.73%、(CF)26.09%、(NFE)45.29%、(EE)4.78%和(CA)9.11%;化学营养类型分析表明SC1与SC3分别属NC型和N型,都是高产高饲用价值的新型饲草.     

Identification of Alfalfa Mosaic Virus in Greek Alfalfa Crops

Alfalfa mosaic virus (AMV) was found to be the prevalent virus disease in alfalfa crops in Central and Northern Greece. The virus was identified on the basis of the host symptomatology, aphid and seed transmission, particle morphology and serological tests. AMV was largely detected in commercial seeds of local grown alfalfa cvs by ELISA. Infected seed lots appear to be the main source responsible for the widespread distribution of the virus in Greek alfalfa fields.     

国家多年生牧草种质圃资源收集、保存及利用

本文简述了国家种质多年生牧草圃概况,介绍了多年生牧草种质资源收集、保存及利用状况.截止到2008年底,共收集保存了600份牧草种质资源材料,隶属10科,49属,152种.禾本科(Gramineae)牧草有24属95种,豆科(Leguminosae)牧草15属35种,占保存材料85%以上,其中野生种有496份材料,引进栽培种有104份材料.每年向国内外相关科研单位及教学单位提供利用种质材料100余份,提供的种质材料多数用于科学研究,还有部分用于推广利用.指出了国家种质多年生牧草圃今后在多年生牧草资源收集、保存、鉴定及利用方面的研究重点.     

Legume-Cereal Intercropping Improves Forage Yield,Quality and Degradability

Intercropping legume with cereal is an extensively applied planting pattern in crop cultivation. However, forage potential and the degradability of harvested mixtures from intercropping system remain unclear. To investigate the feasibility of applying an intercropping system as a forage supply source to ruminants, two consecutive experiments (experiments 1 and 2) involving a field cultivation trial and a subsequent in vivo degradable experiment were conducted to determine the forage production performance and the ruminally degradable characteristics of a harvested mixture from an alfalfa/corn-rye intercropping system. In experiment 1, the intercropping system was established by alternating alfalfa and corn or rye with a row ratio of 5:2. Dry matter (DM) and nutrient yields were determined. In experiment 2, forages harvested from the different treatments were used as feedstuff to identify nutrient degradation kinetics and distribution of components between the rapidly degradable (a), potentially degradable (b) and the degradation rate constant (c) of ‘b’ fraction by in sacco method in Small-Tail Han wether Sheep. The intercropping system of alfalfa and corn-rye provided higher forage production performance with net increases of 9.52% and 34.81% in DM yield, 42.13% and 16.74% in crude protein (CP) yield, 25.94% and 69.99% in degradable DM yield, and 16.96% and 5.50% in degradable CP yield than rotation and alfalfa sole cropping systems, respectively. In addition, the harvest mixture from intercropping system also had greater ‘a’ fraction, ‘b’ fraction, ‘c’ values, and effective degradability (E value) of DM and CP than corn or rye hay harvested from rotation system. After 48-h exposure to rumen microbes, intercropping harvest materials were degraded to a higher extent than separately degraded crop stems from the sole system as indicated by visual microscopic examination with more tissues disappeared. Thus, the intercropping of alfalfa and corn-rye exhibited a greater forage production potential, and could be applied as forage supply source for ruminants. The improved effective degradability of harvest mixture material could be attributed to greater degradable components involving the rapidly degradable fractions (a), potentially degradable (b) fractions, and degradable rate constant (c), than that of corn and rye hay.     

Ammoniated Forage Poisoning: Concentrations of Alkylimidazoles in Ammoniated Forage and in Milk,Plasma and Urine in Sheep and Cow

4-methylimidazolc (4-MeI) has until now been the only identified toxic compound in ammoniated forage considered to be of possible etiological significance in ammoniated forage poisoning. However, several authors have concluded that 4-MeI alone cannot explain the toxicity observed (Morgan & Edwards 1986, Nielsen et al 1986, Motoi et at. 1997). On this background, we have examined samples of ammoniated forage and of milk, plasma, and urine collected from ewes and lambs during a previous experimental poisoning study (Sivertsen et al. 1993). We have also studied similar samples from a Norwegian Red Cattle dairy cow fed ammoniated hay for the first 5 days after calving. We have, in addition to the previously known ingredients 4-MeI and 2-methylimida-zole (2-MeI), identified 5 new compounds in these samples, all of which were found to be di-alkylsubstituted imidazoles: 1,2-dimcthylimi-dazole (1,2-diMeI), 1,4-dimethyl imidazole (1,4-diMeI), 1,5-dimethyl imidazole (1,5-diMeI), 2,4-dimethylimidazole (2,4-diMeI) and 2-ethyl, 4-methylimidazole (2Et-4MeI) (Müller et al. 1998). In this paper we present quantitative measurements of these di- and monoalky 1 imidazoles in a selection of the collected samples.     

Effect of Ditylenchus dipsaci on Alfalfa Mortality,Winterkill, and Yield

Ditylenchus dipsaci-infected and noninfected alfalfa plants in a naturally infested field were studied from July 1980 to September 1982. Forty-one percent of the plants died during the study. Ninety-seven percent of the plants that died were infected with D. dipsaci. Sixty-nine percent of the observed mortality occurred during winter. Forage yield of infected plants was significantly lower than yield of noninfected plants at each harvest. Stored carbohydrates in infected plants were significantly lower than in noninfected plants. In a controlled environment test, significantly greater mortality occurred in frozen severely infected plants than in frozen noninfected plants, while no mortality occurred in severely infected or noninfected plants that were not frozen. Both forage yield and stored carbohydrates were significantly lower in severely infected than noninfected, non-frozen plants. Mortality in greenhouse-grown plants that were transplanted to field plots was significantly greater in D. dipsaci-infected plants than in noninfected plants after one winter.     

Alfalfa,Medicago sativa L., in highly weathered,acid soils

Summary Seedlings of a broad based population of alfalfa, (Medicago sativa L.), were visually selected for 2 generations (cycles) in an acid Cecil soil (pH=4.8). Simultaneously, 2 generations of selections were made in a limed Cecil soil (pH=6.2) amended with phosphorus. When tested in acid soil (pH=4.8) with added P, the cycle 2 acid selections yielded significantly more top yield than either the limed selections or the original seed. When grown in the limed soil (pH=6.2) without added P, the acid selections yielded significantly less. There were no significant differences among selections in other soil conditions (pH=4.8, no P added and pH=6.2, P added). Root weight and length and nodule fresh weight correlated well with top yield in all treatments. The yield of the 10 parent varieties and polycrossed seed of their cycle 1 acid and cycle 1 limed selections were compared under two soil conditions (acid and limed). The results of this test indicate that some varieties were more responsive to acid soil selection than other. Overall, none of the 10 varieties showed any decreases in total top yield due to one cycle of selection in either the acid or limed soil conditions.     

Alfalfa,Medicago sativa L., in highly weathered,acid soils

Summary Rooting into acid subsoils would be a desirable trait for alfalfa which should result in better water extraction and yield. In this study, the rooting depth into acid subsoils and top yield of alfalfa plants selected for acid tolerance were investigated in a repacked profile with a limed, fertile topsoil, but unamended, acid subsoil. The effects of subsoil modification by CaCO₃ and CaSO₄·2H₂O addition on alfalfa rooting, top growth, and water extraction were also studied. Plants from acid selections rooted deeper into acid subsoil when compared to control plants (selected under limed conditions). However, the reverse response was found in the CaSO₄·2H₂O treated subsoil. There were no differences among selections for total top yield for any subsoil treatment. Water extraction from the lower subsoil and top growth yield (data pooled by selections) were improved mainly in the subsoil treatment containing the highest addition of CaCO₃.     

Alfalfa,Medicago sativa L., in highly weathered,acid soils

Summary The effect of lime and P application on yield (top and root weigh), nodulation, intervally collected acetylene reduction (N₂-fixation), and N and Al uptake of young alfalfa (46 days growth) were investigated in greenhouse pots containing acid Bladen or Bradson topsoils. The effect on seed germination and seedling persistence under these greenhouse conditions was also recorded.Alfalfa yield and acetylene reduction increased with lime and P additions in both soils, but, predominately, with P. There was no advantage of increasing these two parameters with liming past pH 6.0 provided P was adequate. Positive relationships (R²) existed between yield and acetylene reduction, and with both factors and root weight, nodule weight, and N uptake. Increased uptake of Al by alfalfa seedlings depressed yield, but data indicate P may block Al uptake at high soil pH. There were no treatment effects on seed germination, but P application increased plant persistence in the Bladen soil.     

Development of Stem Nodules in a Tropical Forage Legume, Aeschynomene afraspera

Rhizobial infection occurred on the stem of Aeschynomene afrasperaat the site of emergence of adventitious root primordia. Rhizobiainvaded cortical cells at the base of the root primordium. Thefirst infected cell enlarged and collapsed after rhizobia hadmultiplied in large numbers. At this time, a meristematic zonewas initiated some distance beneath the first infected cell.Rhizobial penetration into the deeper cortex was by progressivecollapse of infected cells towards the meristematic zone; rhizobiaentering the cortical cells by invagination of the host cellwall. At the entry point, rhizobia were embedded in digitatecell wall material. These infection structures were restricted,always originating from the cell wall of an adjacent infectedcell. Soon after infection, the cell collapsed progressivelyforming infection strand-like structures which developed upto the meristematic zone. When infection had reached the meristematiczone, invaded host cells ceased to collapse but divided repeatedlyto form the nodule. Key words: Aeschynomene afraspera, stem nodulation     

Forage and Turf Grass Biotechnology

Referee: Dr. Ian Ray, Plant Breeding and Genetics, Department of Agronomy & Horticulture, New Mexico State University, MSC 3Q, P.O. Box 30003, Las Cruces, NM 88003-8003 Forage and turf grasses are the backbone of sustainable agriculture and contribute extensively to the world economy. They play a major role in providing high quality and economical meat, milk, and fiber products and are important in soil conservation, environmental protection, and outdoor recreation. Conventional breeding contributed substantially to the genetic improvement of forage and turf grasses in the last century. The relatively new developments in genetic manipulation of these species open up opportunities for incorporating cellular and molecular techniques into grass improvement programs. For some commonly used forage and turf species, significant advances have been achieved in the following areas: (1) establishment of a tissue culture basis for the efficient regeneration of fertile and genetically stable plants, (2) generation of transgenic plants by biolistic transformation and direct gene transfer to protoplasts, (3) recovery of intergeneric somatic grass plants by protoplast fusion, (4) development of molecular markers for marker assisted selection, and (5) sequencing of expressed sequenced tags and the development of DNA array technologies for gene discovery. Although difficulties still exist in genetic manipulation of these recalcitrant monocot species, impressive progress has been made toward the generation of value-added novel grass germplasm incorporating traits such as improved forage quality. The joint efforts of molecular biologists and plant breeders make the available biotechnological methods a useful tool for accelerating forage and turf grass improvement.     

Effects of DCPA,EPTC, and Chlorpropham on Pathogenicity of Meloidogyne hapla to Alfalfa

Treatments wilh the herbicides chlorpropham (isopropyl m-chlorocarbinilate), DCPA (dimethyl tetrachloroterephthalate), and El''TC (S-ethyl dipropylthiocarbamate), alone or in combination with Meloidogyne hapla Chilwood, significantly reduced the growth of both nemalode-resistant ''Nev Syn XX'' atttt susceptible ''Ranger" alfalfa (Medicago saliva L.) seedlings. M. hapla infection of both alfalfas was reduced by all herbicides because of fewer available infective courts in the treated plants. EPTC, however, reduced resistance to M. hapla, as indicated by increased galling of ''Nev Syn XX'' plants.     

Enzymes of Ammonia Assimilation, Photosynthesis, and Respiration in Alfalfa Leaves of Different Ages

The activities of enzymes involved in ammonia metabolism ferredoxin-dependent glutamate synthase (Fd-GOGAT), glutamine synthetase (GS) and glutamate dehydrogenase (GDH), the rates of photosynthetic oxygen evolution, dark respiration, and the activity of RuBP carboxylase (RuBPC) were determined in alfalfa (Medicago sativa L.) leaves taken from the apex (apical leaves), from the second to the fourth internode (mature leaves) and from the bottom of the canopy (basal leaves). Photosynthetic rate and the activities of RuBPC, GS and Fd-GOGAT showed their maximum in the mature leaves. The respiration rate together with amino acid and ammonium contents decreased with leaf age, whereas the opposite was true for GDH activity. Basal leaves still maintained substantial levels of chlorophylls, GS and Fd-GOGAT activities and oxygen evolution rate, thus suggesting that photosynthesis has some role in the reassimilation of the nitrogen liberated during protein degradation. This revised version was published online in June 2006 with corrections to the Cover Date.