Generation of transgenic Lolium temulentum plants by Agrobacterium tumefaciens-mediated transformation

Lolium temulentum L. (Darnel ryegrass) has been proposed to be used as a model species for functional genomics studies in forage and turf grasses, because it is a self-fertile, diploid species with a short life cycle and is closely related to other grasses. Embryogenic calluses were induced from mature embryos of a double haploid line developed through anther culture. The calluses were broken up into small pieces and used for Agrobacterium tumefaciens-mediated transformation. A. tumefaciens strain EHA105 harboring pCAMBIA1301 and pCAMBIA1305.2 vectors were used to infect embryogenic callus pieces. Hygromycin was used as a selection agent in stable transformation experiments. Hygromycin resistant calluses were obtained after 4–6 weeks of selection and transgenic plants were produced in 10–13 weeks after Agrobacterium-mediated transformation. Fertile plants were readily obtained after transferring the transgenics to the greenhouse. Transgenic nature of the regenerated plants was demonstrated by Polymerase chain reaction (PCR), Southern hybridization analysis, and GUS staining. Progeny analysis showed Mendelian inheritance of the transgenes. The transformation system provides a valuable tool for functionality tests of candidate genes in forage and turf grasses.     

我国红壤区土壤钼、硼、硒元素特征及其对牧草生长影响研究进展

实行肥料科学配施与红壤培肥管理是山区草业发展的重要技术环节．我国南方红壤区土壤普遍存在着硼、钼、硒元素缺乏现象,合理施用钼、硼、硒微量元素肥料对豆科与禾本科牧草的植株生长以及提高产草量和种子产量有明显的促进作用．文中概述了我国红壤区土壤中钼、硼、硒元素的存在形态、化学特征、内在变化、可给性及含量状况,探讨了施用3种微量元素肥料对牧草生长过程有效养分吸收与累积的影响及其相应生理功能,综述了牧草植物缺乏钼、硼、硒元素的特征症状、诊断方法及其矫治措施．     

不同刈割强度对牧草地上部和地下部生长性状的影响

研究了不同刈割强度对牧草地上部和地下部生长状况的影响.结果表明,适度刈割可提高牧草地上部植株的再生能力.刈割后牧草再生叶片的叶绿素总量变化不大,而叶绿素a/b比值有所增加,轻刈割和重刈割的牧草叶绿素a/b比值分别增至1.59∶1和1.52∶1、不刈割为1.22∶1,有利于增强植物的光合作用.与不刈割处理相比,在刈割初期,重刈割处理下柱花草根系总长、总表面积和平均直径分别下降了54.9%、66.5%和27.2%,根系活力显著下降;但在中后期,刈割处理的牧草地下部根系形态指标活力可恢复到更高的水平.从一年两次收获的累计生物量来看,以轻刈割最高,为3 179.8 g·m^-2,重刈割次之,为3 006.1 g·m^-2,不刈割最低,为2 936.98 g·m^-2,说明一年两次刈割可以提高牧草产量.     

接种植物乳杆菌(Lactobacillus plantarum)对小规模饲料稻青贮品质的影响

【目的】研究接种植物乳杆菌对小规模饲料稻品质的影响。【方法】以自然发酵的样品为对照,接种不同来源植物乳酸菌发酵饲料稻,发酵30 d后对饲料稻的感官进行评价;通过选择性平板对饲料稻青贮中的不同微生物进行计数;并采用V-Score评价法对发酵品质进行评定。【结果】相对自然发酵的样品而言,接种植物乳杆菌的青贮样品感官评分等级达到优良;乳酸菌为优势菌株,引起腐败变质的好氧菌、霉菌、大肠杆菌等受到抑制;接种发酵的样品中乳酸含量明显增加,氨态氮的产生量为对照的1/2左右,V-Score评分为满分。【结论】供试的植物乳杆菌,尤其是从青饲料和青贮材料中分离的菌株能有效改善饲料稻青贮的品质,可考虑用作青贮饲料稻发酵剂。     

割草对牧草分蘖萌发的影响

对皇草（Ｐｎｎｉｓｅｔｕｍ ｐｕｒｐｕｒｅｕｍ ×Ｐ ｇｌａｕｃｕｍ）杂交狼尾草（ｐｅｎｎｉｓｅｔｕｍ ｇｌａｕｃｕｍ×Ｐ ｐｕｒｐｕｒｅｕｍ）、矮象草（Ｐｅｎｎｉｓｅｔｕｍ ｐｕｒｐｕｒｅｕｍ）和墨西哥玉米（Ｚｅａ ｍｎｙｓ ｓｕｂｓｐ．ｍｅｘｉｃａｎａ）等４种牧草在生长期进行了４次割草试验,探讨了不同割草次数对牧草单兜株数的影响。结果表明：１）在进行１次割草的情况下,４种牧草的营养生长时间分别为５３、９６、１５３和２０８ ｄ时,单兜株数分别为２０．２,８．５,１７．２,１１．７株,牧草的单兜株数随营养生长时间的增加而呈大小相间排列;２）在可靠性为９５％以上时,第二次割草时的单兜株数与第一次割草时有明显的差异,而多次割草后的差异性逐渐减小;３）营养生长的时间长短和前一次的单兜株数对牧草后一次的萌发和分蘖有显著的影响,在一定程度上决定了后一次的单兜株数;４）杂交狼尾草在多次连续割草后,单位面积上的株数变得不均匀,而皇草、矮象草和墨西哥玉米则逐渐均匀化,这个作用使得杂交狼尾草在退化坡地水土保持上的价值减少．     

Quantifying the damage of red deer (Cervus elaphus) grazing on grassland production in southeastern Slovenia

The influence of red deer (Cervus elaphus) grazing on grassland production for forage conservation at the forest border during the vegetation period was studied on three locations (Mala gora, Cvišlerji, and Mačkovec) in the Kočevje region (SE Slovenia). The experiment lasted from the 25th of March until the 8th of October 2002. Portable cages were used to exclude red deer from grazing the herbage. At four sampling dates in the season, herbage air dry matter (DM) yield was measured at three different observations (cage-protected plot, cage-protected plot only two to three weeks before sampling date, otherwise freely grazed (removed), and unprotected plot). The results from the experiment showed that red deer grazed on grassland through the entire season and that the regeneration capability of sward was the highest in summer, middle in spring and smallest in autumn. On unprotected plots, an average reduction of 50% of herbage DM yield was found with the most damaged sites also up to 80% reduction.     

N2 fixation and nitrogen allocation to above and below ground plant parts in red clover-grasslands

Leys, used for grazing or production of forage to be conserved as silage or hay, are very important crops in northern areas. In order to measure the N₂ fixation in leys of varying ages and during different parts of the season, detailed measurements were taken of yield, N₂ fixation and the amounts of N remaining in the field after harvesting red clover (Trifolium pratense L.)-grass leys at a site in northern Sweden, where they are generally harvested twice per growing season. Entire plants, including stubble and roots, were sampled at the time of first and second harvest and, in addition, at the end of the growing season in three neighbouring fields, carrying a first, a second and a third year ley, respectively. N₂ fixation was measured by both ¹⁵N isotope dilution (ID) and ¹⁵N natural abundance (NA) methods. The proportion of clover dry matter (DM) in the stands increased from the first to the second harvest, but the grasses dominated throughout the entire season, especially below ground. The N concentrations, in both herbage and whole plants, were about twice as high in the clover as in the grasses. Seasonal variations in N concentrations were minor, and total N contents followed the same trends as DM. The clover acquired nearly all of its N from N₂ fixation: the proportion of N in clover herbage derived from N₂ fixation was often >0.8 throughout the season. The variations in the amounts of N₂ fixed during the course of the season corresponded well to the seasonal changes in clover biomass. Amounts of fixed N₂ allocated to clover herbage during the whole season were in the range 4 to 6 g N m⁻² in this unusually rainy year. Calculations of daily N allocation rates to herbage showed that N uptake rates were similar, and high, in grasses during May–June and July–August, while N₂ fixation rates in clover were about 10-fold as high in July–August as in May–June, reflecting the need for N in clover growth. The proportion of N remaining in clover stubble and roots after the first and second harvests was about 60 and 25%, respectively, while about 60% of the N in grasses remained in stubble and roots after both harvests. The considerable amounts of biomass and N that were left in field after harvesting red clover-grass leys are important for re-growth of the plants and provide substantial N fertilization for the next crop in the crop rotation.     

Diet selection of sheep shifted from quality to quantity characteristics of forages as sward availability decreased

Understanding the dynamic inter-relationship between grazing animals and the pasture sward is critical for sustainable grazing management. A field study was conducted to investigate the relationships between the quantity and quality characteristics of forages and diet selection of 30-kg Mongolian ewes in different seasons in Bromus inermis improved meadow steppe. Using a residual herbage mass method (1 000 kg/ha in spring, 800 kg/ha in summer and 600 kg/ha in autumn) to adjust stocking rate, three seasonal rest grazing strategies (spring rest, summer rest and autumn rest) combined with continuous grazing were studied. In each season, diet selection of sheep, quantified by diet composition and selectivity index, was estimated using a plant wax marker technique. Quantity (dry weight proportion, coverage, frequency, density and height) and quality (CP, NDF, ADF and DM digestibility) characteristics of forages consumed by sheep were determined simultaneously. Our results showed that in spring with the highest sward availability (herbage mass), diet selection of sheep could be predicted by the positive linear relationship between quality characteristics of forages and their selectivity index. In summer, the diet selection could be predicted by both positive linear relationship between quality characteristics and selectivity index, and the relationship between quantity characteristics and diet composition. While in autumn with the lowest sward availability, it could be predicted by the positive linear relationship between quantity characteristics and diet composition. During the whole grazing season, the diet composition of B. inermis (40.4%) and Leymus chinensis (35.1%) were larger than that of Potentilla bifurca (9.5%) and Carex (15.1%) and the selectivity index of P. bifurca was the highest (0.62), followed by Carex (0.17) and B. inermis (0.05), and L. chinensis (?0.29) was the lowest. The two parameters of diet selection above were positively related to their quantity and quality characteristics, respectively. These results suggested that the influence of quality characteristics on diet selection of sheep decreased gradually as a result of the decline in sward availability, while the influence of quantity characteristics increased. This study provides a comprehensive understanding of diet selection of sheep examining the trade-offs between quantity and quality characteristics of forages. The knowledge of diet selection of sheep and the corresponding prediction regressions acquired in this study could give the basis for designing appropriate grazing management strategies.     

Patterns of prey utilization in a web of orb-weaving spiderAraneus pinguis (Karsch)

The pattern of prey utilization of the orb-weaving spider Araneus pinguis was studies by comparing between arthropods restrained in the empty webs (spiders were removed) and those unattacked in the intact webs (spiders were not removed). The number of arthropods was larger in the empty webs than in the intact webs. In the empty webs, web area, mesh width, number of radii, and signal thread length were presumed to affect the number of arthropods left in a single web. As for the intact webs, web area, mesh width, and web-exposure time were important factors. In the empty webs, the density of arthropods decreased away from the hub. On the other hand, the density of unattacked arthropods in the intact webs was the same throughout the web. Arthropods in the empty webs were larger than those in the intact webs. The upper limit in size of unattacked arthropods increased along with the distance from the hub in the intact webs, but not in the empty webs. These results indicate increase in the minimum size of eaten arthropods increased in the former. This positive sizedistance relation may have resulted from the adaptive switching of spiders’ alternative foraging methods (i.e., the rapid attack at encounter and the later eating during web deconstruction) on the basis of the prey profitability.