黑麦草生产能力及其抗热性评价

综述了黑麦草农艺性状及营养成分两方面的生产能力及差异,总结了黑麦草的育种方法,指出了高温胁迫对黑麦草的危害以及黑麦草抗热性的鉴定方法,提出了今后黑麦草抗热性育种的研究方向。     

Variation in inflorescence characters and inflorescence development in ecotypes and cultivars of Lolium perenne L.

A sufficient database of seed yield components is the prerequisite to predict which component contributes most to the seed yield complex and to dissect the biology of the complex quantitative trait seed yield. Phenotypic variation of eleven vegetative and reproductive traits was characterized for 2481 individuals from fifty Lolium perenne L. (perennial ryegrass) ecotypes and cultivars. Considerable levels of among‐ and within‐population variation were found across several inflorescence characters. Principal component and canonical variate analysis separated ecotypes from cultivars, and cultivars generally had later dates of ear emergence, better spring and summer growth, longer rachis length and more spikelets per spike than ecotypes. Strong positive relationships were seen between inflorescence characters using both correlation and regression analyses. The strong relationship between rachis length and other inflorescence characters suggested that rachis length could be used as a performance predictor for several other characters of the spike. This phenotypic study has helped to determine basic patterns of morphological diversity and correlations between characters. It is discussed in which way further developmental genetic studies can be directed.     

Effects of perennial ryegrass (Lolium perenne L.) cultivars on herbage production, nutritional quality and herbage intake of grazing dairy cows

Four perennial ryegrass (Lolium perenne L.) cultivars were compared for differences in herbage production, nutritive value and herbage intake of dry matter (DM) during the summers of 2002 and 2003. Two paddocks were sown with pure stands of four cultivars in a randomized block design with three replicates. Each plot was subdivided into fourteen subplots (22 m × 6 m) which were grazed by one cow during 24 h. Twelve lactating dairy cows were assigned to one cultivar for a period of 2 weeks in a 4 × 4 Latin square experimental design; the experiment lasted 8 weeks in each year. Sward structure (sward surface height, DM yield, green leaf mass, bulk density and tiller density) and morphological characteristics were measured. The ash, neutral‐detergent fibre, acid‐detergent lignin, crude protein and water‐soluble carbohydrate concentrations, and in vitro digestibility of the herbage were measured. The sward was also examined for infestation by crown rust (Puccinia coronata f. sp. lolii). Herbage intake of dairy cows was estimated using the n‐alkane technique. Cultivar differences for all sward structural characteristics were found except for bulk density and tiller density in 2003. Cultivars differed for proportions of pseudostem, stem (in 2003 only) and dead material. The chemical composition of the herbage was different among cultivars, with the water‐soluble carbohydrate concentration showing large variation (>0·35). Cultivars differed in susceptibility to crown rust. Herbage intake differed among cultivars in 2002 (>2 kg DM) but not in 2003. Herbage intake was positively associated with sward height, DM yield and green leaf mass. Canopy morphology did not affect herbage intake. Crown rust affected herbage intake negatively. It was concluded that options for breeders to select for higher intake were limited. High‐yielding cultivars and cultivars highly resistant to crown rust were positively related with a high herbage intake.     

Effects of an established sward of Lolium perenne L. on the growth and development of Rumex obtusifolius L. seedlings

Seedlings of Rumex obtusifolius L. were grown in gaps (11 cm diameter) in an established sward at Lolium perenne L., Root competition from the surrounding sward was controlled by PVC tubes and shoot competition was controlled by cutting the sward frequently. All combinations, with and without root competition and with and without shoot competition, were used.
Plants received either 40 or 80 kg N ha⁻¹ month⁻¹ and 0 or 300 kg K₂O ha⁻¹ and were harvested 39 d after emergence; a second harvest was made 12 d later, after shading to 20% of full sunlight.
The shoot dry weight per plant of R. obtusifolius was much more affected by root competition than by shoot competition, especially at low nitrogen applications. Potassium supply had no effect.
More dry matter was allocated to the leaf petioles under shaded conditions and the specific leaf area was greater. This morphological plasticity enabled R. obtusifolius to grow well under shading and to be affected only slightly by shoot competition from L. perenne.
The results suggest that competition for nitrogen was the main factor limiting the initial grown of R. obtusifolius in a ryegrass sward and that the morphological characteristics of R. obtusifolius make it less susceptible to competition for light in the early stages of its development.     

In vitro fermentation patterns and methane production as influenced by cultivar and season of harvest of Lolium perenne L.

In some European countries, the majority of annual enteric methane (CH₄) emissions by ruminants occur at pasture – a direct result of the predominance of grazing within ruminant production systems. However, there are only limited data available as to the effect of perennial ryegrass cultivar and season of harvest on CH₄ production. Using the in vitro gas production technique, the effect of perennial ryegrass cultivar on fermentation characteristics and CH₄ production was determined (Experiment 1) and the persistence of these traits throughout the growing season for two cultivars, identified from Experiment 1 as having either a high or low methanogenic potential, was examined (Experiment 2). In Experiment 1, organic matter (OM) digestibility and cumulative total gas production profiles were unaffected by cultivar but, with regard to the kinetics of CH₄ production, the asymptote value (A), cumulative CH₄ yield at 72 h, and the fractional rate (μ) of CH₄ production at both time of 0·5A(T)(μCH₄T) and at 48 h (μCH₄48h) were significantly (P < 0·05) different. The amount of digested OM, as a proportion of cumulative CH₄ production (DigOM/CH₄) at 24 and 72 h after commencement of inoculation, revealed that the amount of substrate required to produce 1 ml of CH₄ also differed significantly between cultivars (P < 0·01). In Experiment 2, regrowth number significantly modified the majority of measured samples (P < 0·01); cultivar effects were limited to the lag phase of the cumulative CH₄ production curve and DigOM/CH₄ at 8 h only (P < 0·05). These results suggest that differences exist between cultivars in how OM is partitioned following microbial fermentation and that these differences demonstrate persistency throughout the growing season. In the course of time it may be possible to exploit these differences through cultivar selection and plant breeding programmes, and thereby reduce enteric CH₄ emissions within pastoral production systems.     

Genotypic variation in patterns of root distribution, nitrate interception and response to moisture stress of a perennial ryegrass (Lolium perenne L.) mapping population

Genotypic variation in patterns of root distribution, nitrate interception and response to moisture stress were assessed in both parents and 198 progeny of a perennial ryegrass (Lolium perenne L.) full‐sibling mapping population. This was carried out in metre‐deep tubes of sand culture in a glasshouse experiment. The proportion of root dry matter (DM) weight in the top 10 cm of sand ranged from 0·33 to 0·75 and values of log₁₀(1 ? K), where K is the constant for an exponential model relating root DM weight and root depth, also showed wide variation among genotypes. The proportion of a pulse of ¹⁵N recovered in whole plants ranged from 0·124 to 0·431. There was a positive linear correlation between the proportion of ¹⁵N recovered and plant total DM weight, but no relationship between nitrate interception and patterns of distribution of DM weight of roots. Some genotypes responded to moisture stress by increasing root growth, and in others root growth was inhibited. It is concluded that this below‐ground variability in root variables may be an evolutionary adaptation by plant populations to survive heterogeneity in soil biotic and edaphic factors.     

The influence of ethofumesate on the growth and development, chlorophyll and nitrogen content of Lolium perenne L.

Pot experiments and a hand-weeded field trial were carried out to investigate the direct effect of ethofumesate on the growth and development of Lolium perenne cv. S24.
In the field trial, ethofumesate was applied in autumn as Nortron 20% ec formulation in a volume of 2001 ha^-1 at rates of 0, 1 or 2 kg a.i. ha^-1. Treatments had no direct effect on yield in the following summer. In both the field trial and pot experiments there was initial growth suppression in the form of a reduction in shoot dry weight, lamina dry weight, tiller number per plant and plant height. However, ethofumesate increased the chlorophyll and nitrogen contents of L. perenne laminae, but only when available soil nitrogen was not limited.
It is concluded that ethofumesate can increase the yield of L. perenne by suppressing weed competition, but there is no evidence of the herbicide directly increasing the growth or yield of cv. S24.     

Allelopathic potential of Lolium rigidum Gaud. on the early growth of three associated pasture species

In Mediterranean areas, the establishment of multi‐species pastures for extensive livestock use is an alternative to the growing of traditional cereal crops. Lolium rigidum Gaud. is one of the most valuable forage grasses adapted to semiarid environments but its performance in mixtures is not fully understood. Field observations suggest that the species exerts allelopathic effects, although there is no evidence in the literature to support this assumption. The objective of the study was to determine whether L. rigidum affects the germination and seedling growth of common forage species by allelopathic means. Two bioassays were conducted to test for the allelopathic potential of seeds and adult (shoot and root) tissues of L. rigidum on two grasses, Lolium multiflorum Lam. and Dactylis glomerata L., and a legume, Medicago sativa L. The three species showed different degrees of sensitivity to L. rigidum with L. multiflorum being particularly sensitive to allelopathy. Positive and negative effects of L. rigidum on seedling development were noted. Shoot extracts of L. rigidum displayed the most consistent negative effects by inhibiting elongation of the radicle of the three target species. The significance of the results is that in drought‐prone environments and where water resources are scarce poor root development decreases the ability of the plants to grow and survive.     

Longevity of seeds of Poa pratensis and Lolium perenne as affected by simulated soil tillage practices and its implications for contamination of herbage seed crops

In grass-seed production, the purity of the product is of major importance and high purity can only be obtained by preventing contamination with other species and cultivars during the whole crop rotation. In this context, seeds of previously grown grass species or varieties are particularly important. This study investigated the influence of different soil tillage practices on persistence of newly shed seeds of two grass species, Poa pratensis and Lolium perenne . Leaving the seeds at or close to the soil surface reduced seed survival of both species to low levels compared with strategies that involved a deep incorporation of the seeds shortly after seed-shedding. Survival rate of seeds of P. pratensis after 1 year was reduced to a low level when seeds were left at the soil surface for 2–3 months before incorporation. Seeds of L. perenne were less persistent and survival rate after 1 year was generally very low if the seeds were left near the soil surface for approximately 1 month before deeper incorporation. Use of the stale seedbed technique to reduce the seedbank of the two species in the autumn ahead of a spring-established grass-seed crop was also found to be effective in reducing the potential risk of contamination.     

Seed growth of three perennial ryegrass cultivars sown on two dates and treated with trinexapac ethyl straw shortener

First‐year crops of diploid perennial ryegrass (cvs. Meridian, Bronsyn and Grasslands Impact) were sown on 1 April and 14 May 2008. Applications of trinexapac ethyl (TE) plant growth regulator at 0, 200 and 400 g a.i. ha^?1 were used to shorten stems to examine the impact of seed growth. Seed filling followed a consistent sigmoidal growth pattern with a lag phase of 127°C days, and linear duration of 390°C days. Time to 95% of final seed weight was 517°C days. Seed yield increases from TE were from higher numbers of first‐grade seeds m^?2, achieved by a higher rate of seed filling during the linear phase of 0·115 mg per °C day per spike. For all cultivars, the maximum stem dry weight occurred at 310–400°C days post‐anthesis, which suggest the stem was a strong sink. As seeds developed, their demand for assimilate increased and they drew more from the stem. At harvest, stem weights from TE treatments were 25% heavier than at anthesis, while untreated ‘Bronsyn’ and ‘Grasslands Impact’ stems were similar to those at anthesis. Thus, stems treated with TE contributed assimilates to increase seed yield but were still a net sink with assimilates in the stem at harvest. Trinexapac ethyl rate induced an inverse relationship between seed yield and stem height. This showed that competition for assimilate between stems and growing seeds limited the seed yield. Management or genetic factors that reduce stem height are likely to increase seed yields of perennial ryegrass.     

The importance of water-soluble carbohydrate reserves on regrowth and root growth of Lolium perenne (L.)

This glasshouse study aimed to determine the relative importance of water-soluble carbohydrates (WSC) and current photosynthate on root and top regrowth of perennial ryegrass (Lolium perenne L.). Individual plants were arranged in one of two miniswards (Experiments 1 and 2) and underwent varying defoliation frequencies designed to obtain a gradient of WSC content at the final harvest of each treatment (H₁), when all treatments were defoliated. In Experiment 1, the plants were defoliated either three times at the one new leaf per tiller stage of regrowth (treatment 3 × 1), once at the two-leaf and again at the one-leaf stage (treatment 2, 1), once at the one-leaf and again at the two-leaf stage (treatment 1, 2) or once only at the three-leaf stage (treatment 1 × 3), up to H₁. Leaf and root growth and other parameters were assessed over 6 d after H₁ in sunlight, and over a 4-week period in darkness, and related to initial plant WSC content. In Experiment 2, plant defoliation treatments were: 3 × 1, 1, 2 or 1 × 3. Leaf regrowth was assessed for 36 d until the plants had three fully expanded new leaves per tiller. Leaf regrowth in both experiments was significantly related to stubble WSC (below 50 mm height). In Experiment 1, plants were almost fully reliant upon plant reserves for the first 3 d of regrowth, with reliance decreasing up to 6 d. When regrowth of plants was compared after 1 week in light or in darkness, it was estimated that one-third of leaf regrowth was due to plant WSC reserves and the remainder due to photosynthesis. However, the capacity to photosynthesize and to grow roots after H₁ was also significantly related to stubble WSC content. In Experiment 2, there was a significant difference (P<0·01) between defoliation treatments on leaf dry matter (DM) yield at 12 d (×1 leaf tiller^?1) of regrowth, and this was, as in Experiment 1, significantly positively related to WSC content in the stubble. However, after 36 d of regrowth, DM yield of plants defoliated at 2 or 3 leaves tiller^?1 up to H₁ were similar, and both were significantly higher (P<0·01) than regrowth of plants defoliated at the one-leaf stage. After defoliation, the period of reliance on WSC reserves may be substantially increased in situations of shading (canopy competition or cloud cover) or if the new regrowth shoot is removed by regrazing.     

A simultaneous effect of selfing and Epichloë endophyte on forage,seed yield and turf characteristics of perennial ryegrass (Lolium perenne L.)

Ryegrass (Lolium perenne L.) is a putative turf and forage plant characterized as mainly outcrossing in which the extent of self‐fertilization and its consequences has not been investigated. In this study, selfed and half‐sib family seeds were obtained from ten clonally propagated ryegrass plants among which two were endophyte‐free (EF) and eight were endophyte‐infected (EI). Then, 20 seed populations plus two commercial varieties of Speedy and Vigor were sown and evaluated in a biennial experiment for their turf and forage characteristics. Selfing caused significant inbreeding depression for plant fresh and dry weight and leaf length and width in the first year for both EI and EF genotypes. In the second year, only leaf length remained depressed among these characters. Also, for the most growth, turf and reproductive traits, EI populations showed less depression. The presence of endophyte in self‐pollinated populations made an increasing effect for the number of seed per spike and days to heading, although seed weight was reduced. Some of the populations derived from self‐pollination and infected with fungal endophyte including S9 and S10 were even superior to the two commercial varieties in terms of both seed production and turf characteristics. However, for seed‐related characteristics including number of spikes per plant, seed weight and seed yield, EF populations including Speedy and Vigor were more reproductive than EI populations. It is concluded that selfing may increase the discrimination between EI and EF ryegrass plants because endophyte infection may mitigate the negative consequences of inbreeding depression in prone populations.     

Effect of Lolium perenne sward density on productivity under simulated and actual cattle grazing

The objective of this study was to quantify the effect of perennial ryegrass (Lolium perenne L.; PRG) sward density on seasonal and total DM yield under simulated grazing and animal grazing by cattle, and to assess the effectiveness of visually estimated ground scores (GSs) for predicting sward PRG density. The study incorporated five different seeding rates of PRG, each replicated three times, to simulate swards ranging in PRG density typical of different ages and conditions. There was no significant difference between defoliation managements for total DM yield, but sward PRG density had a significant effect on both the seasonal and total DM herbage yield under both systems. Under simulated grazing, total DM yield ranged from 10·7 to 12·0 t DM ha^?1 with increasing sward PRG density at a GS range of 1·70–4·28 (mean of 2 years’ data, P < 0·01). Under animal grazing, the yield range was from 10·3 to 12·2 t DM ha^?1 for a GS range of 1·50–3·39 (mean of 2 years’ data, P < 0·01). The largest differences in DM yield occurred during the spring period. The relationship between sward DM yield and GS was significant (P < 0·001) for both simulated and animal‐grazed swards. Each unit increase in midseason GS (June) related to an average yield increase of 350 kg DM ha^?1 under simulated grazing and a 721 kg DM ha^?1 increase under cattle grazing. Every unit increase in the GS at the end of the grazing season (December) was associated with a 460 or 1194 kg DM ha^?1 increase under simulated and animal grazing, respectively. These results show that visual estimates of density were an effective tool in describing PRG density and that this could be related to DM yield potential. Further investigations may provide a threshold value below which the renewal of swards could be advised based on a visual GS of PRG.     

不同时期干旱胁迫对水稻产量和生长特性的影响

为明确水稻生长过程中的水分敏感时期,探索水稻抵御干旱的栽培措施,以常规粳稻楚粳29号和云粳39号为材料,通过盆栽试验准确控制土壤水分(水势),研究不同时期干旱胁迫对水稻产量和生长特性的影响。结果表明,楚粳29号干旱胁迫处理较对照减产10.63%~47.60%,云粳39号干旱胁迫处理较对照减产6.19%~47.27%,减产程度依次为穗分化前期干旱胁迫(T2)﹥有效分蘖期干旱胁迫(T1)﹥穗分化后期干旱胁迫(T3)﹥孕穗期干旱胁迫(T4)。与对照相比,2个品种有效分蘖期干旱胁迫降低了有效穗数,穗分化前期干旱胁迫使每穗粒数明显减少,穗分化后期干旱胁迫使每穗实粒数减少和结实率明显降低,孕穗期干旱胁迫对结实率或千粒重有影响。     

Effects of vernalization on the subsequent rates of leaf extension and photosynthesis of perennial ryegrass (Lolium perenne L.)

Temperature and daylength treatments have been used to investigate the apparent link between the potential for rapid leaf extension in spring and floral initiation and development in Lolium perenne (cv. Vigor). After growth at 5°C for 10 weeks (vernalization treatment) the leaves which developed at 15°C expanded significantly faster than non-vernalized controls under both long and short days. Under long days floral development was initiated in vernalized plants but under short days it was not. Specific leaf area was higher in vernalized than non-vernalized plants under long days.
The photosynthetic capacity of leaves which developed on plants which had been previously vernalized and then grown at 15°C under long days was higher than non-vernalized controls when expressed on a leaf area and dry weight basis, but not on the basis of chlorophyll content. Vernalization followed by short days resulted in a smaller and non-significant increase in the photosynthetic capacity of leaves.
Application of gibberellic acid (GA) as a spray to non-vernalized plants did not affect floral development but did increase the rate of leaf extension. The application of GA did not affect specific leaf area or photosynthetic capacity expressed on an area basis.     

种衣剂对纤维亚麻生长的效应

目前麻田保苗不足已成为限制亚麻生产的瓶颈问题,究其原因除因播种质量外,苗期的立枯病、炭疽病和萎蔫病是造成缺苗的主要因素。针对此问题,开展了亚麻种衣剂的试验研究和筛选工作,试验利用东北农业大学提供的种衣剂1、2、3号与福美霜进行比较,通过苗期调查和收获后测定原茎产量和品质,初步证明所用的亚麻种衣剂对亚麻种苗安全,具有提高苗期抗病力,增加收获株数的效应,并能够增加原茎产量和纤维产量,同时对改善亚麻品质有一定的作用。     

The effect of light intensity after anthesis on dry matter distribution and seed yield of Lolium perenne L.

The effect of light intensity after onset of anthesis on dry matter distribution, water soluble carbohydrate (WSC) concentration and seed filling in Lolium perenne was investigated in a pot experiment. Spaced plants of five clones were brought to flowering and exposed to four light intensities (24%, 57%, 100%, 115% of natural light) from 7 days after onset of anthesis onwards. The two oldest flowering tillers (i.e. the main and the first tiller) were separated from the rest of the plant and dissected after a seed-filling period of 450°Cd (temperature sum counting from 7 days after onset of anthesis). Their stem dry weight and WSC concentration were reduced at the lowest light intensity. WSC amount was more reduced in the first, younger, tiller. Seed yield per ear of the main tiller was reduced by 14% because seed set and average seed weight were lower at the 24% light intensity. Seed yield and seed number per ear of the first tiller were lowered by 21% and 17%, respectively, at the 24% light intensity, but average seed weight was not. The relative contribution of the seeds to total tiller weight was about 20% and was similar for both tillers and all light intensities. WSC concentration and WSC amount in the stem + rachis were reduced only at 24% light in the main tiller and at 24% and 57% light in the first tiller. It is inferred that seed yield was not limited by assimilate availability, but by the ability of the seeds to utilize fully the abundantly available reserves in the stem. The tiller can support seed yield under a wide range of tight intensities.     

Hide and seek – Infection rates and alkaloid concentrations of Epichloë festucae var. lolii in Lolium perenne along a land‐use gradient in Germany

The common forage grass Lolium perenne has evolved with the systemic fungal endophyte Epichloë festucae var. lolii. The endophyte provides herbivore resistance to the grass due to defensive alkaloids, some of which are toxic to grazing livestock. In this field study, we determine whether distribution of the endophyte‐grass association changes along a land‐use intensity gradient on 87 managed grasslands in three German regions. Endophyte infections were detected in 66% of the studied sites and infection rates within infected sites ranged from 1% to 95%. Alkaloid concentrations of lolitrem B (vertebrate toxin) exceeded the toxicity thresholds in 50 (14%) of 351 infected plants and of peramine (invertebrate deterrent/toxin) in 12 (3%) of 351 plants. Infection rates and alkaloid concentrations were not significantly affected by land‐use intensity and region, but alkaloid concentrations were higher in summer compared to spring. We conclude that risks for livestock intoxication are currently low, as (i) average alkaloid concentrations per grassland were always below toxicity thresholds and as (ii) none of the grasslands was dominated by L. perenne. We suggest avoidance of grass monocultures in Europe to keep intoxication risks for livestock low; we also recommend regular examination of seeds and grasslands, as seed producers might accidentally distribute infected seeds, and as climate warming might further enhance the distribution of Epichloë endophytes in European grasslands.     

香根草、黑麦草和高丹草光合生理生态日变化的比较研究

采用LI-6400便携式光合仪测定了香根草、黑麦草和高丹草的叶片光合日变化以及某些生态指标。结果表明：3种植物的净光合速率Pn日变化呈双峰曲线,但峰值出现的时间不同,并且有野午休冶现象。香根草、黑麦草和高丹草的日平均Pn值分别是11.513、16.737、20.565μmolCO2·m-2·s-1曰香根草和黑麦草的蒸腾速率Tr呈双峰曲线,高丹草呈单峰值曲线;3种植物的Pn、Tr、Vpdl及高丹草的气体导度Gs与空气相对湿度RH呈显著负相关(-0.826＜r＜-0.994)、与Tl和PAR则呈显著正相关(0.714＜r＜0.995)。     

Effects of shoot,root and stolon temperature on the development of the potato (Solanum tuberosum L.) plant. I. Development of the haulm

Summary Cultivars Bintje and Désirée were grown in a set-up that allowed temperatures of the shoot, root, and stolon environments to be separately varied. Shoot and root temperatures were either low, 18°C, or high, 28°C. Stolon temperatures were either ‘normal’, i.e. allowed to equilibrate at an ambient that depended on the temperatures of the shoot and root compartments, or ‘in-creased’ by fixed supplementary heating units in the stolon chambers. Haulm longevity was increased by the combination high shoot temperature and low root temperature, but greatly decreased by high shoot temperature combined with high root temperature. The increased stolon temperature also advanced senescence. The number of branches per stem (and thereby the number of leaves) was increased by an increase in stolon temperature, but the interaction with air temperature was significant. A high root temperature reduced the number of leaves significantly. The effects on stem yield were complex; several interactions proved significant. The total drymatter yield was affected by all single factors except shoot temperature.