Compounds from the subterranean part of Johnsongrass and their allelopathic potential

The allelopathic effects of the exotic invasive weed, Johnsongrass, on Lactuca sativa, a native plant in China, were evaluated and the phytotoxins were investigated under laboratory conditions. The crude extracts (chloroform and ethyl acetate fractions) that were obtained from the ethanol extract of the subterranean parts of Johnsongrass inhibited the germination speed and growth of the roots and shoots of the test plant. The four compounds, ethyl p‐hydroxybenzoate, diosmetin, apigenin, and luteolin, were isolated from the extract of the subterranean parts of Johnsongrass first, along with three other compounds (reported previously), p‐hydroxybenzaldehyde, p‐hydroxybenzoic acid, and dhurrin, and they all were evaluated on L. sativa. At the concentration of <0.5 mmol L^?1, ethyl p‐hydroxybenzoate, dhurrin, and the mixture of the compounds delayed the germination speed of the seeds of L. sativa at 24 h of incubation, while apigenin delayed the germination speed of the seeds of L. sativa at 72 h of incubation. Ethyl p‐hydroxybenzoate demonstrated the strongest delaying effect among the phenols and a similar effect was found with apigenin among the flavonoids, wheras ethyl p‐hydroxybenzoate induced a drastic inhibition of the germination at 2 mmol L^?1. In contrast, p‐hydroxybenzaldehyde and luteolin had no effect on the germination at any concentration at any stage. All the substances inhibited the shoot and root growth of L. sativa at 3 mmol L^?1. Increasing the concentration increased the inhibition of the growth of L. sativa. The inhibitory activity of ethyl p‐hydroxybenzoate and p‐hydroxybenzaldehyde was greater than that of the other compounds. This result suggested that the isolated phytotoxins might contribute to the successful invasion by Johnsongrass.     

Spread dynamics and agricultural impact of Sorghum halepense,an emerging invasive species in Central Europe

Sorghum halepense is a serious weed and reservoir for pathogens of crops worldwide that has recently spread in Austria. On the basis of an exhaustive distribution data set (302 records), we analysed the spread dynamics and agricultural impact. The first record of S. halepense was recorded in 1871, but the species remained rare until 1970. After a moderate increase in records until 1990, it has recently expanded strongly (>70% of all records have been collected since 1990), in particular, in the lowlands of eastern and southern Austria. Invasion into fields was first documented in the 1970s, but again, since 1990, S. halepense has spread strongly and fields now account for 32% of all records. In southern Austria, we found that S. halepense invasion already puts approximately 41% of grain maize fields and 40% of oil‐pumpkin fields at risk of yield losses. In cooler regions within Austria, S. halepense is still rarely recorded in fields. Sorghum halepense serves as a reservoir for the maize dwarf mosaic virus, as it was found in 38% of 21 samples collected in southern Austria. Invasion of S. halepense in fields was most likely assisted by frequent secondary dispersal and intensive maize and oil‐pumpkin cultivation. Given the fast and on‐going spread in fields, which is likely to continue under climate warming, our results provide evidence that S. halepense will cause serious impacts for agriculture in Austria and probably in other countries of Central Europe.     

四倍体高粱与约翰逊草杂交种饲用品质分析

利用四倍体高粱品系"四沈甜"、不育系"四6A"和约翰逊草,配置"四沈甜"×约翰逊草、"四6A"×约翰逊草和"四6A"×"四沈甜"杂交种,分析了杂交种及杂种分离世代的不同生长阶段的杂种优势及饲草品质。结果表明,在孕穗期各供试材料粗蛋白质含量最高,杂交种蛋白质含量达到10%～15%,随着发育期的推进,含量有所下降。抽穗期,粗脂肪含量达到6.1%～7.9%。各材料的粗纤维含量都在30%以上,不同生长阶段差异不显著。单位能量值在抽穗期最高,达到18MJ/kg左右。综合各营养成分含量和单位能量分析,初步认为四倍体高粱与约翰逊草杂交种可以作为饲草应用,抽穗期为刈割和利用的最佳时期。     

Glyphosate resistance in perennial Sorghum halepense (Johnsongrass), endowed by reduced glyphosate translocation and leaf uptake

BACKGROUND: In a large cropping area of northern Argentina, Sorghum halepense (Johnsongrass) has evolved towards glyphosate resistance. This study aimed to determine the molecular and biochemical basis conferring glyphosate resistance in this species. Experiments were conducted to assess target EPSPS gene sequences and ¹⁴C‐glyphosate leaf absorption and translocation to meristematic tissues. RESULTS: Individuals of all resistant (R) accessions exhibited significantly less glyphosate translocation to root (11% versus 29%) and stem (9% versus 26%) meristems when compared with susceptible (S) plants. A notably higher proportion of the applied glyphosate remained in the treated leaves of R plants (63%) than in the treated leaves of S plants (27%). In addition, individuals of S. halepense accession R₂ consistently showed lower glyphosate absorption rates in both adaxial (10–20%) and abaxial (20–25%) leaf surfaces compared with S plants. No glyphosate resistance endowing mutations in the EPSPS gene at Pro‐101–106 residues were found in any of the evaluated R accessions. CONCLUSION: The results of the present investigation indicate that reduced glyphosate translocation to meristems is the primary mechanism endowing glyphosate resistance in S. halepense from cropping fields in Argentina. To a lesser extent, reduced glyphosate leaf uptake has also been shown to be involved in glyphosate‐resistant S. halepense . Copyright © 2011 Society of Chemical Industry     

同源四倍体高粱与约翰逊草种间杂交及其细胞遗传学研究

采用人工去雄及塑料袋简便杀雄法获得了６个同源四倍体高粱品系与约翰逊草的种间杂种。研究表明,在４０个染色体水平上两种间杂交不存在遗传障碍;杂种Ｆ１在生长势和生物产量上表现了巨大优势,在主要形态上介于双亲之间;杂种Ｆ１ＰＭＣ减数分裂中期Ⅰ染色体构型为：０１７Ⅰ＋１４１１Ⅱ＋００２８Ⅲ＋２８７Ⅳ＋０００４Ⅴ＋０００７Ⅵ＋００００７Ⅷ;约翰逊草是一节段同源异源四倍体,将约翰逊草染色体组模式表示为ＡＡＡ′Ａ′,能解释减数分裂过程中更多的染色体行为。同源四倍体高粱与约翰逊草杂交成功为约翰逊草优良基因向栽培高粱转移提供了可能。     

同源四倍体高粱与约翰逊草远缘杂种的花药培养初报

以同源四倍体高粱品系四甜－１、保持系四６２２Ｂ、约翰逊草以及同源四倍体不育系四６２２Ａ×约翰逊草和四甜－１×约翰逊草的杂种后代为材料，分别在１／２ＭＳ、Ｎ６和Ｗ１４培养基上进行花药培养。四６２２Ａ×约翰逊草和四甜－１×约翰逊草的杂种后代在Ｗ１４培养基上产生了愈伤组织，同源四倍体亲本６２２Ｂ在Ｎ６培养基上产生了愈伤组织。对一定的培养基，愈伤组织的诱导主要取决于基因型。另外，对Ｗ１４培养基设置了加活性碳与不加活性碳两组试验，结果表明，活性碳可有效控制花药中产生的有害色素的影响。     

The Influence of Johnsongrass Infestation and Nitrogen Rates on Grain Sorghum

Gram sorghum [ Sorghum bicolor (L.) Moench] is grown on marginal land and johnsongrass [Sorghum haiepense (L.) Pers] is the most common and hard to control weed in this crop. The agronomic performance of gram sorghum at different nitrogen (N) and johnsongrass infestation levels in the field has not been adequately investigated. Therefore, research was conducted on a Decatur silty clay loam soil (Rhodic Paleudult) to determine the influence of N rates (0, 40, 80 and 120 kg ha^-1) and johnsongrass infestation levels (0, 2, 4, 6 and 8 plants per 5 m crop row) on the growth and yield of grain sorghum (cv. GK522G) and johnsongrass. Increase in N rates increased seed weight, seed yield and percent protein in grain sorghum as well as dry matter and percent protein of johnsongrass. The increase in johnsongrass infestation (from 0 to 8 plants per 5 m crop row) significantly decreased the performance of grain sorghum and johnsongrass at all the N rates. The results suggest that 40 kg N ha^-1 with up to 2 johnsongrass plants per 5 m crop row or 80 kg N ha^-1 with up to 4 johnsongrass plants per 5 m crop row produced grain sorghum yields equivalent to absence of johnsongrass in the crop.     

Response of Sorghum halepense demographic processes to plant density and rimsulfuron dose in maize

In spatially heterogeneous weed infestations, variable dose technologies could be used to minimise herbicide use; high doses could be applied to reduce high‐density patches and low doses to maintain weed populations in low‐density portions of a field. To assess the potential short‐ and long‐term effects of variable herbicide dose and site‐specific management, the major weed demographic processes were described and parameterised in this study. Various doses of rimsulfuron (from 0 to 12.5 g a.i. ha^?1) were applied to different densities of Sorghum halepense (0–100 plants m^?2). Contrary to similar studies with other weed species, higher herbicide efficacy was not observed at low densities, suggesting that the same rimsulfuron dose should be applied regardless of the S. halepense density. The highest percentage of control was obtained with the full rimsulfuron dose. However, it did not guarantee a decrease of the infestation in the following season in the field areas where the initial S. halepense density was lower than 60 plants m^?2. Reduced doses of rimsulfuron to control S. halepense cannot be recommended based on our results.     

假高梁(Sorghum halepense)颖片生物学特性的研究

从两个方面对假高粱颖片存在的作用进行了研究。一是将3年采收的子实分为带有颖片的子实、剥去颖片的子实和剥下的颖片与子实混放在一起3组进行萌发试验,并以GA3处理。结果表明,颖片的存在有利于子实的体眠,对于实的萌发具有机械阻力和化学抑制2种作用,作用的强度随子实贮藏时间的长短发生变化。二是对颖片进行电镜扫描观察,发现假高粱颖片表面分布有一种特殊结构物,由头部和柄部构成,柄部嵌在颖片的孔洞中,头部顶面观呈哑铃形或8字型。子实休眠期,由于特殊结构物的存在,隔绝了子实与外界的气体交换。干燥贮存1年后,由于失水,哑铃形头部的边缘向上翘起,柄部收缩,气体进入颖片与子实之间,休眠作用逐渐解除。颖片不仅具有保护子实的作用,还具有适应子实萌发的形态结构。颖片这种结构与功能的关系具有重要的生物学意义。     

同源四倍体高粱与约翰逊草种间杂种细胞学特性的相关研究

以6个同源四倍体高梁品系及其与约翰逊草的种间杂种为材料，对两种间细胞学特性的相关性进行了分析，杂种F1后期I，后期II减数分裂的不规则性受到亲本高粱细胞学不规则性的影响，杂种F1减数分裂规则性与约翰逊草相 。