Differential susceptibility of barnyard grass (Echinochloa crus-galli var. crus-galli) ecotypes to Exserohilum longirostratum

Ten barnyard grass ( Echinochloa crus-galli var. crus-galli ) ecotypes collected from several locations in Malaysian and Indonesian granaries were tested for variation in their susceptibility to the leaf blight pathogen ( Exserohilum longirostratum ). Four phenological growth stages of the ecotypes were sprayed with E. longirostratum at the rate of 1 × 10⁷ conidia mL⁻¹ under glasshouse conditions. The results of the study showed that plants inoculated with 1 × 10⁷ conidia mL⁻¹ and exposed for 24 h dew periods were severely infected and the percentage dry weight reduction of all ecotypes significantly increased. The 1–2 and 2–3-leaf stage plants were completely killed within 6 days after inoculation. However, susceptibility reactions among the ecotypes were observed at the 4–5-leaf stage, while the 6–7-leaf stage was resistant. The ecotypes, K-02, PK-04, KN-02, CJ-01, and L-01, were the most susceptible ecotypes as indicated by a higher area under disease progress curve value. The apparent disease progress rates for these ecotypes were significantly faster compared to the other ecotypes. The dry weight reduction among the four growth stages was variable. These findings show that the 1–2 and 2–3-leaf stages are the most susceptible, while the 6–7-leaf stage was resistant. This study has confirmed that a variable response to the fungal pathogen occurred within an intraspecific barnyard grass collection.     

Utilization of Parthenium hysterophorus for the remediation of lead‐contaminated soil

A greenhouse experiment was conducted to study the role of plant growth regulators, a chelating agent, and plant growth‐promoting bacteria in lead (Pb) phytoextraction and their subsequent effect on the weed plant, Parthenium hysterophorus. Gibberellic acid (GA₃) and indole‐3‐acetic acid (IAA) were used as the foliar spray. Ethylenediamine tetra acetic acid (EDTA) was applied in split doses. Bacillus and Rhizobium strains were used as a single culture and as co‐cultures. The accumulation of Pb in different parts of the plant was analyzed by using an atomic absorption spectrophotometer. The amount of lead translocation and accumulation in the stems and leaves was significantly higher in the hormonal and EDTA treatments, while the microbial treatments showed no significant difference in the amount of Pb translocation into the stems and leaves, when compared to the control. The EDTA increased the amount of translocation into the shoots, but the dry biomass declined and subsequently reduced the total Pb phytoextraction. The GA₃ treatment showed the maximum total Pb accumulation, along with a higher dry biomass. The microbial co‐inoculated plants showed a significant increase in their dry biomass but the Pb accumulation did not increase like with the GA₃ and IAA treatments. These findings encourage the use of the GA₃ application for Pb phytoextraction by P. hysterophorus. One important feature of this weed plant is its unpalatable nature to herbivores, which could help in reducing the entrance of Pb into the food chain. Gibberellic acid is environmentally friendly compared to EDTA; therefore, more investigation of GA₃ and P. hysterophorus is required.     

农药污染土壤的植物修复研究

植物可以吸收、转移元素和化合物,可以积累、代谢和稳定污染物,具修复被污染土壤等作用值得关注。本文综述了植物修复被农药污染土壤的机理和研究现状,列举了修复各种有机污染物的典型植物,及对此方法存在的问题和发展前景作了相应的讨论。     

Simple sequence repeat analysis of genetic diversity among Acetyl‐CoA carboxylase inhibitor‐resistant and ‐susceptible Echinochloa crus‐galli and E. oryzicola populations in Korea

Echinochloa species are amongst the most problematic weeds in rice fields of Korea. The steady reliance on the Acetyl‐CoA carboxylase (ACCase) and acetolactate synthase inhibiting herbicides for control of these weeds has led to resistance to these herbicides. The objective of this study was to assess the genetic diversity among populations of ACCase inhibitor‐resistant and ‐susceptible Echinochloa crus‐galli and E. oryzicola in Korea, to better understand their population structure and possible origins of resistance. Seven simple sequence repeat markers were applied to assess the genetic diversity between resistant and susceptible E. crus‐galli and E. oryzicola from 12 populations in Korea. Genetic diversity was slightly higher in the resistant group. The Unweighted Pair Group Method using Arithmetic algorithm (UPGMA) dendrogram generated two distinct clades. One clade consisted of Echinochloa spp. from three populations, i.e. Anmyeondo, Gimje 4 and Gongju, which are resistant and differentiated from the susceptible populations, and the other clade contained the rest of the populations. Structure modelling supported two clades of UPGMA clustering. Based on these data, we can infer that some resistant populations are greatly differentiated, whereas other resistant biotypes are still building up resistance in rice fields in Korea. Resistance traits will be fixed and continue to spread over time without proper control measures.     

灌溉和生草对猕猴桃园土壤质量的影响

为探明灌溉和生草对猕猴桃园土壤质量的影响,于2016—2017年在陕西省眉县猕猴桃园试验地分别布设地面灌溉+除草(Ⅰ)、地面灌溉+自然生草(Ⅱ)、滴灌+除草(Ⅲ)和滴灌+自然生草(Ⅳ)4种处理,对试验地0～50 cm土层的土壤机械组成、物理和化学性质进行了统计分析,并利用土壤质量综合指数对土壤质量进行了评价,结果表明:与其他处理相比,Ⅲ处理使0～30 cm土层土壤容重和砂粒质量分数分别降低了0.02～0.24g·cm~(-3)和0.36%～5.25%,使土壤孔隙度、田间持水量、黏粒质量分数和土壤粒径分形维数分别增大了0.17%～7.17%、0.59%～2.53%、0.99%～7.15%和0.01～0.13;Ⅳ处理在0～30 cm土层中的速效磷和碱解氮与Ⅰ、Ⅱ处理无差异,显著高于Ⅲ处理10.75～109.55 mg·kg~(-1)和20.74～78.91 mg·kg~(-1)(P0.05),可使0～50 cm土层的速效钾、速效磷和碱解氮分别达到猕猴桃施肥标准的丰富、中等及中等水平;与其他处理相比,Ⅳ处理可使0～50 cm土层土壤黏粒质量分数增加了1.21%～2.66%,土壤粉粒质量分数减少了0.81%～1.41%,使土壤分形维数显著增加(P0.05),土壤质量综合指数最大,达0.619。因此,滴灌+自然生草(Ⅳ)的管理方式是猕猴桃园土地可持续性利用的有效措施。     

晋北黄土丘陵区不同林草措施的蓄水保土和土壤水分效应研究

以设在山西省阳高县的大型径流观测场为依托,以2005-2009年的野外实测数据为依据,研究了晋北黄土丘陵区人工植被与鱼鳞坑配合的蓄水保土及土壤水分效应,并与荒坡、苜蓿地进行了对比。结果表明:在观测的5年内,柠条、沙棘、油松的蓄水保土能力随种植年限延长无明显增加趋势,但鱼鳞坑的蓄水能力和保土能力分别高达84.7%～96.0%和95.2%～99.7%;荒坡和苜蓿(Medicago sativa)第一年和第二年的蓄水保土能力较差,第三年和第四年随植被盖度增加能力急剧增强,第四年蓄水能力分别达82.8%和91.2%,保土能力达97.0%和98.0%;土壤水份分析结果表明:不同小区4～9月土壤水分变异系数为7.0%～19.1%,油松区变异系数最大,其次为沙棘、苜蓿和柠条区,荒坡区和裸坡区变异较小,不同小区土壤水分亏缺率为23.98%～52.66%,亏缺顺序为柠条区>苜蓿区>油松区>沙棘区>荒坡区>裸坡区;林草植被有效地减少了水土流失,亦增加了土壤水分的变异及亏缺程度,应注意林草植被的合理选择和配置。     

Sensitivity of Echinochloa crus‐galli populations to maize herbicides: a comparison between cropping systems

Echinochloa crus‐galli is an important maize weed with significant variation in herbicide sensitivity. This differential response may reflect differences in selection pressure caused by years of cropping system‐related herbicide usage. The herbicide sensitivity of E. crus‐galli populations from three divergent cropping systems was evaluated in dose–response pot experiments. Populations were collected from sandy fields with (i) a long‐term organic cropping system, (ii) a conventional cropping system with maize in the crop rotation or (iii) a conventional cropping system with long‐term monocropping of maize. Each cropping system was represented by six E. crus‐galli populations. The effectiveness of three foliar‐applied maize herbicides (nicosulfuron, cycloxydim and topramezone) and two soil‐applied maize herbicides (S‐metolachlor and dimethenamid‐P) was tested at three doses and two runs. Foliar‐applied herbicides were applied at the three true leaves stage. Soil‐applied herbicides were applied immediately after sowing. The foliage dry weight per pot was determined 4 weeks after treatment. Plant responses were expressed as biomass reduction. Herbicide sensitivity was consistently lowest for populations from maize monocropping systems. Compared with populations from organic cropping systems, populations from monocropping systems showed 6.9%, 9.8% and 29.3% lower sensitivity to cycloxydim, topramezone and nicosulfuron respectively. Populations from the conventional crop rotation system showed intermediate sensitivity levels, which did not significantly differ from sensitivity levels of populations from the other cropping systems. Sensitivity to dimethenamid‐P and S‐metolachlor was not affected by cropping system. Environmental conditions influenced herbicidal response . This study indicated that integrated weed management may be necessary to preserve herbicide efficacy over the long term.     

改性生物炭对汞污染土壤黄瓜生长及品质的影响研究

为了探究改性生物炭对汞矿区土壤植物生长及品质的影响,采集陕西旬阳汞矿区的污染土壤,采用改性生物炭的不同添加比例进行黄瓜盆栽试验,分别设置0(CK)、10(T10)、30 g·1.5kg^-1(T30)和50 g·1.5kg^-1(T50)4种处理,测定了黄瓜的生长、生理指标以及各器官的汞及微量元素含量。试验结果表明,T10处理时,黄瓜根的干质量较CK提高了100%,对茎叶的生物量无显著影响,T30和T50处理黄瓜各部分的干质量均显著降低。T10、T30、T50处理使黄瓜果实的汞含量较CK分别降低了70%、62%、65%。T30和T50处理提高了黄瓜果实中的抗坏血酸和硝酸盐含量,导致叶片POD活性降低了59.8%和66.7%,CAT活性降低了16.2%和16.1%。T10处理在汞元素固化效果、黄瓜生物量及营养品质等方面表现最优,对土壤环境和黄瓜自身的生长发育影响较小。可见,较低浓度的改性生物炭可用于汞污染地区生态修复治理及作物营养调控。     

覆草对果园土壤肥力及苹果产量与品质的影响

在苹果园进行的覆草对土壤肥力和苹果产量与品质的影响试验表明:覆草能有效地稳定土壤温度,保持和提高土壤水分;降低土壤容重,协调土壤大小孔隙比例;增加土壤有机质和养分含量,改善果树营养;提高苹果产量和品质。     

四川丘陵旱区不同人工草地土壤水分动态变化规律研究

研究丘陵旱区人工草地土壤水分变化规律,能够明确饲草种植对坡耕地土壤水分的影响,对指导人工草地水分管理具有重要的现实意义。本研究采用长期定位试验的方法,分析了四川丘陵旱区不同人工草地土壤有效含水量、土壤水分剖面分布和水分利用效率等,明确了饲草种植对丘陵坡耕地土壤水分的影响,为该地区人工草地水分管理提供了理论依据。研究结果表明,(1)四川丘陵旱区人工黑麦草地、菊苣地和苜蓿地0~100 cm土层月均土壤有效含水量分别为88.8、189.3 mm和181.7 mm,其中,1—4月土壤有效含水量较低,6—9月土壤有效含水量较高,9—12月土壤有效含水量逐渐下降;(2)从第一季度(1—3月)到第三季度(7—9月)土壤重量含水率呈增加趋势,从第三季度到翌年第一季度土壤重量含水率呈降低趋势;人工草地在第一季度消耗的深层土壤水分在第三季度能得到较好恢复;(3)人工黑麦草地、菊苣地和苜蓿地的土壤蓄水率均在6—8月最小(71%、64%和68%),11月到翌年3月最大(93%、94%和94%);土壤耗水率在8—10月最大(66%、70%和72%),在11月至翌年3月最小(41%、42%和44%);(4)在绵阳丘陵坡耕地,从鲜草产量角度考虑,菊苣和苜蓿较为理想;从干草产量角度考虑,苜蓿和菊苣较为理想;从粗蛋白供应度考虑,苜蓿和黑麦草较为理想;从消化能产量角度考虑,苜蓿和菊苣较为理想。四川丘陵区黑麦草、菊苣和苜蓿的种植不会引起深层土壤干燥化现象,0~100 cm土层土壤水分在第三季度可以得到较好的恢复;从提高饲草产量角度考虑,可以根据饲草生长需要在11月至翌年4月对人工草地进行适当灌溉,尤其是在刈割后,适当灌溉有利于饲草的快速萌发。     

行内生草对土壤微环境和酿酒葡萄品质的影响

以宁夏贺兰山东麓主栽的6 a生酿酒葡萄‘赤霞珠’为研究对象,进行了连续2 a行内自然生草(CZR)和人工种植马齿苋(CMC)试验,以清耕(CK)为对照,研究行内生草对土壤温度、容重、总孔隙度、肥力、酶活性、微生物数量和酿酒葡萄果实产量及品质的影响。结果表明:CZR处理与CK处理相比,在酿酒葡萄幼果期、膨大期和成熟期5～25 cm土层平均土壤温度下降0.94、1.12℃和0.93℃,0～60 cm土层平均土壤容重和总孔隙度分别下降2.23%和1.73%,脲酶、蔗糖酶、碱性磷酸酶和过氧化氢酶活性分别提高22.67%、30.26%、8.46%和66.65%,微生物数量提高34.97%;CMC处理与CK处理相比,在酿酒葡萄幼果期、膨大期和成熟期5～25 cm土层平均土壤温度分别下降1.82℃、2.02℃和1.38℃,0～60 cm土层平均土壤容重和总孔隙度分别下降0.90%和2.87%,土壤有机质、碱解氮、有效磷、速效钾、全氮和全磷含量分别提高37.80%、52.67%、31.73%、31.17%、24.81%和21.13%,脲酶、蔗糖酸酶、碱性磷酸酶和过氧化氢酶活性分别提高72.08%、109.67%、14.93%和154.50%,微生物数量提高103.56%;行内生草对酿酒葡萄产量影响不显著,对改善浆果品质有显著作用,CZR和CMC处理较CK处理可溶性固形物含量分别降低1.33%和3.72%,可滴定酸、单宁、总酚和花色苷含量分别提高14.52%和16.13%、21.23%和25.82%、26.65%和24.41%、32.75%和41.16%。在旱区滴灌条件下,葡萄园连续2 a行内生草能够改善土壤物理性状,提升土壤肥力、土壤酶活性和微生物数量,对产量影响不显著,但有利于酿酒葡萄香气物质累积,能调节糖酸比,以行内种植马齿苋效果最优。     

黄土丘陵区多次降雨补充下草灌地土壤水分空间变化规律

利用黄土丘陵区燕沟流域42场模拟降雨下土壤水分观测数据,研究2种坡度的草地、灌木地在不同经营方式(原状地、刈割地、翻耕地)下的土壤水分对模拟降雨的响应。结果表明:(1)在5次降雨补充下,依据土壤水分的标准差和变异系数,0~100 cm土壤水分受土地经营方式影响表现为:原状草灌地土壤水分可划分为活跃层、次活跃层和相对稳定层;刈割地全剖面为相对稳定层,翻耕地可分为活跃层和相对稳定层。(2)单次降雨事件则随降雨量增加,各经营方式下的水分活跃层逐渐变薄或消失,次活跃层变厚,而相对稳定层变薄,整个土壤剖面水分变化趋于一致。(3)对于受高强度降雨补充后的土壤水分变异性分层,建议采用更加灵敏的土壤水分标准差和变异系数判别标准:活跃层,标准差大于1.4%,变异系数大于12%;次活跃层,标准差1.4%~0.9%,变异系数12%~8%;相对稳定层,标准差小于0.9%,变异系数小于8%。(4)坡度越小土壤水分含量越高,坡度对草灌木地、刈割地的影响较翻耕地显著,且对50~100 cm土层水分影响远大于对表层0~50cm的影响。总之,降雨后土壤水分0~100 cm土层不断增加,且剖面土壤水分逐渐一致,土地经营方式、坡度因素对土壤水分变化强度和在不同深度土层中的表现有显著影响。     

稗草对二氯喹啉酸抗性研究进展

生长素类除草剂二氯喹啉酸在我国使用了20多年,目前,稻田稗草对二氯喹啉酸产生了抗性,抗二氯喹啉酸稗草逐渐成为我国南北稻区的防除难题。稗草抗二氯喹啉酸机理比较复杂,从稗草感知二氯喹啉酸到产生氰化物的过程是通过生长素信号通路到乙烯信号通路传导的,期间发生了复杂的基因调控和相关酶的从头合成。最新研究认为,稗草主要通过提高氰化物解毒酶——氰丙氨酸合成酶(β-CAS)的活性和控制有毒氰化物的产量产生抗药性。本文综述了二氯喹啉酸的除草机理与稗草对二氯喹啉酸抗性这两个密切相关问题的研究进展。     

Small‐scale heterogeneity in the soil environment influences the distribution of lawn grass and weeds

The association of the micro‐scale distribution of six plant species in a lawn, including the lawn grass, Zoysia japonica, with the soil's environmental factors was studied in an urban park in Kyoto, Japan. The cover of each plant species was scored in July and August. The relative elevation, depth of waterlogging after a shower, soil water content, and soil hardness were measured in 144 quadrats in a 12 m × 12 m plot. The subsurface soil was sampled at every fourth quadrat and was analyzed for the percentage of fine earth and the levels of total carbon, total nitrogen, and available phosphate. Three correlation criteria, namely the Pearson's, Mantel, and partial Mantel correlations, showed considerable disagreement in indicating whether or not there was a significant correlation between each plant species and environmental variable. Although the reason for the disagreement was not always clear, some unimodal or inverted unimodal responses of a plant species against an environmental factor, which was not detectable by the Pearson's correlation coefficient, were indicated to be significant by the Mantel or partial Mantel tests. There were four plant–environment pairs that had a significant correlation in all three criteria: Juncus tenuis in August had a positive correlation with the soil water content in July and August and a negative correlation with soil hardness and Z. japonica showed a negative correlation with the water content in August. The results suggest that the small patches of lawn with poor drainage are the sites of invasion by J. tenuis.     

Effects of soil moisture, organic matter and grass mulching on the carpogenic germination of sclerotia and infection of bean by Sclerotinia sclerotiorum

Microplot experiments were carried out during the autumn and winter of 1995 to determine the effects of soil moisture and levels of organic matter on the carpogenic germination of Sclerotinia sclerotiorum and subsequent infection of Phaseolus vulgaris . Soil moisture treatments were established by irrigation to field capacity: (a) when soil had dried to − 25 KPa, (b) when soil had dried to − 54 KPa, and (c) eight days after the soil had dried to − 54 KPa. Three levels of organic matter were established by mixing compost and yellow-red latosol in the following proportions (by volume): (a) 0% compost and 100% soil, (b) 50% compost and 50% soil, and (c) 100% compost and 0% soil. More apothecia and diseased plants were observed in the plots with higher moisture levels. Drier treatments resulted in a reduction in number (in the winter experiment) or elimination (in the autumn experiment) of apothecia. Other experiments were designed to examine the effect of grass mulching and organic matter levels on the carpogenic germination of S. sclerotiorum . In one experiment, grass mulching was compared with no mulching, and in another, the effects of different depths of mulch on the soil surface (0, 1.5, 3, 6 and 9 cm) were examined. Fewer apothecia were formed in mulched soil and the effect was most pronounced with 6 and 9 cm of mulch. The highest level of mulch (9 cm) impaired the vigour and yield of bean plants. In these experiments, carpogenic germination was increased by high soil organic matter content. Control of soil moisture and grass mulching may reduce the production of apothecia of S. sclerotiorum even in soils rich in organic matter.     

Developmental changes in glutathione S‐transferase activity in herbicide‐resistant populations of Alopecurus myosuroides Huds (black‐grass) in the field

Herbicide‐resistant populations of Alopecurus myosuroides Huds (black‐grass) have become widespread throughout the UK since the early 1980s. Clear evidence suggests that more than one resistance mechanism exists, and glutathione S‐transferases (GSTs) have been implicated in resistance due to enhanced metabolism. This study reports the determination of GST activity in four UK black‐grass populations from field sites situated in the East Midlands. Data demonstrate that, as untreated plants in the field mature, there is an accompanying natural elevation of GST activity with natural environmental changes from winter to spring. We speculate that this endogenous change in enzyme activity with plant development in the field contributes to reduced efficacy of some graminicides applied in the spring. These observations are discussed in relation to predicting herbicide efficacy to achieve maximum control of this important grass weed. © 2001 Society of Chemical Industry