Histopathological changes induced by Meloidogyne incognita in some ornamental plants

Histopathological changes induced by the root-knot nematode (Meloidogyne incognita) in five ornamental plants, specifically, Calendula (Calendula officinalis), Centaurea (Centaurea montana), Papaver (Papaver somniferum), Chrysanthemum (Chrysanthemum morifolium) and Dianthus (Dianthus caryophyllus), were investigated. Based on the galling index (GI), Centaurea was classified as susceptible, Calendula as moderately susceptible, and Papaver as moderately resistant, while Chrysanthemum and Dianthus were highly resistant to M. incognita infection. The histopathology of the galled roots of Centaurea, Calendula, and Papaver during later stages of infection showed that nematodes were localized entirely within the cortex and generally oriented horizontally to the vascular cylinder. Most of the females were mature, and a few of them were associated with egg masses. Giant cells with a variation in cell sizes were observed in the galled roots of all three of the plant species and exhibited a granular cytoplasm and hypertrophied nuclei as a typical reaction to nematode feeding.     

Managing Meloidogyne incognita and Bemisia tabaci with thiacloprid in cucumber crops in China

Field trials were conducted to determine the potential use of thiacloprid for integrated Meloidogyne incognita and Bemisia tabaci B biotype control in cucumber (Cucumis sativus Linn.) in China. The following five treatments were evaluated: three thiacloprid doses (7.5, 15, and 30 kg ha⁻¹), an avermectin treatment (7.5 L ha⁻¹) and an untreated control. All thiacloprid application rates were effective for reducing the M. incognita and B. tabaci B biotype populations. M. incognita was reduced by 51.0%∼86.7% on 60th day and B. tabaci B biotype was reduced by about 37.2%∼95.3% within 21 days, respectively. In addition, greater thiacloprid doses resulted in fewer nematodes and whiteflies. Over two successive years, the cucumber plants that were treated with thiacloprid at a dose of 15 kg ha⁻¹ had the greatest plant height, plant vigor and marketable yield, which were 134.1 cm, 91, 1514.3 g plant⁻¹, respectively in 2010–2011 and 151.9 cm, 93, 1651.4 g plant⁻¹, respectively in 2011–2012. In addition, thiacloprid was superior to avermectin. The results of this study demonstrated that thiacloprid could be used in cucumber production for the integrated control of M. incognita and B. tabaci B biotype. Furthermore, a dose of 15 kg ha⁻¹ of thiacloprid was recommended for controlling nematode and whitefly populations according to the control effect and marketable cucumber yield.     

Yield losses of soybean and maize by competition with interseeded cover crops and weeds in organic-based cropping systems

Weed management is a major issue in organic farming systems. Although interseeding cover crops is one alternative to herbicides, cover crops often suppress not only weeds but also main crops. Therefore, using cover crops for weed control without adverse effects on main crop growth is important. To verify the effect of cover crops on competition between main crops, cover crops and weeds in a snowy-cold region, main crops soybean (Glycine max Merr.) in 2005 and maize (Zea mays L.) in 2006 were grown with cover crops winter rye (Secale cereale L.) and hairy vetch (Vicia villosa Roth), respectively. The cover crops were sown on three sowing dates: before main crop planting (Pre-MC), on the same date of main crop planting (Syn-MC) and after main crop planting (Post-MC). A plot without cover crops (Sole-MC) was used as a control. The dry weight (DW), vegetation cover ratio (VCR), vertical community structure and chlorophyll content were measured to estimate the competition between main crops, cover crops and weeds. Weed DW was suppressed significantly by sowing cover crops in both soybean and maize. This weed suppression was associated with the increase of VCR of main crops plus cover crops at the early growth stage of main crops. Soil seed banks of dominant weed also became lower by sowing cover crops, implying the importance of proper weed management for suppressing weeds successively. In addition, the sowing dates of cover crops had large effects on main crops DW especially in maize, i.e., it was significantly lower in Pre-MC and Syn-MC than in Post-MC. Although the cover crop height was markedly shorter than the main crop height, the chlorophyll content of the main crops was significantly lower when cover crops were sown earlier. These results suggest that the growth inhibition of main crops by cover crops was partly caused by competition for nutrients between main crops and cover crops, and this growth inhibition was alleviated when cover crops were sown after the establishment of main crops. Consequently, soybean yield was the highest in Post-MC and decreased by 29%, 18% and 7% in Sole-MC, Pre-MC and Syn-MC, respectively, and maize yield was also the highest in Post-MC and decreased by 68%, 100% and 24% in Sole-MC, Pre-MC and Syn-MC, respectively. It was concluded that weeds could be controlled effectively by sowing cover crops after planting main crops in organic farming systems in a snowy-cold region.     

5个油茶物种对南方根结线虫的抗性研究

采用人工接种的方法,研究了普通油茶、博白大果油茶、广宁红花油茶、香花油茶和陆川油茶对南方根结线虫的抗性。结果表明：普通油茶易感南方根结线虫,广宁红花油茶、香花油茶和陆川油茶中抗南方根结线虫,博白大果油茶高抗南方根结线虫;接种60 d内调查,南方根结线虫侵入博白大果油茶后不能完成其生活史,而普通油茶在28 d内就能完成生活史并繁育后代;接种根结线虫后对博白大果油茶、广宁红花油茶、香花油茶和陆川油茶的生长没有显著性影响,但抑制普通油茶茎、叶的生长的同时促进其侧根的生长。     

Response of selected okra cultivars to Meloidogyne incognita

Root–knot nematodes (Meloidogyne spp.) are major pests of vegetables especially in the tropics and subtropics. All commercial okra varieties are susceptible to root knot nematodes and cause substantial losses. The objective of this study is to find out resistant germplasm in order to facilitate our breeders for gene manipulation. A greenhouse study was conducted to evaluate 28 okra cultivars against Meloidogyne incognita inoculated with 5000 eggs. Five cultivars (Bamya Yalova, 19,232, 19,236, 1,922,121, and Green Wonder) had significantly fewer root galls and eggs and less reduction in plant growth (shoot weight and root length), than most of the other entries. A positive relationship was demonstrated between root galls and reduction in plant growth parameters measured. These cultivars may improve okra production in fields infested with M. incognita. During our study, none of the cultivars tested were observed to be immune or resistant to nematode infection according to a scale where: good host [susceptible] when Pf/Pi (Pf = Final population of nematodes after harvest and Pi = Initial population of nematodes which was used as inoculum during experiment) > 5.0, fair, better [moderately resistant] if 5.0 ≥ Pf/Pi > 1, poor if 1 > Pf/Pi > 0, and non-host [resistant] when Pf/Pi = 0. The cultivars, including 19,224, 19,235, Pusa Sawami, Ikra-1, Ikra-2 and Sabzperi China Red, were found to be susceptible with Pf/Pi > 5.0, and they were declared as good hosts of M. incognita. While all the other cultivars were moderately resistant, with 0 ≥ Pf/Pi > 1 but still a significant penetration of nematodes was found. The regression studies showed positive and significant relationships between the number of galls and the reduction in shoot weight (r² = 0.95), number of galls and reduction in shoot length (r² = 0.81), and number of galls and decrease in root length (r² = 0.89).     

麦套花生套期与密度优化配置研究

采用二次饱和D-最优设计建立了小麦行距为30cm的麦套花生套期和密度与产量的数学模型.进一步分析表明,花生套期和密度对花生产量作用显著,且密度效应大于套期.套种花生最适播期为麦收前22d,与其相配套的最适密度为15.55×104穴/hm2,最高产量可达到4 679.4kg/hm2.适期过后,套期每推迟5d,花生平均减产187.2kg/hm2.花生产量在3 500kg/hm2以上的优化措施组合为:5月10日～5月29日套种,密度14.66×104～20.72×104穴/hm2.     

An economic analysis of potential rotation crops for Maine potato cropping systems

Potato cropping systems in Maine include both continuous potatoes and short-term potato rotations with small grains. Producers recognize the benefits of increased rotations, but the economics of producing a high-valued crop such as potatoes (Solanm tuberosum L.) create incentives for continuous potato production. Research at the USDA-ARS research site in Newport, ME, is evaluating the agronomic and economic impacts of five crops in two-year rotations on potato production and whole-farm profitability. The rotation crops are barley (Hordeum vulgare L.), sweet corn (Zea mays L.) green bean (Phaseolus vulgares L.), soybean (Glycine max L., Mer.), and canola (Brassica napus L.). Enterprise budgets for the five crops were developed. The budgets and historical prices and yields were used as inputs to a Monte Carlo simulation. The simulation was conducted to determine the impact of rotation crops on whole-farm profitability and income risk, as measured by income variability. The net incomes of the five rotation sequences were compared against continuous potatoes. Two rotation crops, sweet corn and green beans, resulted in an increase in net income relative to continuous potatoes. AU of the rotation crops were found to greatly reduce income risk and chance of economic losses. In the case of green beans and sweet corn, the analysis was rerun using data from the research trials on the following potato crop yields. Depending on whether the rotation effect was negative or positive, net income either fell or rose when compared to fist analysis. However, even when the rotation crop led to decreased yields in the following potato crop, income variability and likelihood of economic loss was still superior to the continuous potato rotation. These findings provide support for including rotation crops as a method to improve potato production and sustainability, increase wholefarm profitability, and reduce income risk.     

Clover cover crops under-sown in winter wheat increase yield of subsequent spring barley—Effect of N dose and companion grass

Four two-year field trials, arranged in randomised split-plots, were carried out in southern Sweden with the aim of determining whether reduced N fertiliser dose in winter wheat production with spring under-sown clover cover crops, with or without perennial ryegrass in the seed mixture, would increase the clover biomass and hence the benefits of the cover crops in terms of the effect on the wheat crop, on a subsequent barley crop and on the risk of N leaching. Four doses of nitrogen (0, 60, 120 or 180 kg N ha⁻¹) constituted the main plots and six cover crop treatments the sub-plots. The cover crop treatments were red clover (Trifolium pratense L.), white clover (Trifolium repens L.) and perennial ryegrass (Lolium perenne L.) in pure stands and in mixtures. The winter wheat (Triticum aestivum L.) was harvested in August and the cover crops were ploughed under in November. The risk of N leaching was assessed in November by measuring the content of mineral N in the soil profile (0–30, 30–90 cm). In the following year, the residual effects of the cover crops were investigated in spring barley (Hordeum distichon L.) without additional N. Under-sowing of cover crops did not influence wheat yield, while reduced N fertiliser dose decreased yield and increased the clover content of the cover crops. When N was applied, the mixed cover crops were as effective in depleting soil mineral nitrogen as a pure ryegrass cover crop, while pure clover was less efficient. The clover content at wheat harvest as well as the amount of N incorporated with the cover crops had a positive correlation with barley yield. Spring barley in the unfertilised treatments yielded, on average, 1.9–2.4 Mg DM ha⁻¹ more in treatments with clover cover crops than in the treatment without cover crops. However, this positive effect decreased as the N dose to the preceding wheat crop increased, particularly when the clover was mixed with grass.     

饲料油菜与牧草混合冬播效应研究

为缓解冬季饲料作物缺乏的压力,改进冬季饲草的生产模式,提高饲草油菜的品质和种植效益,通过设置小区试验,将双低甘蓝型油菜（Brassica napus L.）分别与紫云英、黑麦草和光叶苕子等冬季牧草按比例混播,测定各处理的生物学产量、粗蛋白含量等指标,探寻油菜与牧草混播技术的可行性。结果表明,油菜与光叶苕子、紫云英、黑麦草的混播效应存在显著差异。（1）光叶苕子与油菜混播均可以提高饲草的鲜样总产量,且在密度按1:4（油菜按15 000株/hm2的播种量）混播时,各取样时期的饲料鲜、干样产量均较高,油菜终花期时该处理的粗蛋白产量显著高于其他处理。（2）与紫云英混播,也可提高饲料油菜的鲜样产量,但差异不显著,且紫云英因光照不足,油菜初花期时已全部死亡。（3）与黑麦草混播后,饲料鲜样产量、粗蛋白产量均显著下降。因此,油菜与光叶苕子混播是进一步提高长江流域冬季饲料作物生产效应的有效模式。     

Above and belowground litter decomposition of cover crops grazed at different intensities

Grazing cover crops may increase land-use efficiency while promoting sustainability. We investigated how grazing intensity affects cover crop litter quantity, quality, decomposition, and cotton (Gossypium hirsutum L.) N uptake. Cover crops were a mixture of rye (Secale cereale L.) and oat (Avena sativa L.) managed as follows: no grazing +34 kg N ha⁻¹ (NG34), no grazing +90 kg N ha⁻¹ (NG90), heavy grazing (HG), moderate grazing (MG), and light grazing (LG). Grazed treatments received 90 kg N ha⁻¹. After cover crop termination, above- and belowground litter was collected and incubated in situ for 0, 4, 8, 16, 32, 64, and 128 days, with cotton plants sampled on the same days to estimate N recovery and synchrony between N release from litter and uptake by cotton. By Day 128, only 13% of initial NG34 aboveground biomass had disappeared, whereas 42% of HG disappeared. Nitrogen retained in aboveground litter of HG was less than NG90 (27 vs. 60 kg N ha⁻¹), and aboveground final N stock (at Day 128) of HG was less than NG90 and LG (16, 47, and 41 kg N ha⁻¹, respectively). Belowground litter contributed 98 kg N ha⁻¹ versus 46 for aboveground. Belowground N disappearance from litter bags was greater from NG90 than NG34 (39 vs. 21 kg N ha⁻¹). Cotton N uptake by Day 128 was similar across treatments (191 kg N ha⁻¹). Grazing cover crops impact aboveground litter quantity, quality, and decomposition rates, and belowground litter plays an important role on the N cycling.     

Evaluation of resistance to root-knot nematode (Meloidogyne incognita) in okra cultivars

The root-knot nematode, Meloidogyne incognita, is one of the major limiting factors affecting plant growth and yield causing an estimated $100 billion loss per year worldwide. Synthetic pesticides, though instantaneously effective, are usually prohibitively expensive, not readily available, may cause hazards to both man and livestock, and inflict injury to the environment. Notable among the alternatives to nematicides is the use of resistant cultivars which are inexpensive and eco-friendly. In the present studies, twelve okra (Abelmoschus esculentus L) cultivars were evaluated for their resistance against M. incognita under field conditions. Ten-day old okra plants of test cultivars were inoculated with 3000 freshly hatched second stage juveniles of M. incognita. The nematode caused reductions in various growth parameters of all the cultivars to varying levels over their respective controls. None of the cultivars was found completely resistant. The cultivar ‘Sharmeeli’ was highly susceptible as >100 galls were recorded on the roots. Sharmeeli also showed maximum reductions in growth among the cultivars evaluated. The cultivars Anmol and Sindha were susceptible with 71–100 galls. The cultivars Sabz Pari, Super Star, PMS-55 and PMS Beauty were moderately susceptible with 31–70 galls and comparatively less reductions in growth. Cultivars Sanam, Dikshah, Arka Anamika, Ikra-1 and Ikra-2 with 11–30 galls were rated as moderately resistant and showed less damage by the nematode as compared to susceptible cultivars and their planting could provide a useful tool to control root-knot nematodes.     

20种植物提取物对南方根结线虫的毒杀活性

采用浸渍法测定13科20种植物乙醇提取物对南方根结线虫的毒杀活性。结果表明：酸豆、牛角瓜、番荔枝、苦楝乙醇提取物以10 mg/mL处理后24 h,供试2龄线虫校正死亡率分别为82.13%、85.71%、89.28%、89.28%,处理后48 h,校正死亡率分别为89.01%、96.34%、92.67%和96.34%,均具有强杀线虫活性;毒力测定结果表明：处理后24 h和48 h,4种提取物的LC50由小到大顺序为：酸豆＜牛角瓜＜番荔枝＜苦楝。     

Faba bean in cropping systems

The grain legume (pulse) faba bean (Vicia faba L.) is grown world-wide as a protein source for food and feed. At the same time faba bean offers ecosystem services such as renewable inputs of nitrogen (N) into crops and soil via biological N₂ fixation, and a diversification of cropping systems. Even though the global average grain yield has almost doubled during the past 50 years the total area sown to faba beans has declined by 56% over the same period. The season-to-season fluctuations in grain yield of faba bean and the progressive replacement of traditional farming systems, which utilized legumes to provide N to maintain soil N fertility, with industrialized, largely cereal-based systems that are heavily reliant upon fossil fuels (=N fertilizers, heavy mechanization) are some of the explanations for this decline in importance. Past studies of faba bean in cropping systems have tended to focus on the effect of faba bean as a pre-crop in mainly cereal intensive rotations, whereas similar information on the effect of preceding crops on faba bean is lacking. Faba bean has the highest average reliance on N₂ fixation for growth of the major cool season grain legumes. As a consequence the N benefit for following crops is often high, and several studies have demonstrated substantial savings (up to 100–200 kg N ha⁻¹) in the amount of N fertilizer required to maximize the yield of crops grown after faba bean. There is, however, a requirement to evaluate the potential risks of losses of N from the plant–soil system associated with faba bean cropping via nitrate leaching or emissions of N₂O to the atmosphere as a consequence of the rapid mineralization of N from its N-rich residues. It is important to develop improved preventive measures, such as catch crops, intercropping, or no-till technologies, in order to provide farmers with strategies to minimize any possible undesirable effects on the environment that might result from their inclusion of faba bean in cropping system. This needs to be combined with research that can lead to a reduction in the current extent of yield variability, so that faba bean may prove to be a key component of future arable cropping systems where declining supplies and high prices of fossil energy are likely to constrain the affordability and use of fertilizers. This will help address the increasing demand by consumers and governments for agriculture to reduce its impact on the environment and climate through new, more sustainable approaches to food production. The aims of this paper are to review the role of faba bean in global plant production systems, the requirements for optimal faba bean production and to highlight the beneficial effects of faba bean in cropping systems.     

南方根结线虫侵染对不同砧木嫁接冬瓜生长的影响

为了明确南方根结线虫对不同南瓜砧木嫁接冬瓜苗生长发育的影响,以期为冬瓜生产筛选抗根结线虫砧木品种,促进产业可持续发展。本文采用人工接种南方根结线虫,研究比较了‘海砧1号’、‘海砧2号’和‘银龙黄籽’3种南瓜砧木的冬瓜嫁接苗及冬瓜自根苗的抗性水平及植株生物量的差异。结果表明：不同南瓜砧木冬瓜嫁接苗和自根苗的病情指数、根结指数、卵粒指数和繁殖指数均随着生育期延长而不断升高,抗性水平发生不同程度变化;以‘海砧2号’为砧木的嫁接苗在全生育期均表现为抗病,以‘海砧1号’和‘银龙黄籽’为砧木的嫁接苗表现为高感,‘清远黑皮冬瓜’自根苗表现为感病。在茎叶鲜重和单果鲜重方面,生长中后期以‘海砧2号’为砧木的嫁接苗显著高于以‘海砧1号’和‘银龙黄籽’为砧木的嫁接苗以及‘清远黑皮冬瓜’自根苗,但与未接种的‘清远黑皮冬瓜’自根苗无显著差异。研究结果证实,南方根结线虫明显抑制了感病砧木冬瓜嫁接苗的生长和产量,对抗病砧木嫁接苗无明显影响。     

Lowering carbon footprint of durum wheat by diversifying cropping systems

Improving cropping systems may help mitigate greenhouse gas emissions. This study determined the carbon footprint of durum wheat (Triticum turgidum L.) produced in diverse cropping systems. Durum was grown in rotation systems which had different combinations of oilseed, pulse, and cereal crops at five site-years in Saskatchewan, Canada. Total greenhouse gas emissions from the decomposition of crop residues along with various production inputs were used for the estimation of carbon footprint. On average, emissions from the decomposition of crop straw and roots accounted for 25% of the total emissions, those from the production, transportation, storage, and delivery of fertilizers and pesticides to farm gates and their applications 43%, and emissions from farming operations 32%. Durum wheat preceded by an oilseed crop (Brassica napus or Brassica juncea) the previous year had carbon footprint of 0.33 kg CO₂e kg⁻¹ of grain, or 7% lower than durum in cereal-cereal-durum system. Durum preceded by a biological N-fixing crop (Cicer arietinum chickpea, Lens culinaris lentil, or Pisum sativum pea) the previous year lowered its carbon footprint by 17% compared with durum preceded by a cereal crop. Durum produced in a pulse-pulse-durum system had carbon footprint 0.27 kg CO₂e kg⁻¹ of grain, 34% lower than durum grown in cereal-cereal-durum systems. Diversifying cropping systems with oilseeds and biological N-fixers significantly lowered carbon footprint of durum wheat.     

粉红粘帚菌代谢物对南方根结线虫卵孵化及二龄幼虫的影响

粉红粘帚菌(Gliocladium spp.)是一类对植物病原菌具有潜在生物控制作用的真菌,为了探讨粘帚菌对南方根结线虫(Meloidogyne incognita)的抑制作用,实验室条件下研究了粉红粘帚菌挥发性代谢产物和非挥发性代谢产物不同稀释度对南方根结线虫卵孵化及二龄幼虫活性的影响.结果显示非挥发性代谢产物在原液...     

阿扎霉素F5a抗南方根结线虫和香蕉枯萎病菌活性研究

为寻找抗线虫和香蕉枯萎病菌的天然产物。从链霉菌211726的发酵液中分离纯化出阿扎霉素F5a,以南方根结线虫(Meloidogyne incognita)为供试线虫,采用击倒实验,测定阿扎霉素F5a高(1.0%)、中(0.1%)、低(0.01%)3个浓度的抗线虫活性;同时以尖孢镰刀菌(Fusarium oxysporum f. sp. cubense)为供试菌株,采用牛津杯琼脂平板法,对阿扎霉素F5a的抗香蕉枯萎病活性进行研究。结果表明：1.0%的阿扎霉素F5a溶液在24 h内对供试线虫2龄幼虫的平均校正     

Wheat cropping systems and technologies in China

Chinese wheat (Triticum aestivum) production has developed rapidly during the last 57 years, largely due to improved crop management technologies and new varieties. The history of wheat planting technologies in China was reviewed, and the physiological mechanisms that allow wheat to attain high yield under these planting systems were analyzed. The use of leaf number and stage of development to indicate the optimum timing for applications of fertilizers and irrigation water, and uniform seeding at reduced seeding rates to control lodging contributed significantly to the substantial progress in wheat productivity. However, flood irrigation and tillage-based practices also resulted in serious problems, including a decline in soil fertility and quality, environmental pollution, and inefficient use of water resources. The major future challenges facing wheat production are to improve water and nutrient use efficiency. Conservation agriculture-based resource conservation technologies such as zero or reduced tillage, flat or raised bed-planting systems, and rational management of crop residues to eliminate burning in the field are among the strategies we strongly recommend for improving agricultural environments and stabilizing/increasing wheat production in China.     

福建省蔬菜根结线虫卵囊寄生真菌鉴定

调查了福建省部分地区的蔬菜根结线虫卵囊寄生真菌。从8种蔬菜病根上采集根结线虫卵囊样品624份,分离到真菌401株,除34株不产孢及疑难种未鉴定外,已鉴定的真菌有18个属：镰孢菌、拟青霉、根霉、曲霉、厚垣孢普可尼亚菌、丝核菌、弯孢、毛霉、刚毛孢、木霉、链格孢、拟盘多毛孢、青霉、炭疽菌、黑孢霉、小克银汉霉、枝孢霉、横隔霉。镰刀菌属、曲霉属、木霉属为优势真菌,分别占总分离数的31.2%、10.2%、12.7%;淡紫拟青霉和厚垣孢普可尼亚菌分别占8.1%和4.5%。