Root diseases, weeds, and nematodes with poultry litter and conservation tillage in a sweet corn–snap bean double crop

The effect of continuous applications of poultry litter on root diseases, nematodes, and weeds with different tillage practices in vegetable production in Georgia was investigated. Litter treatments (noncomposted and composted broiler or breeder litter) applied 3–5 weeks before planting were compared with no litter. In sweet corn and snap bean there were differences among years, and tillage and litter treatments had a variable effect on yield, post-emergence damping-off and plant stand. Crown and brace root rot in corn induced by Rhizoctonia solani AG 2-2 increased after 3 years conservation tillage, but there were no differences among litter treatments. Population densities of R. solani AG-4 were increased by conservation tillage before planting snap bean the first year but not in later years, while litter treatments had no effect. After 3 years, populations of Pythium spp., Fusarium solani, and Fusarium spp. did not differ among treatments, but noncomposted broiler litter increased populations of saprophytic fungi in soil compared with no litter. Population densities of stylet-bearing nematodes were low and usually not different among treatments. After 3 years of sweet corn populations of Meloidogyne incognita increased with conventional tillage compared with conservation tillage, populations of Paratrichodorus christiei were reduced by litter treatments and populations of Helicotylenchus dihystera were reduced by noncomposted broiler litter compared with no litter. Weed infestation increased in both tillage systems with time, but in snap bean there was a greater infestation in conservation tillage than in conventional tillage. Litter treatments had little effect on weed infestation.     

Modelling nematode population growth and damage

Recent results on the population dynamics and damage relationships of root-knot nematode (RKN, Meloidogyne incognita) and of potato cyst nematode (PCN, Globodera pallida) are modelled, and a computer-based programme is used to explore different strategies for PCN control. Damage by RKN was shown to be density dependent, to increase with increasing duration of plant growth, and to be much greater for good than poor hosts. PCN populations both increase and decline more slowly than those of RKN, and modelling suggested that, when non-hosts are grown, differences in decline rates will have an accumulative effect on the effectiveness of rotation. Similarly, differences in nematicide effectiveness will have a major effect on post-harvest PCN populations, and nematicides were shown to be most effective when PCN populations are small. Host resistance is a key component of integrated management of nematodes and, because gene flow in soil is limited, it can be durable.     

酸类化合物对大豆胞囊线虫防效及寄主生长的影响

以辽豆15为材料,采用人工接种的方法,分别测定了不同酸类化合物对大豆胞囊线虫的温室防治效果和对大豆植株生长情况的影响。结果表明:供试化合物中,甲酸和丙酸对大豆胞囊线虫的抑制率相对较高,对线虫的温室防治效果最好;乙酸和乙二酸次之;柠檬酸和苹果酸对线虫的防效较低。乙二酸、柠檬酸和苹果酸对大豆植株的生长抑制作用较小。综合试验结果,确定乙二酸是较为理想的线虫防治药剂。     

Application of an emulsifiable mixture of 1,3-dichloropropene and chloropicrin against root knot nematodes and soilborne fungi for greenhouse tomatoes in Italy

A mixture of 1,3-dicloropropene 60.5% w/w and chloropicrin 33.3% w/w (Telone C35 EC) may be registered in Italy for soil drip fumigation. Five experiments on greenhouse tomatoes in Northern, Central and Southern Italy compared the effectiveness of this mixture in comparison with methyl bromide to find the optimum application rate in soils infested by Fusarium oxysporum f.sp. lycopersici, F. oxysporum f.sp. radicis lycopersici, Sclerotium rolfsii, Meloidogyne javanica and M. incognita. Its efficacy against F. oxysporum f.sp. radicis lycopersici and M. incognita was confirmed when applied to soils at 100, 200, 300 and 400 l ha⁻¹ (132.4, 268.4, 402.6 and 536.8 kg ha⁻¹) under gas-tight films with 15–45 mm of application water (900–1200 mg Telone C35 EC l⁻¹). In sandy soils, with slight F. radicis lycopersici infections and with heavy nematode (M. incognita) attacks, the mixture, drip applied at 900 mg l⁻¹ during late summer (fumigation: late summer; transplant: late-summer/autumn; last harvest: early spring), performed well up to 132.4 kg ha⁻¹ (100 l ha⁻¹). In sandy loam soils with slight F. radicis lycopersici infections and severe infections of F. lycopersici and galling nematodes (M. javanica), 268.4 kg ha⁻¹ (200 l ha⁻¹) of the mixture applied at 900 mg l⁻¹ as a drip provided yields similar to those of methyl bromide treated plots both in spring and summer cycles. In sandy loam soils, the diseases (F. lycopersici, F. radicis lycopersici) were controlled at rates 268.4 kg ha⁻¹ (containing 90 kg ha⁻¹ of chloropicrin), but the mixture was ineffective against Sclerotium rolfsii occasionally observed in sandy loam soils. In both sandy and sandy loam soils, no significant relationships were found between the rates of mixture applied (132.4, 268.4, 402.6 and 536.8 kg ha⁻¹) and the degree of nematode infestation.     

栀子根结线虫病的病原鉴定

为明确广西贺州市栀子根结线虫病病原种类,采集根部有明显根结的栀子根系进行根结线虫分离鉴定,通过观察根结线虫2龄幼虫、雌成虫、会阴花纹特征对其进行形态学鉴定,并利用核糖体ITS区和28S rDNA D2D3区序列比对和系统发育树分析方法对其进行分子生物学鉴定。结果表明,该病原线虫2龄幼虫和雌成虫形态特征及形态测量值与象耳豆根结线虫（Meloidogyne enterolobii Yang & Eisenback, 1983）相似;该病原线虫核糖体ITS区与NCBI数据库中象耳豆根结线虫相应序列的相似度为100%,28S rDNA D2D3区与NCBI数据库中象耳豆根结线虫相应序列的相似度为99%以上;该病原线虫核糖体ITS序列以99%的支持率与象耳豆根结线虫聚为同一分支。综合形态学和分子生物学鉴定结果将广西贺州市栀子根结线虫病病原种类鉴定为象耳豆根结线虫,栀子（Gardenia jasminoides Eills）是该线虫的新寄主纪录。     

小麦苗期抗旱相关形态指标的灰色关联度分析

为了系统研究小麦苗期形态指标与抗旱性的关系并筛选有效的抗旱性指标,使用PEG-6000模拟干旱胁迫,采用灰色关联度分析法分析了28份小麦品种苗期干旱胁迫下的苗高、最长根长、根数、地上部鲜重、地上部干重、根鲜重、根干重、叶片数、根冠比等9个形态指标与抗旱系数的关联程度,并以所得加权抗旱系数对各品种进行聚类分析.结果显示,各形态指标与抗旱系数的关联度依次为:叶片数(0.817)>苗高(0.766)>地上部干重(0.746)>地上部鲜重(0.729)>根数(0.699)>根干重(0.688)>根鲜重(0.681)>根冠比(0.645)>最长根长(0.399).研究还表明,9个形态指标可分为叶片相关因子、地上部生物量因子和根部生物量因子三大类,地上部生物量因子的关联度大于根部生物量因子;不能只通过差异显著度检验来判断某一指标是否可以用作抗旱性鉴定;聚类结果能较好地反映各小麦品种的地域分布.因此,进行小麦品种苗期抗旱性鉴定时,应加强对地上部形态指标的选择和鉴定,以提高选择效率.     

Effects of Toxic Levels of Aluminium on Seedling Parameters of Rice under Hydroponic Culture

The presence of Al in the rhizosphere of rice in acid soil restricts root growth and significantly reduces crop productivity.In this study,the effects of Al(30,60 and 90μg/mL)on seedling root growth,number of primary roots per seedling,seedling shoot length,number of leaves per seedling,seedling fresh weight,and seedling dry weight were studied.Rice genotypes were classified into three different classes,namely,tolerant,moderately tolerant,and susceptible,based on root tolerance index.The method of hydroponic culture was modified,and elaborated in the text.Toxic levels of Al in nutrient solution significantly decreased seedling root growth,number of primary roots,seedling shoot length,number of leaves per seedling,seedling fresh weight,and seedling dry weight.Few genotypes showed longer root length at 30μg/mL Al in nutrient solutions compared with the control.High levels of Al in nutrient solutions were highly toxic for rice seedlings.Based on root tolerance index,Radhunipagal,Gobindobhog,Badshabhog,Kalobhog,UBKVR-11,UBKVR-16,UBKVR-18,Khasha and IVT4007-B were classified as tolerant genotypes,and these genotypes may be used as donors for breeding of Altoxicity tolerance.     

Effects of sulfosulfuron soil residues on barley (Hordeum vulgare), sunflower (Helianthus annuus) and common vetch (vicia sativa)

The phytotoxicity and sensitivity of succeeding crops to the new sulfonylurea, sulfosulfuron, have been reported although there is insufficient data on the phytotoxic effect of field soil residues. Growth chamber bioassays were conducted to detect the presence of residues in soil samples previously treated with sulfosulfuron at the recommended rate and double rate (20 and 40 g a.i./ha) that could affect the succeeding crop. Soil samples were collected between 7 and 9 months after sulfosulfuron application in field selectivity assays at nine different locations in Northern and Central Spain. The bioassay test species were barley (Hordeum vulgare L.) ‘Graphic’, sunflower (Helianthus annuus L.) ‘Albasol’ and common vetch (Vicia sativa L.) ‘Neska’, typical crops grown in rotation with wheat (Triticum aestivum L.) in this area. Sulfosulfuron residues did not affect barley and common vetch, but inhibited shoot length, root length and root dry weight of sunflower seeded into some soils treated with the 2× rate (40 g a.i/ha) 9 months earlier.     

Effects of insecticides applied to control cucumber beetles (Coleoptera: Chrysomelidae) on watermelon yields

Foliar insecticides applied to control the striped and spotted cucumber beetles, Acalymma vittatum (Fab.) and Diabrotica undecimpunctata howardi Barber, on watermelon, Citrullus lanatus, were of little or no value in three studies conducted in two locations over 2 years. However, an at-planting application of the systemic, soil insecticide carbofuran resulted in higher early yields, although the differences were not statistically significant in small plots. In 1991, large plots comparing carbofuran-treated watermelons with untreated watermelons in two commercial fields showed large and statistically significant increases in melon yield when carbofuran was applied, especially in early yield. Studies in 1992 and 1993 showed that the application of carbofuran at planting stimulated root and shoot growth after transplating and increased yields when compared with untreated plots, plots treated with methyl bromide, or another soil insecticide, terbufos. These studies suggest that carbofuran may be acting as a growth stimulant, as well as an insecticide.     

根袋法获取木薯根际土壤及其细菌群落特征研究

为了获取木薯根际土壤并研究其细菌群落特征,加深对木薯根际微生态的认知,开展根袋试验,以粘土和砂质壤土根袋内不同土壤质量（100~500 g）为处理。结果表明,根袋内土质量影响株高,但不影响茎叶重。根袋内100 g土的速效养分受到根系强烈影响,其中铵态氮和速效钾显著高于根袋外。Illumina Hiseq高通量测序结果表明,细菌优势菌门包括变形菌门（31.272%）、放线菌门（25.753%）、酸杆菌门（12.761%）、绿弯菌门（8.799%）等。2种土壤根袋内细菌α多样性增加,粘土细菌丰度也增加。RDA分析表明,土壤速效磷与放线菌门和绿弯菌门正相关,与变形菌门负相关;速效氮、速效钾、铵态氮、硝态氮与芽单胞菌门、酸杆菌门、Parcubacteria等负相关,与厚壁菌门、蓝藻门、梭杆菌门、拟杆菌门正相关;从根袋内外土壤速效养分和土壤细菌多样性综合判定,根袋内100 g土壤时可视为根际土壤,且铵态氮和速效钾可作为判断是否根际土壤的指示指标。根际微生物多样性显著提高。鞘脂杆菌目是木薯品种SC205在不同土质下共同富集的根际细菌。发现了土壤速效养分与部分细菌门的相关性。     

Influence of water and soil salinity on emergence and early development of potato (Solanum tubersum L.) cultivars and effect of physiological age of seed tubers

Summary Applying saline solutions (EC 3.2 up to 7.0 dS/m) to seed tubers of different cultivars planted in tuff delayed shoot emergence and root and shoot development. Fresh weight of most cultivars was decreased by 60% but cv. Serrana Inta was more tolerant to salinity and fresh weight was decreased by 20%. When planted in 500 cm³ pots containing loessial soil some seed tubers rotted and plant growth was severely inhibited, possibly because soil aeration was impeded. Physiologically ageing seed tubers for 33 days at 6°C decreased sensitivity of most cultivars to moderate salinity whereas ageing for 68 days increased sensitivity to high salinity. Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 2977-E, 1990 series.     

Global status of nematode problems of groundnut, pigeonpea, chickpea, sorghum and pearl millet, and suggestions for future work

Analysis of responses received from 40 cooperators in 20 countries to a questionnaire on nematode problems of groundnut, pigeonpea, chickpea, sorghum and pearl millet suggested that Meloidogyne spp. are internationally important nematode pests of groundnut, chickpea and pigeonpea. Pratylenchus spp. are important on all the five crops. In India, Heterodera cajani and Rotylenchulus reniformis are important pathogens of pigeonpea. Over the last 10–15 years, extensive nematode disease surveys have been undertaken for these crops in Australia, Egypt, India, Jamaica, Senegal, Sudan, Thailand and Zimbabwe; however, < 10% of the total crop areas were covered by these surveys. Except for Brazil, Egypt, USA and Zimbabwe, growers do not use nematicides to control the nematodes. Cultural practices, especially crop rotations, are the most commonly used control measures. Species of Meloidogyne, Pratylenchus and Rotylenchulus on the legumes, and species of Hoplolaimus, Pratylenchus, Quinisulcius and Xiphinema on the cereals, are strongly suspected of increasing the severity of fungal diseases. Work aimed at finding host resistance is being done in Brazil, Fiji, India and the USA, and some sources of resistance have been identified against Meloidogyne arenaria, M. incognita, M. javanica and R. reniformis. Facilities for resistance screening work now exist in many countries. Information on damage thresholds of important pest species are available only from Brazil, Fiji, India and the USA.     

生物质炭源可溶性有机物消减土霉素生物毒性的效应比较

为探究生物质炭源溶解性有机物（DOM）对土霉素生物毒性的影响,采用水溶液和土壤模拟培养方式,研究不同温度（350 ℃、500 ℃、650 ℃）制备的木薯渣基生物质炭中溶解性有机物对土霉素胁迫小白菜（Brassica rapa var. glabra）种子发芽、根伸长和芽伸长的影响。结果表明,DOM350和DOM500分别对水培和土培种子的发芽率呈现促进作用,促进率分别为3.33%和10.00%;生物质炭源DOM对土霉素胁迫种子发芽存在缓解作用（P<0.05）;土霉素胁迫下DOM浓度与小白菜种子芽伸长呈显著相关（P<0.05）;土培条件下,DOM与低浓度土霉素（<34.78 mg/kg）共同促进种子根、芽伸长,对高浓度土霉素（>94.09 mg/kg）存在缓解作用;水培条件下,低浓度DOM对土霉素胁迫种子（B. rapa var. glabra）根伸长呈现缓解作用,DOM浓度与种子芽伸长呈极显著正相关（P<0.01）。     

施用木醋液甜瓜根系生长及根际土壤生物学性状与细菌多样性变化

以盆栽甜瓜为研究对象,基于传统与现代分析技术,探究木醋液对于甜瓜根系生长、根际土壤生物学性状和细菌群落结构的影响,旨在开发木醋液作为液态肥料及土壤改良剂的可行性。结果表明,稀释600倍木醋液处理不仅显著促进甜瓜根系生长、显著提高甜瓜根际土壤中可培养微生物数量以及微生物生物量碳、氮、磷和涉及土壤碳、氮、磷循环相关酶的活性,而且有效地提高了甜瓜根际土壤细菌丰富度Chao 1指数和多样性Shannon指数;另一方面,门或属分类水平上,无论施用何种浓度的木醋液,其优势菌门与对照之间无显著差异,均为变形菌门（Proteobacteria）、放线菌门（Actinobacteria）、酸杆菌门（Acidobacteria）、疣微菌门（Verrucomicrobia）、绿弯菌门（Chloroflexi）;优势菌属均为Subgroup 6_no rank、Saccharibacteria、Gemmatimonadaceae（芽单胞菌属）、Sphingomonas（鞘脂单胞菌属）、Soil Crenarchaeotic Group、Bacillus（芽孢杆菌属）、Rhodospirillaceae（红螺菌属）、Roseiflexus（玫瑰弯菌属）、Lactococcus（乳球菌属）和Acidimicrobiales。施用木醋液没有改变甜瓜根际土壤中细菌优势菌门或菌属的组成,但稀释300倍或600倍木醋液更有利于甜瓜根际土壤形成细菌群落结构更为多样的微环境。综合甜瓜根系生长及指示根际土壤肥力指标的生物学性状,施用稀释600倍木醋液更有助于促进甜瓜生长、提高甜瓜根际微环境的土壤肥力和抵御土传病害的能力。     

FURTHER STUDIES ON THE RELATIONSHIP BETWEEN SHOOT AND ROOT SYSTEMS OF GRASSES

In young grass plants it is possible to relate the weight of the root to that of the shoot through the allometric formula y = bx ^k . Using this formula it was found that flower formation was associated with an increase in shoot growth relative to that of the root. Within varieties of Lolium , the greater the intensity of heading the more was the growth of the shoot relative to that of the root. Perenniality was associated with a high rate of root growth relative to that of the shoot. A decrease in the light intensity or soil water reduced the growth of the plant as a whole, but light decreased root growth more than that of the shoot while water supply had the opposite effect.     

Isolation and characterization of chitinolytic rhizobacteria for the management of Fusarium wilt in tomato

Sixty-three chitinase producing rhizobacteria (CRB) were isolated from 57 rhizospheric soil samples of tomato (Lycopersicon esculentum Mill.) growing in different regions of Karnataka, India. Among these, 13 CRB isolates were selected based on their ability to produce chitinase, colonize roots of tomato seedlings and reduce Fusarium wilt incidence. Four of these isolates produced statistically higher levels of chitinase and also zone of clearance/colony size (CZ/CS) ratios. One Bacillus subtilis isolate (CRB20) substantially reduced the severity of Fusarium wilt under greenhouse conditions. Combined application of chitin or crude fungal cell wall (CFCW) along with this isolate, substantially enhanced the ability of the isolate to colonize tomato roots and reduced the severity of Fusarium wilt. Under greenhouse conditions, amendments of chitin and CFCW along with isolate CRB20 significantly enhanced plant height, fresh weight, number of fruits per plant and average weight of fruit compared to the untreated control. The study clearly established the significance of CRB isolates and chitin/CFCW amendment in promoting plant growth and suppression of Fusarium oxysporum, and indicated the possibility of their use for Fusarium wilt management in tomato cultivation.     

Effects of Pseudomonas fluorescens CHA0 on the Resistance of Wheat Seedling Roots to the Take-all Fungus Gaeumannomyces graminis var. tritici

Abstract

The aim of this study was to verify that wheat seedlings treated with Pseudomonas fluorescens CHA0 (CHA0 hereafter) before inoculation with Gaeumannomyces graminis var. tritici (Ggt), a pathogen of take-all, acquire induced resistance to Ggt. The soil with wheat seedlings growing on it was drenched with a suspension of CHA0 cells and inoculated with Ggt 24 h later. Then, the seedlings were grown in a glasshouse, and severity of take-all disease, fresh weights of root and shoot and lengths of root and shoot, and also the activities of soluble peroxidase (SPOX), ionically cell-wall-bound peroxidase (CWPOX), β-1,3-glucanase, β-1,4-glucanase and the concentration of total phenolic compounds in the root of the seedlings were examined. The results indicated that the treatment with CHA0 before inoculation with Ggt mitigated the disease severity significantly, and increased the root and shoot lengths and root and shoot fresh weights. The treatment with CHA0 increased the activities of SPOX, CWPOX, β-1-3-glucanase, β-1,4-glucanase and phenolic compounds in the wheat roots and the activities of SPOX and β-1,4-glucansee activities were highest at day 4 and those of CWPOX and β-1,3-glucanase at day 6 after inoculation with Ggt. The concentration of total phenolic compounds was also highest at day 6 after the inoculation with Ggt. The results suggest that the take-all suppressing effect of CHA0 may be related to enhanced defense response of the wheat roots.     

Drought-induced root plasticity of two upland NERICA varieties under conditions with contrasting soil depth characteristics

To identify differences in root plasticity patterns of two upland New Rice for Africa (NERICA) varieties, NERICA 1 and 4, in response to drought under conditions with contrasting soil profile characteristics, soil moisture gradients were imposed using a sloping bed system with depths ranging 30–65 cm and a line-source sprinkler system with a uniformly shallow soil layer of 20 cm depth. Varietal differences in shoot and root growths were identified only under moderate drought conditions, 11–18% v/v soil moisture content. Further, under moderate drought soil conditions where roots could penetrate into the deep soil layer, deep root development was greater in NERICA 4 than in NERICA 1, which contributed to maintaining dry matter production. However, under soil conditions with underground impediment to deep root development, higher shoot dry weight was noted for NERICA 1 than for NERICA 4 at 11–18% v/v soil moisture content, which was attributed to increased lateral root development in the shallow soil layer in NERICA 1. Enhanced lateral root development in the 0–20-cm soil layer was identified in NERICA 1 even under soil conditions without an impediment to deep root development; however, this did not contribute to maintaining dry matter production in upland rice. Thus, we show different root developmental traits associated with drought avoidance in the two NERICA varieties, and that desirable root traits for upland rice cultivation vary depending on the target soil environment, such as the distribution of soil moisture and root penetration resistance.     

Preventing spread of Fusarium wilt of Hiemalis begonias in the greenhouse

To develop strategies to manage Fusarium wilt of Hiemalis begonias (Begonia×Hiemalis), caused by Fusarium foetens, studies were conducted to understand how the disease might be spread in the greenhouse. Inoculum density studies showed that as few as 100 conidial ml⁻¹ were sufficient to cause significant disease indicating that shared irrigation systems need strict sanitation along with bench tops, pots, and trays. The role of fungus gnats (Bradysia spp.) in vectoring F. foetens within a greenhouse was studied using nylon tent cages with diseased and healthy Hiemalis begonias. Fungus gnats were released into half of the cages. In cages where fungus gnats were present only healthy plants became diseased, indicating the effectiveness of fungus gnats in spreading Fusarium wilt. The pathogen was also isolated from adult fungus gnats. In vitro studies showed that two commercially available H₂O₂-based compounds, ZeroTol^® (2.0% peroxyacetic acid and 27.0% hydrogen peroxide), and SaniDate^® (12.0% peroxyacetic acid and 18.5% hydrogen peroxide), were effective in causing 100% spore mortality at rates that would allow their use in irrigation water. Seven cultivars of Hiemalis begonias (Begonia×Hiemalis) grown in soil infested with F. foetens were highly susceptible. No other Begonia species showed typical symptoms of chlorosis and wilt, but two cultivars of Rex begonia (Begonia rex) exhibited significant stunting in repeated trials.     

优化栽培模式对水稻根-冠生长特性、水氮利用效率和产量的影响

【目的】探明优化栽培模式对水稻根冠发育以及产量与肥水利用效率的影响。【方法】以甬优1540(三系籼/粳杂交稻)为材料,设置3个处理：0N(空白)栽培模式、当地农户习惯栽培模式(对照)以及优化栽培模式。【结果】优化栽培处理两年的平均产量为11.5 t/hm²,与对照差异不显著;但其氮肥偏生产力、产谷利用率以及水分利用率较对照显著提高。与对照相比,优化栽培处理改善了水稻根系形态与生理特征,降低了根系生物量与根-冠比,提高了深根比与比根长,增加了齐穗期与灌浆中期根系活跃吸收表面积,提高了灌浆中后期根系氧化力与根系伤流液中玉米素(Z)+玉米素核苷(ZR)的浓度。此外,与对照相比,优化栽培处理显著提高了灌浆中后期剑叶净光合速率、叶片中Z+ZR含量以及籽粒中蔗糖-淀粉代谢途径关键酶活性。【结论】优化与集成现有栽培技术,可以改善水稻根系形态与生理特征,提高地上部生理活性,进而实现肥水利用效率的提高。