Management of late leaf spot of groundnut (Arachis hypogaea) with chlorothalonil-tolerant isolates of Pseudomonas aeruginosa

Fifteen groundnut-associated bacterial isolates that inhibited by > 90% the in vitro conidial germination of Phaeoisariopsis personata , causal agent of late leaf spot disease of groundnut, were applied as a prophylactic spray (10⁸ cfu mL⁻¹) and tested for control of the disease in the glasshouse. Two groundnut seed-associated bacterial isolates, GSE 18 and GSE 19, identified as Pseudomonas aeruginosa , reduced the lesion frequency (LF) by up to 70%. A 90-day-old peat-based formulation of P. aeruginosa GSE 18 reduced LF measured 15 days postinoculation by up to 60%. Both P. aeruginosa GSE 18 and GSE 19 were tolerant to chlorothalonil (Kavach®) up to 2000  µ g mL⁻¹ in LB broth. In glasshouse trials, GSE 18 and GSE 19 tested in combination with reduced concentrations of chlorothalonil were highly efficient in management of the disease. The disease was completely controlled by chlorothalonil (> 250  µ g mL⁻¹), and in the presence of GSE 18 or GSE 19, 100  µ g mL⁻¹ chlorothalonil was equally effective. Application of rifamycin-resistant mutants of GSE 18 or GSE 19 together with chlorothalonil significantly increased the survival of these isolates in the groundnut phylloplane. In the field, a combination of GSE 18 and 500  µ g mL⁻¹ chlorothalonil reduced disease severity comparable to 2000  µ g mL⁻¹ chlorothalonil alone. Use of chlorothalonil-tolerant pseudomonads together with a quarter concentration of the recommended field dose of chlorothalonil doubled pod yield compared with the untreated unsprayed control.     

Integrated pest management in groundnut (Arachis hypogaea L.) in India

A large number of pests are associated with groundnut but not all are economically important. The distribution of, losses and damage caused by groundnut pests are discussed, along with a variety of control measures and methods for their integration for effective pest management. Disease resistant/tolerant varieties, including Girnar 1, ALR 1, ICGV 87160, ICGV 86590, DH 8, TG 3, MH 16, ICGS 37 and TAG 24 from India have been released for general cultivation and could be used in integrated pest management (IPM) programmes. A large number of advanced breeding lines possessing resistance to major diseases and insect pests have been identified. Biocontrol agents have been used successfully for insect and disease control. Intercrops such as pearlmillet and soybean suppress thrips, jassids and leaf miner; castor suppresses jassids and Spodoptera, and pigeonpea suppress early leaf spot, late leaf spot and rust. These plants act as traps or barriers for reducing pest incidence. The use of pheromone traps for gram pod borers, tobacco caterpillars and leaf miners, and the use of neem products against major insect pests and diseases, are novel approaches that may reduce the cost of groundnut production. If pest control measures are integrated in an optimum proportion and pest surveillance activity is strengthened further, maximum returns could be realized     

Management of Cercospora leaf spot of groundnut (Arachis hypogaea L.) with a single fungicidal spray

Field trials were conducted during the rainy seasons of 1993/94 for chemical control of groundnut leaf spot using a single spray. A fungicide mixture ofcarbendazim 0.05%+mancozeb 0.2% was applied once in different treatments. Spray timings varied from 30 d.a.s. to 80 d.a.s. at 10-day intervals. Spray application reduced the percent disease index in all treatments. A statistically significant increase in pod yield was obtained in treatments sprayed up to 50 d.a.s. in 1993. The yield data were not significantly different in 1994. Sprays at 40 d.a.s. in 1993 and 50 d.a.s. in 1994 gave maximum returns. The cost of treatmentdid notvary significantly. The benefitto cost ratio oftreatments ranged from 1.1 to 8.1 in 1993 and 4.1 to 5.5 in 1994.     

Weed control in groundnut (Arachis hypogaea L.) with polyethylene film mulching

Studies conducted during the winters of 1997 - 98 and 1998 - 99 (December - March) at the Regional Research Station, Tamil Nadu Agricultural University, Vridhachalam, India, revealed the usefulness of polyethylene film mulching in arresting weed growth and maximizing pod yield in groundnut. Among the various treatments, two (1) crop grown under polyethylene film mulching and (2) pre-planting incorporation of fluchloralin in the flat-bed system of sowing registered the lowest weed numbers at harvest (106.7 and 113.7/plot of 27 m 2 in 1997 - 98 and 1998 - 99 respectively), the lowest weed dry-matter production (51.2 and 54.5 g/plot of 27 m 2 ), maximum weed control efficiency (62.1 and 57.4%) and weed control index (83.0 and 81.1%), the highest number of matured pods/plant (17.6 and 18.0), 100 kernel weight (48.6 and 48.7 g), percentage shelling (72.6 and 72.8) and a dry pod yield of 2451 and 2468 kg ha -1 when compared with non-mulched plots. The net return and benefit:cost ratio was also highest with the same treatment in both the study periods.     

Peanut (Arachis hypogaea) response to weed and disease management in northern Ghana

Weeds and diseases can reduce peanut (Arachis hypogaea L.) yield or increase cost of production to maintain acceptable yield. While herbicides and fungicides have limited availability in many areas of Ghana and currently are too expensive for resource-poor farmers, control by these pesticides can have a major positive impact on peanut yield. Field experiments were conducted during the rainy seasons of 2009 and 2010 in northern Ghana to determine the effects of herbicide and hand weeding in combination with fungicides on pest management and peanut yield. Peanut pod yield was often more highly correlated with disease severity and canopy defoliation resulting from early leaf spot (caused by Cercospora arachidicola Hori) and late leaf spot (caused by Cercosporidium personatum (Berk. & M.A. Curtis) Deighton) than weed biomass. In some instances, less disease and canopy defoliation were observed when weeds were not controlled effectively compared with increased weed management through hand weeding or herbicide. Two hand weedings or applying pendimethalin preemergence with one hand weeding in combination with 4 applications of triadimefon and chlorothalonil resulted in the lowest weed density and canopy defoliation and often resulted in the highest peanut yield.     

Biocontrol strain of Bacillus subtilis AF 1 rapidly induces lipoxygenase in groundnut (Arachis hypogaea L.) compared to crown rot pathogen Aspergillus niger

Metabolic products of polyunsaturated fatty acids have been variously implicated in control of microbial pathogens. Induced resistance has been shown as one of the mechanisms of biological control by plant growth promoting rhizobacteria (PGPR). This paper reports a significant lipoxygenase (LOX) activity in groundnut seedlings with production of 13-hydroperoxyoctadecadienoic acid (13-HPODE) and 13-hydroperoxyoctadecatrienoic acid (13-HPOTrE) as major products with linoleic acid (LA) and -linolenic acid (ALA), respectively. Both the hydroperoxides are inhibitory to the growth of Aspergillus niger as measured in micro titer plates. Ours is the first report on induction of LOX activities in groundnut on treatment with a PGPR strain Bacillus subtilis AF 1, and with crown-rot pathogen, A. niger. Treatment with B. subtilis AF 1 enhanced LOX levels in groundnut similarly but earlier to A. niger – treatment. This induction of LOX during activation of growth and pathogen infection was discussed in light of the reported involvement of LOX both in growth and development as well as in plant-pathogen interaction, particularly induced disease resistance.     

Silicon,biological seed treatment and cutting reduce the intensity of leaf spot diseases affecting Lolium multiflorum

Italian ryegrass is a major pasture crop cultivated mainly for feeding cattle in southern Brazil. The choice of crop is based on nutritional quality and the shortage of pastures that occur during the winter in the southernmost part of Brazil. In this region, the production of biomass and seeds are threatened by diseases, in particular fungal diseases that affect the foliage. In this study we identified and monitored the natural occurrence of a complex of leaf spotting diseases and evaluated the effects of combined management practices to reduce the intensity of foliar diseases: seed treatment with Trichoderma atroviride, soil amendment with silicon and cutting frequency (none, one or two cuts). Three diseases were present in a two-season experiment: grey leaf spot (Pyricularia oryzae), brown leaf spot (Bipolaris sorokiniana) and parrot's eye leaf spot (Cercospora sp.). Grey leaf spot had the highest severity, regardless of treatment, during the first season, and was the only disease present in the following season. Grey leaf spot dominated, and plants receiving only one cut were more prone to P. oryzae infection. The treatments with silicon or T. atroviride reduced the relative disease by 40% to 80%, in relation to untreated and uncut regimes. This study showed the main leaf spot diseases associated with L. multiflorum. Moreover, it demonstrates for the first time in the region the effectiveness of reducing leaf spot via the application of silicon in the soil, inoculation of seeds with T. atroviride and managing the cutting regime.     

Isolation and biochemical diagnosis of cell lines of groundnut (Arachis hypogaea L) selected on glyphosate†

Three cell lines of groundnut (Arachis hypogaea L), an important oilseed legume, were selected on glyphosate using in-vitro culture techniques. The cell lines isolated through single as well as stepwise selection procedures showed c 20-fold increase in glyphosate tolerance as compared to the unselected control cell line. Studies on the biochemical mechanism of glyphosate tolerance in these cell lines showed a significant increase in the total extractable activity of the target enzyme, 5-enolpyruvyl shikimate-3-phosphate (EPSP) synthase (EC 2.5.1.19), which was further confirmed with immunological data. The over-expressed EPSP synthase activity was, however, subject to inhibition by glyphosate in vitro. Two other key regulated enzymes of the shikimic acid pathway, 3-deoxy-D -arabino heptulosonate 7-phosphate (DAHP) synthase (EC 4.1.2.15) and chorismate mutase (CM) (EC 5.4.99.5) did not show any change in specific activity in the selected cell lines. The enhanced activity of EPSP synthase in the tolerant cell lines was found to be stably inherited in the absence of selection pressure. © 1999 Society of Chemical Industry     

Cloning and characterization of an NBS-LRR resistance gene from peanuts (Arachis hypogaea L.)

The nucleotide-binding site (NBS)-leucine-rich repeat (LRR) gene family accounts for the largest number of known disease resistance genes and is one of the largest gene families in plant genomes. In this study, resistance gene analogs (RGAs) were isolated from peanuts based on the NBS domain. A full-length cDNA, PnAG₃, was obtained by rapid amplification of cDNA ends (RACE). Sequence analysis indicated that the length of PnAG₃ was 1882 bp, which included a complete open reading frame of 1335 bp that encoded for the PnAG₃ protein composed of 444 amino acids. Multiple analyses showed that this protein had homology with known resistance proteins, the highest being 48.01% with a resistance protein from Arachis cardenasii. The polypeptide has a typical non-TIR-NBS-LRR gene structure. Real-time fluorescence quantitative PCR analysis showed that after Aspergillus flavus infection, expression of the PnAG₃ gene in J11 (A. flavus-resistant species) increased by 16.68, 11.16 and 25.96 in the seed coat, kernel and pericarp, respectively. However, it only increased 2–3 times in JH1012 (A. flavus-sensitive species). Cloning of the putative resistance gene from peanut provides a basis for studying the structure and function of peanut disease resistance-related genes and disease resistance genetic breeding in peanuts.     

Effect of the new pyrazole carboxamide fungicide penthiopyrad on late leaf spot and stem rot of peanut

BACKGROUND: Management of early leaf spot (Cercospora arachidicola Hori.), late leaf spot [Cercosporidium personatum (Berk. & MA Curtis) Deighton] and stem rot (Sclerotium rolfsii Sacc.) of peanut (Arachis hypogaea L.) in the southeastern USA is heavily dependent upon sterol biosynthesis inhibitor (SBI) and quinone outside inhibitor (QoI) fungicides. Effective new fungicides with different modes of action could improve overall disease control and extend the utility of the current fungicides. Penthiopryad is a pyrazole carboxamide fungicide being evaluated for use on peanut. Field experiments were conducted from 2004 to 2007 to determine the effect of a range of rates (0–0.36 kg AI ha^?1) of penthiopyrad on leaf spot and stem rot and the relative efficacy of penthiopyrad and current fungicide standards chlorothalonil, tebuconazole and azoxystrobin. RESULTS: Leaf spot control in plots treated with penthiopyrad at 0.20 kg AI ha^?1 or higher was similar to or better than that for the chlorothalonil standard. The incidence of stem rot for all penthiopyrad treatments was usually less than that for the tebuconazole or azoxystrobin standard treatments. Pod yields for all penthiopyrad treatments were similar to or higher than those for the respective standards. CONCLUSION: Penthiopyrad has excellent potential for management of late leaf spot and stem rot of peanut, and may complement current SBI and QoI fungicides. Copyright © 2008 Society of Chemical Industry     

Evaluation of fungicide application rates,spray schedules and alternative management options for rust and angular leaf spot of snap beans in Uganda

Yield losses due to rust and angular leaf spot (ALS) of snap beans may reach 100% in Eastern Africa. Where susceptible varieties are grown, farmers control these diseases with routine fungicide applications. To determine an optimum application rate and spray schedule for Orius® (tebuconazole 250 g/L), we sprayed 10 mL and 20 mL Orius® per 15 L spray water twice at two trifoliate leaf stage and 50% flowering, and three times at the same stages, with an additional application at pod initiation. In farmers’ fields, we tested the effect of fungicide sprays, use of resistant variety, intercropping, increased plant spacing and farmyard manure on rust and ALS diseases. Application three times of 20 mL Orius® per 15 L spray water reduced rust severity scores by 5.7 and 2.4 in 2010 and 2011, respectively. Lowest rust and ALS severities were observed when a resistant variety, fungicide or farmyard manure was used. Pod yield increments due to disease management ranged between 13% and 242%. Prophylactic fungicide application, use of resistant varieties and farmyard manure can be used to reduce disease severity and improve snap bean quality on smallholder farms.     

Biology,ecology and management of the invasive parthenium weed (Parthenium hysterophorus L.)

Parthenium weed (Parthenium hysterophorus L.) is one of the most aggressive invasive weeds, threatening natural ecosystems and agroecosystems in over 30 countries worldwide. Parthenium weed causes losses of crops and pastures, degrading the biodiversity of natural plant communities, causing human and animal health hazards and resulting in serious economic losses to people and their interests in many countries around the globe. Several of its biological and ecological attributes contribute towards its invasiveness. Various management approaches (namely cultural, mechanical, chemical and biological control) have been used to minimise losses caused by this weed, but most of these approaches are ineffective and uneconomical and/or have limitations. Although chemical control using herbicides and biological control utilising exotic insects and pathogens have been found to contribute to the management of the weed, the weed nevertheless remains a significant problem. An integrated management approach is proposed here for the effective management of parthenium weed on a sustainable basis. © 2014 Society of Chemical Industry     

Weed control with pre-sowing herbicides in irrigated cotton (Gossypium barbadense L.) and groundnut (Arachis hypogaea L.) in the Sudan. II. Economic, labour requirement, crop safety and operational aspects of trifluralin and benfluralin

Soil incorporated. pre-sowing application of trifiuralin in cotton or of benfluralin in gruundnut, each at 1–68 kg a.i., ha, cut labour requirement for handweeding to levels where the tenant could he largely independent of hired labour, Economic returns from a combination of these herbicides plus supportive hand- weeding for herbicide-resistant species compared favourably with those from hand- weeding only as presently recommended. Application and incorporation of trifluralin and benfluralin fited well into existing practices for seedbed preparation and any likely modifications of these. There was no evidence of crop phytoxicity and crop maturity was not affected. Residue analysis indicated no soil residue problems for crops in rotations and no residues were detected in crop seed. Trifluralin applied many months in advance of cotton planting in the dry season, did not start to disappear until the soils were wetted just before couon planting.     

辽宁花生主栽品种(系)对褐斑病和网斑病抗性鉴定

本研究旨在明确辽宁花生主栽品种(系)对花生褐斑病和网斑病的抗性,以期为抗病育种及田间病害防治提供理论依据。试验采用田间自然病圃法,对辽宁主栽的16个花生品种(系)进行了褐斑病和网斑病田间抗性鉴定。结果表明,供试花生品种(系)对两种叶部病害抗性存在显著差异,但缺乏免疫和高抗品种。对花生褐斑病抗性鉴定结果表明,‘阜花17’属抗病类型,‘鲁花11’、‘铁引花2号’、‘良青8号’、‘新花2号’和‘锦花15’属中抗类型,其余属高感或感病类型。对花生网斑病抗性鉴定结果显示:‘鲁花11’、‘铁引花2号’和‘白花生’属抗病类型,‘黑花生’、‘新花2号’、‘花育20’、‘锦花14’、‘新花1号’、‘锦花15’和‘良青8号’属中抗类型,其余属高感或感病类型。多数花生品种(系)对花生叶斑病综合抗性较差。     

槟榔黄化病病原研究及防控中存在的问题及展望

槟榔黄化病是一种由植原体引起的毁灭性病害,现已成为严重制约中国海南槟榔产业健康发展的瓶颈.本文详细介绍了黄化病病原研究方面的进展并分析了存在的问题和争议,归纳了防控中存在的问题;预测了中国槟榔产业发展前景及槟榔黄化病发展趋势,进而对政府、科研院所、高等院校、企业和农户5方提出了建议.最后,对槟榔黄化病治理作了展望.     

不同杀菌剂对当归主要病害的防效及经济效益比较

针对甘肃当归病害逐年加重态势, 采用田间随机区组试验, 分析比较70%噁霉灵WP?50%氯溴异氰尿酸WP和80%代森锰锌WP对当归主要病害防效及经济效益, 以期筛选出最佳防控药剂?结果表明:3种杀菌剂均能不同程度防治当归病害, 其中以50%氯溴异氰尿酸WP 1.86 g/L对褐斑病?麻口病防效最佳, 分别为70.38%~78.75%?84.48%~91.04%, 70%噁霉灵WP 0.34 g/L和80%代森锰锌WP 7.92 g/L次之, 对褐斑病防效分别为59.14%~63.72%?58.14%~62.84%, 对麻口病防效分别为78.61%~83.57%?78.97%~83.57%?50%氯溴异氰尿酸WP 1.86 g/L能很好地抑制当归抽薹, 抑制率达58.63%~63.15%?3种杀菌剂均能明显提高当归药材产量构成因子, 以80%代森锰锌WP 7.92 g/L处理增产增收效果最好, 两年平均增产量高达5 559.91 kg/hm2, 平均经济效益为194 136.65元/hm2, 但投入产出比最低, 为1∶480.63?50%氯溴异氰尿酸WP 1.86 g/L对当归病害防效及抽薹抑制率最高, 投入产出比为1∶634.02, 在此基础上综合考虑病害防效和经济效益, 50%氯溴异氰尿酸WP 1.86 g/L可作为生产上防控当归主要病害的主推药剂?     

植物病害的定义刍议、利弊分析及综合控制

植物病害是一个植物病理学的基本专业术语,是理解和判断植物是否发病的依据。因此,对植物病害的准确定义具有重要意义,有利于正确认知和诊断植物病害。植物病害的发生是一自然现象,其既有“弊”的一面,同时也有“利”的一面,对其利弊的分析和认知,有利于指导病害的综合控制。     

Assessment of the inheritance of resistance and tolerance in cherry (Prunus sp.) to Blumeriella jaapii,the causal agent of cherry leaf spot

Cherry leaf spot (CLS), caused by Blumeriella jaapii, is a serious fungal disease of sour cherry (Prunus cerasus). Cultivar Montmorency, the major cultivar grown in the United States, is highly susceptible to CLS. As many as 10 fungicide sprays can be required each growing season to combat this disease; therefore, developing CLS‐resistant cultivars is a top breeding priority. Germplasm previously reported to be resistant or tolerant to CLS was acquired and incorporated into the sour cherry breeding programme at Michigan State University (MSU) and included three cherry species: sour cherry, sweet cherry (P. avium), and the wild species P. canescens. This study aimed to: (i) compare the CLS disease progression profile of the susceptible cultivar Montmorency with those of the resistant and tolerant germplasm; and (ii) gain an understanding of the inheritance of these resistance and tolerance traits by evaluating the host response of progeny individuals belonging to families derived from this germplasm. Significant differences were observed between the susceptible Montmorency and the tolerant and resistant accessions in their response to CLS and its progression during the growing season. Evaluation of the CLS host responses of progeny individuals derived from this germplasm supported a dominant two‐gene model for P. canescens‐derived resistance and a recessive gene model for sweet cherry‐derived tolerance. These insights into disease progression and trait inheritance improve the efficiency and potential success of breeding sour cherry cultivars with durable resistance to CLS.     

Black leaf spot and circular leaf spot of <Emphasis Type="Italic">Farfugium japonicum</Emphasis> (L.) Kitamura caused by <Emphasis Type="Italic">Phoma</Emphasis> spp.

In May 1998 and 1999, two types of leaf spot (black type and brown type) caused by Phoma spp. were found on Farfugium japonicum in Tokyo and in Gunma Prefecture, Japan. The fungus isolated from black-type lesions caused only black-type lesions, and the fungus from brown-type lesions caused only brown-type lesions. We propose to name these diseases black leaf spot of F. japonicum (kokuhan-byo in Japanese) for the disease with black lesions and circular leaf spot of F. japonicum (rinmon-byo in Japanese) for the disease with brown lesions. This is the first report on leaf diseases of F. japonicum caused by Phoma spp.     

松针褐斑病病原、抗病机制和综合治理技术研究

湖南省1994年8月首次发现松针褐斑病，主要分布在江华县、江永县和双牌县11个乡镇场，面积为467．8hm^2，1995年至1997年，通过实施砍、剪、清、造、防、监、检综合治理，病害的危害面积减少到22．7hm^2，下降了95．1％，发病区严重死亡株率控制在1％以下。同时研究证实不同的湿地松病原菌株之间的脂酶图谱中存在不同的差异，湿地松、黄山松和马尾松在超尾化物歧化酶（SOD）活性、苯丙氨酸角氨酶（PAL）活性和木质素含量的差异反映出寄主的抗病性差异；病害发生流行区域性研究结果表明全省处于主要流行区县（市）有12个，偶然流行区的县（市）25个，相对安全区的县（市）71个。