Rice Diseases in Nigeria

Abstract

The two major fungal diseases of rice in Nigeria are rice blast (Pyricularia oryzae Cav.) and brown spot (Cochliobolus miyabeanus (Ito and Kuribayashi) Dreschler ex Dastur). The loss in grain yield attributable to these diseases ranges from 11.5–39.6% and 12–43% respectively, Mancozeb, blasticidin-S, fentin hydroxide, benomyl and edifenphos as foliar sprays effectively control rice blast in the laboratory and field. Brown spot is controlled by spraying with thiram, mancozeb or blasticidin-S. A more useful approach to the control of these diseases being adopted in Nigeria is the search for horizontally resistant varieties. Other fungal diseases of rice in Nigeria are the green smut (Ustilaginoidea virens (Cooke) Tak.), basal sheath rot (Rhizoctonia solani Kühn), sheath blight (Corticium sasakii (Shirai), Matsumoto.), leaf scald (Rhynchosporium oryzae Hashioka and Yokogi), narrow brown leaf spot (Cercospora oryzae Miyake) and bakanae disease, a foot rot caused by Fusarium moniliforme Sheldon. Two suspected cases of virus diseases have been reported; grassy stunt disease (transmitted by Nilaparvata lugens Stal.), and orange leaf disease (transmitted by Inazuma dorsalis (Motschulsky). No bacterial disease of rice has been found in Nigeria.     

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     

Agricultural and Horticultural Fungicides - Past,Present and Future

Abstract

Maize is produced primarily in temperate and warm-temperate zones of the world, but its production is increasing in many tropical regions. Some diseases are common to both of these environmental zones even though their importance may vary greatly. Other diseases are confined to a single zone. The important factors influencing the geographical distribution of maize diseases and some of their vectors are temperature, moisture, cultural practices, and the type and diversity of maize germplasm used. Within tropical zones maize diseases may be segregated into those in humid environments and those favoured by drier, upland climatic conditions. Elevation within the tropics, as this influences temperature, is a factor in distribution of maize diseases.

Late wilt, banded leaf and sheath blight, and Rhizoctonia, Botryodiplodia and grey ear rots occur only in the tropical zone and the warm, temperate areas, while the Sclerospora-incited downy mildew diseases, southern rust, Pythium and bacterial stalk rots, Curvularia leaf spot, and ear rot caused by Diplodia macrospora are much more prevalent there, occurring only occasionally beyond latitudes 34°N and 34°S. Conversely, bacterial wilt, eye spot, and yellow leaf blight have been found to occur only in the temperate zones. Ergot has been found only in a few locations at high elevation (250–270 m) in Central Mexico. Northern leaf blight, common rust, and stalk and ear rots caused by Diplodia maydis and Gibberella zeae prevail in the temperate zones and at high elevations and in winter seasons within tropical latitudes.     

Cylindrocladium brown leaf spot on Howea belmoreana caused by Calonectria ilicicola (anamorph: Cylindrocladium parasiticum) in Japan

Brown leaf spot disease caused by Cylindrocladium was found on Howea belmoreana on Hachijojima Island, Tokyo, Japan, in December 2001. Typical symptoms were incited after artificial inoculation. A culture of white mycelia, isolated from leaf spot symptoms, produced reddish perithecia of a nectriaceous fungus. Based on morphological and molecular analyses, this fungus was identified as Calonectria ilicicola (anamorph: Cylindrocladium parasiticum). Pathogenicity of this fungus on five plants cultivated on Hachijojima Island was confirmed by artificial inoculation. This report is the first on Cylindrocladium brown leaf spot of H. belmoreana caused by C. ilicicola (anamorph: Cy. parasiticum).     

Pseudostem rot caused byCorticium rolfsii,a new disease ofMusa sp. in Tamil Nadu,India

In 1987 a new disease, called pseudostem rot, was observed on 3–5-month-old banana plants(Musa sp.) cv. ’Robusta’. The pathogen was isolated in pure culture and identified asCorticium rolfsii (Sacc.) Curzi, teleomorph ofSclerotium rolfsii Sacc. The teleomorphic stage of the fungus was observed inside the pseudostem sheath. The pathogen produced leaf spot diseases (by basidiospores) on 16 tested host plants from various families.     

Chemical Weed Control in Tobacco in Trinidad

Abstract

Ramie, the vegetable fibre, is obtained from the stem of Boehmeria nivea (L.) Gaud, and is used in many textile products. It is grown in tropical, sub-tropical and temperate regions and the main countries where it is grown are China, Brazil and the Philippines. However, it is only a minor crop in terms of world trade. The diseases of ramie are discussed in relation to their occurrence, symptoms and control measures. The major and most widespread diseases are white fungus caused by Rosellinia necatrix, leaf spot caused by Cercosporo spp. and Phyllosticta spp., seedling rot caused by Rhizoctonia solani, cane rot caused by Macrophomina phaseolina and eye rot caused by Myrothecium roridum. A number of diseases of minor importance are also reviewed.     

A survey of rice diseases in Bangladesh

Abstract

A survey conducted during 1979–81 in Bangladesh revealed 20 rice diseases, including two viral, two bacterial, 13 fungal, two nematode and one micronutrient deficiency problem. Of these diseases. 16 appeared as major during the period under report. The number of diseases were 17, 16 and 16 during the Boro. Aus and transplant Aman seasons, respectively, with 12 common in all three seasons. Thirteen diseases including bacterial blight, bacterial leaf streak, sheath blight, sheath rot, blast, brown spot, grain spot, stem rot and leaf scald were classified as major; and tungro, bakanae, cercospora leaf spot and zinc‐deficiency were classified as either major or minor, and were common to all regions. Diseases not common in all regions were stack burn, root knot, and ufra classified as major or minor, and false smut, seedling blight. Yellow dwarf and damping off which were always classified as minor. Diseases which were typical for Boro. Aus and transplant Aman seasons were seedling blight and damping off. Yellow dwarf, and false smut respectively. Aus the most humid and warmest season, and the coastal humid areas experienced more major diseases. Seasonal and regional differences in the disease incidence appeared related to agro‐climatic variations.     

玉米几种重要病害蛋白质组学研究进展

 本文介绍了玉米镰孢菌和黄曲霉穗腐病、腐霉菌苗期病害抗性相关蛋白, 以及在我国曾严重发生的玉米弯孢霉叶斑病菌致病性相关蛋白质组和寄主抗性相关蛋白质组的研究进展, 探讨了利用蛋白质组学技术深入研究玉米-病原菌互作的优势和重要方向。     

Relating plant and pathogen development to optimise fungicide control of phoma stem canker (<Emphasis Type="Italic">Leptosphaeria maculans</Emphasis>) on winter oilseed rape (<Emphasis Type="Italic">Brassica</Emphasis><Emphasis Type="Italic">napus</Emphasis>)

In winter oilseed rape experiments at Rothamsted in 2000/01 to 2002/03 growing seasons, the severity of phoma stem canker epidemics in summer depended on the timing of phoma leaf spot epidemics in the previous autumn, and hence on the timing of Leptosphaeria maculans ascospore release. The first major release of L. maculans ascospores was earlier in 2000 (26 September) and 2001 (18 September) than in 2002 (21 October). Consequently, the autumn phoma leaf spot epidemic was also earlier in 2000 and 2001 than in 2002. The resulting stem canker epidemics were severe by harvest (July) in 2001 and 2002 but not in 2003. No correlation was found between the severity or duration of phoma leaf spotting (lesion days or lesion °C-days) and the subsequent severity of phoma stem canker epidemics. Rates of leaf production and loss were similar in the three growing seasons. Out of ca. 25 leaves produced on plants during each season, leaf numbers 10–14 generally remained on plants for the longest. Treatment with flusilazole + carbendazim in autumn decreased the severity of phoma leaf spotting for several weeks after treatment, decreased the severity of stem canker the following summer and increased yield significantly in 2001 and 2002 but not in 2003. The most effective timings for flusilazole + carbendazim application were when leaves 7–11 were present on most plants and at least 10% of plants were affected by phoma leaf spot. Two half-dose applications of fungicide reduced phoma stem canker and increased yield more than a single full dose application when phoma leaf spot epidemics were early (<800 °C-days after sowing).     

甘肃省红豆草病原真菌鉴定及病害发生动态调查

为明确甘肃省红豆草的病害种类、发生动态和危害状况,采用病原物分离与培养、形态学及分子生物学鉴定和致病性测定确定红豆草病害种类,于2012—2013年在通渭、渭源、榆中和碌曲4县调查各病害的发病率以确定发生动态,观察病害田间发生特点并结合调查数据评价其重要性。结果表明,4县共发生真菌性病害12种,分别为大茎点霉叶斑病(病原为大茎点霉属真菌Macrophoma sp.)、壳针孢叶斑病(病原为歪头菜壳针孢Septoria orobina)、炭疽病(病原为白蜡树刺盘孢Colletotrichum spaethianum)、黑秆病(病原为红豆草壳二孢Ascochyta onobrychis、菠菜刺盘孢C.spinaciae和链格孢Alternaria alternata混合侵染)、壳二孢叶斑病、茎点霉叶斑病、尾孢叶斑病、柱格孢白斑病、匍柄霉叶斑病、链格孢黑斑病、锈病和白粉病,其中大茎点霉属真菌、白蜡树刺盘孢和菠菜刺盘孢在红豆草上首次发现;尾孢叶斑病和壳针孢叶斑病为甘肃新记录病害;大茎点霉叶斑病为世界新病害,仅于碌曲县发现。白粉病、锈病、链格孢黑斑病发生于红豆草生长后期,其它病害则始于6月;6—9月危害加重的为黑秆病和柱格孢白斑病,发病率最高达89.7%和96.0%;危害渐轻的为茎点霉叶斑病、壳二孢叶斑病和壳针孢叶斑病,发病率最高达88.7%、57.4%和45.1%。黑秆病和茎点霉叶斑病在甘肃省目前危害最重。     

杀菌剂银泰对5种植物病害的药效试验

银泰是以银杏中具有生物活性的化学物质的结构为先导化合物，采用人工模拟技术创新合成的一种农用杀菌剂，田间对5种植物病害的药效试验证明：对苹果腐烂病、苹果轮纹病、番茄灰霉病、玉米大斑病及小麦纹枯病均具有良好的防治效果，且优于常用的杀菌剂。     

玉米三种叶斑病混发时的流行过程及产量损失研究

 通过2年的田间小区人工接种试验,观察比较了玉米大斑病、弯孢叶斑病和灰斑病单独及混合发生时的流行过程及对玉米产量损失的影响。结果表明,在病害混发初期,病害间无明显的负相关性,随着病情的发展,病害间的负相关性逐渐增大并达到显著水平,说明病害间有明显的抑制作用。病害混发时造成产量损失并不完全等于各病害单独造成损失之和,其中大斑病和弯孢叶斑病、弯孢叶斑病和灰斑病混合发生所造成的损失约为各病害单独造成损失之和的76%～88%,大斑病和灰斑病混合发生所造成的损失可近似看作两种病害各自引起产量损失之和,3种病害同时发生时最终损失率约为各自造成损失之和的67%～72%。     

新化合物吡唑并嘧啶衍生物(BDO-1)和哒嗪酮衍生物(PDZ-1)的诱导抗病性研究

吡唑并嘧啶衍生物 ((E)-N-(2-氟-4-三氟甲基苯乙烯基)-1-甲基-1H-吡唑并[3,4-d]嘧啶-4-胺,简称BDO-1) 和哒嗪酮衍生物 (4-羟基-1-(4-甲氧基苯基)-6-氧代-1,6-二氢吡嗪-3-甲酸甲酯,简称PDZ-1) 是由华东理工大学创制并合成的新化合物,本研究分别测定了其离体抑菌活性及其诱导抗病活性,并对田间应用技术进行了研究。结果表明:离体抑菌试验结果显示,BDO-1和PDZ-1对供试黄瓜的尖孢镰孢菌和多主棒孢菌并无杀菌活性;温室盆栽试验发现,2个化合物对7种蔬菜病害具有明显的诱导抗病活性,其中:BDO-1在10 mg/L下对黄瓜细菌性角斑病、黄瓜棒孢叶斑病、黄瓜枯萎病、黄瓜霜霉病、番茄早疫病、番茄灰叶斑和辣椒疫病的防治效果分别为58.81%、61.79%、69.88%、64.14%,54.42%、54.85%和63.59%;PDZ-1在10 mg/L下对黄瓜细菌性角斑病和黄瓜棒孢叶斑病的防治效果分别为62.33%和59.15%。田间防治效果验证结果表明,BDO-1和PDZ-1对黄瓜枯萎病的防治效果分别为62.95 %和48.45%。研究发现,BDO-1和PDZ-1在质量浓度为10 mg/L、诱导5次、每次间隔5d的条件下施用,对黄瓜枯萎病和棒孢叶斑病可发挥最佳防治效果。     

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.     

Characterization of Lasiodiplodia species causing leaf blight,stem rot and fruit rot of fig (Ficus carica) in Malaysia

Fig (Ficus carica) is an exotic deciduous plant that is grown worldwide. Fungal diseases pose a major threat to fig plants, affecting their fruit quality and production. This study was conducted to characterize the fungal isolates associated with leaf blight, stem rot and fruit rot of F. carica in Malaysia through morphological analysis, DNA sequencing, multigene phylogenetic analysis and pathogenicity tests. From September 2018 to March 2019, 30 blighted leaves and 30 rotted stems and fruits of F. carica were collected from several nurseries in Malaysia. Thirty fungal isolates that belonged to Lasiodiplodia theobromae (27 isolates) and L. brasiliensis (three isolates) were identified based on morphological characteristics, comparison of DNA sequences and phylogenetic analysis of the internal transcribed spacer (ITS), elongation translation factor 1-α (tef1-α), β-tubulin (tub2) and DNA-directed RNA polymerase II subunit (rpb2). Among the 27 isolates of L. theobromae, nine isolates were obtained from leaves, eight isolates from stems and 10 isolates from fruits, whereas the three isolates of L. brasiliensis were obtained from stems (two isolates) and a leaf (one isolate). The results of pathogenicity tests revealed that L. theobromae and L. brasiliensis isolates were responsible for leaf blight and stem rot of F. carica, whereas fruit rot was caused by L. theobromae isolates. The present study highlighted two different species, L. theobromae and L. brasiliensis, as the causal agents of leaf blight and stem rot of F. carica. Additionally, L. theobromae caused fruit rot of F. carica in Malaysia.     

海南省胡椒主要病害现状初步调查

为明确海南省胡椒主要病害种类及发生情况,对海南省琼海、文昌、万宁、海口、定安、临高、儋州、澄迈、屯昌等9个市(县)进行了调查,结果表明:(1)目前危害海南胡椒生产的主要病害有9种,其中真菌病害5种,为胡椒瘟病、胡椒枯萎病、胡椒根腐病、胡椒炭疽病和胡椒煤烟病;细菌病害1种,为胡椒细菌性叶斑病;病毒病害1种,为胡椒花叶病;其他病害2种,为胡椒根结线虫病和胡椒藻斑病。(2)分布广且危害严重的有胡椒瘟病、胡椒花叶病、胡椒根结线虫病和胡椒枯萎病。     

World-Wide Importance of Phoma Stem Canker (Leptosphaeria maculans and L. biglobosa) on Oilseed Rape (Brassica napus)

Phoma stem canker is an internationally important disease of oilseed rape (Brassica napus, canola, rapeseed), causing serious losses in Europe, Australia and North America. UK losses of €56M per season are estimated using national disease survey data and a yield loss formula. Phoma stem canker pathogen populations comprise two main species, Leptosphaeria maculans, associated with damaging stem base cankers, and Leptosphaeria biglobosa, often associated with less damaging upper stem lesions. Both major gene and quantitative trait loci mediated resistance to L. maculans have been identified in B. napus, but little is known about resistance to L. biglobosa. Leptosphaeria maculans, which has spread into areas in North America and eastern Europe where only L. biglobosa was previously identified, now poses a threat to large areas of oilseed rape production in Asia. Epidemics are initiated by air-borne ascospores; major gene resistance to initial infection by L. maculans operates in the leaf lamina of B. napus. It is not clear whether the quantitative trait loci involved in the resistance to the pathogen that can be assessed only at the end of the season operate in the leaf petioles or stems. In countries where serious phoma stem canker epidemics occur, a minimum standard for resistance to L. maculans is included in national systems for registration of cultivars. This review provides a background to a series of papers on improving strategies for managing B. napus resistance to L. maculans, which is a model system for studying genetic interactions between hemi-biotrophic pathogens and their hosts.     

Occurrence,genetic diversity and pathogenicity characteristics of Pseudomonas viridiflava inducing alfalfa bacterial wilt and crown root rot disease in Iran

Alfalfa (Medicago sativa), the world’s most influential forage crop, is infected by many diseases such as alfalfa bacterial wilt disease. The causal agent of bacterial crown and root rot and wilt disease is Pseudomonas viridiflava, which is a substantial pathogen of alfalfa worldwide. This pathogen spreads through the xylem and under field conditions, plants show growth stunting, chlorosis and wilting symptoms not previously reported. In this study- the first on Pseudomonas viridiflava on alfalfa from Iran, we have investigated the pathogenicity and genetic diversity of Pseudomonas viridiflava in some parts of Iran. To survey the causal agent of the disease, symptomatic plants were collected from the main alfalfa growing area. Pathogenicity of the collected strains was confirmed on alfalfa plants under green-house conditions using a completely randomized design. Determination of bacterial strains was done based on standard bacteriological methods and PCR assay using specific primers. Effects of bacterial strains on wet weight, dry weight, stem length and root length of infected plants were measured and the data were analyzed by SAS software and Duncan’s assessment. The diversity of liquid cellular proteins of bacterial strains was examined on Polyacrylamide gel. To delineate of genetic diversity the total DNA was drawn out. Fourteen random primers were used in a RAPD test. To sketch the dendrogram, RAPD fragments were used to calculate genetic diversity with NTSYS software. This data showed pathogenicity and genetic diversity of Pseudomonas viridiflava in Iran.     

The first report of tomato foot rot caused by <Emphasis Type="Italic">Rhizoctonia solani</Emphasis> AG-3 PT and AG-2-Nt and its host range and molecular characterization

Foot rot of mature tomato plants was found in four cities of Hokkaido, Japan, from 2004 to 2007. Six of eight isolates obtained from damaged tissues were identified as Rhizoctonia solani anastomosis group (AG)-3, and the remaining two isolates belonged to AG-2-1. We compared these isolates with nine reference isolates including the different subgroups in AG-3 (PT, TB and TM) and AG-2-Nt (pathogen of tobacco leaf spot) within AG-2-1 in terms of pathogenicity to tomato, tobacco and potato. All eight isolates caused foot rot on tomato. The six AG-3 isolates caused stem rot on young potato plants. While, all reference isolates of AG-3 PT causing stem rot of young potato plants incited foot rot on tomato. The two AG-2-1 isolates and an AG-2-Nt reference isolate caused severe leaf spot on tobacco leaves. The sequences of rDNA- ITS region and rDNA-IGS1 region of the AG-3 isolates showed high similarity to that of AG-3 PT isolates. Phylogenetic tree based on ITS and IGS1 regions of rDNA indicated that the AG-2-1 isolates from tomato formed a single clade with AG-2-Nt isolates and that they were separate from Japanese AG-2-1 isolates (culture type II). Pathogenicity tests and DNA sequence evaluation of the causal fungi revealed that the present isolates of AG-3 and AG-2-1 belonged to AG-3 PT and AG-2-Nt, respectively. This is the first report of tomato foot rot caused by R. solani in Japan.