Effect of rice growth stages and silicon on sheath blight development

ABSTRACT The objective of this study was to determine the effect of silicon (Si) and rice growth stages on tissue susceptibility to sheath blight (Rhizoctonia solani Kühn) under controlled conditions. Rice plants (cv. Rio Formoso) were grown in pots containing low-Si soil amended with Si at 0, 0.48, 0.96, 1.44, and 1.92 g pot(-1) and inoculated with R. solani at the following days after emergence: 45 (four-leaf stage), 65 (eight-leaf stage), 85 (tillering), 117 (booting), and 130 (panicle exsertion). For plants inoculated with R. solani at all growth stages, Si concentration in straw increased as rate of Si increased from 0 to 1.92 g pot(-1). Concentration of calcium in the straw did not differ among plant growth stages. Although incubation period was not affected by the amount of Si added to the soil, this variable was shorter at booting and panicle exsertion stages. As the rates of Si increased in the soil, the total number of sheath blight lesions on sheaths and total area under the relative lesion extension curve decreased at all plant growth stages. The severity of sheath blight was lower at booting and panicle exsertion stages as the rates of Si increased in the soil. In general, plants grown in Si-nonamended pots and inoculated with R. solani were more vulnerable to infection at all growth stages, but especially at 45 days after emergence. Plant dry weights for inoculated plants increased as the Si rates increased from 0 to 1.92 g pot(-1). The greatest dry weight increases occurred for plants inoculated at booting and panicle exsertion stages. Si fertilization is a promising method for controlling sheath blight in areas where soil is Si deficient and when cultivars that exhibit an acceptable level of resistance to sheath blight are not available for commercial use.     

云南籼稻主栽品种对白背飞虱的抗性筛选

为明确云南籼稻主栽品种对白背飞虱Sogatella furcifera(Horváth)的抗虫性及其影响产量的水稻关键生育期,为抗虫品种选育和推广提供参考依据,本文利用苗期和分蘖盛期单株接虫鉴定、成株期(移栽期—乳熟期)田间自然种群发生鉴定等方法,测定了云南籼稻区31个水稻主栽品种对白背飞虱的抗虫性及其产量。结果表明,苗期有7个品种表现高抗,23个品种表现中抗—中感,1个品种表现高感;分蘖期有20个品种表现高抗,有11个表现中抗—中感;成株期田间自然种群鉴定,31个品种成株期白背飞虱田间自然种群的累计虫量都超过了对照品种TN1,均表现为感虫。单株接虫鉴定多数品种表现抗虫,而大田期自然种群鉴定则全部表现为感虫,一定程度说明了云南籼稻区主栽品种对白背飞虱具有耐害性而无抗生性。移栽期、孕穗期、抽穗期百丛虫量与有效穗数呈显著的负相关性;移栽期、孕穗期和抽穗期的百丛虫量是造成有效穗数少和产量低的关键因子。移栽期、孕穗期和抽穗期是防治白背飞虱的关键时期。     

水稻穗腐病病菌致病性、发生规律及防控技术研究

穗腐病是近年发生危害严重的水稻穗部病害.本研究对穗腐病的发生、流行原因进行了分析,分离了病原菌并测定了致病性,筛选了防治该病的杀菌剂并进行了田间防效试验.结果表明,紧穗型的粳稻及籼/粳杂交稻组合较穗型松散的籼稻及其杂交组合更易感病.水稻孕穗后期-抽穗扬花期遇阴雨高湿、温暖天气该病发生危害重.用分离到的4个菌(层出镰刀菌、澳大利亚平脐蠕孢菌、新月弯孢菌和细交链孢菌)进行人工接种,均能使稻粒感病,初步确定层出镰刀菌为主要初侵染菌.室内抑菌测试结果显示,5 mg/L以上浓度的多菌灵、咪鲜胺和苯醚甲环唑·丙环唑(爱苗)对层出镰刀菌生长的抑制效果达到81.31％～100％.抑制中浓度为0.000 7～0.947 6 mg/L.田间试验结果表明,在水稻孕穗后期和抽穗扬花期用三唑酮、多菌灵或甲基硫菌灵喷雾防治一次,防效在70％左右.     

江西省细菌性条斑病菌的致病型划分和水稻抗性资源的鉴定

为探明江西省水稻细菌性条斑病菌(Xanthomonas oryzae pv.oryzicola,Xoc)的致病力分化水平和品种资源的抗病性,本研究利用IRBB5、IRBB14、IR24、IRBB4、IRBB21和金刚30等6个鉴别品种,将分离自江西6个稻区的129株Xoc菌株划分为C1~C9 9个致病型;发现仅C5对鉴别品种IRBB4、C7对鉴别品种IRBB21表现为强互作关系;不同稻区的Xoc优势种群呈现多样性。孕穗期抗性测定结果显示:124个籼稻品种中,对C2型菌株5-16表现为中抗的品种仅占8.06%,对C6型菌株08-3-2表现为抗的品种占14.5%;252个东乡野生稻单株中,1株单株(东113)对C2型菌株表现高抗,14个单株表现抗性。东乡野生稻苗期注射接种结果显示,苗期抗病性与孕穗期抗性呈显著相关性,但苗期抗病性普遍低于孕穗期抗性,仅东113表现为中抗。但东乡野生稻对于Xoc的抗病性明显强于栽培稻,从野生稻中寻找抗性资源将是培育抗病品种的理想途径之一。     

水稻穗部农艺性状与稻曲病抗性的相关性分析

 人工接种试验和田间多年自然发病调查发现,目前生产上应用的水稻品种均感稻曲病;但在自然条件下,不同水稻品种稻曲病的发生程度存在较大差异,可以人为的分为多病粒高感品种和寡病粒相对抗病的品种。为了探究水稻穗部性状与其病害抗性间的关系,本文对孕穗期不同阶段的不同水稻品种的穗部性状进行了比较分析。结果发现表型为多病粒的高感多病粒品种与表型为寡病粒的相对抗病的品种之间在穗子大小、小花密度、穗鞘闭合程度和密封性、旗叶面积等方面均存在明显差异,寡病粒相对抗病的水稻品种穗鞘闭合程度优于高感多病粒品种。     

Weeds

Abstract

The effects of simulated rat damage (stem cutting) on IR-8 rice yield was examined. Fields were subjected to four damage levels: 0 (control), 10, 25 and 50% of the stems cut. A modified split-plot sampling design was used with ten 1 m² plots tested at each damage level in three growth stages: tillering, booting and maturity. Each of the 120 plots (2,400 hills) was harvested and yields compared by Analysis of Variance and Least Significant Difference (LSD) tests. Ten perpent of all stems removed during the tillering stage produced growth compensation and a higher yield resulted. Trends in rice yields for different damage levels showed that the later damage occurred, the greater the yield loss. An LSD analysis of yields for the damage levels revealed no significant differences during tillering. At booting, significant differences (P < 0.05) in yields were noted with > 10% of the stems cut. At maturity, yields for all damaged levels differed significantly (P < 0.01). The results of this study demonstrated that rat damage in rice up to the booting stage did not affect yield significantly. From an economic standpoint, rodent control by field baiting before booting stage is not recommended in monsoon rice.     

水稻稻曲病室内人工接种技术

为提高稻曲病人工接种的发病效果和稳定性,在温棚条件下采用水稻孕穗期注射接种法分别研究了稻曲病菌不同接种体、培养时间、接种浓度和接种时期的接种效果。采用病菌马铃薯蔗糖液体培养基（potato sucrose broth,PSB）作为接种体,其穗发病率为100%,明显好于病菌米糠培养液（23.33%）。病菌在PSB中培养5～7天接种效果较好,随病菌培养天数的延长,接种效果明显下降。接种的分生孢子浓度越低水稻病穗率和病粒数也越低。在水稻品种两优培九孕穗中后期,采用含分生孢子浓度为4×106个/mL的病菌PSB培养液注射接种,穗发病率达100%,平均病粒数35.1粒,最高达87粒。研究表明,温棚条件下建立的稻曲病人工接种技术能获得稳定的发病效果,并可区别水稻品种间的抗性差异。     

强化栽培条件下干湿灌溉对水稻生长的影响

在中国水稻研究所试验场研究了强化栽培条件下干湿灌溉对水稻生长的影响.结果表明:在强化栽培条件下采取干湿灌溉处理,在返青期、分蘖期、孕穗期和抽穗开花期比对照分别节水1.4%、12.4%、9.0%和11.2%;水分生产效率达0.93 kg/m3,比CK处理提高34.2%;干4～5 d之后,再复水4～5 d,土壤氧化还原电位循环变化,有利于提高土壤氧化还原电位,改善土壤的通气状况,提高根系活力,促进大穗,穗粒致明显增加,单产平均提高6.9%.     

Geographic distribution of false smut disease of rice in India and efficacy of selected fungicides for its management

False smut disease of rice caused by the fungus Ustilaginoidea virens, has become a serious production constraint in various rice-growing regions of India. Analysis of rice false smut disease survey data of last 24 years revealed significant changes in the intensity of the disease in various rice-growing regions of India over the years. We evaluated three fungicide formulations viz., trifloxystrobin-tebuconazole (TT) combination (0.04%), kresoxim methyl (KM) (0.1%) and propiconazole (PC) (0.1%) for their effectiveness against false smut disease of rice. Under in vitro condition, TT and PC completely inhibited the fungal growth while KM inhibited the growth by 80%. We evaluated the efficacy of these chemicals in a multi-location trial in 3 hot spot locations, consecutively for three years. A single fungicide spray was given in 3 different crop stages (booting, 50% panicle emergence and 100% panicle emergence). The results indicated that all the treatments significantly reduced the percentage of both infected panicles and spikelets in all the three locations. Both TT and PC were most effective in reducing the disease intensity and increasing the yield when applied either in booting or in 50% panicle emergence stage.     

水稻品种抗褐飞虱不同生物型与其主要农艺性状的关系研究

对水稻品种抗褐飞虱不同生物型与其主要农艺性状的关系研究结果表明,水稻品种抗褐飞生物型Ⅱ与分蘖力相关显著,与始穗期、抽穗期、齐穗期、生育期、株高、有效穗、穗粒数、结实率、千粒重相关不显著。水稻品种抗褐飞虱孟加拉型与始穗期、抽穗期、齐穗期、有效穗相关显著;与生育期相关极显著;与分蘖力、株高、穗粒数、结实率、千粒重相关不显著。     

四川水稻不同生育阶段的干旱风险评估

水稻是四川最主要的粮食作物,而干旱是制约水稻生产的主要因素,四川省春旱、夏旱和伏旱灾害频发,常导致水稻减产。本研究基于气象资料、水稻灾情史料和生育期资料,选取湿润指数距平率作为水稻干旱指标,构建了四川水稻干旱等级,并利用灾情样本进行了验证。在此基础上,分析了1961-2015年四川水稻不同种植区不同生育阶段的干旱时空变化特征及风险分布状况。结果表明:从时间变化看,近55年来,水稻移栽～孕穗期干旱总站数平均每10年增多0.56个,其中轻旱和重旱平均每10年分别增多0.20个和0.41个,而中旱基本不变;孕穗～开花期干旱总站数平均每10年减少0.49个,其中中旱和重旱平均每10年均减少0.22个,而轻旱基本不变;开花～成熟期干旱总站数平均每10年增多0.54个,其中轻旱和重旱平均每10年分别增多0.23个和0.55个,而中旱基本不变。干旱频率的分布特征为:移栽～孕穗期的干旱频率呈现中部高、西南部和东北部低的特征,高发区主要分布在北部的绵阳-南部的宜宾一线(36%～58.2%);孕穗～开花期的干旱频率由西向东递增,高发区主要分布在盆地北部和东北部(36%～61.9%);开花～成熟期的干旱频率呈由西向东递增的趋势,高发区主要分布在盆地东北部和盆南的局部地区(30%～47.3%)。水稻干旱风险分布为:移栽～孕穗期较高风险区和高风险区主要集中在德阳、资阳和宜宾等地;孕穗～开花期较高风险区和高风险区主要在盆地中部和东北部;开花～成熟期较高风险区和高风险区主要在盆地东北部和盆南的局部地区。     

稻飞虱自然种群变动与药剂防治技术研究

模拟稻飞虱迁入和田间系统调查结果表明：褐飞虱增殖倍数与迁入基数关系不显著，而与水稻生育期有密切关系，最高虫量在孕穗至齐穗期。白背飞虱最高虫量在分蘖末期，其数量和结构变化与水稻生育期无明显关系。若虫是为害水稻的主要虫态。药剂防治试验结果表明：选用虱纹灵防治稻飞虱可兼治纹枯病，优于叶蝉散和甲胺磷。防治１次以水稻孕穗初期施药（均在低龄若虫高峰时）为好。防治２次以始穗期为适期。     

褐稻虱为害损失测算方法的研究

进行盆栽单株罩笼接虫试验,测定褐稻虱三龄若虫在水稻分蘖末、孕穗和乳熟期,一龄若虫和成虫在孕穗期为害15天所造成的产量损失。根据褐稻虱的发育历期及其与累计取食量的关系,推算出每头褐稻虱在各虫龄期内的平均为害损失,由此推导出不同虫龄若虫和成虫的逐日为害损失率模型。探讨了一种较为准确的褐稻虱为害损失的测算方法。     

稻飞虱自然种群变动与药剂防治技术研究

模拟稻飞虱迁入和田间系统调查结果表明：褐飞虱增殖倍数与迁入基数关系不显著，而与水稻生育期有密切关系，最高虫量在孕穗至齐穗期。白背飞虱最高虫量在分蘖末期，其数量和结构变化与水稻生育期无明显关系。若虫是为害水稻的主要虫态。药剂防治试验结果表明：选用虱纹灵防治稻飞虱可兼治纹枯病，优于叶蝉散和甲胺磷。防治1次以水稻孕穗初期施药（均在低龄若虫高峰时）为好。防治２次以始穗期为适期。     

沿淮中稻害虫优化防治技术研究

在田间系统调查和试验的基础上,研究了安徽沿淮中稻主要害虫稻纵卷叶螟和稻飞虱的防治策略和优化防治措施。结果表明,采用在水稻大田生长前期（水稻移栽至7月上旬）不施药,保护和培育天敌对害虫的自然控制作用,在水稻大田生长中期（7月中旬至8月初）和后期（8月上旬及以后）抓关键期防治的策略,以及在水稻大田生长中期/后期使用氯虫苯甲酰胺+噻嗪酮/氯虫苯甲酰胺+噻嗪酮、氯虫苯甲酰胺+噻嗪酮/丙溴磷+吡蚜酮、丙溴磷+吡蚜酮/氯虫苯甲酰胺+噻嗪酮等药剂组合的防治措施,可以有效控制害虫为害、满足生产实际的需要。     

超级稻甬优6号褐飞虱发生危害与防治指标研究

通过对超级籼粳杂交稻甬优6号不同生育期接入不同虫量褐飞虱研究其危害与产量损失的关系,结果表明超级稻甬优6号分蘖期、孕穗期、灌浆期褐飞虱接入虫量（X）与其产量损失率（Y）呈显著或极显著的相关关系,其相关模型分别为：分蘖期Y=9.08X-8.333 3(n=6,R=0.842 5*)、孕穗期Y=3.741 4X-6.057 1(n=6,R=0.900 8*〖KG-*2〗*)、灌浆期Y=0.122X-1.0(n=6,R=0.958 3*),从而拟定超级稻甬优6号分蘖期、孕穗期、灌浆期的防治指标分别为2.0、3.0、35.0头/丛,确保超级稻甬优6号优质高产,为超级稻甬优6号褐飞虱的持续控制提供直接的依据。     

茉莉酸甲酯诱导大田水稻抗白叶枯病的效应研究

本研究以感白叶枯病水稻品种‘温229’为试验材料,通过茉莉酸甲酯(MeJA)浸种和喷雾处理幼苗期和孕穗期水稻,探索MeJA诱导大田水稻抗白叶枯病的效应。水稻幼苗期,0.004mmol/L MeJA浸种、0.1mmol/L MeJA喷雾、0.004mmol/L MeJA浸种后再用0.1mmol/L MeJA喷雾处理,均表现诱导幼苗抗白叶枯病的作用,其诱导效果最高达27.65%;其中,MeJA浸种再喷雾双重处理的效果与单一喷雾处理差异不显著,但与单一浸种处理达到显著性差异水平;水稻孕穗期,0.05~2.00mmol/L的MeJA喷雾后均可降低白叶枯病的病情指数,其中2011年MeJA诱导效果最佳的浓度为0.50mmol/L,而2012年和2013年则为1.00mmol/L,诱导效果最高为17.17%。以上结果表明,MeJA处理可有效缓解大田水稻幼苗和孕穗期白叶枯病的发生,其诱导效果可能与MeJA处理浓度、方法及水稻生育期有关。     

江苏省水稻品种对水稻细菌性条斑病抗性鉴定及评价

为明确江苏省水稻条斑病菌致病力分化状况和不同类型水稻品种对条斑病抗感特性,在孕穗期采用针刺接种法对徐淮稻区2007—2009年采集分离获得的45株条斑病菌进行致病力测定,根据病原菌在6个水稻鉴别品种IRBB4、IRBB5、IRBB14、IRBB21、IR24和金刚30上的抗感反应划分致病型,从中选择具有代表性的3种不同致病型条斑病菌,并鉴定了240个不同类型的水稻品种对条斑病的抗感性。根据菌株在鉴别品种上的抗感反应将供试菌株划分为8个致病型,其中优势致病型为C3致病型,所占比例为35.5%;大多数菌株与鉴别品种间表现出弱互作关系,少数菌株表现出强互作关系。粳稻品种对条斑病的抗性明显高于籼稻,但常规粳稻和杂交粳稻对强致病力菌抗性比例仅为59.8%和37.5%。表明水稻细菌性条斑病流行仍具有潜在的威胁。     

A major quantitative trait locus for rice yellow mottle virus resistance maps to a cluster of blast resistance genes on chromosome 12

ABSTRACT Two doubled-haploid rice populations, IR64/Azucena and IRAT177/ Apura, were used to identify markers linked to rice yellow mottle virus (RYMV) resistance using core restriction fragment length polymorphism (RFLP) maps. Resistance was measured by mechanical inoculation of 19-day-old seedlings followed by assessment of virus content by enzyme-linked immunosorbent assay tests 15 days after inoculation. IR64/Azucena and IRAT177/Apura populations, 72 and 43 lines, respectively, were evaluated, and resistance was found to be polygenic. Resistance was expressed as a slower virus multiplication, low symptom expression, and limited yield loss when assessed at the field level. Bulked segregant analysis using the IR64/Azucena population identified a single random amplified polymorphic DNA marker that mapped on chromosome 12 and corresponded to a major quantitative trait locus (QTL) evidenced by interval mapping. When pooling RFLP data, integrated mapping of this chromosome revealed that the QTL was common to the two populations and corresponded to a small chromosomal segment known to contain a cluster of major blast resistance genes. This region of the genome also reflected the differentiation observed at the RFLP level between the subspecies indica and japonica of Oryza sativa. This is consistent with the observation that most sources of RYMV resistance used in rice breeding are found in upland rice varieties that typically belong to the japonica subspecies.     

Sarocladium attenuatum as one of the causes of rice grain spotting in Nigeria

The cause of rice grain spotting (dirty panicles) in Nigeria was studied. The fungus isolated most frequently from discoloured grains was Sarocladium attenuatum . Pathogenicity studies showed that it was capable of causing dirty panicle disease in the absence of insects. Disease severity increased with increasing inoculum. This is the first evidence that S. attenuatum is one of the major causes of dirty panicle disease of rice in Nigeria. Four isolates of S. attenuatum from different locations did not differ significantly in their virulence to three rice cultivars under upland conditions. Inoculations of cultivar BG 6850 at panicle initiation and booting resulted in severe disease and indicated the potential of the fungus to reduce yields. Trials under upland conditions of 69 cultivars of Oryza sativa and 89 of O. glaberrima indicated considerable variation in reactions, dwarf cultivars being generally more susceptible than taller ones.