Integrated Approach to Control False Smut in Hybrid Rice in Sichuan Province,China

Severe epidemic of false smut, caused by Ustilaginoidea virens(Cooke) Takahashi(teleomorph Villosiclava virens) has been reported in different parts of Asia and America. Different fungicides or bio-control agents against false smut were applied at different times before heading on a susceptible rice variety Pu-6. A control efficiency as high as 91.92% was resulted from spraying 2.5% Wenquning, a suspension of Bacillus subtilis in solution of validamycin with 4.5 L/hm2 at 6 d before heading. Among the 186 hybrid rice screened in 2010, low significant correlations between the dates of full heading, rates of infected plants and panicles as well as the number of infected florets were found, with the correlation coefficients ranging from 0.2331 to 0.5212. However, significant difference in susceptibility coefficients was also found between the varieties which had the same dates of full heading. In the plot experiments to compare the susceptibility in 2011, the average rates of infected panicles of Yixiangyou 2168, Chuanxiangyou 3, Dexiang 4103, Yixiangyou 2115, Nei5 you 317, Yangxinyou 1 were significantly lower than those of the control varieties Gangyou 725 and Gangyou 188 at the disease nursery located at Qionglai, Sichuan Province, China. When Neixiangyou 8156 and Nei5 you 317 were sprayed with 2.5% Wenquning at 4.5 L/hm2 for two times at 6 d before and 1 d after heading, respectively, the control efficiencies of Nei5 you 317 and Neixiangyou 8156 were respectively 100% and 82.24% compared to that of Gangyou 725. Satisfactory control effects had also obtained by single spray of 2.5% Wenquning at 4.5 L/hm2 at 5–6 d before heading. Therefore, less susceptible hybrid rice in combination with spraying Wenquning at 5–6 d before heading was suggested for the disease control in Sichuan Province, China.     

UvWhi2 Is Required for Stress Response and Pathogenicity in Ustilaginoidea virens

Some stress response-related genes have been identified in Ustilaginoidea virens, but it is not clear whether and how defects of stress responses affect the pathogenesis processes of U. virens. In this study, we identified a general stress response factor UvWHI2 as a homolog of Saccharomyces cerevisiae Whi2 in U. virens. The relative expression level of UvWhi2 was significantly up-regulated during infection, suggesting that UvWHI2 may be involved in pathogenesis. Furthermore, knockout of UvWhi2 showed decreased mycelial growth, increased conidiation in the potato sucrose medium and a defect in pathogenicity. In addition, the RNA-Seq and phenotypic analysis showed that UvWHI2 was involved in response to oxidative, hyperosmotic, cell wall stress and nutrient limitation. Further studies revealed that the defects of stress responses of the ΔUvwhi2 mutant affected the formation of secondary spores on the nutrient limited surface and the rice surface, resulting in a significant reduction of pathogenicity of U. virens. Our results suggest that UvWHI2 is necessary for fungal growth, stress responses and the formation of secondary spores in U. virens. In addition, the defects of stress responses can affect the formation of secondary spores on the rice surface, and then compromise the pathogenicity of U. virens.     

Ustilaginoidea virens: A Fungus Infects Rice Flower and Threats World Rice Production

Rice false smut disease, which is caused by the fungus Ustilaginoidea virens, is currently one of the most devastating rice fungal diseases in the world. Rice false smut disease not only causes severe yield loss and grain quality reduction, but also threatens food safety due to its production of mycotoxins. In this review, the most recent progresses regarding the life cycle, infection processes, genome and genetic diversity, pathogenic gene and disease resistance in rice were summarized in order to provide theoretical basis for the control of U. virens. We also proposed some future directions and key questions that need to be addressed for a better understanding of the molecular mechanism that leads to rice false smut disease and the prospects for sustainable control of rice false smut.     

两优培九稻曲病的发生及其与抽穗后温湿度的关系

分析了两优培九稻曲病的发病程度及其与抽穗后0～15d的平均气温和相对湿度的关系。结果表明，两优培九易感稻曲病。其发病率与抽穗后0～15d的平均气温呈显著正相关，温度是影响其稻曲病发生的主要气象因素，相对湿度起协同作用。提出了发病率为2％和5％时的温湿度指标。根据我国南方一季稻区18个城市42a(1951—1992)8—10月的气象资料，分析了稻曲病的易发区域和适宜抽穗期，为两优培九稻曲病的预防提供依据。     

UvSMEK1, a Suppressor of MEK Null,Regulates Pathogenicity,Conidiation and Conidial Germination in Rice False Smut Fungus Ustilaginoidea virens

Rice false smut, which is caused by Ustilaginoidea virens, is an emerging disease of rice spikelets in rice-growing areas worldwide. However, the infection mechanism of U. virens on rice spikelets is still unclear. Here, we characterized a suppressor of mitogen-activated protein kinase kinase or ERK kinase(MEK) null(UvSMEK1) in U. virens that is conserved among filamentous fungi. Compared with wild type U. virens strain P-1, Uv SMEK1 deletion mutants were defective in pathogenicity and conidial germination. In addition, conidiation of UvSMEK1 deletion mutants was significantly reduced on yeast extract tryptone(YT) plates, but increased in YT broth compared with the wild type. Compared with Uv SMEK1 expression level during the vegetative mycelia and conidiation stages, UvSMEK1 dramatically increased during infection of rice florets. Surprisingly, the Uv SMEK1 deletion mutants exhibited higher tolerance to H2 O2 and NaCl. In summary, presented evidence suggested that UvSMEK1 positively regulated pathogenicity, conidial germination and conidiation in YT broth, and negatively regulated conidiation on YT medium and tolerance to oxidative and osmotic stresses. The results enhance our understanding of the regulatory mechanism of pathogenicity of U. virens, and present a potential molecular target for blocking rice infection by U. virens.     

优质稻品种稻瘟病和稻曲病田间抗病性状调查

对12个优质稻品种的稻瘟病、稻曲病田间抗性调查认为,田间抗性表现与品种抗性和品种种性特征存在相关性。品种在试验阶段表现抗稻瘟病的其抗性强,大穗型,直立密穗型品种易感稻曲病。在生产上除了选用抗病品种,应做到科学栽培,同时注意化学防治,减轻病害发生流行,提高品种产量和稻米品种的卫生质量。     

不同药剂防治水稻稻曲病田间药效试验

为筛选防治水稻稻曲病的高效药剂,同时验证在孕穗末期—破口初期施药对稻曲病的防效,2019—2020年连续2年开展了不同药剂防治水稻稻曲病田间试验。结果表明:19%啶氧·丙环唑SC 70 mL/667 m²、125 g/L氟环唑SC 50 mL/667 m²、40%咪铜·氟环唑SC 30 mL/667 m²、25%噻呋·嘧菌酯SC 40 mL/667 m²平均病指防效分别为89.95%、89.85%、87.05%、85.60%,体现了较高防效;75%肟菌·戊唑醇WG 15 g/667 m²,平均病指防效为81.30%,也有较高防效;而36%丙环·咪鲜胺SC 50 mL/667 m²平均病指防效仅为78.20%,防效稍差。前5种药剂可结合稻瘟病防治,在水稻孕穗末期—破口初期使用,能有效控制水稻稻曲病为害。     

湖南省水稻新品种稻曲病抗性鉴定研究

2011年,在湖南安仁以自然诱发结合人工接种鉴定了158个湖南省水稻区试新品种(组合、系)对稻曲病的抗性.结果显示,中籼组的稻曲病抗性较弱,只有1个组合抗病;一季晚籼表现出较好的抗性,中抗的达65.2％;双季晚籼抗性弱,中感以上的达60％;优质稻抗性较弱,中感以上的占80.0％.因此,必须重视水稻品种对稻曲病的抗性遗传改良.     

生产上主要杀菌剂对稻瘟病的防效及施药时期研究

稻瘟病是最主要的世界性水稻病害,化学防治是目前最为有效的防控措施。通过室内生测和田间试验相结合的方法,测试了多个特效药剂和广谱药剂对稻瘟病的防治效果,探讨了稻瘟病的最优防治适期和穗颈瘟、稻曲病兼防的可能性。结果表明,三环唑仍然是预防穗颈瘟的特效杀菌剂,而嘧菌酯、肟菌酯·戊唑醇和嘧菌酯·苯醚甲环唑等广谱杀菌剂对叶瘟表现出更好的防控效果。始穗期是防治穗颈瘟的关键时期,在发病严重的情况下在齐穗期再施1次药是必要的。如果选用合适的药剂,破口前施药对穗颈瘟也有一定的防控作用。由于防治稻曲病的最佳施药时期是破口前,因此,一次施药兼防穗颈瘟和稻曲病是可行的。     

利用重组自交系分析水稻稻曲病抗性位点及效应

利用157个家系组成的大关稻/IR28重组自交系群体,采用高效引发稻曲病人工接种方法,以病情指数作为稻曲病的表型值,鉴定了亲本及157个重组自交系群体对水稻稻曲病的抗性。利用QTL Cartographer 软件,对水稻稻曲病抗性基因进行检测分析。检测到qFsr1、qFsr4、qFsr10、qFsr11和qFsr12共 5个QTL位点,分别位于第1、4、10、11和12染色体上,贡献率为9.8%~22.5%。根据抗性位点加性效应方向,在qFsr1、qFsr10、qFsr11和qFsr12位点上,亲本IR28存在抗稻曲病的增效等位基因,大关稻具有减效等位基因;而qFsr4位点抗性效应来源于大关稻。     

国内外稻曲病研究现状

稻曲病是我国水稻上常见的一种真菌性病害，随着该病发生情况日趋严重，有关该病害的研究报道也日渐增多。本文综述近几十年来国内外稻曲病的分布与寄主、生物学特性、危害与危害机理、划级标准、病害循环、流行规律及防治，并对研究中存在的问题进行简单阐述。     

江西一季籼粳杂交稻稻曲病防治药剂及次数研究

选择合适的防治药剂和防治次数是减轻稻曲病危害的关键。本研究以籼粳杂交稻甬优12为材料,比较了6种药剂和3种喷施次数对稻曲病的防控效果和产量性状差异。结果表明,在6种药剂中,阿米妙收处理的病穗率防效和病指防效最好,分别达到91.53%和96.63%,但与其他药剂无显著性差异。在防治次数上,爱苗和拿敌稳均为防治3次的处理病指防效最好,分别为81.73%和80.15%,显著高于防治次数3次以下的处理。阿米妙收处理的产量最高,达11 719.52 kg/hm~2,显著高于其他处理。     

稻曲病大发生关键因子及药剂防治研究

针对稻曲病在水稻生产上危害日趋加重的现状，2002-2005年对引起该病大发生的关键因子及药剂防治技术进行了连续4年的研究。结果表明：感病品种（组合）和水稻孕穗至抽穗期间5d以上降水天气是引起稻曲病大发生的二个关键因子‘同时，稻曲病为害程度还与水稻栽培方式、种植密度、肥水管理及施药水平等因素有关。稻曲病药剂防治技术关键：一是选用有效药剂。二是抓住施药适期施药。筛选出防治稻曲病的有效药剂有30％爱苗EC，43％好力克SC和62．25N仙生WP。稻曲病施药适期是水稻分蘖末期、破口前3～7d、始穗期3个时期。     

安徽省水稻品种(系)对稻瘟病和稻曲病的抗性评价

2013年对安徽省103份水稻品种(系)进行稻瘟病和稻曲病田间抗病性鉴定。结果表明,参试材料对稻瘟病表现抗病和中抗的分别有5份和9份,占13.59%;表现中感的有25份,占24.27%;表现感病和高感的分别有33份和31份,占62.14%。对稻曲病表现抗病和中抗的分别有6份和7份,占12.62%;中感的有55份,占53.40%;感病和高感的分别有29份和6份,占33.98%。对两种病害均能达到抗病或中抗的只有3份,分别是G优6号、Y两优1500和协优118。     

超级杂交中稻主要病虫药剂防治新技术研究

2004～2005年，在稻曲病防治新药剂筛选及药剂防治适期研究的基础上，针对超级杂交中稻纹枯病、稻曲病、稻飞虱和螟虫等主要病虫发生量大及危害严重的特点，开展了药剂防治试验．形成了一套适合超级杂交中稻主要病虫药剂防治的专用技术。该技术对超级杂交中稻主要病害防效达80％左右，对虫害防效达90％以上。与常规病虫防治技术相比，该技术成本相当，增产增效非常明显，同时可减少对环境及稻谷的污染，实现超级杂交中稻无公害生产的目的。     

稻曲病对水稻产量的影响及水稻新品种抗病性测定

在田间调查稻曲病病粒数对水稻秕谷率和产量损失率的影响,同时采用自然诱发方法测定62个水稻新品种对稻曲病的抗性。结果表明,单穗稻曲球病粒数的增加能引起水稻秕谷率和产量损失率的增加;当单穗病粒数在5粒以上时,引起产量损失率可达36％以上;62个水稻品种中表现中抗稻曲病的品种有7个,占供试品种数量的11.29％,表现中感稻曲病的品种有22个,感稻曲病的品种有33个,分别占35.48％和53.23％。     

金华市单季稻主栽品种对稻曲病的田间抗性评价

2016年采用自然诱发方法测定了金华市10个单季稻主栽品种稻曲病的发病情况,并对其抗性进行了评价。结果表明,深两优5814、甬优17、春优84、中浙优8号、甬优1540、丰两优香1号和Y两优2号对稻曲病的抗性较好,而甬优15、甬优9号、浙优18的抗性较差。     

稻曲病菌UvHog1基因的克隆及表达分析

稻曲病由稻曲病菌引起,是水稻穗部的重要病害。利用同源克隆和RACE技术,根据丝状真菌相对保守的氨基酸序列设计简并引物,从稻曲病菌中分离了丝裂原活化蛋白激酶(MAPK)编码基因的全长cDNA序列,命名为UvHog1。UvHog1含有MAPK保守的蛋白激酶激活域(TGY),序列与稻瘟病菌MgOsm1(AAF09475.1)、球孢白僵菌BbHog1(AAS77871.1)、烟曲霉AfOsm1(XP752664.1)和隐球酵母CrHog1(AAM26267.1)等MAPK高度同源,相似性分别为95%、93%、88%和81%。系统聚类结果表明,UvHog1与酵母Hog1MAPK同源。在盐胁迫条件下,UvHog1的相对表达量明显降低,表明UvHog1参与了对盐胁迫的信号响应。     

bZIP Transcription Factor UvATF21 Mediates Vegetative Growth,Conidiation, Stress Tolerance and Is Required for Full Virulence of Rice False Smut Fungus Ustilaginoidea virens

bZIP proteins are widely distributed in eukaryotic organisms and regulate a diverse range of physiological processes. Several bZIP proteins have previously been identified in Ustilaginoidea virens. However, the biological roles of these bZIP proteins in this pathogen are still unknown. Here, one of these bZIP protein coding genes, UvATF21, was functionally characterized. Targeted deletion of UvATF21 resulted in reduced conidiation and pathogenicity despite of the increased vegetative growth. The deletion mutants also significantly decreased the sensitivity to osmotic and oxidative stresses. Interestingly, deletion of UvATF21 exhibited different performances to cell wall integrity stress. These results indicated that UvATF21 played crucial roles in vegetative growth, conidiation, stress response, and full virulence in U. virens.     

水稻幼穗响应稻曲病菌毒素胁迫早期的转录组分析

【目的】由稻曲病菌引起的稻曲病不仅造成水稻减产,而且还会产生对动物和植物有毒的真菌毒素。探明水稻幼穗对稻曲病菌毒素胁迫响应的分子机制,可为发掘水稻抗稻曲病基因以及抗病分子育种开辟新的思路。【方法】用稻曲病菌毒素处理水稻幼穗,采用转录组测序技术对水稻幼穗进行转录组测序,以水稻9311基因组作为参考基因组进行对比,利用TPM法计算基因表达量,设定参数（差异倍数的绝对值不小于2,且q值不大于0.05）筛选差异表达基因。结合基因差异表达分析、富集功能分析,鉴定水稻响应胁迫的关键基因,并利用实时荧光定量PCR技术对差异表达基因进行验证。【结果】在稻曲病菌毒素胁迫12 h后,水稻幼穗出现2526个差异表达基因（DEG）;通过GO富集、KEGG代谢途经和KOG功能分析,将差异基因划分为GO功能下的64个条目、32个代谢途径和KOG功能下23个类别,包括淀粉和蔗糖代谢、苯丙类生物合成、碳代谢、糖酵解/糖异生、氨基糖和核苷酸糖代谢等生物学过程。DEG中有66个植物转录因子,分属7种植物转录因子家族,包括WRKY和Myb两大转录因子。分析二萜类生物合成与淀粉和蔗糖代谢途径相关基因发现,OsCPS2、OsKSL4和细胞色素P450等基因表达量上调,而淀粉酶、β-呋喃果糖苷酶和UDP-焦磷酸化酶等基因表达量下调,推测这些基因在水稻响应稻曲病菌毒素胁迫时发挥重要的作用。【结论】稻曲病菌毒素作为非生物胁迫因素对水稻幼穗具有毒性;通过干扰淀粉和蔗糖代谢等途径而影响种子营养物质的合成,降低水稻抵抗病原菌侵染水稻的能力。