Development of Spectral Features for Monitoring Rice Bacterial Leaf Blight Disease Using Broad-Band Remote Sensing Systems

As an important rice disease, rice bacterial leaf blight (RBLB, caused by the bacterium Xanthomonas oryzae pv.oryzae), has become widespread in east China in recent years. Significant losses in rice yield occurred as a result ofthe disease’s epidemic, making it imperative to monitor RBLB at a large scale. With the development of remotesensing technology, the broad-band sensors equipped with red-edge channels over multiple spatial resolutionsoffer numerous available data for large-scale monitoring of rice diseases. However, RBLB is characterized by rapiddispersal under suitable conditions, making it difficult to track the disease at a regional scale with a single sensorin practice. Therefore, it is necessary to identify or construct features that are effective across different sensors formonitoring RBLB. To achieve this goal, the spectral response of RBLB was first analyzed based on the canopyhyperspectral data. Using the relative spectral response (RSR) functions of four representative satellite or UAVsensors (i.e., Sentinel-2, GF-6, Planet, and Rededge-M) and the hyperspectral data, the corresponding broad-bandspectral data was simulated. According to a thorough band combination and sensitivity analysis, two novel spectralindices for monitoring RBLB that can be effective across multiple sensors (i.e., RBBRI and RBBDI) weredeveloped. An optimal feature set that includes the two novel indices and a classical vegetation index was formed.The capability of such a feature set in monitoring RBLB was assessed via FLDA and SVM algorithms. The resultdemonstrated that both constructed novel indices exhibited high sensitivity to the disease across multiple sensors.Meanwhile, the feature set yielded an overall accuracy above 90% for all sensors, which indicates its cross-sensorgenerality in monitoring RBLB. The outcome of this research permits disease monitoring with different remotesensing data over a large scale.

OsWRKY65 enhances immunity against fungal and bacterial pathogens in rice

Diverse bacterial and fungal pathogens attack plants,causing biotic stress and severe yield losses globally.These losses are expected to become more serious as climate change improves conditions for many pathogens.Therefore,identifying genes conferring broad-spectrum disease resistance and elucidating their underlying mechanisms provides important resources for plant breeding.WRKY transcription factors affect plant growth and stress responses.However,the functions of many WRKY proteins remain to be elucidated.Here,we demonstrated the role of rice(Oryza sativa)WRKY groupⅢtranscription factor OsWRKY65 in immunity.OsWRKY65 localized to the nucleus and acted as transcriptional repressor.Genetic and molecular functional analyses showed that OsWRKY65 increases resistance to the fungal pathogen Fusarium fujikuroi through downregulation of GA signaling and upregulation of JA signaling.Moreover,OsWRKY65 modulated the expression of the key genes that confer susceptibility or resistance to Xanthomonas oryzae pv.oryzae to enhance immunity against the pathogen.In particular,OsWRKY65directly bound to the promoter region of OsSWEET13 and repressed its expression.Taken together,our findings demonstrate that the OsWRKY65 enhances resistance to fungal and bacterial pathogens in rice.

Utilization Situation and Prospect of Gene xa5 Against Pathotype Ⅴ of Rice Bacterial Blight

In recent years,the strong virulence pathotype Ⅴ of rice bacterial blight grew up quickly in Southern China,which has become a major population and spread to the rice regions of Jiangsu and Zhejiang provinces in Southern China.Since pathotype Ⅴ caused serious bacterial blight disease in rice production regions,it is urgent to breed and promote resistant varieties against pathotype Ⅴ.The most economic and effective measure to control rice bacterial blight is to breed resistant cultivars for widely planting using resistance genes.The Institute of Plant Protection,Guangdong Academy of Agricultural Sciences,and Agricultural Science Research Institute of Panyu District of Guangzhou used IRBB5 carrying the recessive xa5 gene from IRRI that is resistant to pathotype Ⅴ to breed resistant varieties with rice blast resistance source,through hybridization,multiple cross,pedigree selection and synchronous resistance evaluation.We successfully bred series of new resistant rice varieties such as Baijiangzhan,Baijingzhan and Baisizhan,which showed resistance to strong virulence pathotype Ⅴ(grade 1-3)of bacterial blight and rice blast(mediate to high resistance),good grain quality(level 3 of rice quality of Guangdong),and yield equivalent to major cultivars(compared with region trial control cultivars of Guangdong).These new resistant varieties were promoted and planted in the strong virulence pathotype Ⅴ region along the west coast of Guangdong,which showed favorable superiority and wide application prospect in controlling rice bacterial blight with resistance varieties.

Gram-Positive Bacteria Associated with Rice in China and Their Antagonists Against the Pathogens of Sheath Blight and Bakanae Disease in Rice

It is necessary to understand the bacterial populations associated with rice so as to provide more information and natural resources for effective management of major diseases in rice. A survey on screening and identification of gram-positive bacteria was conducted during 1998 2004. Seven hundred and fifty-six rice samples were collected from Zhejiang, Jiangsu, Fujian and Yunnan Provinces, China. Over 1000 bacterial isolates were isolated and tested for colony morphology, pathogenicity, and some characteristics of bacteriology including Gram staining, fluorescent pigment on Kings medium B and microscopic observation for endospore. Together with five standard reference strains, 74 representative gram-positive bacterial isolates were confirmed by Biolog and gas chromatographic analysis of fatty acid methyl esters. Five bacterial species of Bacillus and other three genera were identified and isolates from Bacillus sublitis and Bacillus megaterium, exhibited the most effective inhibition against the pathogens of sheath blight and bakanae disease of rice. A few isolates from Bacillus pumilus and Bacillus megaterium showed weak virulent on rice together with some virulent isolates, risk should be considered when isolates from these species were screened for biocontrol agents.

Hybrid Rice Resistant to Bacterial Leaf Blight Developed By Marker Assisted Selection

Through recurrent backcrossing in combination with molecular marker-assisted selection (MAS), restorer lines R8006 and Rl176 carrying Xa-21, a gene having broad-spectrum resistance to rice bacterial leaf blight, were selected. By crossing the two lines to CMS line Zhong 9A, two new hybrid rice combinations, Zhongyou 6 and Zhongyou 1176 were developed. The hybrids showed high resistance to diseases, good grain quality and high yielding potential in national and provincial adaptability and yield trials.

Breeding of Selectable Marker-Free Transgenic Rice Lines Containing AP1 Gene with Enhanced Disease Resistance

In order to obtain marker-free transgenic rice with improved disease resistance, the AP1 gene of Capsicum annuum and hygromycin-resistance gene （HPT） were cloned into the two separate T-DNA regions of the binary vector pSB130, respectively, and introduced into the calli derived from the immature seeds of two elite japonica rice varieties, Guangling Xiangjing and Wuxiangjing 9, mediated by Agrobacterium-mediated transformation. Many cotransgenic rice lines containing both the AP1 gene and the marker gene were regenerated and the integration of both transgenes in the transgenic rice plants was confirmed by either PCR or Southern blotting technique. Several selectable marker-free transgenic rice plants were subsequently obtained from the progeny of the cotransformants, and confirmed by both PCR and Southern blotting analysis. These transgenic rice lines were tested in the field and their resistance to disease was carefully investigated, the results showed that after inoculation the resistance to either bacterial blight or sheath blight of the selected transgenic lines was improved when compared with those of wild type.

Thailand Experience in Developing Wellness-driven Rice as the Key to Fight NCDs and Farmer Poverty

Prevalence of chronic noncommunicable diseases(NCDs)is rapidly increasing and has become a global problem in modern day.Over consumption of simple,processed carbohydrate foods is considered one of the main causes of NCD in young and elderly populations.Whole grain rice is an important source of a complex carbohydrate,dietary fiber,enriched with vitamins,minerals,and antioxidants.However,palatability of brown rice is the key success factor among white-rice-addicted communities.In the initial phase,we successfully breed rice strains with aromatic,soft-whole grain,white rice contains high grain-Fe/Zn density and intermediate glycemic index(GI).The most successful variety was uniquely soft-textured black purple rice named Riceberry,depicting rice enriched with blueberry nutritional characteristics.Product development for fiber-rich,high antioxidant has been extremely active from academia,real sectors,and SMEs.In total,39 patent applications(18 granted patents),12 international publications,and 18,700 Youtubes related to Riceberry.From 2017,Riceberry has become the most popular choice for product development surpassing Thai Hommali Rice.More than 200 food and non-food products were commercialized as dairy replacement,side dishes,meals,hot beverages,bakery,and breakfast cereals.In the second phase,we successfully breed low GI rice strains named Pink+4 equipped with farmers’preferred resistance to flash flooding,bacterial leaf blight,leaf blast,and devastating brown planthopper adapted to organic rice production.Innovative products combined of low GI rice flour with purple Riceberry have been the next trend for functional ingredients and foods.These healthy rice products have high potential globally as healthy foods,gluten-free,fiber-rich,complex carbohydrate,and nutrient-dense from sustainable organic farming.

Obtaining transgenic rice resistant to rice fungal blast disease by controlled cell death strategy

The strategy of the two-component system, composed of Barnase and Barstar which encode RNase and a specific inhibitor to the RNase respectively, is adopted to obtain transgenic rice resistant to rice fungal blast disease. In this study, two chimeric promoters, induced by rice blast fungus pathogen (Magnaporthe grisea), are fused with Barnase respectively to construct two plant expression vec-tors, pWBNBS and pPBNBS together with the Barstar driven by CaMV 35S promoter. The resistance of the transgenic rice lines to rice blast fungus disease and rice blight disease are evaluated. The results show that (1) the expression of Barnase is induced in rice leaves when inoculated with the spores of Magnaporthe grisea; (2) the induced expression level of Barnase surpasses the level of Barstar, which elicits a similar hypersensitive response (HR) in the leaves, and the transgenic plant shows high resistance to the rice fungal blast disease; and (3) transgenic rice plants also show obvious re-sistance to rice bacterial blight disease. Taken together, these results suggest that the transgenic rice plants harboring this two-component system acquire relatively broad spectrum resistance against pathogens, especially high resistance to rice fungal pathogen.

Enhancement of innate immune system in monocot rice by transferring the dicotyledonous elongation factor Tu receptor EFR

The elongation factor Tu （EF-Tu） receptor （EFR） in cruciferous plants specifically recognizes the N-terminal acetylated elf18 region of bacterial EF-Tu and thereby activates plant immunity. It has been demonstrated that Arabidopsis EFR confers broad-spectrum bacterial resistance in the EFR transgenic solanaceous plants. Here, the transgenic rice plants （Oryza sativa L. ssp. japonica cv. Zhonghua 17） and cell cultures with constitutive expression of AtEFR were developed to investigate whether AtEFR senses EF-Tu and thus enhances bacterial resistance in the monocot plants. We＇demonstrated that the Xanthomonas oryzae-derived elf18 peptide induced oxidative burst and mitogen-activated protein kinase activa- tion in the AtEFR transgenic rice cells and plants, respectively. Pathogenesis-related genes, such as OsPBZ1, were upregulated dramatically in transgenic rice plant and cell lines in response to elf18 stimulation. Importantly, pretreatment with elf18 trig- gered strong resistance to X. oryzae pv. oryzae in the transgenic plants, which was largely dependent on the AtEFR expressionlevel. These plants also exhibited enhanced resistance to rice bacterial brown stripe, but not to rice fungal blast. Collectively, the results indicate that the rice plants with heterologous expression of AtEFR recognize bacterial EF-Tu and exhibit enhanced broad-spectrum bacterial disease resistance and that pattern recognition receptor-mediated immunity may be manipulated across the two plant classes, dicots and monocots.

Dynamic and Coordinated Expression Changes of Rice Small RNAs in Response to Xanthomonas oryzae pv.oryzae

Endogenous small RNAs are newly identified players in plant immune responses, yet their roles in rice （Oryza sativa） responding to pathogens are still less understood, especially for pathogens that can cause severe yield losses. We examined the small RNA expression profiles of rice leaves at 2, 6, 12, and 24 hours post infection ofXanthomonas oryzae pv. oryzae （Xoo） virulent strain PXO99, the causal agent of rice bacterial blight disease. Dynamic expression changes of some miRNAs and trans-acting siRNAs were identified, together with a few novel miRNA targets, including an RLK gene targeted by osa-miR159a. 1. Coordinated expression changes were observed among some small RNAs in response to Xoo infection, with small RNAs exhibiting the same expression pattern tended to regulate genes in the same or related signaling pathways, including auxin and GA signaling pathways, nutrition and defense-related pathways. These findings reveal the dynamic and complex roles of small RNAs in rice-Xoo interactions, and identify new targets for regulating plant responses to Xoo.

Marker-Assisted Breeding of Thermo-Sensitive Genic Male Sterile Line 1892S for Disease Resistance and Submergence Tolerance

Rice line 1892S is an elite thermo-sensitive genic male sterile(TGMS)line for two-line hybrid rice production.However,1892S is susceptible to rice blast,bacterial blight and submergence.Here we reported the introduction of blast resistance(R)gene Pi9,bacterial blight R gene Xa21 and submergence tolerance gene Sub1A into 1892S genetic background through backcrossing and marker-assisted selection.The improved TGMS line 31892S and its hybrids conferred disease resistance to rice blast and bacterial blight,and showed submergence tolerance for over 14 d without significant loss of viability.The sterility-fertility conversion of 31892S was similar to that of 1892S.31892S and its derived hybrid rice had similar agronomic traits and grain quality with 1892S and the control hybrid rice,respectively.The newly developed 31892S provided an improved TGMS line for two-line hybrid rice production with disease resistance to rice blast and bacterial blight,and submergence tolerance with no yield penalty or change in grain quality.

Paladin, a tyrosine phosphatase-like protein, is required for XA21-mediated immunity in rice

XA21 encodes a rice immune receptor that confers robust resistance to most strains of the Gram-negative bacterium Xanthomonas oryzae pv.oryzae(Xoo).XA21-mediated immunity is triggered by recognition of a small protein called RaxX-sY(required for activation of XA21-mediated immunity X,tyrosine-sulfated)secreted by Xoo.To identify components regulating XA21-mediated immunity,we generated and screened a mutant population of fast-neutron-mutagenized rice expressing Ubi:Myc-XA21 for those susceptible to Xoo.Here,we report the characterization of one of these rice mutants,named sxi2(suppressor of XA21-mediated immunity-2).Whole-genome sequencing revealed that sxi2 carries a deletion of the PALADIN(PALD)gene encoding a protein with three putative protein tyrosine phosphatase-like domains(PTP-A,-B,and-C).Expression of PALD in the sxi2 genetic background was sufficient to complement the susceptible phenotype,which requires the catalytic cysteine of the PTP-A active site to restore resistance.PALD coimmunoprecipitated with the full-length XA21 protein,whose levels are positively regulated by the presence of the PALD transgene.Furthermore,we foundd that sxi2 retains many hallmarks of XA21-mediated immunity,similar to the wild type.These results reveal that PALD,a previously uncharacterized class of phosphatase,functions in rice innate immunity,and suggest that the conserved cysteine in the PTP-A domain of PALD is required for its immune function.

噬菌体裂解酶在畜禽生产中的应用研究进展

畜禽生产中抗生素的长期、大量不规范使用,导致细菌耐药性问题日益严重,给畜禽细菌性疾病的预防和治疗带来极大困难,甚至已经威胁到公共卫生安全。噬菌体裂解酶是噬菌体编码的一种肽聚糖水解酶,能够高效、特异地杀灭细菌且具有抗生物被膜活性,已经成为一种新型抗菌药物,逐渐被纳入细菌尤其是耐药菌感染的治疗策略。畜禽生产中,噬菌体裂解酶已经成功应用于金黄色葡萄球菌、链球菌等革兰阳性菌引起的畜禽细菌性疾病的防控与治疗中,其在大肠杆菌、沙门菌等革兰阴性菌上的应用尚处于体外研究阶段。笔者对噬菌体裂解酶的结构特点、作用机制及其在畜禽生产中的应用进行综述,探究噬菌体裂解酶在畜禽生产中的应用现状及前景,以期为噬菌体裂解酶更进一步地应用于防控和治疗细菌性疾病提供参考。

生防放线菌Sc-7的分离、鉴定、抑菌活性及其对水稻的促生作用

为了筛选出能够显著抑制水稻白叶枯病菌Xanthomonas oryzae pv. oryzae (以下简称Xoo)和水稻细菌性条斑病菌X. oryzae pv. oryzicola (以下简称Xoc)的放线菌,本研究从不同植物根际采集土壤,采用稀释涂布法和平板划线法共分离得到60株放线菌,通过共培养法和牛津杯法筛选得到对Xoo和Xoc具有显著抑制作用的1株放线菌Sc-7。依据形态和显微结构观察、生理生化试验和多基因聚类分析,构建系统发育进化树,鉴定菌株Sc-7为淡紫灰链霉菌Streptomyces lavendulae。盆栽防效试验结果表明:先喷洒菌株Sc-7发酵稀释液(2倍),再接种病原菌对水稻白叶枯病和水稻细菌性条斑病的防治效果分别为74.57%和65.33%,并且病斑长度明显变短。Xoo和Xoc病菌经过菌株Sc-7发酵滤液处理后,细胞大面积溶胀、皱缩和穿孔,细胞膜通透性增加,胞外多糖分泌量减少。浸种促生试验结果表明:不同浓度的菌株Sc-7发酵稀释液皆能促进水稻种子的芽和根生长。与无菌水对照相比,菌株Sc-7发酵稀释液10倍和50倍处理,使芽长分别增加32.79%和37.70%,使根长分别增加75.00%和97.00%。试管促生试验结果表明:菌株Sc-7发酵稀释液10倍和50倍处理,使水稻幼苗株高增长幅度分别为16.68%和10.53%。盐胁迫缓解试验结果表明:菌株Sc-7发酵稀释液10倍处理,在一定程度上能够缓解水稻盐胁迫后的症状。上述结果表明,菌株Sc-7具有显著的促生和防病潜能,有望开发成为一种生物农药和生物肥料。

水稻白叶枯病免疫与抗性机制研究进展

水稻(Oryza sativa L.)白叶枯病是由革兰氏阴性菌黄单胞杆菌(Xanthomonas oryzae pv.oryzae,Xoo)引发的细菌性疾病,是一种全球性的水稻病害。该病害在我国发病面积广,其病原菌具有传播速度快和易突变的特点。挖掘和克隆新的白叶枯病抗病基因并对其进行育种应用是目前防治该病害的有效途径。本文对目前已报道的44个白叶枯病抗病基因进行了分类,概述了水稻白叶枯病免疫应答与主效抗病基因的分子机制,主要包括:1)水稻应对白叶枯病的防御机制;2)水稻白叶枯病抗病基因的挖掘与鉴定;3)水稻白叶枯病主效抗病基因的功能及分类;4)水稻抗白叶枯病的分子机制。此外,本文对水稻白叶枯病抗病基因及免疫机制的研究进行了展望。这些内容可为水稻白叶枯病的后续研究及育种应用提供参考。

抗白叶枯病杂交水稻的分子标记辅助育种

应用分子标记辅助回交 ,育成了带广谱抗白叶枯病基因 Xa- 2 1的两个杂交水稻恢复系 R80 0 6和 R1176 ,所配的杂交水稻组合中优 6号、中优 1176在中国南方稻区及多个省级区试中表现抗病、优质、高产 ,具有较广的商业开发潜力。

高覆盖率水稻BAC库的构建及抗病基因相关克隆的筛选

利用含Xa4、xa5和xa13 3个水稻白叶枯病抗性基因的累加系IRBB56构建了一个水稻细菌人工染色体文库。该文库包含55 296个克隆，平均插入片段为132kb。按水稻基因组为450Mb计，该文库覆盖14倍基因组，筛选出任一水稻基因或序列的概率为99.99%。用均匀分布的3个叶绿体基因和4个线粒体基因克隆作探针筛选文库，结果显示该文库中含细胞器基因组DNA同源序列的克隆数小于1%。用分布于水稻3条不同染色体、分别与Xa4、xa5和xa13连锁的DNA标记筛选文库，分别检测出11～106个阳性克隆，为克隆这些基因打下了基础。 该文库对水稻基因组的高度覆盖率和较大的插入片段，非常适合于物理作图和基因的分离和克隆。

水稻抗白叶枯病基因X_(a-14)在分子标记连锁图上的定位

选取对水稻白叶枯病原菌６个菲律宾小种均为感病的籼稻品种珍珠矮为母本，携带抗病基因Ｘａ－１４的粳稻近等基因系ＣＢＢ１４（抗菲律宾５号小种Ｐ５）为父本配制杂交组合。Ｆ１植株对相对应的菌系Ｐ５表现全生育期抗病，Ｆ２群体在分蘖前期接种鉴定结果表明，抗、感植株的分离符合３∶１显性单基因分离比。根据对Ｆ２群体中选择的９９个单株进行的ＲＦＬＰ分析的结果，构建了水稻第４连锁群的分子图谱，并把抗病基因Ｘａ－１４定位于ＲＧ６２０和Ｇ２８２之间。

水稻穗腐病和穗枯病的研究进展

水稻穗腐病和穗枯病是我国新上升或新出现的两个水稻后期穗部病害。近年来,随着气候的变化、耕作栽培制度及肥水管理的改变以及品种(组合)的更替,两病在我国的发生和危害程度越来越严重。穗腐病和穗枯病病原菌有色,可产生毒素,不但直接影响水稻产量,还导致稻米品质降低,危害食用者的健康。穗腐病和穗枯病在发病时期、发生部位和危害程度上具有相似性。综述了两病害的发生、流行规律、危害状况、病原菌生物特性和毒素研究以及防治方法,提出了研究上目前存在的问题和今后的研究方向。

空间诱变育成抗稻瘟病和白叶枯病水稻突变体浙101

早籼浙 92 4 8经卫星搭载诱变处理 ,种子的发芽率及当代植株的性状均没有明显的变化 ,但对秧苗的生长表现出一定的刺激作用 ;SP2 在株高、生育期、穗长、每穗粒数、千粒重、结实率及抗病性等性状上出现了较大的分离。经病区多代筛选培育成的突变体浙 10 1,在熟期、抗病性和产量等性状上比原亲本有明显改良 ,2 0 0 1～2 0 0 2年经浙江省多点稻瘟病和白叶枯病联合鉴定 ,叶瘟平均级分别为 1.4和 1.7级 ,最高级为 5 .0级 ;穗瘟平均级分别为 1.6和 1.3级 ,最高级为 3.0级 ;抗谱频率分别为 70 %和 6 0 % ;对白叶枯病抗性平均级为 1.4级 ,最高级为 5 .0级。抗病性比原亲本和对照有显著提高。试验表明 ,浙 10 1是一个高抗稻瘟病兼抗白叶枯病的水稻突变体 ,可作为水稻品种改良的新抗源。