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.

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.

Marker-Assisted Selection of Xa21 Conferring Resistance to Bacterial Leaf Blight in indica Rice Cultivar LT2

Bacterial leaf blight of rice (BLB), caused by Xanthomonas oryzae pv. oryzae, is one of the most destructive diseases in Asian rice fields. A high-quality rice variety, LT2, was used as the recipient parent.IRBB21, which carries the Xa21 gene, was used as the donor parent. The resistance gene Xa21 was introduced into LT2 by marker-assisted backcrossing. Three Xoo races were used to inoculate the improved lines following the clipping method. Eleven BC_3F_3 lines carrying Xa21 were obtained based on molecular markers and agronomic performance. The 11 lines were then inoculated with the three Xoo races. All the 11 improved lines showed better resistance to BLB than the recipient parent LT2. Based on the level of resistance to BLB and their agronomic performance, five lines (BC_3F_3 5.1.5.1, BC_3F_3 5.1.5.12, BC_3F_3 8.5.6.44, BC_3F_3 9.5.4.1 and BC_3F_3 9.5.4.23) were selected as the most promising for commercial release. These improved lines could contribute to rice production in terms of food security.

Interactive Effect of Different Nitrogen and Potash Levels on the Incidence of Bacterial Leaf Blight of Rice (<i>Oryza sativa L.</i>)

An experiment was conducted at Rice Research Institute, Kala Shah Kaku in 2010 during kharif season to study the influence of nitrogen (N) and potash (K) on severity of Bacterial leaf blight (BLB) of rice (Oryza sativa L.) aimed at improving productivity. The experiment was laid out in randomized complete block design with factorial arrangement with three replications. Treatments comprised of: 0 kg N ha-1, 75 kg N ha-1, 100 kg N ha-1, 125 kg N ha-1 and 0 kg K ha-1, 50 kg K ha-1, 75 kg K ha-1, 100 kg K ha-1. Data on disease severity and paddy yield were recorded using standard procedures. Paddy yield was affected significantly by various combinations of N & K. In case of bacterial leaf blight, minimum diseased incidence percentage was observed when nitrogen alone was applied @ 75 kg·ha-1 in contrast to fertilizer applied @ 125 kg N ha-1 + 50 kg K ha-1 which showed maximum diseased incidence percentage. Maximum paddy yield (4.32 t·ha-1 ) was recorded when rice was fertilized @ 75 kg N ha-1 + 100 kg K ha-1 as compared to sole fertilization of 75 kg K ha-1 that produced minimum paddy yield (2.40 t·ha-1). Maximum gross income, net returns and benefit cost ratio were obtained where rice crop was fertilized @ 75 kg N ha-1 and 100 kg K ha-1.

Inhibitory Activity of <i>Paenibacillus</i>sp. Isolated from Soil in Gotsu City, Shimane Prefecture, Against Xanthomas <i>oryzae</i>pv. <i>oryzae</i>, the Causal Agent of Rice Bacterial Leaf Blight

Microorganism isolates (n = 49) were obtained from the soil samples collected from field in Gotsu city (Kawahira), Shimane. Isolate GT2-E culture inhibited the growth of Xanthomonas oryzae pv. oryzae in disk diffusion method. Rice bacterial leaf blight was suppressed by GT2-E culture in the pre- and post-treated rice leaves. Sequence analysis of 16S rDNA region of the GT2-E isolate indicated that it shared 99% similarity with Paenibacillus polymyxa. The growth of GT2-E on LB medium was observed at 15°C, 28°C, 37°C, and 45°C, but not at 4°C. GT2-E isolate could be grown even in the presence of agrochemicals (Amister, Blasin and Kasumin). Furthermore, the growth of X. oryzae pv. oryzae was inhibited by the culture filtrate of GT2-E isolate in disk diffusion method. However, the inhibitory activity of the culture filtrate was heat-unstable. This result suggested that GT2-E isolate can produce heat-unstable inhibitory compound(s). In conclusion, GT2-E isolate might contribute to the development of a new bactericide and biological agent against rice bacterial leaf blight.

G ×E Analysis of Rice Germplasm and NILs Having Bacterial Leaf Blight (BLB) Resistant Genes against Local Isolates of <i>Xanthomonas oryzae</i>at Diverse Agro-Ecological Zones

Rice is food for more than half of the world population and the most consumable cereal in most of the countries. Pakistan is the fifth largest exporter of rice. However, Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae is the most devastating and serious threat to rice production in many countries of the world including Pakistan. To combat this disease, innate genetic resistance of the plant plays vital role along with being environmentally friendly and economical. In this study, thirty-one (31) Near Isogenic Lines (NILs) having Xa4, xa5, Xa7, xa13 and Xa21 reported BLB tolerant genes and 34 locally developed rice lines were investigated under natural field conditions at three agro-ecologically different locations with highest disease occurrence records (BLB hotspots) viz., Sheikhupura, Hafizabad and Gujranwala, Punjab, Pakistan in order to assess their respective genetic resistance and G × E interactions against the disease. Thirty-one (31) lines were categorized under resistant cluster, twenty-eight (28) were moderately resistant, six (6) were moderately susceptible and one (susceptible check) was in susceptible category. Grouping of different lines/varieties under same cluster shows their significantly similar response against BLB disease in corresponding environment. Among the studied NILs, only one line showed polymorphism for all five resistant genes, two lines had four;seven lines had three genes, seven lines showed di-genic while five lines showed mono-genic polymorphism. These resistant lines with multiple-genes for BLB resistance can be evolved as a new BLB resistant variety and also be utilized as donor parent in breeding programs for developing new cultivars with horizontal resistance against more than one target pathotypes and environments. Xa4 and xa13 were found to deliver significant resistance against the local pathotypes in studied germplasm and NILs.

Preliminary evaluation of resistance genes in rice against bacterial leaf blight in Guilan Province—Iran

The reactions of rice bacterial leaf blight races were identified in Guilan province—Iran on 12 near-isogenic lines and 14 pyramiding lines from International Network for Genetic Evaluation of rice (INGER) and 8 local and improved Iranian varieties were evaluated under natural photoperiod condition in the field. Inoculation was done at panicle initiation by clipping the sterilized scissors in the bacterial suspension to booting stage. Scoring of inoculated plants was made 21 days after inoculation. Infection levels of pyramiding lines containing two to five resistance genes, expect, IRBB53 and IRBB61 with respectively resistance gene combination, Xa5 + Xa13 and Xa4 + Xa5 + Xa7, were not so clear. Among near-isogenic lines IRBB1, IRBB2, IRBB4 and IRBB10 carrying resistance gene Xa1, Xa2, Xa4 and Xa10 were susceptible;IRBB8, IRBB11, IRBB3, IRBB5 and IRBB13 were moderately susceptible;(having resistance gene Xa8, Xa11, Xa3, Xa5 and Xa13) IRBB14, IRBB21 and IRBB7 with respectively resistance gene Xa14, Xa21 and Xa7 were moderately resistance to bacterial blight. Furthermore, most of the time gene combinations support the strategy of pyramiding appropriate resistance gene. Local varieties were more susceptible than improved varieties to leaf blight disease. Among local varieties, Tarom was the most susceptible. And also, there were no significant differences among improved varieties and all of them were moderately resistance.

Identification and Genetic Analysis of a Novel Rice Spotted-Leaf Mutant with Broad-Spectrum Resistance to Xanthomonas oryzae pv. oryzae

A spotted-leaf mutant of rice HM143 was isolated from an EMS-induced IR64 mutant bank. Brown lesions randomly distributed on leaf blades were observed about 3 wk after sowing. The symptom lasted for the whole plant growth duration. Histochemical analysis indicated that cell death occurred in and around the site of necrotic lesions accompanied with accumulation of hydrogen hyperoxide. Agronomic traits were largely similar to the wild type IR64 except seed setting rate and 1 000-grain weight which were significantly decreased in the mutant. Disease resistance of the mutant to multiple races of Xanthomonas oryzae pv. oryzae was significantly enhanced. Genetic analysis showed that the mutation was controlled by a single recessive gene, tentatively termed splHM143. In addition, using molecular markers and 1023 mutant type individuals from an F2 segregating population derived from the cross HM143/R9308, the spotted-leaf gene was finally delimited to an interval of 149 kb between markers XX25 and ID40 on the long arm of chromosome 4. splHM143 is likely a novel rice spotted-leaf gene since no other similar genes have been identified near the chromosomal region.

Characteristic analysis of tetra-resistant genetically modified rice

In this study, the characteristic of three transformants named as B1C106-1, B1C106-2, and B1C106-3 were studied that carried three innate resistant genes Bph14, Bph15, and Xa23, and two enthetic resistant genes CrylCa# and Bar. The five resistant genes were all verified by PCR and the two enthetic genes were identified in single copy insertion by Southern blot. At tillering stage, the CrylC and PAT （phosphinothricin acetyl transferase） protein contents in leaf, sheath, and stem of T2 generation were in the similar pattern： leaf〉stem〉sheath, and showed significant difference （P〈0.01） among three organs. The average contents of CrylC protein in plant of B1C106-1, B1C106-2, and BIC106-3 were 12.95, 6.57, and 11.30 μg g-1, respectively, and showed significant difference （P〈0.01） among them. However, the average contents of PAT in plant of B1C106-1, B1C106-2, and B1C106-3 were 28.54, 27.66, and 28.02 pg g-1, respectively, and there were no significant difference among three transformants. The glufosinate tolerable concentration of three transformants of T3 generation reached at least 6 g L-1, and the mortality of rice leaf rollers were above 97.4% in 5 days after being fed with fresh transformants＇ leaves. The CrylC protein toxicity was also assessed by silkworms, and the mortality of silkworms feeding mulberry leaves smeared with Cry1C protein extracts of leaves of B1 C106-1, BIC106-2, and B1 C106-3 were 90, 67.8, and 87.8%, respectively, that were positive correlation （r=0.993） with CrylC protein contents in plant of three transformants. The three transformants also maintained high resistance to brown planthopper and bacterial blight as the original version. The above results indicate the tetra-resistant rice germplasm was well-developed by pyramiding innate and enthetic resistant genes in an elite line to provide with resistances of glufosinate, rice leaf roller, brown planthopper, and bacterial blight.

水稻白叶枯病常态化预防控制技术应用

水稻白叶枯病是水稻生产过程中重要的病害,尽管对该病害的防治做了大量工作,但2015年以来,该病害又有上升趋势,特别是2019年后,衢江区水稻白叶枯病发生面积呈多点式、暴发式增长,尤其是单季晚稻与连作晚稻,对该区水稻生产构成严重威胁。借鉴“中医治未病”理论,探索采用“3+X”模式防控水稻白叶枯病。结果表明,与常规防治方法相比,在水稻种植关键环节,用20%噻唑锌提早进行预防处理,不仅能有效降低病害的发生程度,延缓田间病害扩展速度,对水稻植株生长功能也有一定的改善作用,作物安全性好。利用此模式防控效果达到85%以上,产量比常规防治区增加10%以上。

Establishment of a system for screening and identification of novel bactericide targets in the plant pathogenic bacterium Xanthomonas oryzae pv. oryzae using Tn-seq and SPR

Xanthomonas spp. cause severe bacterial diseases. However, effective strategies for prevention and management of these diseases are scarce. Thus, it is necessary to improve the efficiency of control of diseases caused by Xanthomonas. In this study, Xanthomonas oryzae pv. oryzae(Xoo), which causes rice bacterial leaf blight, has been studied as a representative. A transposon insertion library of Xoo, comprising approximately 200,000 individual insertion mutants, was generated. Transposon sequencing data indicated that the mariner C9 transposase mapped at 35.7–36.4% of all potential insertion sites, revealing 491 essential genes required for the growth of Xoo in rich media. The results show that, compared to the functions of essential genes of other bacteria, the functions of some essential genes of Xoo are unknown, 25 genes might be dangerous for the Xanthomonas group, and 3 are specific to Xanthomonas. High-priority candidates for developing broad-spectrum, Xanthomonas-specific, and environment-friendly bactericides were identified in this study. In addition, this study revealed the possible targets of dioctyldiethylenetriamine using surface plasmon resonance(SPR) in combination with high performance liquid chromatography–mass spectrometry(HPLC–MS). The study also provided references for the research of some certain bactericides with unknown anti-bacterial mode of action. In conclusion, this study urged a better understanding of Xanthomonas,provided meaningful data for the management of bacterial leaf blight, and disclosed selected targets of a novel bactericide.

水稻细菌性条斑病和白叶枯病抗性遗传研究

分析了Ｈａｓｈｉｋａｌｍｉ，Ｄｕｌａｒ和９０ＩＲＢＢＮ４４三个抗源品种对水稻细菌性条斑病Ｓ－１０３菌株和白叶枯病Ｐ１菌系的抗性遗传。结果表明，Ｈａｓｈｉｋａｌｍｉ和Ｄｕｌａｒ对Ｓ－１０３的抗性均由２对隐性基因所控制，９０ＩＲＢＢＮ４４则带有１对隐性抗性基因。经等位性测定表明，Ｈａｓｈｉｋａｌｍｉ和Ｄｕｌａｒ的２对基因中至少有１对是等位的，但它们与９０ＩＲＢＢＮ４４的１对基因均不等位。３个抗源品种对Ｐ１的抗性都受１对隐性基因控制，该基因与ｘａ－５等位。连锁遗传分析表明，Ｈａｓｈｉｋａｌｍｉ和Ｄｕｌａｒ对Ｓ－１０３的２对抗细条病基因中的１对与ｘａ－５相连锁，而９０ＩＲＢＢＮ４４的１对抗性基因与ｘａ－５呈独立遗传。本文还就开展水稻抗细菌性条斑病育种进行了讨论。

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。

稻瘟菌诱导的广谱抗性

以稻瘟弱致病菌对关东51、爱知旭、新2号作诱导接种,又用稻瘟强致病菌、稻胡麻叶斑菌、稻白叶枯病菌进行挑战接种,水稻均获得对这3种病害的诱导抗性。又以稻胡麻叶斑菌为诱导因子,也同样使水稻表现了不同程度的抗瘟性。

创制农药噻唑锌对水稻细菌性病害的田间药效

噻唑锌是噻二唑类有机锌杀菌剂，对水稻细菌性病害有较好的防治效果。两次药后14d调查结果表明，对水稻白叶枯病，20％噻唑锌SC225—375g a．i．／hm^2防治效果均极显著高于20％叶枯唑WP300g a．i．/hm^2的防治效果；对水稻细菌性条斑病，20％噻唑锌SC 300～375g a．i．／hm^2防治效果极显著高于20％叶枯唑WP 300g a．i．／hm^2的防治效果，225g a．i．／hm^2防治效果与20％叶枯唑WP 300g a．i．／hm^2的防治效果相当。生产上使用20％噻唑锌SC，推荐剂量为225-375g a．i．／hm^2，间隔7d左右，连续施药两次，对水稻白叶枯病、水稻细菌性条斑病均有较好的防治效果。

云南稻种对水稻白叶枯病抗性的评价

2000～2001年鉴定了近300份水稻品种(包括云南省主栽品种、近等基因系材料、基因聚合品种等育种材料)对白叶枯病的抗性。其中对测试的白叶枯病菌系表现抗病的有51个,占供试品种的17%,云南省主栽品种如合系等粳稻品种及籼型杂交稻高度感病,说明云南省主栽品种多数对白叶枯病系表现感病,近等基因系材料抗感表现不一,基因聚合品种高抗白叶枯病。

松毛虫赤眼蜂携带质型多角体病毒防治马尾松毛虫

在湖南两个林场试验的结果显示，用携带松毛虫质型多角体病毒的赤眼蜂防治松毛虫比未携带病毒寄生蜂的防治效果要高。两者的防治效果分别为９４．１％～９７．３％和７４．６％～８１．２％。赤眼蜂对寄主卵的发育程度有明显的选择性，寄主卵发育超过３０小时的很少受赤眼蜂寄生。用携带病毒赤眼蜂传播病毒可以增加松毛虫的死亡率。用赤眼蜂传播病毒的方法比在林间喷洒病毒可节省大量的病毒剂。

茉莉酸甲酯浸种对水稻幼苗白叶枯病抗性及抗氧化酶活性的影响

以温229(感白叶枯病)和嘉早312(抗白叶枯病)为材料,研究外源茉莉酸甲酯(methyl jasmonate,MeJA)浸种对水稻幼苗接种白叶枯病菌后抗氧化酶活性及膜脂过氧化的影响。结果表明,MeJA浸种显著降低了水稻幼苗白叶枯病病情指数,对抗病品种的诱导效果优于感病品种;幼苗叶片超氧化物歧化酶(superoxide dismutase,SOD)、过氧化物酶(peroridase,POD)、过氧化氢酶(catalase,CAT)和抗坏血酸过氧化物酶(ascorbate peroxidase,APX)等酶活性随MeJA浓度的升高先增强后减弱,丙二醛(Malondialdehyde,MDA)含量先降低后升高,MeJA浓度为0.5mmol/L时表现为毒害作用。不同抗性品种幼苗抗氧化酶活性和MDA含量对MeJA浸种响应不同,表明MeJA浸种可有效减轻水稻幼苗白叶枯病的发生,其中,抗氧化物酶活性的提高和MDA的下降与水稻对白叶枯病的抗性反应有关。

早籼稻空间诱变新品种“浙101”的选育

早籼“浙9248”经卫星搭载诱变处理,SP2在株高、生育期、穗长、每穗粒数、千粒重、结实率、抗病性等性状上出现了较大的分离,经病区多代筛选培育获得早籼突变体“浙101”,在熟期、抗病性和产量等性状上比原亲本有明显改良。2003-2004年浙江省两年区试平均每公顷产量7189.5 kg,比对照“嘉育293”增产3.7%,表现株型适中,穗、粒、重兼顾,茎秆粗壮,抗倒性强,抗稻瘟病等特点。2002-2004年经浙江省多点稻瘟病和白叶枯病联合鉴定,平均叶瘟0.8级,穗瘟1.5级,穗瘟损失率2.6%;白叶枯病4级,抗病性比原亲本和对照有显著提高。2005年10月通过浙江省农作物品种审定委员会审定,是浙江省第1个通过空间诱变技术选育成功的早籼稻新品种,适宜在浙江省及长江中下游稻区作早籼稻种植。该品种的选育成功表明空间诱变同步改良早籼稻多个性状的可能性与有效性,为改良水稻品种的抗性提供了新的途径。

水稻黄单胞细菌的无毒基因

水稻黄单胞细菌白叶枯致病变种与水稻品种的互作关系符合基因 基因假说。病菌无毒基因 (A)与寄主抗病基因(R)显性互作表现抗性反应。许多黄单胞细菌的无毒基因属于avrBs3/ pth家族。已报道的avrxa5、avrXa7、avrXa10以及本实验室从水稻白叶枯病菌菌株JXOⅢ克隆的avrXa3均属于avrBs3/ pth家族。最近的研究还发现 ,PR6菌株中有2个硫同化基因簇成员raxP和raxQ对决定avrXa2 1活性是必需的。笔者在研究无毒基因avrXa3时 ,从JXOⅢ的基因组文库克隆中发现一个与甘蓝黑腐黄单胞菌烯醇化酶 磷酸酶基因的同源序列也具有无毒基因活性。在介绍黄单胞细菌无毒基因类群和avrBs3/ pth家族基因结构与功能的同时 。