The Effect of Fish on the Abundance of the Rice Caseworm Nymphula depunctalis (Guenee) (Lepidoptera: Pyralidae) in Direct Seeded,Concurrent Rice-Fish Fields

In the 1996-97 dry season, a rice caseworm (Nymphula depunctalis (Guenee)) outbreak occurred at the Co Do rice-fish experimental station, Can Tho province, Mekong Delta, Vietnam. A polyculture of Thai silver barb, common carp and Nile tilapia was able to reduce the number of rice caseworm larvae (P< 0.001) by at least 93%. As a result, the number of rice caseworm adults (P< 0.001) and the percentage of damaged rice leaves (P< 0.001) were also reduced compared with rice fields without introduced fish. As the pest reduction did not differ in fields with high and low seeding densities, it was concluded that the access of fish into the rice field was not severely hampered by high rice seeding densities. The presence of fish or rice caseworms had no effect on the rice yield. The broader acceptance of rice-fish culture could lead to a reduction of the number of pesticide sprays used against highly visible defoliators like the rice caseworm. This would enforce the concept that rice-fish culture and integrated pest management are complementary.     

Can Fish Control Planthopper and Leafhopper Populations in Intensive Rice Culture?

Planthoppers and leafhoppers are important rice pests. We tried to find out whether a polyculture of silver barb, common carp and Nile tilapia could control hoppers in intensively cropped rice fields. We used the data of five rice-fish experiments conducted between 1995 and 1998 at the Co Do rice-fish research station, Can Tho province, Mekong Delta, Vietnam. Our results showed that the number of Nilaparvata lugens (Stål), Sogatella furcifera (Horváth), Nephotettix virescens (Distant) and Recilia dorsalis (Motschulsky) was the same in fields with and without stocked fish. We concluded that the three stocked fish species are not able to control hopper numbers. Other, predatory fish species might be more effective in hopper control.     

Transgenic Bt Rice Does Not Challenge Host Preference of the Target Pest of Rice Leaffolder,Cnaphalocrocis medinalis (Lepidoptera: Pyralidae)

Background

Transgenic Bt rice line T2A-1 expresses a synthesized cry2A gene that shows high resistance to Lepidoptera pests, including Cnaphalocrocis medinalis (Guenée) (Lepidoptera: Pyralidae). Plant volatile orientation cues and the physical characteristics of the leaf surface play key roles in host location or host-plant acceptance of phytophagous insects. These volatile compounds and physical traits may become altered in Bt rice and it is not known whether this influences the behavior of C. medinalis when searching for oviposition sites.

Results

The results of electronic nose analysis showed that the Radar map of Bt rice cultivars was analogous to the non- Bt rice cultivars at each growing stage. PCA analysis was able to partly discriminate between some of the Bt vs. non-Bt rice sensors, but could not to separate Bt cultivars from non-Bt cultivars. The total ion chromatogram between Bt and non-Bt rice cultivars at the seedling, booting and tillering stages were similar and 25 main compounds were identified by GC-MS. For most compounds, there was no significant difference in compound quantities between Bt and non-Bt rice cultivars at equivalent growth stages. The densities of the tubercle papicles and the trichomes on the upper and lower surfaces were statistically equal in Bt and non-Bt rice. The target pest, C. medinalis, was attracted to host rice plants, but it could not distinguish between the transgenic and the isogenic rice lines.

Conclusions

There were no significant differences between the Bt rice line, T2A-1 and the non-Bt rice for volatiles produced or in its physical characteristics and there were no negative impacts on C. medinalis oviposition behavior. These results add to the mounting evidence that Bt rice has no negative impact on the target insect oviposition behavior.     

Effect of talc-formulated entomopathogenic fungus Beauveria against leaffolder (Cnaphalocrosis medinalis) in rice

Thirteen Beauveria strains were isolated from the soil and infected insects. Among the various isolates, B₂ isolate (Arachalore) showed a higher percentage of mortality against C. medinalis (73.3%) under in vitro conditions. Conidial concentration of 1 × 10⁸ of the B2 strain registered maximum mortality of 76.7%. The least LT₅₀ value of 4.4 days was registered in B2 isolate with the spore concentration of 1 × 10⁸ and the LC₅₀ value was 3.4 × 10⁴. Beauveria strains altered the feeding behavior of C. medinalis, reduced the pupal weight, prolonged the pupation period, malformed the pupa and adult under in vitro. The efficacy of the talc-based bioformulation of Beauveria (B2) strain was tested as seed treatment + seedling dip + soil application + foliar spray against rice leaffolder under in vitro and greenhouse conditions. The percentage damage was significantly less (5.5) in B2 as compared to untreated healthy control (25.8). In addition, the same treatment increased the activities of defense-related enzymes, namely peroxidase, polyphenol oxidase, phenylalanine ammonia-lyase, chitinase, and phenolics in rice.     

Feeding site selection of first-instar larvae of Cnaphalocrocis medinalis on susceptible and resistant rice plants

More first-instar larvae of the rice leaffolder, Cnaphalocrocis medinalis (Guenée), were recovered from susceptible IR36 and Roxoro rice varieties than resistant TKM6 and Oryza perennis, 24 h after infestation. Within a rice plant, a higher proportion of larvae was recovered from young whorl leaf, followed by mature leaves and leafsheaths on all the four rice varieties tested. However, differences were observed between susceptible and resistant varieties in the distribution of larvae on these three plant parts. In laboratory choice tests, first-instar larvae preferred to settle on the young leaves of IR36 and TKM6 when presented with their respective mature leaves. No such preference was observed in tests with Rexoro and O. perennis. Larval survival was similar on young and mature leaves of Rexoro. Young leaves of IR36 and TKM6 were more suitable for survival in comparison with their respective mature leaves while the reverse was true for O. perennis. Larval movement was slower on the mature leaves and larvae took longer to reach the whorl leaf of TKM6 than on IR36. The density of trichomes of the abaxial surface of TKM6 was higher than that of the other varieties tested. Adaptive significance of feeding in the leafwhorl to young larvae is discussed.     

粽管巢蛛和拟水狼蛛对稻纵卷叶螟和稻褐飞虱捕食作用研究

应用二次正交旋转组合设计方法建立粽管巢蛛和拟水狼蛛对稻纵卷叶螟和稻褐飞虱捕食作用的数学模型。结果表明,粽管巢蛛是稻纵卷叶螟的重要天敌,粽管巢蛛和拟水狼蛛均是稻褐飞虱的重要天敌。当稻褐飞虱密度较高时,随着蜘蛛密度的增加,由于蜘蛛之间的干扰作用,导致稻褐飞虱被捕食量下降。     

东台市水稻纵卷叶螟的发生规律与防治技术

20世纪90年代以来,水稻纵卷叶螟Cnaphalocrocismedinalis(Guenee)在江苏省东台市连年重发,对水稻的正常生长威胁极大,已成为制约该地区水稻生产的重要因素之一。研究表明水稻品种、迁入时间、气候条件、人为措施等多种因素对稻纵卷叶螟的发生和危害影响较大,加强虫情监测、选用有效的药剂、适期开展防治,能有效地控制害虫的发生和危害。     

水稻品种对稻纵卷叶螟抗性的物理及生化机制

稻纵卷叶螟Cnaphalocrocis medinalis连年大发生,为在其治理中培育和推广抗虫品种,本文应用扫描电镜和生化测定研究了5个常用水稻栽培品种扬辐粳8号、扬稻6号、扬粳9538、淮稻9号和宁梗1号叶片中的硅含量、硅颗粒大小、蜡质含量等物理指标和一些生化指标与抗虫性的关系,并比较了稻纵卷叶螟幼虫危害不同水稻品种后其体内生化反应的差异。结果表明抗虫品种宁梗1号、淮稻9号叶片表面的硅含量显著高于感虫品种,硅颗粒大小在品种间无显著差异。宁粳1号叶片蜡质含量显著高于其他品种。由此表明叶片表面硅和蜡质含量与抗性有关。稻纵卷叶螟幼虫取食后,抗虫品种体内的过氧化物酶（POD）、超氧化物岐化酶（SOD）活性显著高于感虫品种,但丙二醛(MDA)含量低于感虫品种。稻纵卷叶螟幼虫取食不同品种后,其体内一些酶的活性明显不同,取食抗虫品种的幼虫体内POD和谷胱甘肽-S-转移酶(GST)活性显著高于取食其他品种的幼虫,SOD活性显著低于取食感虫品种的幼虫, 表明抗虫品种对稻纵卷叶螟幼虫有毒害作用。     

药剂防治稻纵卷叶螟幼虫的田间效果

为了筛选替代甲胺磷防治稻纵卷叶螟Cnaphalocrocismedinalis幼虫的药剂 ,对毒死蜱及其混配剂、氟虫腈 (锐劲特 )及其混配剂等 1 0多种农药进行了防治试验。试验结果表明 ,3 5 %纵卷清 (毒死蜱与乙酰甲胺磷 )可湿性粉剂、3 5 %毒斯威乳油、毒死蜱与敌敌畏混配剂以及高剂量的氟虫腈及其混配剂3 6%雄斯等药剂防治稻纵卷叶螟中高龄幼虫都有较显著的防治效果。 3 5 %纵卷清 80g 667m2 、3 5 %毒斯威 80mL 667m2 等药剂已在生产中大面积应用。在纵卷叶螟发生量大、虫龄偏高情况下 ,应适当增加用药量。     

Effect of Prey and Predator Density on Predation of Rice Leaffolder Eggs by the Cricket Metioche vittaticollis

Cage experiments were conducted to quantify the predation rate of the cricket Metioche vittaticollis (Sta ˚l) on the eggs of rice leaffolder Marasmia patnalis Bradley. Egg predation by adult females was measured in response to changes in egg density, predator density and leaf area per cage. The number of eggs consumed per predator increased with egg density, without reaching a plateau. The predation rate decreased with increasing leaf area. The functional response could be adequately described with a linear Type I model, with the effect of leaf area included. This type of response to leaffolder egg density means that predation was not limited by prey handling time or satiation, but by the search rate. The search rate is here interpreted as the leaf area effectively searched for leaffolder eggs by a single predator in one day. Estimated search rates averaged 0.13 m 2 day -1 for M. vittaticollis females. The search rate of the predators increased with prey density, but a model describing a density dependent search rate explained only 3% of the total variation in search rate. Increasing predator density per cage led to a decrease in the per capita egg predation rate when predator density was more than two per m 2 leaf area. Interference might thus reduce the potential to enhance leaffolder egg predation by conservation or augmentation of predatory cricket populations.     

Characterization of hostplant innate immunity from Kharif-II rice cultivars against rice leaf folder (Cnaphalocrocis medinalis Guen.) via in-situ screening and physicochemical assays

In 2019 and 2020, ten rice (Oryza sativa) cultivars including check commonly grown in the Kharif-II season (June-November) were in-situ screened against rice leaf folder (RLF, Cnaphalocrocis medinalis) in RLF-prone experimental plots in Bagerhat, Bangladesh, following RCBD (Randomized Complete Block Design) with three replicates and physicochemical analyses in the lab to evaluate their innate immunity to the pest. Of ten cultivars, only BRRI (Bangladesh Rice Research Institute) rice 72 and 87 tended to be moderately resistant (damage scale 3.00–4.99), while BRRI rice 73, 80, and 90 were susceptible to RLF (damage scale 7.00–8.99) and none appearing to be highly resistant or susceptible. In-field evaluation of Kharif-II rice cultivars against RLF, principal component analysis identified 14 key variables of 30 contributing maximum variance of PCA1 and PCA2. Cluster analysis grouped studied rice cultivars into four clades with clade II of BRRI rice 72 and 87 belonging to resistant club with high tannin and phenol contents (mg/g) assuring relatively higher yield (MT/ha) over others. A 3-D surface plot demonstrated, upsurge of larvae/ hill speeded up RLF incidence and severity (%) while bubble plot depicted, tiller infection (%) and RLF-fold length (cm) enhanced by leaf width (cm) limited the grain yield (MT/ha) in rice, well-supportive to correlation analysis. As per regression analysis, unit increment of tannin and phenol content (mg/g) declined tiller infection by 11 and 14%. Identified these two resistant cultivars could be used as potential parents in further breeding programs to develop an elite high yielding Kharif-II rice line by combining their novel resistance through hybridization.     

贺氏菱头蛛和食虫沟瘤蛛对稻纵卷叶螟和稻褐飞虱的捕食作用研究

应用二次正交旋转组合设计方法建立贺氏菱头蛛Bianor hotingchiehi和食虫沟瘤蛛Ummeliata insecticeps对稻纵卷叶螟Cnaphalocrocis medinalis和稻褐飞虱Nilaparvata lugens捕食作用的数学模型分别为:Y'cm=3.9984-0.2083 x1 0.7917 x2 2.1250 x3 0.2917 x4 0.5625 x1x2-0.1875 x1x3 0.1875 x1x4 0.8125 x2x3 0.1875 x2x4 0.1875 x3x4-0.4703 x21 0.0305 x22 0.0305 x23-0.0940 x24;Y'nl=6.2832 0.2917 x1 0.5417 x2-0.1250 x3 3.625 x4-0.0625 x1x2 0.5625 x1x3 0.4375 x1x4-0.4375 x2x3 0.4375 x2x4-0.4375 x3x4-0.2299 x21-0.1047 x22 0.0250 x23 0.2709 x24 .结果表明,食虫沟瘤蛛是稻纵卷叶螟和稻褐飞虱的更为重要的捕食性天敌.贺氏菱头蛛对各种干扰作用表现更为敏感.     

几种药剂及施药方式对稻纵卷叶螟的防治效果

对稻纵卷叶螟Cnaphalocrocis medinalis Guen e高龄幼虫防治药剂31%氟虫腈.三唑磷ME和当地几种常用药剂及不同施药方法对防治效果影响进行试验。结果表明:(1)毒死蜱(48%乐斯本EC)有较好速效性,药后1 d可达理想防效,三唑磷与氟出腈、氟铃脲复配的药剂(31%氟虫腈.三唑磷ME、21%氟虫腈.三唑磷EC、15%氟铃脲.三唑磷EC)药后3d才能达到理想防效;(2)药后3d,各处理均达到理想防效,防效依次为31%氟虫腈.三唑磷ME1.5L/hm2>31%氟虫腈.三唑磷ME1.05L/hm2>21%氟虫腈.三唑磷EC1.5L/hm2>48%毒死蜱EC1.5L/hm2>15%氟虫腈.三唑磷EC1.5L/hm2>15%阿维菌素.毒死蜱EC1.5L/hm2;(3)分虫龄防效统计,药后3d供试药剂对1龄以下(施药时虫龄,后同)幼虫防效均在91%以上,对2~3龄幼虫,31%氟虫腈.三唑磷ME保持90%以上的防效,其它处理防效明显下降,对4龄以上高龄幼虫,31%氟虫腈.三唑磷1.5L/hm2细喷雾处理防效仍达95.6%,其它处理防效很低。(4)细喷雾可提高31%氟虫腈.三唑磷ME对稻纵卷叶螟的防治效果,尤其是对高龄幼虫,与工农16型1.8mm孔径喷片的常规喷雾相比,1.2mm孔径喷片细喷雾处理药后3 d防效提高5.5%,东方红18型弥雾处理防效提高7.8%,其中,弥雾处理对1~2龄幼虫防效提高4.7%,对4~5龄幼虫防效提高了20.8%。     

影响水稻幼穗培养体细胞胚胎发生因素的研究

用水稻幼穗为外植体进行组织培养,研究了影响其体细胞胚胎发生的有关因素,建立了高频率体细胞胚胎发生的培养程序。结果表明不同基因型之间体细胞胚胎发生率的差异达到61．2％;生长素2,4－D对诱导水稻体细胞胚起重要的调控作用,细胞分裂素BA有一定的协同促进作用。干燥处理可提高愈伤组织体细胞胚胎发生率,愈伤组织含水量在60％～80％范围的培养效果较好;外源DNA溶液浸泡发育早期的心状体细胞胚．其进一步发育时异常胚的频率显著增加．成苗率降低。     

Cloning,characterization, and RNAi effect of the chitin synthase B gene in Cnaphalocrocis medinalis

The rice leaf folder (RLF), Cnaphalocrocis medinalis, is one of the major pests of rice, and chitin synthase is a key enzyme for the chitin synthesis pathway in insects. In this study, the chitin synthase B gene from C. medinalis (CmCHSB) was cloned and characterized. The cDNA of CmCHSB is 4824 bp in length, containing an open reading frame of 4578 nucleotides that encodes 1525 amino acids. The CmCHSB zymoprotein consists of 10 transmembrane domains (TMDs) in the N-terminus, a middle conserved catalytic domain, and 7 TMDs in the C-terminus. Homology and phylogenetic analyses revealed that CmCHSB possesses the closest relationship with its homolog in Ostrinia furnacalis. CmCHSB was expressed throughout development and in all of the adult tissues tested, with the highest expression level in the adult and in the midgut. Silencing of CmCHSB through RNA interference (RNAi) severely affected RLF larval growth and caused larval lethality. Our results revealed that CmCHSB is essential for RLF growth and development, which sheds new light on the characteristics and functions of this gene. These findings will be helpful for green control of RLF, by targeting the CmCHSB gene using RNAi technology.     

Calcium Effect on the Process of Cold-Hardening of Rice Seedlings

Rice seedlings for cold-hardening were germinated from seeds treated with or without immersion in 30 mmol/L of CaCl2 solution. Change of membrane system protectivity in leaves at various periods (viz: following cold-hardening, chilling stress and on the 3rd day of recovery); the ratio of seedling survival and the ability of recovery were investigated. The results showed that cold-hardening increased the contents of endogenous antioxidants (the reduced form of glutathione, GSH; ascorhic acid, ASA), SOD activity and the content of heat stable protein in soluble protein. Cold-hardening combined with the CaC12 treatment of seeds enhanced the above-mentioned effects of cold-hardening, and obviously increased the activities of catalase (CAT) and peroxidase (POD). Both cold-hardening with or without the CaCl2 treatment reduced the declining degree of GSH, AsA content, the SOD activity and the heat stable protein content caused by chilling stress, augmented the increase in the level of GSH, AsA, CAT, SOD, POD and heat stable protein in the recovery periods. The CaC12 pretreatment especially had more effect on the level of heat stable protein, augmenting the A protein to rise to the level in normal seedlings. Furthermore, cold-hardened seedlings from seeds pretreated with CaClz grew faster and better in the recovery period of chilling stress than those from seeds without CaClz pretreatment. This promotive effect of CaC12 treatment on seeds prior to cold-hardening of seedling could be associated with an aug- mentation of membrane protectivity induced by the combined treatment.     

赤霉素对三个黑稻品种生长的作用

用 3个浓度的赤霉素对 3个品种的黑稻 (黑丰糯 ,黑粳 ,黑优粘 )的幼苗进行处理 ,结果表明 ,黑丰糯对GA的反应较为敏感 ,其生长的增加量与GA的浓度有近乎线性的关系 ,而黑粳及黑优粘对赤霉素处理的反应不明显。     

水稻幼穗组培及白化苗的电镜观察

木文报道了五份水稻材料的幼穗组培的诱导率和分化率,对继代８次后的幼穗愈伤分化出的白苗和绿苗及其各自的愈伤进行电镜扫描,发现白苗的质体结构不完整,不能正常合成叶绿素。