Mechanisms and genetic diversity for host plant resistance to spotted stem borer,Chilo partellus in sorghum,Sorghum bicolor

Levels of resistance to spotted stem borer, Chilo partellus, in the germplasm are low to moderate and therefore we evaluated 25 sorghum genotypes for resistance to stem borer to identify lines with diverse mechanisms of resistance to this insect. Leaf glossiness was significantly and negatively associated with low deadheart formation. Dwarf genotypes with fewer nodes showed more deadheart formation. Antixenosis and/or antibiosis for leaf feeding, and reduced deadheart formation, tunnelling, and number of exit holes resulted in lower losses owing to C. partellus damage. Axillary tillers compensated for loss in grain yield owing to borer infestation as a result of deadheart formation, but their synchrony for maturity with the main plant is quite important. Path coefficient analysis revealed that direct effects of stem tunnelling on loss in grain yield were greater than leaf feeding and deadhearts. However, leaf feeding via stem tunnelling showed maximum indirect effects on loss in grain yield. Estimates for broad‐sense heritability and genetic advance suggested that it is possible to improve for grain yield under stem borer infestation. Heritability estimates for grain yield were usually higher than for stem borer damage parameters. Multi‐trait cluster analysis placed the test genotypes into four and five clusters in rainy and post‐rainy seasons, respectively. The genotypes placed in different groups, and showing resistance to leaf feeding, deadheart formation, stem tunnelling, and/or compensation in grain yield can be used for sorghum improvement.     

Effect of mannose-binding lectin from peanut and pea on the stem borer Chilo partellus

A mannose-binding lectin found in vegetative tissues of peanut, Arachis hypogaea, was compared with mannose-binding lectin from pea, Pisum sativum, for toxic effects on larvae of the stem borer Chilo partellus (Swinhoe). After 10 days, the mortality of larvae fed on artificial diet containing 0.5% (m/m) peanut lectin was 46.2%. The mortality of larvae fed on 1.0% peanut lectin was similar (48.1%) but insects were significantly smaller than those of the 0.5% treatment. Larvae of both lectin treatments stopped feeding within three days. Larval size and mortality was not significantly reduced by 0.1% peanut lectin and 1% heat-treated lectin did not show toxic effects. The mannose-binding lectin from pea was not toxic to C. partellus at concentrations up to 1%. Peanut lectin bound to the apical membranes of columnar epithelial cells in the mid-gut of C. partellus. This suggests that peanut lectin has an antinutritive action and that it may protect vegetative tissues of peanut against insect pests.     

Field resistance in maize cultivars to stem borer Chilo partellus

The Kenyan maize varieties, Hybrid 511, Hybrid 622, Pwani hybrid, Katumani Composite B, and local populations were evaluated along with the varieties of Multiple Insect-Resistant Tropical (MIRT) pool and experimental varieties from The Maize and Wheat Improvement Centre (CIMMYT), Mexico for resistance to the stem borer, Chilo partellus (Swinhoe). The artificial infestation by first-generation C. partellus on maize during the early whorl stage revealed that the leaf feeding damage, the dead heart formation, and the stem damage on the Kenyan hybrids and populations were significantly greater than on the MIRT varieties. The experimental varieties of CIMMYT were also susceptible to C. partellus. When the maize was infested at anthesis, the Kenyan varieties displayed a moderate level of resistance in terms of stem tunnelling and grain damage by C. partellus. The varieties of Multiple Insect Resistance Tropical pool can be effectively used by the breeders to enhance the resistance of agronomically good, but susceptible, varieties of Kenya.     

Parasites of the spotted stalk borer,Chilo partellus [Lepidoptera: Pyralidae] in South Africa

One egg parasite, 7 larval parasites, 2 pupal parasites and 3 larval hyperparasites were recorded parasitizing the spotted stalk borer,Chilo partellus (Swinhoe) on maize and grain sorghum in South Africa.Trichogrammatoidea lutea Girault [Trichogrammatidae] parasitized eggs ofC. partellus mainly in mid-summer. The larval parasites were active throughout the season with occasional peaks of up to 75% parasitism.Apanteles sesamiae Cameron [Braconidae], proved to be the most abundant larval parasite. It was recorded fromca. 93% of parasitized larvae but its efficiency was reduced by the hyperparasite,Aphanogmus fijiensis (Ferriére) [Ceraphronidae], which reached sometimes up to 100% parasitism on cocoons ofA. sesamiae. The efficiency ofIphiaulax sp. [Braconidae], the 2^nd most abundant larval parasite, was also hindered by the hyperparasite,Eurytoma sp. [Eurytomidae] Pupal parasites were sometimes very abundant reaching up to 100% parasitism without any interference by hyperparasites. The most abundant pupal parasites wereDentichasmias busseolae Heinrich [Ichneumonidae] andPediobius furvus (Gahan) [Eulophidae].      

Effect of sorghum phenology on the control of Chilo partellus with Nosema marucae (microspora: Nosematidae)

An aqueous suspension of Nosema marucae spores was sprayed on foliage of sorghum plants that had been infested with neonate Chilo partellus larvae at 3, 5, 7 and 9 weeks after (plant) emergence (WAE). These periods corresponded to plants at the tillering, early booting, soft dough and late maturation phenological stages, respectively. The extent of borer infestation and plant damage was monitored until crop harvest, and compared with plants which had been similarly infested but not sprayed with the pathogen, and with plants in insect‐free control plots. When applied early, infestation with neonate borer larvae caused most damage to the plants and the greatest reduction in yield in the untreated plots. Early treatment with N. marucae spores at 3 and 5 WAE resulted in the greatest reduction in damage to plants and the highest improvement in yield of seeds. It is apparent, therefore, that for maximum crop protection the microsporidian needs to be applied when sorghum is in an early phenological stage.     

Evidences of the extraglandular origin of two secretory proteins in the male accessory reproductive glands of Chilo partellus (Pyralidae,Lepidoptera, Insecta)

Summary

The male accessory reproductive glands (MARG) play an important role in contributing proteins for the formation of the spermatophore, a structure that transports sperm from the male to the female. Several studies have shown that these proteins could be either of intraglandular or extraglandular origin. SDS-PAGE analysis revealed proteins in the adult MARG of Chilo partellus, which comigrate with the larval hemolymph proteins (LHP). Ouchterlony's immunodiffusion showed that the antiserum raised against MARG extract cross-reacts with the proteins present in the adult hemolymph and fat body. Immunoprecipitates of labelled hemolymph proteins with anti-LHP or anti-MARG proteins reveal two polypeptides that comigrate with LHPs. Thus, there appear to be some proteins of extraglandular origin in the MARG of C. partellus, and the LHP could belong to this category.     

Duration of diapause in the stem borers, Busseola fusca and Chilo partellus

The duration of diapause in the stem borers Busseola fusca (Fuller) and Chilo partellus (Swinhoe) was studied in South Africa by collecting diapausing larvae from the field throughout winter (April–August). B. fusca larvae emerged as moth around the middle of October regardless of the date of collection and the length of time they were kept in the laboratory under constant 21 °C. C. partellus larvae collected in April–June emerged in November, those collected in July emerged in October, and those collected in August emerged in September. Regardless of the collection date C. partellus started to emerge from diapause earlier and moth emergence lasted up to twice as long as in B. fusca. Under laboratory conditions at 60% RH both borer larvae lost about 50% of their body mass during diapause. When provided with water B. fusca larvae lost about 30% of their body mass and adults emerged 20 days earlier than when kept dry. C. partellus, on the other hand, lost only 13% of their body weight and emerged 34 days earlier. The differences between the two species are discussed in light of different types of diapause; i.e., obligatory diapause in B. fusca and facultative diapause in C. partellus.     

二化螟滞育生物钟蛋白TIME-EA4基因的克隆及时空和温度诱导表达分析

【目的】生物测时蛋白TIME-EA4是昆虫特有的一种滞育生物钟蛋白。本文旨在克隆二化螟Chilo suppressalis TIME-EA4基因,研究其在二化螟不同发育时期和不同组织中的时空表达模式及在不同田间种群和不同温度诱导下的滞育和非滞育种群中的表达水平。【方法】通过RACE技术克隆二化螟TIME-EA4基因全长c DNA序列,利用荧光定量PCR的方法检测TIME-EA4基因在二化螟不同发育时期、6龄幼虫不同组织中的表达模式,及在不同季节采集的田间种群和不同温度处理1h后的滞育和非滞育种群6龄幼虫中的表达量变化。【结果】从二化螟中克隆获得TIME-EA4的c DNA序列(Gen Bank登录号:KU356855),全长821 bp,开放阅读框516 bp,编码172个氨基酸;TIME-EA4基因在二化螟不同发育时期和不同组织中均有表达,且在早期蛹、雌雄成虫以及6龄幼虫的头部、脂肪体和中肠中表达水平较高,同时在滞育幼虫组织中的表达高于非滞育幼虫。此外,TIME-EA4基因在滞育种群中的表达量是非滞育种群的3倍左右,同时在非滞育种群中,该基因的表达明显受10℃及以下低温的诱导,且在10℃时表达量最高,而在滞育种群中该基因的表达受温度影响不明显。【结论】结果说明TIME-EA4基因与二化螟的抗低温胁迫以及低温滞育相关。本研究为TIME-EA4在农业害虫滞育的分子作用机制研究奠定了基础。     

Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae) a new invasive species in Israel

Chilo partellus, the spotted stem borer (SSB), is reported for the first time from the fields of sorghum and corn in Israel. Spotted stem borer larvae were first discovered in July 2010 on sorghum and corn plants in the Western Galilee. The new pest had spread all over northern Israel by the end of 2011. The identity of the new pest was confirmed using the morphology of the dissected male genitalia and its attraction to SSB sex pheromone.     

Some aspects of feeding responses in the stem borer Chilo partellus swinhoe (Lepidoptera: Pyralidae).

Feeding responses of Chilo partellus larvae to different food sources, were studied. Maize and sorghum were more preferred to artificial diet by the larvae irrespective of their rearing media. Larvae fed on maize and sorghum leaves as well as maize and sorghum stems. The rearing medium did not have any effect on the feeding preference; it could only improve but not induce the feeding behaviour.     

Development of transgenic sorghum for insect resistance against the spotted stem borer (Chilo partellus)

Transgenic sorghum plants expressing a synthetic cry1Ac gene from Bacillus thuringiensis (Bt) under the control of a wound-inducible promoter from the maize protease inhibitor gene (mpiC1) were produced via particle bombardment of shoot apices. Plants were regenerated from the transformed shoot apices via direct somatic embryogenesis with an intermittent three-step selection strategy using the herbicide Basta. Molecular characterisation based on polymerase chain reaction and Southern blot analysis revealed multiple insertions of the cry1Ac gene in five plants from three independent transformation events. Inheritance and expression of the Bt gene was confirmed in T₁ plants. Enzyme-linked immunosorbant assay indicated that Cry1Ac protein accumulated at levels of 1–8 ng per gram of fresh tissue in leaves that were mechanically wounded. Transgenic sorghum plants were evaluated for resistance against the spotted stem borer (Chilo partellus Swinhoe) in insect bioassays, which indicated partial resistance to damage by the neonate larvae of the spotted stem borer. Reduction in leaf damage 5 days after infestation was up to 60%; larval mortality was 40%, with the surviving larvae showing a 36% reduction in weight over those fed on control plants. Despite the low levels of expression of Bt -endotoxin under the control of the wound-inducible promoter, the transgenic plants showed partial tolerance against first instar larvae of the spotted stem borer.     

Laboratory evaluation of the virulence of Beauveria bassiana isolates to the sorghum shoot borer Chilo partellus Swinhoe (Lepidoptera: Pyralidae) and their characterization by RAPD-PCR

Beauveria bassiana has long been used as a mycopesticide. It has a wide host range; isolates have been reported to differ in host range and virulence to a given insect species. Identification of a molecular marker linked to a virulent phenotype to a target pest would be useful in screening for isolates effective against it. Twenty B. bassiana isolates were tested for their virulence to the second instar larvae of Chilo partellus Swinhoe in laboratory bioassays and their DNA fingerprints were generated by RAPD-PCR. Three arbitrary categories of aggressiveness were chosen; isolates that caused >70%, between 70 and 40% and <40% larval mortality were grouped as highly, medium and less aggressive types, respectively. In the random amplified polymorphic DNA (RAPD) analysis a 30% variability was observed among the isolates; which clustered into three major groups. The groups based on virulence rating did not match with the RAPD clusters. One of the highly aggressive isolates clustered with less aggressive isolates in one cluster and the other grouped along with the medium aggressive isolates in a different cluster. The B. bassiana isolates were classified phenotypically based on the taxonomic order of the original insect host and the climatic zone (tropical/temperate) from which they were isolated. No correlation between the aggressiveness of the isolate and the relatedness of the original insect host to the tested insect was observed; both the highly aggressive isolates were from coleopteran insects. A correlation was found between the RAPD grouping and the phenotypic classification of the isolates. All the lepidopteran isolates grouped into one major cluster, most sub clusters were constituted by isolates from the same climatic zone.     

Biology of Tetrastichus howardi (Olliff) (Hymenoptera: Eulophidae): A facultative Hyperparasitoid of stem borers

The biology of the parasitoid Tetrastichus howardi, which was introduced from the Philippines into South Africa for the biological control of the stem borer Chilo partellus, was studied in the laboratory. On average, a T. howardi female produced 101 progeny (92% females) which developed in 4.3 hosts. The upper threshold temperature for development was around 33°C, the minimum threshold was calculated as 12.8°C and the thermal constant as 239.8 day‐degrees. With hosts, females lived 23.6 and males 16.7 days. T. howardi was found to be a facultative hyperparasitoid with a very wide host range. As a primary parasitoid, it developed in pupae of various Lepidoptera as well as Coleoptera and Hymenoptera and as a hyperparasitoid in dipteran and hymenopteran parasitoids. A linear relation was found between the number of emergent parasitoids and the volume of the host from which they emerged. Preference tests indicated that T. howardi preferred to parasitize the phytophagous insects C. partellus and Heliothis armigera, over their parasitoids Xanthopimpla stemmator and Palexorista laxa. The host selection of inexperienced T. howardi females was different from the experienced parasitoids. When given a choice, females showed preference for the host species they were allowed to parasitize previously and the host species from which they had been reared. The use of facultative hyperparasitoids in biological control in general and against stem borers in South Africa in particular is discussed.     

Twelve nuclear microsatellite loci for rice stem borer (Chilo suppressalis W.)

We developed 12 polymorphic microsatellite markers for the rice stem borer Chilo suppressalis (Walker). These loci were screened for 96 individuals from eight populations across China. The total number of alleles ranged from 3 to 33 and the expected heterozygosity at these loci ranged from 0.131 to 0.671. These molecular markers will be useful for fully investigating the population structure and host preference of C. suppressalis at fine spatial scales.     

温度胁迫对二化螟滞育幼虫生理指标的影响

为从生理生化水平上探讨二化螟滞育幼虫应对温度胁迫的生理机制,分别对系列温度胁迫(STS)和梯度温度胁迫(GTS)处理后的幼虫水、脂质、总糖、小分子碳水化合物含量及超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性进行了测定.结果表明:随着温度的降低,两种处理二化螟滞育幼虫虫体含水量趋于减少,且0℃以下时GTS处理下降幅度较STS处理显著;两种处理脂质含量均逐步下降且二者间无显著差异;两种处理总糖含量分别先减后增和持续下降,均检测出4种小分子碳水化合物,其中STS处理葡萄糖、甘油和果糖含量先增后减,海藻糖含量变化与此相反,而GTS处理海藻糖含量先减后增,葡萄糖和甘油含量呈相反变化,果糖含量无变化;14～-14℃范围内STS处理SOD和POD活性较GTS处理低,CAT活性相反.二化螟滞育幼虫生理指标的变化反映了其应对不同温度胁迫的生理响应.     

Mechanisms of resistance/susceptibility of certain sorghum cultivars to the stem borer Chilo partellus: role of behaviour and development

The role of the following colonising responses of Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae) in determining the resistance or susceptibility of seven sorghum cultivars was elucidated: (1) behavioural responses including (a) oviposition, (b) larval orientation in respect of arrest as well as attraction, (c) larval feeding, and (2) larval development. The cultivars studied were IS Nos. 18363 (Highly susceptible), 18463 and 2146 (moderately susceptible), 18520 (Serena) (tolerant), 4660 and 2205 (moderately resistant), 1044 (highly resistant). Certain responses of the insect to a cultivar were lower and others higher than those of another cultivar. Lower responses, reflecting non-preference in respect of behavioural responses and antibiosis in respect of development, would hamper colonisation of a cultivar and thus determine its resistance to the pest. On the contrary, higher responses would promote colonisation of a cultivar and render it susceptible. The net resistance or susceptibility of one cultivar, relative to another, would be determined by an interaction of the responses. In order to understand the patterns of such an interaction, a profile of all the responses for each cultivar has been developed. These profiles show that IS 1044 is the only one of the cultivars studied for which all the above responses are low, thus determining its high resistance. On the other hand, two of the responses to IS 18363 are very high and the remainder are medium thus rendering it highly susceptible. The profiles for the remaining cultivars fall between the above two extremes.Cette étude a mis en évidence l'importance des réactions suivantes de C. partellus Swinhoe (Lep.: Pyralidae) sur la résistance et la sensibilité de 7 cultivars de sorgho:

Role of membrane transport of water and glycerol in the freeze tolerance of the rice stem borer, Chilo suppressalis Walker (Lepidoptera: Pyralidae)

Overwintering larvae of the rice stem borer, Chilo suppressalis accumulate glycerol and are freezing tolerant to about -25 degrees C. However, non-diapausing larvae cannot accumulate glycerol and are killed by freezing. We compared the extent of tissue damage, the effects of glycerol concentration, and the transport of glycerol and water in fat body tissues from these larvae at selected freezing temperatures. Tissues from overwintering larvae, but not non-diapausing larvae, survive when frozen at -20 degrees C with 0.25 M glycerol, but the protection afforded by glycerol is offset by the water-channel inhibitor mercuric chloride. Glycerol in higher concentration (0.75 M) affords some protection even to the fat body of non-diapausing larvae. Radiotracer assays of overwintering larvae show that water leaves the tissues during freezing while glycerol enters, and that mercuric chloride disrupts this process. Transport is also disrupted after lethal freezing at -35 degrees C. Therefore, membrane transport of water and glycerol is involved in the avoidance of freezing injury to fat body cells of the rice stem borer, apparently by mediating the replacement of water with glycerol in freezing-tolerant tissues.     

Effects of water stress, nitrogen stress and certain sensory stimuli on infestation and damage by Chilo partellus (Swinhoe) to maize

Foliar, stalk and dead heart damage caused by Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae) to several maize genotypes (Inbred A, MBR 8637, Poza Rica 7832, ER-29SVR, Across 7844, Bulk CG 4141, MMV 600 and ICZ2-CM) subjected to water stress were significantly lower than those observed when plants were grown in the absence of water stress. Resistance of maize genotypes to C. partellus was distinguished clearly when there was no water stress to the plants. Resistance/susceptibility of maize genotypes Inbred A, MMV 400, MBR 8637 and Poza Rica 7832 to C. partellus was the same at 0, 60, 90 and 120 kg of N per hectare. At each nitrogen level, the genotypes MMV 400, MBR 8637 and Poza Rica 7832 suffered significantly lower damage than the susceptible Inbred A. The humidity stimuli from maize plants and the olfactory/hygro stimuli from the plants infested with larvae were the most important factors affecting host plant selection by ovipositing C. partellus females.     

Records of two sugarcane pests Eumetopina flavipes Muir (Hemiptera: Delphacidae) and Chilo terrenellus Pagenstecher (Lepidoptera: Pyralidae) from Torres Strait and far north Queensland

Abstract  The State of Queensland includes islands within Torres Strait. However, Quarantine legislation separates these islands from mainland Australia, and divides them into two Quarantine zones. Details of the Torres Strait and far north Queensland distribution and damage levels of Eumetopina flavipes Muir (sugarcane leafhopper) and Chilo terrenellus Pagenstecher (sugarcane stem borer) are published here for the first time. The delphacid is a known vector of the sugarcane disease, Ramu stunt, which occurs in northern Papua New Guinea (PNG) and possibly other locations. Eumetopina flavipes has been known to occur on islands within Torres Strait and the communities near the tip of Cape York Peninsula since 1983. The disease is not known to be present in this population of the bugs. The sugarcane stem borer, C. terrenellus , has been detected on a number of occasions in sugarcane on two of the three Torres Strait islands closest to PNG (Saibai and Dauan). Its 'appearance' at these two sites is intermittent and damage levels are never as high as in the nearby communities in the Western Province of PNG. The majority of sugarcane plantings on Torres Strait islands are yellow and purple varieties of chewing cane ( Saccharum officinarum ) which is the host for all records reported here. Recent detection of Chilo crypsimetalla (Turner) on several islands in Torres Strait is reported, although this is not thought to be a pest of sugarcane.     

Diapause induction, maintenance and termination in the rice stem borer Chilo suppressalis (Walker)

The rice stem borer, Chilo suppressalis, enters facultative diapause as fully grown larvae in response to short-day conditions during the autumn. Our results showed that the critical night length for diapause induction in C. suppressalis was between 10 h 22 min and 10 h 45 min at 22, 25 and 28 °C, 11 h 18 min at 31 °C, and between 10 h 5 min and 10 h 20 min under field conditions (average temperature ranged from 27.2 to 30.7 °C). The diapause incidence declined in ultra-long nights (18-22 h scotophases) and DD, and increased in ultra-short nights (2-6 h scotophases) and LL. Moreover, we found that the third instar was the stage most sensitive to the photoperiod, and night length played an essential role in the initiation of diapause. Night-interruption experiments with a 1-h light pulse at LD 12:12 (light 12:dark 12) exhibited two troughs of diapause inhibition, with one occurring in early scotophase and the other in late scotophase. Field observations for six years showed that most larvae entered winter diapause in August in response to declining day lengths, despite the high temperatures prevailing during August. By periodically transferring the field-collected overwintering larvae to different photoperiods and temperatures, the results showed that photoperiod had a significant influence on diapause development during the early phase of diapause, while high temperature significantly accelerated the termination of larval diapause.