Search

Plant resistance mechanisms to pathogens can lead to a lowered efficacy of insect microbial biocontrol agents, but the influence of plant variety has been little-studied. Leaves and stalks from twelve maize (Zea mays L.) inbreds with different plant pathogen resistance were evaluated for their influence on the efficacy of Beauveria bassiana (Bals.-Criv.) Vuill. against European corn borers (Ostrinia nubilalis (Hübner)). For leaf assays with first instar caterpillars, mortality on day 2 ranged from an inbred-dependent high of 76.1% to a low of 10.0% for European corn borers in leaf assays. For stalk assays with third instar caterpillars, mortality on day 4 ranged from an inbred dependent high of 83.0% and 75.0% to a low of 0.0% and 8.3% for fall armyworms and European corn borers, respectively. Lesion size ratings due to Fusarium graminearum (Schwabe) applied to tissues were often significantly correlated with the mortality levels of B. bassiana-treated caterpillars that fed on leaves and stalks. This study suggests that the influence of plant varieties on the efficacy of insect microbial pathogens can vary depending on the insect species involved and the plant tissue, and this is worth considering when new plant varieties and biocontrol strains are being developed whenever practical.

Abstract Tianshan Mountains provide a model for studying biological evolution and speciation. Here we assess the evolutionary history of Ostrinia furnacalis (ACB) and Ostrinia nubilalis (ECB), which are sympatric in the Yili River Valley in Xinjiang, China. Our study is based on the historical gene flow analyses of two species by using three mitochondrial DNA (mtDNA, COI, COII, Cytb) and four nuclear DNA (nuDNA, EF‐1α, Wingless, RPS5, CAD) markers obtained from representatives of HC (Huocheng), YN (Yining), XY (Xinyuan), and MNS (Manasi). Our results reveal that there is an asymmetrical gene flow pattern between the four populations. The population migratory pathways between these different populations show inflow into HC and YN, outflow from XY, and that MNS maintained a flow balance. Bayesian divergence time dating based on the COI gene suggests that the genetic divergence between the two species in this area may have occurred in Holocene at 0.008 Mya. Neutrality tests (Tajima's D, Fu's Fs), and mismatch distribution test results suggest that population expansion events may not have occurred in the recent past. The demographic history and gene flow pattern between ACB and ECB may follow the “mountain isolation” hypothesis. The ML and BI trees of the mtDNA haplotype dataset show that ECB haplotypes are grouped together in a distinct clade and are clearly separate from ACB haplotypes. However, the geographical pattern of haplotype distribution is less clear for both ACB and ECB, supporting that there has been frequent gene flow among the geographic populations in the Tianshan Mountains. These findings indicate that the Tianshan Mountains are less likely a barrier to gene flow of the two species.

The complete mitochondrial genome of Ostrinia kasmirica (Moore, 1888) was sequenced in this study. The circular mitogenome is 15,214 bp in length, containing 37 typical encoded genes and a non-coding control region. The gene organization and nucleotide composition are similar to those of most other sequenced Ostrinia species. All protein-coding genes (PCGs) initiate with ATN and terminate with TAN, except cox1 starts with CGA and cox1, cox2, nad5 terminate with an incomplete codon T. The control region of 308 bp contains three conserved features including the motif ‘TTAGA’ preceded a poly-T stretch, a microsatellite-like (TA)n element, and a poly-A stretch upstream of trnM. Phylogenetic analysis based on mitogenome sequences revealed that the O. kasmirica (the second species group) was more closely related to the third species group of the genus and the first species group was not at the basal position of this genus as that Mutuura and Munroe indicated.

Morphological characterization of three genere of insect borer (Lepidoptera: Pyraloidea). The objective of the research was to characterize the morphological differences of insect borers between Genus Etiella (Pyralidae: Phycitinae), Scirpophaga (Crambidae: Schoenobiinae), and Ostrinia (Crambidae: Pyraustinae). Observed characters were based on external morphology and genitalia. The result showed that Crambidae has praecinctorium in the tympanic organs, while lack of in Pyralidae. Phycitinae had chaetosema, proboscis, cubital pecten and the elongated forewing. Pyraustinae was lack of chaetosema and their forewings are wide towards termen. Whereas, Schoenobiinae had chaetosema with elongated forewing. Etiella had scales on antemedial area and their veins M2-M3 are fused. Forewing of Ostrinia had 11 veins and the corpus bursae shape was round irregular. Forewing of Scirpophaga had 12 veins, anal hair tuft, coremata, and the corpus bursae is round. The main characteristics used in identification at family and subfamily level were the praecinctorium, chaetosema, the shape of the forewings, proboscis, and cubital pecten. Whereas at genus level; anal hair tuft, coremata, and shape of the corpus bursae formed the basis of characterization. The morphological characterization was used to make the key identification of insect borers in Indonesia.

To understand mitogenome characteristics and reveal phylogenetic relationships of the genus Ostrinia, including several notorious pests of great importance for crops, we sequenced the complete mitogenomes of four species: Ostrinia furnacalis (Guenée, 1854), Ostrinia nubilalis (Hübner, 1796), Ostrinia scapulalis (Walker, 1859) and Ostrinia zealis (Guenée, 1854). Results indicate that the four mitogenomes—O. furnacalis, O. nubilalis, O. scapulalis, and O. zealis—are 15,245, 15,248, 15,311, and 15,208 bp in size, respectively. All four mitogenomes are comprised of 37 encoded genes and a control region. All 13 protein-coding genes (PCGs) initiate with ATN and terminate with TAN, with the exception of cox1 that starts with CGA, and cox1, cox2, and nad5 that terminate with an incomplete codon T. All transfer RNA genes (tRNAs) present the typical clover-leaf secondary structure except for the trnS1 (AGN) gene. There are some conserved structural elements in the control region. Our analyses indicate that nad6 and atp6 exhibit higher evolution rates compared to other PCGs. Phylogenetic analyses based on mitogenomes using both maximum likelihood (ML) and Bayesian inference (BI) methods revealed the relationship (O. palustralis + (O. penitalis + (O. zealis + (O. furnacalis + (O. nubilalis + O. scapulalis))))) within Ostrinia.

A sequence analysis of the mitochondrial cytochrome oxidase subunit II (COII) gene in Russian and Turkish maize-associated populations of Ostrinia nubilalis and a Slovenian population of O. nubilalis probably infesting maize revealed little diversity. This lack of diversity may have resulted from bottleneck event(s) when the maize-associated population of O. nubilalis expanded from small population(s) in association with the cultivation of maize in Europe ca. 500 years ago. In the genealogy of COII genes obtained in the present and previous studies, Eurasian samples were substantially differentiated from North American samples. Since the North American population of O. nubilalis came from Europe, our finding suggests that there is geographical differentiation in European maize-associated O. nubilalis, and that maize-associated populations of O. nubilalis expanded multiple times in Europe. Finally, a phylogenetic analysis of the COII gene did not support that O. nubilalis and O. furnacalis are the closest relatives within the O. furnacalis species group.

PCR-based O. nubilalis population and pedigree analysis indicated female specificity of a (GAAAAT)n microsatellite, and male specificity of a CAYCARCGTCACTAA repeat unit marker. These loci were respectively named Ostrinia nubilalis W-chromosome 1 (ONW1) and O. nubilalis Z-chromosome 1 (ONZ1). Intact repeats of three, four, or five GAAAAT units are present among ONW1 alleles, and biallelic variation exists at the ONZ1 locus. Screening of 493 male at ONZ1 and 448 heterogametic females at ONZ1 and ONW1 loci from eleven North American sample sites was used to construct genotypic data. Analysis of molecular variance (AMOVA) and F-statistics indicated no female haplotype or male ONZ1 allele frequency differentiation between voltinism ecotypes. Four subpopulations from northern latitudes, Minnesota and South Dakota, showed the absence of a single female haplotype, a significant deviation of ONZ1 data from Hardy-Weinberg expectation, and low-level geographic divergence from other subpopulations. Low ONZ1 and ONW1 allele diversity could be attributed either to large repeat unit sizes, low repeat number, reduced effective population (Ne) size of sex chromosomes, or the result of recent O. nubilalis introduction and population expansion, but likely could not be due to inbreeding. These sequences have been deposited in GenBank AF442958, and AY102618 to AY102620.