Quantitative genetic analysis of Cry1Ab tolerance in Ostrinia nubilalis Spanish populations 2

Abstract 2 Tolerance to Bacillus thuringiensis Cry1Ab toxin in Spanish Ostrinia nubilalis 3 populations was analyzed by quantitative genetic techniques, using isolines established 4 from field-derived insects. F1 offspring was tested for susceptibility to trypsin activated 5 Cry1Ab using a concentration that caused a mean larval mortality of 87% (± 17% SD). 6 The progeny of the most tolerant isolines (that had shown mortalities lower than 60%) 7 was crossed to obtain the F2 generation that was exposed to the same Cry1Ab 8 concentration. A clear reduction in mortality (62% ± 17% SD) was observed. The upper 9 limit for heritability was estimated to range between 0.82 and 0.90, suggesting that a 1

Multiple mutations in the nicotinic acetylcholine receptor Ccα6 gene associated with resistance to spinosad in medfly

Spinosad is an insecticide widely used for the control of insect pest species, including Mediterranean fruit fly, Ceratitis capitata. Its target site is the α6 subunit of the nicotinic acetylcholine receptors, and different mutations in this subunit confer resistance to spinosad in diverse insect species. The insect α6 gene contains 12 exons, with mutually exclusive versions of exons 3 (3a, 3b) and 8 (8a, 8b, 8c). We report here the selection of a medfly strain highly resistant to spinosad, JW-100 s, and we identify three recessive Ccα6 mutant alleles in the JW-100 s population: (i) Ccα63aQ68* containing a point mutation that generates a premature stop codon on exon 3a (3aQ68*); (ii) Ccα63aAG>AT containing a point mutation in the 5' splicing site of exon 3a (3aAG > AT); and (iii) Ccα63aQ68*-K352* that contains the mutation 3aQ68* and another point mutation on exon 10 (K352*). Though our analysis of the susceptibility to spinosad in field populations indicates that resistance has not yet evolved, a better understanding of the mechanism of action of spinosad is essential to implement sustainable management practices to avoid the development of resistance in field populations

Expression of a barley cystatin gene in maize enhances resistance against phytophagous mites by altering their cysteine-proteases

Phytocystatins are inhibitors of cysteine-proteases from plants putatively involved in plant defence based on their capability of inhibit heterologous enzymes. We have previously characterised the whole cystatin gene family members from barley (HvCPI-1 to HvCPI-13). The aim of this study was to assess the effects of barley cystatins on two phytophagous spider mites, Tetranychus urticae and Brevipalpus chilensis. The determination of proteolytic activity profile in both mite species showed the presence of the cysteine-proteases, putative targets of cystatins, among other enzymatic activities. All barley cystatins, except HvCPI-1 and HvCPI-7, inhibited in vitro mite cathepsin L- and/or cathepsin B-like activities, HvCPI-6 being the strongest inhibitor for both mite species. Transgenic maize plants expressing HvCPI-6 protein were generated and the functional integrity of the cystatin transgene was confirmed by in vitro inhibitory effect observed against T. urticae and B. chilensis protein extracts. Feeding experiments impaired on transgenic lines performed with T. urticae impaired mite development and reproductive performance. Besides, a significant reduction of cathepsin L-like and/or cathepsin B-like activities was observed when the spider mite fed on maize plants expressing HvCPI-6 cystatin. These findings reveal the potential of barley cystatins as acaricide proteins to protect plants against two important mite pests

The whole genome sequence of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), reveals insights into the biology and adaptive evolution of a highly invasive pest species

The Mediterranean fruit fly (medfly), Ceratitis capitata, is a major destructive insect pest due to its broad host range, which includes hundreds of fruits and vegetables. It exhibits a unique ability to invade and adapt to ecological niches throughout tropical and subtropical regions of the world, though medfly infestations have been prevented and controlled by the sterile insect technique (SIT) as part of integrated pest management programs (IPMs). The genetic analysis and manipulation of medfly has been subject to intensive study in an effort to improve SIT efficacy and other aspects of IPM control

Susceptibility to the Cry1F toxin of field populations of Sesamia nonagrioides (Lepidoptera: Noctuidae) in Mediterranean maize cultivation regions

9 páginas, 3 figuras, 3 tablas -- PAGS nros. 214-221Maize hybrids expressing the Cry1F toxin provide efficient control of lepidopteran pests. The Mediterranean corn borer, Sesamia nonagrioides (Lefèvre), is one of the most damaging pests of maize in the Mediterranean basin. In this work we firstly determined the efficacy of maize hybrids expressing the Cry1F toxin (event TC1507) to control neonates of S. nonagrioides. Leaf tissue feeding bioassays revealed that TC1507 maize is highly effective against this pest, and the percentage mortality obtained was comparable to that obtained with a Cry1Ab-expressing maize hybrid (Compa CB, event 176), which is known to be highly efficacious against S. nonagrioides. Secondly, interpopulation variation in the susceptibility to the Cry1F insecticidal protein was established for nine field-collected populations of S. nonagrioides (three Spanish, two French, two Italian, one Greek, and one Turkish). Estimates of the susceptibility of larvae to the Cry1F toxin showed low variability in lethal concentrations and growth inhibition concentrations among field populations. Moreover, no significant differences were found when they were grouped by geographical areas [Western Mediterranean (Spain and France) versus Eastern Mediterranean (Italy, Greece and Turkey)] or by history of exposure to Bt plants (Spanish vs. other populations). Therefore, the minor differences found in field populations can be attributed to natural variation in sensitivity to Cry1F. The importance of establishing baselines of susceptibility for resistance detection is discussed. Future changes in susceptibility of S. nonagrioides populations to Cry1F could be documented based on this baseline dataPeer reviewe

Wound‐induced changes in DIMBOA (2, 4 dihydroxy‐7‐methoxy‐2H‐1, 4 benzoxazin‐3(4H)‐one) concentration in maize plants caused by Sesamia nonagrioides (Lepidoptera Noctuidae)

Two maize (Zea mays) inbred lines, A‐619, (high DIMBOA content) and W‐117 (low DIMBOA content) were artificially infested, at similar physiological stages, with 10 first‐instar larvae of Sesamia nonagrioides. The DIMBOA concentration in stem and leaf tissues of damaged and undamaged plants was measured quantitatively in response to larval attack. After 60 h of infestation, both inbred lines were found to respond to insect attack by increasing significantly (P< 0·01) the DIMBOA content in leaf tissues compared with uninfested controls. Similar results were observed 5 days after infestation. No significant differences were found between the stem tissues of the two cultivars during this period. After 9 days infestation, significant increases (P <0·01) could still be found in the stem tissues of the two lines, these showing signs of wounding due to direct insect damage. Thereafter, until day 25 following infestation (the last day of measurement) no significant increased level of DIMBOA was recorded in stem and leaves of the infested lines in any sampling. The production of this compound appears to be a physiological response of the plant to attack induced by physical disruption of its tissues. Copyright © 1988, Wiley Blackwell. All rights reserve

Quantitative genetic analysis of Cry1Ab tolerance in Ostrinia nubilalis Spanish populations

30 p.-2 fig.-3 tab.Tolerance to Bacillus thuringiensis Cry1Ab toxin in Spanish Ostrinia nubilalis populations was analyzed by quantitative genetic techniques, using isolines established from field-derived insects. F1 offspring was tested for susceptibility to trypsin activated Cry1Ab using a concentration that caused a mean larval mortality of 87% (±17% SD). The progeny of the most tolerant isolines (that had shown mortalities lower than 60%) was crossed to obtain the F2 generation that was exposed to the same Cry1Ab concentration. A clear reduction in mortality (62 ± 17% SD) was observed. The upper limit for heritability was estimated to range between 0.82 and 0.90, suggesting that a high part of phenotypic variation in tolerance to Cry1Ab was attributable to genetic differences. An estimate of the minimum number of segregating factors indicated that the loci involved in tolerance to Cry1Ab were at least two. The role of the cadherin gene, which is a B. thuringiensis resistance gene in Lepidoptera, was assessed in the most tolerant isolines by using an EPIC-PCR marker specifically developed for this study. Association between cadherin and tolerance was obtained in one tolerant isoline; however it could be not confirmed by segregation analysis in the F2 progeny because F2 offspring was not viable. Our results indicate that the tolerance trait is common in Spanish field populations. Quantitative genetic techniques may be helpful for estimating the influence of genetic factors to Cry1Ab tolerance in O. nubilalis.Support for this project was provided by the EU Fifth Framework Project ‘‘ProBenBt’’ (Ref. QLK3-CT-2002-01969), by the Spanish Ministerio de Educación y Ciencia (project Ref. at the University of Valencia AGL2006-11914) and by the Spanish Ministerio de Ciencia e Innovación (project Ref. at the Centro de Investigaciones Biológicas of Madrid AGL 2009-08813). Cristina Crava was funded by a V Segles grant from the University of Valencia (Ref. UV-BVS- 07-2083).Peer reviewe

Citrus-orchard ground harbours a diverse, well-established and abundant ground-dwelling spider fauna

11 p.-5 tab.-3 fig.[EN]Ground-dwelling spider assemblages comprise one of the most representative predatory groups to be found in many crops. There is some evidence of the role that ground-dwelling spiders play in controlling certain citrus pests; however, there are almost no studies about the abundance and composition of this predatory group in citrus orchards. A three-year survey conducted using pitfall traps in three citrus orchards in Eastern Spain yielded more than five-thousand ground-dwelling spiders belonging to more than 50 species and 20 families. Wandering families such as Lycosidae, Gnaphosidae and Zodariidaewere the most numerous in terms of captures. The generalist predator Pardosa cribata Simon (Araneae: Lycosidae) was the most common species, representing a quarter of all captures, followed by Zodarion cesari Pekar. (Araneae: Zodariidae) and Trachyzelotes fuscipes (Koch) (Araneae: Gnaphosidae). Spiders were active throughout the year with a peak population in summer. The species abundance data for the three spider assemblages sampled fitted a log normal statistical model which is consistent with a well-established community. The presence of a cover crop provided higher abundance of alternative prey and consequently higher abundance and diversity of ground-dwelling spiders. This work demonstrates that the citrus-orchard ground harbours a diverse and abundant ground-dwelling spider fauna, which is also active throughout the year. A challenge for future studies will be to establish conservation management strategies for these predators, that will improve biological control of those citrus pests that inhabit or spend part of their life cycle on the orchard floor.[ES]Las arañas que habitan en el suelo constituyen uno de los grupos de depredadores más representativos que se encuentran en numerosos cultivos. En cítricos existen evidencias sobre el papel que pueden desempeñar algunas de estas arañas en el control de ciertas plagas. Sin embargo, en este cultivo la información disponible actualmente sobre la abundancia y composición de este grupo de depredadores es muy escasa. Por ello, se llevó a cabo un estudio de tres años mediante trampas de gravedad en campos comerciales de cítricos localizados al este de la Península Ibérica. En este, se obtuvieron más de cinco mil individuos pertenecientes a más de 50 especies y 20 familias. Lycosidae, Gnaphosidae y Zodariidae fueron las familias más abundantes en número de capturas. La especie generalista Pardosa cribata Simon (Araneae: Lycosidae) fue la especie más común, seguida por Zodarion cesari Pekar (Araneae: Zodariidae) y Trachyzelotes fuscipes (Koch) (Araneae: Gnaphosidae). Las arañas se mostraron activas durante todo el año con una población máxima en verano. La abundancia de especies para las tres localizaciones se ajustó a un modelo log normal lo cual indica que se trata de comunidades bien establecidas. Este trabajo demuestra que el suelo de cítricos alberga una abundante y diversa fauna de arañas que además se encuentra activa durante todo el año. Un reto para el futuro será establecer estrategias de gestión para la conservación de estos depredadores, y así mejorar el control biológico de aquellas plagas de los cítricos que habitan o pasan parte de su ciclo de vida en el suelo de los cítricosThis work was partly funded by FEOGA Cooperación, the Conselleria d’Agricultura, Pesca i Alimentació de la Generalitat Valenciana, INIA (RTA03-103-C6-01) and MICINN (AGL2006-13346-C02-01/AGR and AGL2008-05287-C04-01/AGR).Peer reviewe

Estimation of the intrinsic rate of natural increase and its error by both algebraic and resampling approaches

The intrinsic rate of natural increase or Malthusian parameter plays a key role fields as diverse as ecology, genetics, demography and evolution. It characterizes the growth of a population in a determinate environment. Since its rigorous statistical estimation requires of intensive calculation, the use of a computer becomes essential. The two main approaches to the calculation of the Malthusian parameter, its error and confidence intervals have been implemented in a program and have been compared by means of an example. © 1993, Oxford University Press. All rights reserved