Symbiotic and competitive properties of motility mutants of Rhizobium trifolii TA1

Non-motile mutants of Rhizobium trifolii defective in either flagellar synthesis or function were isolated by transposon Tn5 mutagenesis. they were indistinguishable from motile control strains in growth in both laboratory media and in the rhizosphere of clover roots. When each non-motile mutant was grown together with a motile strain in continuous culture, the numbers of motile and non-motile organisms remained in constant proportion, implying that their growth rates were essentially identical. When inoculated separately onto clover roots, the mutants and wildtype did not differ significantly in the number of nodules produced or in nitrogen fixing activity. However, when mixtures of equal numbers of mutant and wild-type cells were inoculated onto clover roots, the motile strain formed approximately five times more nodules than the flagellate or non-flagellate, non-motile mutants, suggesting that motility is a factor in competition for nodule formation.     

Survival of inoculated Laccaria bicolor in competition with native ectomycorrhizal fungi and effects on the growth of outplanted Douglasfir seedlings

The survival, development and mycorrhizal efficiency of a selected strain of Laccaria bicolor along with naturally occurring ectomycorrhizal fungi in a young plantation of Douglas fir was examined. Symbionts were identified and their respective colonization abilities were determined. Eight species of symbiotic fungi, which may have originated in adjacent coniferous forests, were observed on the root systems. Mycorrhizal diversity differed between inoculated (5 taxa) and control (8 taxa) seedlings. Ectomycorrhizal fungi which occurred naturally in the nursery on control seedlings (Thelephora terrestris and Suillus sp.) did not survive after outplanting. Both inoculated and naturally occurring Laccaria species, as well as Cenococcum geophilum, survived on the old roots and colonized the newly formed roots, limiting the colonization by other naturally occurring fungi. Other fungi, such as Paxillus involutus, Scleroderma citrinum and Hebeloma sp. preferentially colonized the old roots near the seedling's collar. Russulaceae were found mainly in the middle section of the root system. Mycorrhizal colonization by Laccaria species on inoculated seedlings (54%) was significantly greater than on controls (13%) which were consequently dominated by the native fungi. Significant differences (up to 239%) were found in the growth of inoculated seedlings, especially in root and shoot weight, which developed mainly during the second year after outplanting. Seedling growth varied with the species of mycorrhizae and with the degree of root colonization. Competitiveness and effectiveness of the introduced strain on improving growth performances of seedlings are discussed.     

Discrete differences between strains of different Rhizobium spp. for competitive nodule occupancy on beans

Rhizobium etli strain TAL182 and R. leguminosarum bv phaseoli strain 8002, both of which produce melanin pigment, were tested for their nodulation competitiveness on beans by paired inoculation with two strains which do not produce melanin: R. tropici strain CIAT899 and Rhizobium sp. strain TAL1145. An assay was developed to distinguish nodules formed by the melanin-producing and non-producing strains. Strain TAL182 had discrete competitive superiority over CIAT899 and TAL1145 for nodulation of beans. Nodulation competitiveness was not correlated with the ability to produce melanin pigment or the host range of the Rhizobium strains tested.The authors are with the Department of Plant Molecular Physiology, University of Hawaii, 3050 Maile Way, Gillmore 402, Honolulu, HI 96822, USA     

Sterilization of Hulecoeteomyia japonica japonica (= Aedes japonicus japonicus) (Theobald, 1901) by high‐energy photon irradiation: implications for a sterile insect technique approach in Europe

Hulecoeteomyia japonica japonica (= Aedes japonicus japonicus) (Diptera: Culicidae) (Theobald 1901), a container‐breeding invasive species in North America and Europe, is attracting particular attention for its high local abundances and possible roles in the transmission of human and animal pathogens. The preferential habitats of this species are forested and bushy areas, which renders control measures extremely inefficient. Use of the sterile insect technique (SIT) may contribute to the implementation of area‐wide integrated pest management strategies, as has been successfully proven with other aedine mosquito species. The present study investigates the effects of irradiation at a dose of 40 Gy on fitness parameters in H. j. japonica. Irradiation was performed on 16–24‐h‐old pupae from a colonized strain (PA) using a TrueBeam linear accelerator. Males from the PA strain were crossed with females of the same colony or with field‐collected females. Irradiation induced a slight increase in mortality in male pupae, but did not alter the survival and mating abilities of emerging adult males. Rates of blood feeding and fertility were lower when PA strain males were kept with field‐collected females rather than PA females. Irradiated males induced reductions in fertility (residual fertility: 2.6%) and fecundity in mated females. The data indicate that the SIT is a suitable technique to enhance the control of this species.     

Improving male mating competitiveness and survival in the field for medfly,Ceratitis capitata (Diptera: Tephritidae) SIT programs

The success of the sterile insect technique (SIT) depends critically upon mating between released sterilized males and wild females. In Hawaii, improvements in the efficiency of sterile males were attempted on two separate fronts – mating enhancement and survival improvement. In the former, two methods have been investigated – selective breeding and aromatherapy. In the latter, flies which survived in field cages for several days were selected and bred to produce progeny with enhanced survival ability compared to control flies. Regarding mating selection, standard laboratory-reared males that successfully mated with wild females in field cages were allowed to breed. F1 offspring were inbred, then the selection procedure was repeated for four additional cycles. In the aromatherapy procedure, laboratory-reared males were exposed to ginger root oil for several hours 1 day prior to testing in field cages. Compared to controls, the selected flies improved the mating competitiveness of male flies ca. 3-fold, irradiation reduced this increase to ca. 2.5-fold. Exposing the selected, hybrid strain raised the fitness of the lab males to ca. 9-fold that of wild males. In the ongoing survival selection study, we have obtained lines in which the selected males survived ca. 2-fold better than laboratory control males over several days in an outdoor field cage, with food and water provided. The goal is to combine the traits of higher survival and mating ability into a single strain for SIT release.     

Aquaculture: global status and trends

Aquaculture contributed 43 per cent of aquatic animal food for human consumption in 2007 (e.g. fish, crustaceans and molluscs, but excluding mammals, reptiles and aquatic plants) and is expected to grow further to meet the future demand. It is very diverse and, contrary to many perceptions, dominated by shellfish and herbivorous and omnivorous pond fish either entirely or partly utilizing natural productivity. The rapid growth in the production of carnivorous species such as salmon, shrimp and catfish has been driven by globalizing trade and favourable economics of larger scale intensive farming. Most aquaculture systems rely on low/uncosted environmental goods and services, so a critical issue for the future is whether these are brought into company accounts and the consequent effects this would have on production economics. Failing that, increased competition for natural resources will force governments to allocate strategically or leave the market to determine their use depending on activities that can extract the highest value. Further uncertainties include the impact of climate change, future fisheries supplies (for competition and feed supply), practical limits in terms of scale and in the economics of integration and the development and acceptability of new bio-engineering technologies.In the medium term, increased output is likely to require expansion in new environments, further intensification and efficiency gains for more sustainable and cost-effective production. The trend towards enhanced intensive systems with key monocultures remains strong and, at least for the foreseeable future, will be a significant contributor to future supplies. Dependence on external feeds (including fish), water and energy are key issues. Some new species will enter production and policies that support the reduction of resource footprints and improve integration could lead to new developments as well as reversing decline in some more traditional systems.     

Effects of the juvenile hormone analogue methoprene and dietary protein on male melon fly Bactrocera cucurbitae (Diptera: Tephritidae) mating success

The effect of access to dietary protein (P) and the topical application of a juvenile hormone analogue (methoprene (M)) on mating behaviour of male melon fly Bactrocera cucurbitae was assessed in the laboratory and in field cages. Age, dietary protein and methoprene application increased the mating success and influenced the mating behaviour. Treatment with methoprene (M+) to protein-deprived (P−) males had only a modest effect on the acceleration of sexual maturity, but application of methoprene (M+) to protein-fed (P+) males greatly accelerated sexual maturity. Protein diet (P+) increased mating success of males in comparison to protein-deprived (P−) males. Protein and methoprene have a synergistic effect on mating behaviour, since M + P+ treated males exhibit reduced mating latency and achieved higher mating in younger ages than methoprene and/or protein-deprived males. Copulation duration was correlated with nutritional status and M + P+ males copulated longer at the age of advanced sexual maturity than M − P+ males. Our results suggest that in this species with a lek mating system, females discriminate between the males based on their sexual signals, which were influenced by protein in the adult diet, methoprene application and age. The results are discussed in the light of mating competitiveness of precocious treated young males and their relevance to Sterile Insect Technique application against this pest species.     

转cry1Ac＋cry2Ab基因棉与转cry1Ac＋剧咯邢基因棉荒地的生存竞争能力

【背景】此研究为“十二五”转基因生物新品种培育国家项目中创建新的转基因棉花品种环境安全评价技术而设。【方法】以转双价双成抗虫基因（cry1Ac＋cry2Ab）棉和转双价抗虫、抗除草剂基因（cry1Ac＋肼强阳）棉为观察品种,非转基因棉赣棉11号为对照品种,在荒地用撒播和3cm深度播种2种方式,于2011年5月一2012年3月对棉花出苗率、株高、生育进程、棉吐絮瓣数、絮瓣脱落率、自生苗等生存竞争能力进行比较,检测、评价其杂草化的风险,并探讨、验证检测技术的可行性。【结果】在荒地条件下,以2种方式播种的转cry1Ac＋cry2Ab基因棉和转cry1Ac＋EP5P5基因棉与非转基因棉相比,上述各项指标的竞争能力总体上未表现显著优势。【结论与意义】转cry1Ac＋cry2Ab基因棉和转cry1Ac＋EPSPS基因棉在荒地条件下生长无杂草化风险。同时,研究证明,在荒地自然生态条件下,可以采用撒播和3cm深度播种方法检测新的转基因棉花品种在生存竞争能力上的杂草化风险,在测评上有互为参照效应,为定性评价新的转基因棉花品种的杂草化风险提供了保障。     

Growth and Parasite Defence in Plants; the Balance between Resource Sequestration and Retention: In Lieu of a Guest Editorial

Abstract: A hypothesis on regulation of the balance between growth and parasite defence in plants is formulated, namely that plants regulate their resource allocation in a way where stress tolerance and resistance inherently lead to constraints on growth and competitiveness. Seven reviews and the subsequent article in this issue of Plant Biology contributing to this problem are briefly introduced in context.     

Isolation and characterization of a bacteriocin produced by Cicer-Rhizobium

A constitutively expressed bacteriocin from Cicer-Rhizobium was purified to homogeneity. The purified preparation yielded a homogenous protein with a molecular weight of about 29 kDa. This protein was heat stable, unaffected by nucleases and was found to have an iso-electric point (pI) of 4.6. The N-terminal sequence of the protein was found to be M-N-N-N-Y-R-E-L-L-P-I-I-G-P-P-W-A-E-I-E, sharing 78% homology with linocin M18. Bacteriocin bioactivity was correlated with the presence of a 29 kDa protein in the growth diffusates of the culture. A mutant strain unable to produce this bacteriocin was found to have a statistically significant reduction in nodule occupancy and competitiveness against the wild type and indigeneous populations under unsterile conditions. Bacteriocin production by the mutant carrying the complement clone pJNP365 was found to be stable even in an unsterile environment.