Effect of temperature on development, growth and feeding of Coccinella septempunctata and Hippodamia convergens reared on the tobacco aphid, Myzus persicae nicotianae

Preimaginal development, mortality, aphid consumption rate, and size and weight upon reaching the adult stage of the aphidophagous coccinellids Hippodamia convergens Guérin-Méneville and Coccinella septempunctata L. collected from Karditsa, central Greece, were examined at four constant temperatures (14, 17, 20 and 23 °C) and L16:D8. The coccinellids fed on the tobacco aphid, Myzus persicae nicotianae Blackman. Egg, larval and pupal mortality was highest at 14 °C reaching 85.0, 73.8 and 29.4% in H. convergens and 49.3, 75.4 and 58.8% in C. septempunctata, respectively. Total preimaginal development ranged from 57.2 to 70.4 days at 14 °C, and to 16.9 and 22.1 days at 23 °C in H. convergens and C. septempunctata, respectively. Heavier and larger adults of H. convergens were obtained at 17 and 20 ° C. In C. septempunctata temperature did not affect adult weight while the lowest size was observed at 14 and 17 °C. Day-degrees requirements for preimaginal development in H. corvengens were 212.9 above a developmental threshold of 11.0 °C. The corresponding values for C. septempunctata were 281.5 and 10.7 °C. In H. convergens total and daily aphid consumption ranged from 46.8 aphids at 14 °C to 85.0 aphids at 23 °C and from 1.5 aphids at 14 °C to 9.2 aphids at 23 °C, respectively. The corresponding values for C. septempunctata were 112.0 and 2.7 at 14 °C and 157.7 and 12.4 at 23 °C. The results show the high potential of both predators as biological control agents against the tobacco aphid. The knowledge obtained could be essential for their appropriate use and for the improvement of mass rearing systems.     

Negative dietary effects of Colorado potato beetle eggs for the larvae of native and introduced ladybird beetles

Aphidophagous ladybird beetles (Coleoptera: Coccinellidae) are attracted to and feed heavily on aphids, but many species will also feed opportunistically on other prey that they encounter. In potatoes (Solanum tuberosum L.) in Washington State, USA, coccinellids feed on both green peach aphids (“GPA,” Myzus persicae Sulzer) and eggs of the Colorado potato beetle (“CPB,” Leptinotarsa decemlineata Say). The guild of aphidophagous ladybirds includes two native species, Hippodamia convergens Guérin-Méneville and Coccinella transversoguttata Brown. Recently, an introduced species, Coccinella septempunctata L., has invaded and apparently displaced its native congener. A second exotic, Harmonia axyridis Pallas, has colonized the area and is becoming more abundant. We compared larval development of each species on a monotypic diet of GPA, a monotypic diet of CPB eggs, or a mixed diet of both GPA and CPB eggs. Our goal was to answer two questions: (1) do larvae of the four ladybird species benefit from including CPB eggs in their diet and (2) do the four ladybird species differ in their ability to utilize CPB eggs as prey? No larva of any species completed development on a pure diet of CPB eggs, and survivorship was highest for all species when they fed on a pure diet of GPA. One native species, H. convergens, and one exotic species, H. axyridis, exhibited significantly lower survivorship on a mixed diet of both CPB eggs and GPA, compared to a pure GPA diet; H. axyridis also took longer to develop from egg to adult when both prey were provided. Survivorship of the two Coccinella spp. was not altered by the inclusion of CPB eggs with GPA, although CPB eggs lengthened the development time of C. transversoguttata. Adult size was not consistently affected by diet for any of the coccinellids. Overall, no ladybird species benefited from the inclusion of potato beetle eggs in its diet. The two Coccinella species responded similarly to the inclusion of CPB eggs, and so we would not expect any difference in the success of coccinellid larval development in potato fields following the replacement of C. transversoguttata by C. septempunctata. Hippodamia convergens and H. axyridis, the two species whose survivorship was depressed by combining CPB egg and aphid prey, were also the two species that consumed the greatest number of CPB eggs during successful larval development. A comparison of total egg consumption by each species cohort suggested that displacement of the other species by H. axyridis would not alter CPB biological control, because the higher per capita feeding rate by H. axyridis larvae compensated for individuals’ greater mortality risk on a diet including CPB eggs.     

Detection of QTLs for Stagonospora glume blotch resistance in Swiss winter wheat

Stagonospora nodorum is the causal agent of the Stagonospora glume blotch disease in hexaploid wheat. The Swiss winter bread wheat cv. 'Arina' has a highly effective, durable and quantitative glume blotch resistance. We studied 240 single seed descent (SSD)-derived lines of an 'Arina × Forno' F_5:7 population to identify and map quantitative trait loci (QTLs) for glume blotch resistance under natural infestation. Using composite interval mapping (CIM) and LOD>4.5, we detected two chromosomal regions on chromosome arms 3BS and 4BL which were specifically associated with glume blotch resistance. These identified QTLs were designated QSng.sfr-3BS and QSng.sfr-4BL, respectively. QSng.sfr-3BS peaked at the locus Xgwm389 in the telomeric region of the short arm of chromosome 3B and explained 31.2% of the observed phenotypic variance for the resistance within the population. The responsible QSng.sfr-3BS allele originated from the resistant parent 'Arina'. The QTL QSng.sfr-4BL (19.1%) mapped to chromosome arm 4BL ('Forno' allele) very close to two known genes, TaMlo and a catalase (Cat). Both QTL alleles combined could enhance the resistance level by about 50%. Additionally, they showed significant epistatic effects (4.4%). We found PCR-based microsatellite markers closely linked to QSng.sfr-3BS (gwm389) and QSng.sfr-4BL (gwm251) which make marker-assisted selection (MAS) for Stagonospora glume blotch resistance feasible. We also found one resistance QTL, QSng.sfr-5BL, on the long arm of chromosome 5B which overlapped with QTLs for plant height as well as heading time.Communicated by H. C. Becker     

WCS120 protein family and proteins soluble upon boiling in cold-acclimated winter wheat

The amount of proteins soluble upon boiling (especially WCS120 proteins) and the ability to develop frost tolerance (FT) after cold acclimation was studied in two frost-tolerant winter wheat cultivars, Mironovskaya 808 and Bezostaya 1. Protein gel blot analysis, mass spectrometry (MS) and image analysis of two-dimensional gel electrophoresis (2-DE) gels were used to identify and/or quantify the differences in protein patterns before (non-acclimated, NA) and after 3 weeks of cold acclimation (CA) of the wheats, when FT increased from -4 degrees C (lethal temperature (LT(50)), for both cultivars) to -18.6 degrees C in Bezostaya 1 and -20.8 degrees C in Mironovskaya 808. Only WCS120 protein was visible in NA leaves while all five WCS120 proteins were induced in the CA leaves. Mironovskaya 808 had higher accumulation of three members of WCS120 proteins (WCS120, WCS66 and WCS40) than Bezostaya 1. MS analysis of total sample of proteins soluble upon boiling showed seven COR proteins in the CA samples and only three COR proteins in the NA samples of cultivar Mironovskaya 808 (MIR). In conclusion, the level of the accumulation of WCS120, WCS66 and WCS40 distinguished our two frost-tolerant winter wheat cultivars. Moreover, the differences of CA and NA samples of the MIR were shown by liquid chromatography (LC)-tandem mass spectrometry (MS/MS).     

Effects on winter wheat seedling growth by toxin-producing rhizobacteria

Summary Root-colonizing pseudomonads capable of inhibiting seedling winter wheat (Triticum aestivum L.) root growth in an agar seedling bioassay also significantly inhibited wheat root growth in vermiculite; however, the inhibitory trait is quite labile in laboratory culturing. The extent of inhibition in both the agar and vermiculite medium depended on inoculum level. These pseudomonads were found to produce a toxin capable of inhibiting growth ofEscherichia coli C-la andBacillus subtilis. Field isolates that strongly inhibit growth of indicator bacteria also inhibited root growth. Toxin production by the bacteria appeared necessary for inhibition of root growth and indicator bacteria as toxin-negative (TOX^–) mutants no longer inhibited either. Antibiosis towardsE. coli as well as wheat seedling root inhibition in agar was reversed by L-methionine, providing further evidence that a toxin, produced by these organisms, is involved in growth retardation.Contribution in cooperation with the College of Agric. Res. Center, Washington State Univ., Pullman, WA 99164. Scientific Paper No. 6837.     

Variation in nitrogen use efficiency among soft red winter wheat genotypes

Summary Nitrogen use efficiency (NUE), defined as grain dry weight or grain nitrogen as a function of N supply, was evaluated in 25 soft red winter wheat genotypes for two years at one location. Significant genotypic variation was observed for NUE, nitrogen harvest index, and grain yield. Genotype x environment interaction for these traits was not significant. Several variables including N uptake efficiency (total plant N as a function of N supply), grain harvest index, and N concentration at maturity were evaluated for their role in determining differences in NUE. Nitrogen uptake efficiency accounted for 54% of the genotypic variation in NUE for yield and 72% of the genotypic variation in NUE for protein. A path coefficient analysis revealed that the direct effect of uptake efficiency on NUE was high relative to indirect effects.The investigation reported in this paper (No. 85-3-122) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with approval of the Director     

Identification of quantitative trait loci and associated candidate genes for low-temperature tolerance in cold-hardy winter wheat

Low-temperature (LT) tolerance is an important economic trait in winter wheat (Triticum aestivum L.) that determines the plants’ ability to cope with below freezing temperatures. Essential elements of the LT tolerance mechanism are associated with the winter growth habit controlled by the vernalization loci (Vrn-1) on the group 5 chromosomes. To identify genomic regions, which in addition to vrn-1 determine the level of LT tolerance in hexaploid wheat, two doubled haploid (DH) mapping populations were produced using parents with winter growth habit (vrn-A1, vrn-B1, and vrn-D1) but showing different LT tolerance levels. A total of 107 DH lines were analyzed by genetic mapping to produce a consensus map of 2,873 cM. The LT tolerance levels for the Norstar (LT₅₀=−20.7°C) × Winter Manitou (LT₅₀=−14.3°C) mapping population ranged from −12.0 to −22.0°C. Single marker analysis and interval mapping of phenotyped lines revealed a major quantitative trait locus (QTL) on chromosome 5A and a weaker QTL on chromosome 1D. The 5A QTL located 46 cM proximal to the vrn-A1 locus explained 40% of the LT tolerance variance. Two C-repeat Binding Factor (CBF) genes expressed during cold acclimation in Norstar were located at the peak of the 5A QTL.     

Effects of a microsporidium from the convergent lady beetle, Hippodamia convergens Guérin-Méneville (Coleoptera: Coccinellidae), on three non-target coccinellids

A microsporidium from Hippodamia convergens was transmitted horizontally to three non-target coccinellid hosts (Adalia bipunctata L., Coccinella septempunctata L. and Harmonia axyridis Pallas) under laboratory conditions. For all species examined, microsporidia-infected larvae took significantly longer to develop than did uninfected larvae but the microsporidium had no effect on larval mortality. Adult sex ratios of uninfected and microsporidia-infected adults were about 1:1 (♀:♂) and did not differ significantly. At the end of a 90-day trial, microsporidia-infected H. convergens produced significantly fewer eggs and did not live as long as uninfected individuals. Differences in fecundity and longevity were not observed for the three non-target coccinellids that were examined. Mean spore counts from smear preparations of microsporidia-infected A. bipunctata did not differ significantly from H. convergens, suggesting that A. bipunctata (a native coccinellid) is a suitable host for the microsporidium but infection was lighter in C. septempunctata and H. axyridis (introduced species). Vertical transmission of the pathogen was observed during the 90-day trial by examining eggs and larvae that were produced by microsporidia-infected adults. For all species examined, 100% vertical transmission of the pathogen was eventually observed. Three eugregarines were found in two adult A. bipunctata: Gregarine A trophozoites are similar in size to those of Gregarina katherina Watson (described earlier from Coccinella spp.), Gregarine B trophozoites are similar in size to those of Gregarine A but are morphology distinct, and Gregarine C trophozoites are similar in size to G. barbarara Watson (described earlier from A. bipunctata).     

Root growth and water uptake in winter wheat under deficit irrigation

Root growth is critical for crops to use soil water under water-limited conditions. A field study was conducted to investigate the effect of available soil water on root and shoot growth, and root water uptake in winter wheat (Triticum aestivum L.) under deficit irrigation in a semi-arid environment. Treatments consisted of rainfed, deficit irrigation at different developmental stages, and adequate irrigation. The rainfed plots had the lowest shoot dry weight because available soil water decreased rapidly from booting to late grain filling. For the deficit-irrigation treatments, crops that received irrigation at jointing and booting had higher shoot dry weight than those that received irrigation at anthesis and middle grain filling. Rapid root growth occurred in both rainfed and irrigated crops from floral initiation to anthesis, and maximum rooting depth occurred by booting. Root length density and dry weight decreased after anthesis. From floral initiation to booting, root length density and growth rate were higher in rainfed than in irrigated crops. However, root length density and growth rate were lower in rainfed than in irrigated crops from booting to anthesis. As a result, the difference in root length density between rainfed and irrigated treatments was small during grain filling. The root growth and water use below 1.4 m were limited by a caliche (45% CaCO₃) layer at about 1.4 m profile. The mean water uptake rate decreased as available soil water decreased. During grain filling, root water uptake was higher from the irrigated crops than from the rainfed. Irrigation from jointing to anthesis increased seasonal evapotranspiration, grain yield, harvest index and water-use efficiency based on yield (WUE), but did not affect water-use efficiency based on aboveground biomass. There was no significant difference in WUE among irrigation treatments except one-irrigation at middle grain filling. Due to a relatively deep root system in rainfed crops, the higher grain yield and WUE in irrigated crops compared to rainfed crops was not a result of rooting depth or root length density, but increased harvest index, and higher water uptake rate during grain filling.     

Genetic analysis of gliadin components in winter wheat using two-dimensional polyacrylamide gel electrophoresis

Summary Blocks of gliadin components found both in a number of varieties and in single F₂ grains of winter wheat intervarietal hybrids have been studied by two-dimensional electrophoresis combining electrophoresis in acidic aluminium-lactate buffer (pH3.1) and SDS-electrophoresis. Gliadin components (spots) have been shown to be inherited as linked groups (blocks), codominantly and in accordance with a gene dosage in triploid endosperm. Blocks include components differing in their electrophoretic mobility and molecular weight. Some allelic variants of blocks differ only in presence of few additional components or in the electrophoretic mobility of components with similar molecular weights; other variants may contain no similar components. Apparently, in the course of evolution, mutations in individual genes of gliadin-coding loci and processes changing the number of expressing genes and the sizes of their structural part occurred.     

Sequential sampling for adult coccinellids in wheat

Adult aphidophagous coccinellids are important predators of cereal aphids in wheat in the Great Plains of the United States for which sampling methods are needed to facilitate improved management. An equation relating the mean number of adult coccinellids per m² in a wheat field to its variance was obtained using Taylor's power law. A sequential sampling procedure was developed to estimate the number of adult coccinellids per m² with constant average statistical precision (standard error/mean). The procedure was constructed by an equation relating the number of adult coccinellids per m² to the number of adult coccinellids per minute of counting incorporating into the Taylor's power law relationship. The procedure involves conducting a series of 1-min counts while walking through a field at a constant velocity of 10 m per minute. After each 1-min count sequential sampling stop-lines are consulted to determine if the specified level of precision has been achieved. Two methods, a statistical procedure and comparison with independent data, were used to assess the consistency with which the specified level of precision was achieved by the procedure. Results indicated that observed precision was close to that specified by the user over a wide range of adult coccinellid density.     

O3浓度升高和太阳辐射减弱对小麦根际土壤微生物功能多样性的影响

采用开顶箱(OTC)法和遮光网技术,设置100 n L/L臭氧熏气与3个辐射减弱梯度结合,模拟臭氧浓度升高和太阳辐射减弱的复合大气背景。用BIOLOG生态测试板,采用孔平均颜色变化率法(AWCD)测定冬小麦根际土壤微生物利用不同碳源的能力,计算微生物群落多样性指数,对不同碳源的利用率进行了主成分分析。两年试验结果显示,臭氧熏气与太阳辐射减弱复合作用,降低了土壤微生物对碳源的利用速度和利用总量;除了聚合物以外其它碳源利用率显著降低;对土壤微生物多样性没有直接的影响;对碳源降解的抑制效应大于增强的O3与减弱的太阳辐射两因素各自的单独作用。太阳辐射减弱20%,一定程度上增加了对聚合物类的分解。O3熏气条件下太阳辐射减弱,糖类、胺类代谢变异度较高,受环境影响较大。     

Effectiveness of SC2053 as a chemical hybridizing agent for winter wheat

The use of chemical hybridizing agents (CHA) allows production of hybrid wheat seeds. We evaluated the effectiveness of a new CHA (SC2053) to induce male sterility on winter wheat in controlled growth conditions. CHA effectiveness was measured with the application of 4 doses (0–400–700–1000 g.ha^–1) at 7 stages. These stages were defined by the length of the main stem spike (1–4–7–11–15–20–40 mm). At heading, individual ears were isolated with a greaseproof paper bag. The seeds formed were counted on treated and control ears. The spikes' sterility was calculated three weeks after flowering. The sterility of the main stem's spike reached 95% to 100% for application of 700 g.ha^–1 and 1000 g.ha^–1 for main stem spike length of 7 mm to 20 mm. The effects of ear tillering (5 tillers per plant) on CHA effectiveness were also investigated. We observed a significant delay of ear development between the main stem and tillers so that complete sterilities were not reached for each dose. Since tillering in field conditions rarely exceeds 3 ears per plant, CHA effectiveness was studied on plants bearing 3 ears. The mean sterility of the first 3 ears was close to 100% for applications with 700 g.ha^–1 and 1000 g.ha^–1 at stages from 11 mm to 20 mm of main stem spike length.     

Heat-induced accumulation of chloroplast protein synthesis elongation factor, EF-Tu, in winter wheat

Chloroplast protein synthesis elongation factor, EF-Tu, has been implicated in heat tolerance in maize (Zea mays). Chloroplast EF-Tu is highly conserved, and it is possible that this protein may be of importance to heat tolerance in other species including wheat (Triticum aestivum). In this study, we assessed heat tolerance and determined the relative levels of EF-Tu in mature plants (at flowering stage) of 12 cultivars of winter wheat experiencing a 16-d-long heat treatment (36/30 degrees C, day/night temperature). In addition, we also investigated the expression of EF-Tu in young plants experiencing a short-term heat shock (4h at 43 degrees C). Heat tolerance was assessed by examining the stability of thylakoid membranes, measuring chlorophyll content, and assessing plant growth traits (shoot dry mass, plant height, tiller number, and ear number). In mature plants, relative levels of EF-Tu were determined after 7 d of heat stress. High temperature-induced accumulation of EF-Tu in mature plants of all cultivars, and a group of cultivars that showed greater accumulation of EF-Tu displayed better tolerance to heat stress. Young plants of all cultivars but one did not show significant increases in the relative levels of EF-Tu. The results of the study suggest that EF-Tu protein may play a role in heat tolerance in winter wheat.     

An improved medium for in vitro grain development from detached wheat spikelets

Wheat spikelets detached from the spike at anthesis were cultured on solidified media and successfully produced mature grains. These grains resembled normal grains and contained well-developed, embryos. Lower concentrations of glutamine favored dry weight increase in developing grains. Such grains were indistinguishable from grains from greenhouse-grown plants in germination on moist blotting sheets. The technique of individual spikelet culture can be used to study physiology and development of wheat grains and kernels and to study host-pathogen interactions in wheat floret diseases such as Karnal bunt.     

Blocks of gliadin components in winter wheat detected by one-dimensional polyacrylamide gel electrophoresis

Summary Inheritance of gliadin components in winter wheat has been studied by one-dimensional polyacrylamide gel electrophoresis. Single F₂ grains from 36 intervarietal hybrid combinations have been analysed. The genetic analysis has revealed blocks, including 1–6 gliadin components, which are inherited as individual mendelian traits. About 80 variants of blocks have been detected. On the basis of the allelism test they are grouped into 6 series in accordance with the number of known gliadin-coding loci located on chromosomes of the homoeologous groups 1 and 6. Each series includes 8–18 blocks controlled by different alleles of one gliadin-coding locus. Blocks of components have been confirmed to be inherited codominantly in accordance to the gene dose in the triploid endosperm. The highest similarity between members of one series is observed in groups of blocks controlled by chromosomes ID and 6D. On the contrary, many blocks controlled by chromosomes 1A and 1B have no bands in common. The presented catalogue of blocks of components may be used to make up gliadin genetic formulae and to compare electrophoregrams obtained by different authors. Blocks of gliadin components are suitable genetic markers for use in revealing and studying heterogeneity of wheat varieties, in tracing their origin, in identifying recombinations, translocations and substitutions of the genetic material and in solving many other problems of the origin, evolution and selection of hexaploid wheat.     

Identification of QTLs for resistance to Fusarium head blight, DON accumulation and associated traits in the winter wheat variety Arina

Fusarium head blight (FHB) of wheat has become a serious threat to wheat crops in numerous countries. In addition to loss of yield and quality, this disease is of primary importance because of the contamination of grain with mycotoxins such as deoxynivalenol (DON). The Swiss winter cultivar Arina possesses significant resistance to FHB. The objective of this study was to map quantitative trait loci (QTL) for resistance to FHB, DON accumulation and associated traits in grain in a double haploid (DH) population from a cross between Arina and the FHB susceptible UK variety Riband. FHB resistance was assessed in five trials across different years and locations. Ten QTL for resistance to FHB or associated traits were detected across the trials, with QTL derived from both parents. Very few of the QTL detected in this study were coincident with those reported by authors of two other studies of FHB resistance in Arina. It is concluded that the FHB resistance of Arina, like that of the other European winter wheat varieties studied to date, is conferred by several genes of moderate effect making it difficult to exploit in marker-assisted selection breeding programmes. The most significant and stable QTL for FHB resistance was on chromosome 4D and co-localised with the Rht–D1 locus for height. This association appears to be due to linkage of deleterious genes to the Rht-D1b (Rht2) semi-dwarfing allele rather than differences in height per se. This association may compromise efforts to enhance FHB resistance in breeding programmes using germplasm containing this allele.