Impact of Field Dodder (<Emphasis Type="Italic">Cuscuta campestris</Emphasis> Yunk.) on Chlorophyll Fluorescence and Chlorophyll Content of Alfalfa and Sugar Beet Plants

The impact that the parasitic plant field dodder (Cuscuta campestris Yunk.) has on chlorophyll fluorescence and chlorophyll content of infested alfalfa (Medicago sativa L.) and sugar beet (Beta vulgaris L.) was examined under controlled conditions. Several parameters of chlorophyll fluorescence were measured in infested and non-infested alfalfa and sugar beet plants over a period of twenty days, beginning with the day of infestation. Chlorophyll contents (total, relative and ratio of chlorophyll a to b) were determined 1, 7, 14 and 20 days after infestation (DAI). Field dodder was found to affect both the total and relative chlorophyll contents in infested alfalfa and sugar beet, causing significant reduction in chlorophyll content in both host plants. This parasitic plant also affects a number of parameters of chlorophyll fluorescence (F_o, F_v/F_m, Φ_PSII, F_v and IF), showing that these parameters may be considered sensitive indicators of the impact that field dodder has on its host plants.     

Host Foraging Behavior of <Emphasis Type="Italic">Dastarcus helophoroides</Emphasis> (Coleoptera: Bothrideridae) Adults,a Coleopteran Parasitoid of <Emphasis Type="Italic">Monochamus alternatus</Emphasis> (Coleoptera: Cerambycidae)

Dastarcus helophoroides adults, a coleopteran parasitoid of Monochamus alternatus, were reared in the laboratory. The objectives of this paper are to investigate the host foraging behavior of D. helophoroides, and the evidence for learning in such behaviors. Choice and no-choice experiments were carried out. The choice experiments show that the number of D. helophoroides adults choosing the Pinus massoniana log infested with M. alternatus larvae was significantly higher than that choosing the blank (a flavorless simulative log made of brown kraftpaper), and the number of D. helophoroides adults choosing the uninfested P. massoniana log was also significantly higher than that choosing the blank. The no-choice experiment shows no significant difference between the number of D. helophoroides adults that chose the infested log and that chose the uninfested log, despite previous experience with uninfested log, infested log, or neither of them. No evidence of learning in host foraging behavior in D. helophoroides adults was found. The results indicate that the volatile chemicals emitted by uninfested P. massoniana logs and infested logs with M. alternatus larvae are equally attractive to D. helophoroides.     

Localization of Genes Controlling Spherical Grain and Compact Ear in <Emphasis Type="Italic">Triticum antiquorum</Emphasis> Heer ex Udacz.

The inheritance of two taxonomically important characters was studied in hexaploid wheat species (2n = 6x = 42). The monogenic control of spherical grain was demonstrated for Triticum antiquorum Heer ex Udacz. The recessive gene controlling spherical grain in this species was localized to chromosome 3D by monosomic genetic analysis and was shown to be allelic to the s gene determining the same character in the endemic Indian species T. sphaerococcum Perciv. The T. antiquorum and T. sphaerococcum dominant genes controlling compact ears proved to be nonallelic to the corresponding T. compactum Host gene and were designated as C2. Problems of phylogeny and classification of hexaploid wheats are discussed.     

The effect of intercultivar substitution of wheat <Emphasis Type="Italic">Triticum aestivum</Emphasis> L. chromosomes on lipoxygenase activity and its correlation with the technological properties of flour

The effects of intercultivar substitution of individual chromosome pairs (except for 1B, 6D, and 7A) in the wheat cultivars Saratovskaya 29 and Janetzkis Probat, differing in quality, on specific lipoxygenase activity, the grain yield per spike, and the main technological properties of flour and dough were studied. It was demonstrated that the substitution of individual chromosomes of the recipient cultivar Saratovskaya 29 with the homologous chromosomes of the donor cultivar Janetzkis Probat caused significant changes in lipoxygenase activity and several other quality characteristics. The correlations between the lipoxygenase activity and the parameters of physical dough properties were determined. Three molecular forms of lipoxygenase (Lpx-1, Lpx-2, and Lpx-3), differing in the value of surface charge and enzymatic activity, were detected by native PAGE.     

Contributions of <Emphasis Type="Italic">TaSUTs</Emphasis> to grain weight in wheat under drought

Key message

The homologous genes to OsSUT1-5 in wheat were identified and detailed analysed. TaSUT1 was the predominant sucrose transporter group and it illustrated the genotypic variations towards drought during grain filling.

Abstract

Sucrose transporters (SUT) play crucial roles in wheat stem water soluble carbohydrate (WSC) remobilization to grain. To determine the major functional SUT gene groups in shoot parts of wheat during grain development, drought tolerant varieties, Westonia and Kauz, were investigated in field drought experiments. Fourteen homologous genes to OsSUT1-5 were identified on five homeologous groups, namely TaSUT1_4A, TaSUT1_4B, TaSUT1_4D; TaSUT2_5A, TaSUT2_5B, TaSUT2_5D; TaSUT3_1A, TaSUT3_1D; TaSUT4_6A, TaSUT4_6B, TaSUT4_6D; TaSUT5_2A, TaSUT5_2B, and TaSUT5_2D, and their gene structures were analysed. Wheat plants above the ground were harvested from pre-anthesis to grain maturity and the stem, leaf sheath, rachis, lemma and developing grain were used for analysing TaSUT gene expression. Grain weight, thousand grain weight, kernel number per spike, biomass and stem WSC were characterized. The study showed that among the five TaSUT groups, TaSUT1 was the predominant sucrose transporting group in all organs sampled, and the expression was particularly high in the developing grain. In contrast to TaSUT1, the gene expression levels of TaSUT2, TaSUT3 and TaSUT4 were lower, except for TaSUT3 which showed preferential expression in the lemma before anthesis. The TaSUT5 gene group was very weakly expressed in all tissues. The upregulated gene expression of TaSUT1 Westonia type in stem and grain reveal a crucial role in stem WSC remobilization to grain under drought. The high TaSUT1 gene expression and the significant correlations with thousand grain weight (TGW) and kernel number per spike demonstrated the contribution in Kauz’s high grain yield in an irrigated environment and high TGW in Westonia under drought stress. Further molecular level identification is required for gene marker development.

     

A novel allele of <Emphasis Type="Italic">TaGW2</Emphasis>-<Emphasis Type="Italic">A1</Emphasis> is located in a finely mapped QTL that increases grain weight but decreases grain number in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Key message

A novel TaGW2-A1 allele was identified from a stable, robust QTL region, which is pleiotropic for thousand grain weight, grain number per spike, and grain morphometric parameters in wheat.

Abstract

Thousand grain weight (TGW) and grain number per spike (GNS) are two crucial determinants of wheat spike yield, and genetic dissection of their relationships can help to fine-tune these two components and maximize grain yield. By evaluating 191 recombinant inbred lines in 11 field trials, we identified five genomic regions on chromosomes 1B, 3A, 3B, 5B, or 7A that solely influenced either TGW or GNS, and a further region on chromosome 6A that concurrently affected TGW and GNS. The QTL of interest on chromosome 6A, which was flanked by wsnp_BE490604A_Ta_2_1 and wsnp_RFL_Contig1340_448996 and designated as QTgw/Gns.cau-6A, was finely mapped to a genetic interval shorter than 0.538 cM using near isogenic lines (NILs). The elite NILs of QTgw/Gns.cau-6A increased TGW by 8.33%, but decreased GNS by 3.05% in six field trials. Grain Weight 2 (TaGW2-A1), a well-characterized gene that negatively regulates TGW and grain width in wheat, was located within the finely mapped interval of QTgw/Gns.cau-6A. A novel and rare TaGW2-A1 allele with a 114-bp deletion in the 5′ flanking region was identified in the parent with higher TGW, and it reduced TaGW2-A1 promoter activity and expression. In conclusion, these results expand our knowledge of the genetic and molecular basis of TGW-GNS trade-offs in wheat. The QTLs and the novel TaGW2-A1 allele are likely useful for the development of cultivars with higher TGW and/or higher GNS.

     

Dynamic changes in energy metabolism and electron transport of photosystem II in <Emphasis Type="Italic">Nicotiana tabacum</Emphasis> infested by nymphs of <Emphasis Type="Italic">Bemisia tabaci</Emphasis> (Middle East-Asia Minor 1)

Bemisia tabaci Middle East-Asia Minor 1 (MEAM1) infestation adversely affected photosynthesis of host plants. In the current study, chlorophyll a fluorescence was measured to determine the effects of MEAM1 nymph infestation of tobacco local and systemic leaves on energy metabolism and electron transport of photosystemII(PSII). The results showed that the density of PSII reaction centres per excited cross section (CS) (RC/CS) of infested and systemic leaves was reduced at 14 and 20 days. In systemic leaves, the number of PSII closed reaction centres (1-qP) increased significantly at 14 and 20 days. Absorption flux per Q_A^? reducing PSII reaction centre (RC) (ABS/RC), trapped energy flux per RC (TRo/RC), and electron transport per RC (ETo/RC) of infested and systemic leaves increased with MEAM1 nymph infestation. The most obvious increase in absorption flux per CS (ABS/CSo) and trapped energy flux per CS (TRo/CSo) of infested and systemic leaves occurred at 14 days. MEAM1 nymph infestation significantly reduced the energy required for PSII Q_A to be completely reduced (Sm) in tobacco leaves. These results suggested that MEAM1 nymph infestation caused changes in light-harvesting antenna system and deactivation of the reaction centre, resulting in the reduction of photons absorbed by reaction centres per unit area. MEAM1 nymph infestation, particularly the 3rd instar nymphs, decreased light utilization ability and increased excess excitation energy in tobacco leaves. With MEAM1 nymph infestation, the relative electron transport capacity of the entire electron transport chain decreased, and more light energy was used to reduce Q_A.     

Characterization of an IAA-glucose hydrolase gene <Emphasis Type="Italic">TaTGW6</Emphasis> associated with grain weight in common wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

In rice, the TGW6 gene determines grain weight and encodes a protein with indole-3-acetic acid (IAA)-glucose hydrolase activity. Its homolog in wheat, TaTGW6, is considered as a candidate gene related to grain development. To amplify this gene, we designed primers based on a homologous conserved domain of the rice TGW6 gene. Sequence analysis indicated that TaTGW6 comprises only one exon, with 1656 bp in total and an open reading frame of 1035 bp. Three alleles at TaTGW6 locus detected by the primer pair TG23 were designated as TaTGW6-a, TaTGW6-b and TaTGW6-c, respectively. Compared with TaTGW6-a, TaTGW6-b had a 6-bp InDel at the position 170 downstream of initiation codon, and TaTGW6-c was a null mutant. Both TaTGW6-b and TaTGW6-c could significantly increase grain size and weight other than TaTGW6-a; however, the former two alleles showed a low frequency distribution in modern varieties. TaTGW6 was located on chromosome 4AL using a recombinant inbred line population and a set of Chinese Spring nullisomic-tetrasomic lines. It was linked to the SSR locus Xbarc1047 with a genetic distance of 6.62 cM and explained 15.8–21.0 % of phenotypic variation of grain weight in four environments. Association analysis using a natural population and Chinese wheat mini-core collections additionally validated the relationship of TaTGW6 with grain weight; the gene could explain 7.7–12.4 % of phenotypic variation in three environments. Quantitative real-time PCR revealed that TaTGW6-b showed relatively lower expression than TaTGW6-a in immature grain at 20 and 30 days post-anthesis and in mature grain. The low expression of TaTGW6 generally associated with low IAA content, but with high grain weight. The novel functional marker, designated as TG23, can be used for marker-assisted selection to improve grain weight in wheat and also provides insights into the regulatory mechanism underlying grain weight.     

Biological activity of <Emphasis Type="Italic">Claviceps gigantea</Emphasis> in juvenile New Zealand rabbits

The Ascomycete fungus Claviceps gigantea infects maize kernels and synthetizes several alkaloids, mostly dihydrolysergamides. There is limited information on the damage these toxins cause in mammals, despite reports from infested areas with 90% presence of the fungus sclerotia. With this background, it was decided to determine the biological activity of chemical compounds present in sclerotia of C. gigantea in rabbits 38 days after weaning. Sclerotia of C. gigantea were collected in fields with high incidence of the disease, ground and analysed for nutrients. Experimental diets were prepared with four treatments, where sclerotial powder was added, substituting for alfalfa flour in increasing proportions [C. gigantea/alfalfa flour (0:100, 5:95, 15:85 and 25:75)]. Total ergot alkaloid content was analysed by high-performance liquid chromatography. Male juvenile rabbits were utilised and distributed in completely randomised design with four replications. Initial weight was recorded in each animal, and experimental diet was offered. In this study, weight of animals, feed consumption and feed conversion were evaluated in individual animals. Blood samples were taken for haemograms, and finally euthanasia was practiced. The consumption of C. gigantea had a negative effect on body weight and feed consumption. The necropsies showed anomalies proportional to the consumption of feed contaminated with the fungus.     

Kernel softness in wheat is determined by starch granule bound Puroindoline proteins

Wheat has a vital position in agriculture because it is a staple food for masses and variation in grain hardness governs its applications. Soft wheats have softer endosperm texture that mills easily, so needs less energy to mill, produces smaller particles, and small amount of starch is damaged after milling as compared to hard wheat. Soft texture results from higher level of friabilin whereas hard texture results from low level of friabilin on starch granule surface. Friabilin, a marker of kernel texture is primarily composed of Puroindolines (PINs) and its genes (Pins) are located on the Hardness (Ha) locus. The Pins are the molecular-genetic basis of kernel softness in wheat. When both Pins are in their ‘wild state’ (Pina-D1a and Pinb-D1a), wheat kernel is soft. Absence or mutation in one of the Pins results in hard grain texture with different effects on end use and milling qualities. Pina-D1b genotypes gave harder grain texture, higher protein content, water absorption of flour, damaged starch granules and greater flour yield than hard wheat. Recently, other Pins like genes, Pin b variant genes located on the long arm of chromosome 7A were reported in bread wheat with more than 70% similarity to Pinb (Pinb-D1a) at the DNA level. Other genes located on chromosomes 1A, 2A, 5A, 7A, 5B, 2D and 6D also affect kernel texture. However the main determinants are the variants in the allelic diversity of Puroindoline family genes. Contemporary studies show that Pins are multifunctional family of genes having a range of functions from grain hardness to natural defense against insects and pathogens such as viruses, bacteria and fungi.     

Characterisation of a novel quantitative trait locus, <Emphasis Type="Italic">GN4</Emphasis>-<Emphasis Type="Italic">1</Emphasis>, for grain number and yield in rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Key message

A novel QTL for grain number, GN4-1, was identified and fine-mapped to an ~ 190-kb region on the long arm of rice chromosome 4.

Abstract

Rice grain yield is primarily determined by three components: number of panicles per plant, grain number per panicle and grain weight. Among these traits, grain number per panicle is the major contributor to grain yield formation and is a crucial trait for yield improvement. In this study, we identified a major quantitative trait locus (QTL) responsible for rice grain number on chromosome 4, designated GN4-1 (a QTL for Grain Number on chromosome 4), using advanced segregating populations derived from the crosses between an elite indica cultivar ‘Zhonghui 8006’ (ZH8006) and a japonica rice ‘Wuyunjing 8’ (WYJ8). GN4-1 was delimited to an ~ 190-kb region on chromosome 4. The genetic effect of GN4-1 was estimated using a pair of near-isogenic lines. The GN4-1 gene from WYJ8 promoted accumulation of cytokinins in the inflorescence and increased grain number per panicle by ~ 17%. More importantly, introduction of the WYJ8 GN4-1 gene into ZH8006 increased grain yield by ~ 14.3 and ~ 11.5% in the experimental plots in 2014 and 2015, respectively. In addition, GN4-1 promoted thickening of the culm and may enhance resistance to lodging. These results demonstrate that GN4-1 is a potentially valuable gene for improvement of yield and lodging resistance in rice breeding.

     

Coffee volatiles induced after mechanical injury and beetle herbivory attract the coffee berry borer and two of its parasitoids

The coffee berry borer (CBB), Hypothenemus hampei (Ferrari), is the most important insect pest of coffee worldwide. In this study, we used headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry to sample and identify volatile compounds from Robusta coffee berries, Coffea canephora Pierre ex Froehner, infested with CBB and with mechanical damage. Furthermore, we evaluated the behavioral responses of the CBB and two of its parasitoids, Prorops nasuta Waterstone and Phymastichus coffea LaSalle, to three selected coffee volatile compounds in a Y-tube olfactometer. We found in the effluvia of red coffee berry compounds not previously reported for this coffee species. Our results show that Robusta coffee berries release induced volatiles either by insect herbivory or by mechanical damage. Small amount of butyl acetate, unknown compound 2, α-longipinene, longiborneol and longiborneol acetate are produced only in infested coffee berries fruits. Quantitatively, nine compounds account for the difference between healthy berries, infested, or mechanically damaged berries. Trans-ocimene, 4,8-dimethyl-3,7-nonadien-2-ol, α-copaene and kaurene increased amount levels in infested berries, while amount of methyl salicylate and linalool increased in mechanically damaged coffee berries. The olfactometric bioassays showed that CBB females and its two parasitoids were attracted to methyl salicylate. In addition, H. hampei and P. nasuta were attracted to linalool, and P. nasuta and P. coffea were attracted to trans-ocimene.     

Consequences of the arms race between <Emphasis Type="Italic">Maculinea teleius</Emphasis> social parasite and <Emphasis Type="Italic">Myrmica</Emphasis> host ants for myrmecophilous butterfly conservation

The arms race between Maculinea butterflies and Myrmica host ants leads to local host-parasite adaptations. In our study, we assessed whether sympatric and allopatric Myrmica scabrinodis populations exhibit behavioural differences towards Maculinea teleius larvae during the adoption-period when butterfly larvae need to be taken inside the Myrmica nest. The second aim was to assess the butterfly survival rate inside ant colonies from different populations. We used one sympatric host population and three allopatric populations: one infested by M. teleius and two uninfested populations. We found that ants from the sympatric population showed a higher number of positive behaviours toward M. teleius larvae during adoption than ants from the allopatric populations. There were no differences in the number of inspection or negative behaviour events. The survival of butterfly larvae was highest inside sympatric host colonies and differed from the survival of M. teleius reared by ants from the allopatric, uninfested populations. No difference was found for the survival rate of M. teleius raised by infested, allopatric host colonies compared to sympatric host populations. Our results suggest the lack of behavioural counter-adaptations of local hosts of M. teleius that more easily adopt and rear butterfly caterpillars compared to naive M. scabrinodis colonies. Our results may also have implications for Maculinea butterfly conservation, especially for reintroduction programmes. We suggest that the existence of behavioural host defences should be checked for the source host population, as well as for the Myrmica population from the reintroduction site. It may also be reasonable to introduce several Myrmica host colonies from the source butterfly host population.     

Use of foreign genetic variability to improve the quality of wheat grain

Foreign genetic variability, which is represented by different wild-growing relatives of wheat such as Ae. umbellulata (UU, 2n = 14), Ae. cylindrica (CCDD, 2n = 28), Ae. tauschii (DD, 2n = 14), Ae. ventricosa (DDUnUn, 2n = 28), Ae. variabilis (UUSS, 2n = 28), and T. palmovae (AADD, 2n = 28) is used in interspecies crossings with the wheat cultivar T. aestivum for the purpose of transferring exotic Gli/Glu alleles into the genome of the crop. As a result, a series of new exotic Gli/Glu alleles is introgressed into the genome of wheat cultivar. An essential negative as well as positive influence of the wild exotic alleles on the baking quality indicators of the flour and the consistency of the wheat endosperm is discovered in the course of the study. The new genetic material with the improved grain quality indicators is recommended for use in wheat selection.     

Expression of sorghum gene <Emphasis Type="Italic">SbSGL</Emphasis> enhances grain length and weight in rice

Grain weight is a major determining factor of rice (Oryza sativa L.) yield and the comprehensive embodiment of grain length, width, and thickness. Here, we describe the molecular and functional characterization of SbSGL (Sorghum bicolor L. stress tolerance and grain length), a sorghum gene that encodes a putative member of the DUF1645 protein family of unknown function. Expression of SbSGL in rice promoted cell division and grain filling, which affected an array of traits of rice, including grain length, grain weight, and seed setting rate. Expression of SbSGL also affected the expression of genes related to the plant cell cycle and grain size.     

Grain yield of common bean (<Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> L.) varieties is markedly increased by rhizobial inoculation and phosphorus application in Ethiopia

A field experiment was conducted to assess plant growth, symbiotic performance and grain yield of common bean in response to rhizobial incoculation and phosphorus application at Galalicha in Southern Ethiopia during the 2012 and 2013 cropping seasons under rain-fed conditions. The treatments consisted of 2 released common bean varieties (Hawassa Dume and Ibbado), 3 levels of Rhizobium inoculation (uninoculated, inoculated with strain HB-429 or GT-9) and 4 levels of phosphorus application (0, 10, 20 and 30 kg P ha^?1) using a split-split plot design with four replications. Here, phosphorus levels, Rhizobium inoculation and common bean varieties were assigned as main, sub- and sub-sub treatments, respectively. The results revealed marked varietal differences in plant growth, grain yield and symbiotic performance. Of the two common bean varieties studied, Hawassa Dume generally showed superior performance in most measured parameters in 2013. Rhizobium inoculation significantly (p?≤?0.05) increased plant growth, symbiotic performance and grain yield. Applying Rhizobium strain HB-429 to bean crop respectively increased plant growth, %Ndfa, amount of N-fixed and grain yield by 19, 17, 54 and 48% over uninoculated control. Similarly, the application of 20 kg P ha^?1 to bean plants respectively resulted in 36, 20, 96 and 143% increase in plant growth, %Ndfa, N-fixed and grain yield when compared to the control. These results clearly indicate that plant growth, symbiotic performance and grain yield of common bean can be significantly increased by Rhizobium inoculation and phosphorus fertilization in Ethiopia. Rhizobium inoculants are a cheaper source of nitrogen than chemical fertilizers and when combined with moderate phosphorus application can markedly increase grain yield for resource-poor farmers.     

Interactions between <Emphasis Type="Italic">Glu-1</Emphasis> and <Emphasis Type="Italic">Glu-3</Emphasis> loci and associations of selected molecular markers with quality traits in winter wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) DH lines

The quality of wheat depends on a large complex of genes and environmental factors. The objective of this study was to identify quantitative trait loci controlling technological quality traits and their stability across environments, and to assess the impact of interaction between alleles at loci Glu-1 and Glu-3 on grain quality. DH lines were evaluated in field experiments over a period of 4 years, and genotyped using simple sequence repeat markers. Lines were analysed for grain yield (GY), thousand grain weight (TGW), protein content (PC), starch content (SC), wet gluten content (WG), Zeleny sedimentation value (ZS), alveograph parameter W (APW), hectolitre weight (HW), and grain hardness (GH). A number of QTLs for these traits were identified in all chromosome groups. The Glu-D1 locus influenced TGW, PC, SC, WG, ZS, APW, GH, while locus Glu-B1 affected only PC, ZS, and WG. Most important marker-trait associations were found on chromosomes 1D and 5D. Significant effects of interaction between Glu-1 and Glu-3 loci on technological properties were recorded, and in all types of this interaction positive effects of Glu-D1 locus on grain quality were observed, whereas effects of Glu-B1 locus depended on alleles at Glu-3 loci. Effects of Glu-A3 and Glu-D3 loci per se were not significant, while their interaction with alleles present at other loci encoding HMW and LMW were important. These results indicate that selection of wheat genotypes with predicted good bread-making properties should be based on the allelic composition both in Glu-1 and Glu-3 loci, and confirm the predominant effect of Glu-D1d allele on technological properties of wheat grains.     

Innate Olfactory Responses of <Emphasis Type="Italic">Asobara japonica</Emphasis> Toward Fruits Infested by the Invasive Spotted Wing Drosophila

Insect parasitoids are often manipulated to improve biological control programs for various arthropod pests. Volatile compounds can be a relevant cue used by most parasitoid hymenoptera for host or host microhabitat location. Here, we studied olfactory responses of the braconid Asobara japonica Belokobylskij, an Asiatic endoparasitoid of the invasive pest Drosophila suzukii (Matsumura), toward its host and host substrates. Adult A. japonica displayed an innate attraction to undescribed volatile cues from infested host fruits irrespectively of the juvenile rearing experience, i.e. they respond to a novel cue subsequently used for microhabitat selection. These data suggest that A. japonica parasitoids mass-reared on artificial diet and factitious host (D. melanogaster) can successfully locate their hosts. Naïve female parasitoids did not show a preference towards any of the tested host media. However, the enforced adult experience with the rearing host medium modified the olfactory preference patterns toward non-natal host fruits. These findings provide evidence of associative learning during the adult stage of A. japonica, and demonstrate its plasticity in exploiting the volatiles from various fruits infested by D. suzukii.     

The fungal matrices of <Emphasis Type="Italic">Ophiostoma ips</Emphasis> hinder movement of the biocontrol nematode agent, <Emphasis Type="Italic">Deladenus siricidicola</Emphasis>, disrupting management of the woodwasp, <Emphasis Type="Italic">Sirex noctilio</Emphasis>

Deladenus (=?Beddingia) siricidicola (Tylenchida: Neotylenchidae) is the most effective biocontrol agent used against the invasive wood wasp, Sirex noctilio (Fabricius) (Hymenoptera: Siricidae). The nematodes feed and reproduce on the wood-inhabiting fungus, Amylostereum areolatum (Chaillet ex Fr.) Boidin (Russulales: Amylostereaceae) and parasitise larvae of S. noctilio. In the nematode biocontrol program, the nematodes are inoculated into herbicide-weakened ‘trap trees’. Recent declines in nematode parasitism of S. noctilio in Australia have coincided with an increased incidence of an exotic bark beetle, Ips grandicollis (Eichhoff) (Coleoptera: Curculionidae), attacking trap trees and vectoring a wood-inhabiting fungus, Ophiostoma ips (Rumbold) Nannfelt (Ophiostomatales: Ophiostomataceae), which may inhibit migration of the nematode within the tree to the detriment of S. noctilio biocontrol. Several in vitro and in vivo experiments were conducted to investigate the effect of fungal interactions on the ability of D. siricidicola to locate and reproduce on A. areolatum. Deladenus siricidicola showed preference to A. areolatum in the presence and absence of O. ips, but the presence of O. ips negatively affected the choice response and the number of eggs laid by the nematodes. Deladenus siricidicola was unable to survive and reproduce on O. ips. Results give a clearer understanding of the choice response of D. siricidicola in I. grandicollis infested trees, explaining the disruptive impact of bark beetles on biocontrol of S. noctilio, an effect that could extend from Australia to other important pine growing countries.