Gall Production Research Articles

A New Method to Obtain Infective Ustilago maydis Binucleate Conidia for Corn Smut Production

The fungus Ustilago maydis produces galls or tumors on corn ears called corn smut or huitlacoche. Used for human consumption in several countries for its nutritional and sensory traits, huitlacoche is considered a delicacy in Mexican cuisine and has a significant economic value. Hybrid U. maydis strains are regularly used for the large-scale production of huitlacoche; however, depending on the genetic characteristics of the parent strains, the pathogenicity and infection rate of hybrid fungi are often suboptimal due to compatibility issues between different strains. Using double-loaded organisms is common in agriculture to improve product characteristics, performance, and shelf-life. A methodology to obtain unicellular U. maydis strains with a double genetic load (n + n) capable of producing galls on corn ears without mating (hybridization) is reported herein. This methodology resulted in 206 U. maydis isolates. Screening showed that 147 corn plants (>70%) underwent infection and gall production. Of the 147 gall-producing U. maydis strains, those with the highest field performance were selected. Three strains, Um-UAEMor-78 (yielding 21.65 ton/ha), Um-UAEMor-120 (22.31 ton/ha), and Um-UAEMor-187 (22.99 ton/ha), showed higher yields than the control strain, CP-436(a1b1) × CP-437(a2b2) (17.80 ton/ha). A specific methodology to obtain unicellular U. maydis strains with a double genetic load capable of infecting baby corn ears and forming galls is described for the first time, providing a novel alternative for producing huitlacoche and helping to improve the yields and morphological traits of galls.

First Report of a New Species, Chrysofolia galloides sp. nov., Causing Black Spots on Gallnuts of Rhus punjabensis var. sinica in China

In June 2021 and 2022, 30-40% ensiform galls of Rhus punjabensis var. sinica (Diels) Rehd. et Wils. showing similar black spots were observed at a same woodland in Zhuyu town (E 107"42', N 32"10', altitude 560 m), Wanyuan, Southwest China. The lesions were usually dotted, rounded to irregular black or blackish brown spots, and scattered to gather into patches on the gall surfaces; the central areas of the lesions were often depressed. The infected galls often grow slowly or even fall off early. Fresh symptomatic galls were randomly collected in June 2021 (9 galls) and 2022 (13 galls). Tissues from the infected galls (ca. 3×5 mm) were surface-disinfected by 75% ethyl alcohol and 10% sodium hypochlorite (NaOCl), then plated on potato dextrose agar (PDA) at 25°C in the dark for six days. Nine isolates from different galls showed similar colony morphology. Similar dominant fungal colonies were isolated from 44.0% and 38.5% of the infected galls in 2021 and 2022, respectively. After sub-culturing of hyphal tips on PDA and oat meal agar (OA)，the colonies showed cottony-felty, annular, whitish to grey-brown after 10 days. Four isolates, IFRDCC1022 and IFRDCC1023 from 2021, and IFRDCC1024 and IFRDCC1025 from 2022 were randomly selected for molecular and morphological evaluations. Selected isolates were cultured on OA and incubated at 21°C at a 12 h/12 h day/night regime to induce sporulation (Jiang et al. 2020). Pycnidia (up to 500 µm diam.) developed within six days or longer. Conidiogenous cells lined the inner cavity of base, which were hyaline, occasionally brownish, ampulliform, 6-12 × 2-4.5 µm. Conidia were solitary, hyaline, guttulate, elliptic, sometimes subcylindric or ovoid, straight to curved, aseptate, (3.5-) 4-6.5 (-8) × 2-3.5 (-4) µm (n=60). Respective DNA fragments were amplified and sequenced with primers ITS1/ITS4 for ITS, LR0R/LR5 for LSU, EF1-728F (Carbone and Kohn 1999) /EF-2 (O’Donnell et al. 1998) for tef1-α, and Bt2a/ Bt2b for tub2 (Glass and Donaldson 1995). The obtained sequences were deposited in GenBank (accession Nos. ITS: OR363211 - OR363214, LSU: OR363215 - OR363218, tef1-α: OR344509 - OR344512, and tub2: OR344513 - OR344516). The morphological characteristics of the new isolates were consistent with the genus Chrysofolia (Crous et al. 2015). The conidiogenous cells (6-12 × 2-4.5 µm) are larger than those of C. colombiana Crous, Rodas & M.J. Wingf. 2015 (5–8 × 2–3 μm) and C. barringtoniae Suwannar., Kumla & Lumyong 2016 (3–7.5 × 2–3 μm), while shorter and wider than those of C. coriariae S.Y. Wang, Yong Wang bis, and Y. Li 2022 (5–20 × 1–3.5 μm). Maximum likelihood (ML), Maximum parsimony (MP) and Bayesian phylogenetic trees generated from the datasets all showed similar topologies, four strains formed a well-supported clade (BS = 99-100%, PP=0.99-1) in Chrysofolia genus, and clearly separated from the other three Chrysofolia spp. and clustered as sister to C. coriariae with high supported values (BS = 97-100%, PP=0.97-1). Based on morphological characteristics and DNA phylogeny, the new isolates were described as a new species, Chrysofolia galloides T. Ma & Z. X. Yang, sp. nov. (Mycobank: MB850312). The two isolates from 2021 (IFRDCC1022 and IFRDCC1023) were randomly selected for pathogenicity tests. Mycelial plugs (ca. 6×6 mm) of a two-week-old colony were placed onto the surface of wounded and unwounded healthy ensiform galls with six or seven replicates. Sterile PDA agar plugs were used as controls. The inoculated galls were incubated at 25°C in sterile plastic containers (21.4×14.0×5.0 cm) lined with wet filter paper for high humidity. The typical symptom appeared within 3 days on 83.3-100% wounded galls, while the unwounded galls and the controls remained asymptomatic. All wounded galls and 20.0-85.7% of unwounded galls showed symptoms within 5 days, while the controls remained asymptomatic. The fungus was reisolated from the lesions and showed identical morphology and 100% sequence similarity of ITS, LSU, tef1-α and tub2 with the initial isolates. No fungus was isolated from the controls. Neofusicoccum parvum is the first fungal pathogen demonstrated to induce brown spots on Chinese gallnuts (Ma and Yang 2022). Therefore, C. galloides is the second fungus confirmed to cause black spots lesions on gallnuts. These findings provide foundations for the comprehensive management of gall production, which have significant economical implication for Chinese gallnut production.

A chromosome-level genome assembly of the Rhus gall aphid Schlechtendalia chinensis provides insight into the endogenization of Parvovirus-like DNA sequences

The Rhus gall aphid, Schlechtendalia chinensis, feeds on its primary host plant Rhus chinensis to induce galls, which have economic importance in medicines and the food industry. Rhus gall aphids have a unique life cycle and are economically beneficial but there is huge gap in genomic information about this group of aphids. Schlechtendalia chinensis induces rich-tannin galls on its host plant and is emerging as a model organism for both commercial applications and applied research in the context of gall production by insects. Here, we generated a high-quality chromosome-level assembly for the S. chinensis genome, enabling the comparison between S. chinensis and non-galling aphids. The final genome assembly is 344.59 Mb with 91.71% of the assembled sequences anchored into 13 chromosomes. We predicted 15,013 genes, of which 14,582 (97.13%) coding genes were annotated, and 99% of the predicted genes were anchored to the 13 chromosomes. This assembly reveals the endogenization of parvovirus-related DNA sequences (PRDs) in the S. chinensis genome, which could play a role in environmental adaptations. We demonstrated the characterization and classification of cytochrome P450s in the genome assembly, which are functionally crucial for sap-feeding insects and have roles in detoxification and insecticide resistance. This genome assembly also revealed the whole genome duplication events in S. chinensis, which can be considered in comparative evolutionary analysis. Our work represents a reference genome for gall-forming aphids that could be used for comparative genomic studies between galling and non-galling aphids and provides the first insight into the endogenization of PRDs in the genome of galling aphids. It also provides novel genetic information for future research on gall-formation and insect-plant interactions.

Fine-Scale analysis of both wild and cultivated horned galls provides insight into their quality differentiation

BackgroundGalla chinensis is a traditional Chinese medicine (TCM) produced due to the interaction between the Fordinae aphids and the Rhus plant species. Horned galls with high tannin content are the most widely cultivated gall type, and Wufeng county of Hubei province in China is the center of cultivation. However, long-term artificial cultivation and domestication of horned galls to meet the increasing production demand have led to quality degradation. Understanding the reasons underlying quality degradation is urgent for horned gall production and application. The present study used a combination of metabolic, genetic, and ecological analyses to investigate the quality and genetic differentiation of the horned galls under long-term domestication as well as the potential relationships between them.ResultsAnalysis of gallic acid content and other three phenotypic traits (fresh weight, gall size, and wall thickness) revealed quality differentiation of horned galls collected from five locations in Wufeng, in which the cultivated samples from Wang Jiaping (WJP) showed the highest degradation. Genetic differentiation between the cultivated and wild Rhus chinensis trees in WJP, and between WJP and the other populations was detected based on SSR molecular markers, however, no significant difference in genetic structure was seen for the aphid populations. Among the various ecological factors examined, temperature was identified as the primary one affecting the quality of horned galls.ConclusionsBoth genetic and ecological factors caused quality differentiation of horned galls. The collection of diverse germplasm of host trees and aphids will help reduce the quality degradation of horned galls in Wufeng.

Transcriptome Analysis Identifies Plasmodiophora brassicae Secondary Infection Effector Candidates.

Plasmodiophora brassicae (Wor.) is an obligate intracellular plant pathogen affecting Brassicas worldwide. Identification of effector proteins is key to understanding the interaction between P. brassicae and its susceptible host plants. To date, there is very little information available on putative effector proteins secreted by P. brassicae during a secondary infection of susceptible host plants, resulting in root gall production. A bioinformatics pipeline approach to RNA‐Seq data from Arabidopsis thaliana (L.) Heynh. root tissues at 17, 20, and 24 d postinoculation (dpi) identified 32 small secreted P. brassicae proteins (SSPbPs) that were highly expressed over this secondary infection time frame. Functional signal peptides were confirmed for 31 of the SSPbPs, supporting the accuracy of the pipeline designed to identify secreted proteins. Expression profiles at 0, 2, 5, 7, 14, 21, and 28 dpi verified the involvement of some of the SSPbPs in secondary infection. For seven of the SSPbPs, a functional domain was identified using Blast2GO and 3D structure analysis and domain functionality was confirmed for SSPbP22, a kinase localized to the cytoplasm and nucleus.

Plants make galls to accommodate foreigners: some are friends, most are foes.

At the colonization site of a foreign entity, plant cells alter their trajectory of growth and development. The resulting structure - a plant gall - accommodates various needs of the foreigner, which are phylogenetically diverse: viruses, bacteria, protozoa, oomycetes, true fungi, parasitic plants, and many types of animals, including rotifers, nematodes, insects, and mites. The plant species that make galls also are diverse. We assume gall production costs the plant. All is well if the foreigner provides a gift that makes up for the cost. Nitrogen-fixing nodule-inducing bacteria provide nutritional services. Gall wasps pollinate fig trees. Unfortunately for plants, most galls are made for foes, some of which are deeply studied pathogens and pests: Agrobacterium tumefaciens, Rhodococcus fascians, Xanthomonas citri, Pseudomonas savastanoi, Pantoea agglomerans, 'Candidatus' phytoplasma, rust fungi, Ustilago smuts, root knot and cyst nematodes, and gall midges. Galls are an understudied phenomenon in plant developmental biology. We propose gall inception for discovering unifying features of the galls that plants make for friends and foes, talk about molecules that plants and gall-inducers use to get what they want from each other, raise the question of whether plants colonized by arbuscular mycorrhizal fungi respond in a gall-like manner, and present a research agenda.

Effect of Combined Inoculation of Xanthomonas and Meloidogyne Pathogens on the Development of Tomato Root Knot Disease

Bacteria (Xanthomonas campestris pv. vesicatoria) and root-knot nematode (Meloidogyne incognita) independently can damage and cause considerable damage to tomato (Solanum lycopersicum L.). In a disease complex, interrelationship of 2 or more pathogenic species can produce different symptoms on the same host plant. Generally simultaneous occurrence of these pathogens in a field can infect hosts plant at the same time. During development of a disease complex pathogens could influence and/or suppress each other, through synergism and or antagonism respectively. In this study the pathogens (Meloidogyne incognita and Xanthomonas campestris pv. vesicatoria), were used to determine how co-occurrence affects development of pathogens and disease severity, and define prerequisites for interrelation between pathogens. Root knot infection did not occur when tomato plants were inoculated with Xanthomonas campestris 1 week prior to inoculation with Meloidogyne incognita. When M. incognita was inoculated 1 week prior to X. campestris, infection by root knot nematode was highest compared to bacterial spot incidence in susceptible plants. Simultaneous inoculation of M. incognita + X. campestris caused severe gall production with moderate severity of bacterial spot disease. The reproduction of 1 pathogen can be affected by a subsequent inoculation of other pathogen. It is suggested that bacterial spot disease enhances the development of root knot disease.

Zoosporangial root infection of tomato by Spongospora subterranea in hydroponic and glasshouse culture results in diminished plant growth

AbstractTomato plants are highly susceptible to root infection by Spongospora subterranea and are commonly used as bioassay hosts. The impacts of root infection with S. subterranea on plant productivity and yield have been debated. Recent experiments with potato, the major economic host of S. subterranea, have indicated significantly reduced plant growth and potato yield following heavy infection. However, there have been very few similar studies that have examined the possible impacts of S. subterranea infection on tomato plant growth. Three tomato cultivars, “Grape,” “Roma” and “Truss,” were challenged with S. subterranea inoculum in hydroponic culture. Moderate to severe zoosporangial infections were observed with minor but statistically significant differences in susceptibility among the three tomato cultivars. Zoosporangial root infection in the absence of root gall formation resulted in significantly diminished shoot lengths and plant fresh weights in pathogen challenge tests conducted both in hydroponic culture and glasshouse‐grown plants in potting mix. Root lengths were reduced, but the differences were statistically significant in a single trial only. The findings from this study demonstrate that, as with potato, root infection by S. subterranea can result in reduced tomato plant growth and that root gall production associated with root infection was not necessary for this retardation of growth response. This further suggests that possible yield impacts in other crop species that are hosts for S. subterranea root infection are worthy of examination.

Entomophytophagy ('Sequential Predatory, then Phytophagous Behaviour') in an Indian Braconid 'Parasitoid' Wasp (Hymenoptera): Specialized Larval Morphology, Biology and Description of a New Species.

The vast majority of braconid wasps are parasitoids of other insects. Although a few cases of pure phytophagy (primary gall production and seed predation) are known, no previous entomophytophagous species (i.e. ones that display entomophagy and phytophagy sequentially), has been discovered among braconids. We describe the detailed biology and specialized larval morphology for the first confirmed entomophytophagous braconid species. Leaf galls on Garuga pinnata Roxb. (Burseraceae) in India, induced by the psyllid, Phacopteron lentiginosum Buckton (Hemiptera: Psylloidea, Phacopteronidae) were sampled throughout a period of several months and found to suffer a high level of attack by a new species Bracon garugaphagae Ranjith & Quicke which is here described and illustrated. The wasps oviposit singly into the galls without paralysing the psyllids. The larvae first attack psyllid nymphs which they seek out within the gall, kill them with a single bite and consume them. Unique dorsal abdominal tubercles, with eversible tips present on the abdominal segments of the larvae that are used to help maintain larval position while feeding, are illustrated. After consuming all available prey, the larvae continue feeding on gall tissue until mature enough to spin cocoons and pupate. The new species illustrates, for the first time, a possible intermediate stage in the evolution of pure phytophagy within the Braconidae. Interestingly, the two unrelated seed predator Bracon species are also associated with Burseraceae, perhaps indicating that this plant family is particularly suited as a food for braconine wasps.

Ability to gall: the ultimate basis of host specificity in fig wasps?

1. Fig trees (Ficus spp.) and their host‐specific pollinator fig wasps (Agaonidae) are partners in an obligate mutualism. Receptive phase figs release specific volatiles to attract their pollinators, and this is generally effective in preventing pollinator species from entering figs of the wrong hosts.2. If entry is attempted into atypical host figs, then ostiole size and shape and style length may also prevent reproduction. In spite of these barriers, there is increasing evidence that fig wasps enter atypical hosts, and that this can result in hybrid seed and fig wasp offspring.3. This study examines the basis of pollinator specificity in two dioecious fig species from different geographical areas. Kradibia tentacularis pollinates Ficus montana in Asia. Ficus asperifolia from East Africa is closely related but is pollinated by a different species of Kradibia.4. In glasshouses, K. tentacularis was attracted to its normal host, F1s and backcrosses, but only rarely entered figs of F. asperifolia. Foundresses were able to lay eggs in hybrids, backcrosses, and F. asperifolia, although flower occupancy was lowest in F. asperifolia figs and intermediate in hybrids.5. The fig wasp failed to reproduce in female F. montana, male F. asperifolia, and male F1s, and most but not all backcrosses to F. montana. This was a result of the failure to initiate gall production.6. Host specificity in this fig wasp is strongly influenced by host volatiles, but the ability to gall may be the ultimate determinant of whether it can reproduce.

Phytohormone Dynamics Associated with Gall Insects, and their Potential Role in the Evolution of the Gall-Inducing Habit

While plant galls can be induced by a variety of organisms, insects produce the most diverse and complex galls found in nature; yet, how these galls are formed is unknown. Phytohormones have long been hypothesized to play a key role in gall production, but their exact role, and how they influence galls, has been unclear. Research in the past decade has provided better insight into the role of plant hormones in gall growth and plant defenses. We review and synthesize recent literature on auxin, cytokinins, and abscisic, jasmonic, and salicylic acids to provide a broader understanding of how these phytohormones might effect gall production, help plants defend against galls, and/or allow insects to overcome host-plant defenses. After reviewing these topics, we consider the potential for phytohormones to have facilitated the evolution of insect galls. More specialized research is needed to provide a mechanistic understanding of how phytohormones operate in gall-insect-plant interactions, but current evidence strongly supports phytohormones as key factors determining the success and failure of insect galls.

Effect of nitrogen fertilization on growth of Arundo donax and on rearing of a biological control agent, the shoot gall-forming wasp Tetramesa romana

The shoot tip-galling wasp Tetramesa romana Walker (Hymenoptera: Eurytomidae) has been released for biological control of giant reed or arundo (Arundo donax L.) (Poaceae), an invasive grass in the USA and Mexico. The role of urea fertilization to improve plant-based mass-rearing was examined. In a greenhouse study, rhizomes were fertilized with urea pellets at rates equivalent to 1000 kg (low), 2000 kg (moderate), and 4000 (high) kg N per ha–1. Total nitrogen content of ungalled stems was significantly 0.60–0.65% higher under low and moderate fertilization compared to unfertilized pots, and shoot water content was elevated 3–4% at all urea levels. Moderate fertilization significantly (by 1.4-fold) increased the relative growth rate of all shoots in pots, but did not affect final dry biomass. Fertilization did not affect number and duration of probing events by females. The percentage of shoots colonized by wasps that were galled, progeny production per shoot and per female, and emergent wasp size were not affected. However, average generation time (adult to adult) of emergent wasps was 4–5 days shorter on shoots in pots under moderate and high urea fertilization. After a four-week wasp emergence period, only 3–9% of progeny remained in fertilized shoots, while 21% of progeny remained inside unfertilized shoots. In field plots, fertilization did not affect gall density per m shoot length or per female released. Urea fertilization increased the efficiency of greenhouse rearing of the arundo wasp and availability of adults for release, even without direct effects on gall production.

Infection of Plasmodiophora brassicae in Chinese cabbage.

Brassica crops infected by Plasmodiophora brassicae can produce root galls (clubroots) and be prevented from growing normally. To understand the series of changes that occur in the host root during root gall production, the resistance character of 21 Chinese cabbage lines were identified and then resistant and susceptible lines were used for infection observation. Hydroponic technology system was used for plants growing, and the infection process of P. brassicae in the roots of resistant and susceptible Chinese cabbage was examined based on morphology and microscopic characteristics using micoscope. In susceptible Chinese cabbage, the root hair infection stage occurred over approximately 7 days after inoculation, the cortical infection happened over approximatly 14 days after inoculation, and clubroots formed in approximately 30 days after inoculation. However, in resistant Chinese cabbage, the pathogen could be prevented and maintained in the root hair infection stage. This research provides a foundation for the subsequent studies of cabbage resistance of P. brassicae.

Seed treatment and soil drench with dl-β-amino butyric acid for the suppression of Meloidogyne javanica on tomato

Due to the recent environmental concerns, increasing amounts of research have been diverted to investigating natural products for the control of nematodes. dl-β-Amino butyric acid (BABA) could play a part in limiting nematode damage to plants. In this study, different concentrations of BABA were used as soil drench and seed treatment to determine if they can control Meloidogyne javanica on tomato. In an in vitro test, BABA did not impair mobility of second-stage juveniles of the nematode but 10 and 25 mg/l concentrations reduced hatch. Both of the application methods tested (drenching soil and/or pre-treating seeds with 25 mg/l of BABA) for the treatment of nematode infested tomato plants reduced the numbers of galls and egg masses by 82 %; nematode reproduction rates on these plants were reduced to one and, compared with untreated control plants, final nematode density was decreased by nearly 87 %. Increasing BABA concentrations of the treatment solutions to 200 and 500 mg/l resulted in further reduction in nematode damage and reproduction on treated plants, although the differences between the concentrations were not significant. Compared with untreated tomato, gall and egg mass production were decreased by an average of 92 %, and reproduction rates were held below one by both the 200- and 500-mg/l BABA rates. When seeds pretreated with 25 mg/l were also soil drenched with three BABA concentrations, the effects were slightly greater than when each method was used alone. Treated plants showed slight improvement in growth and weight.

Evaluation of resistance in wheat against Rhopalosiphumpadi (L.) (Homoptera:Aphididae) Under laboratory Conditions

AbstractAims and introduction All over the world aphids are pests of economic importance, affecting all varieties of plants like cereal crops, vegetables, ornamental plants and fruits. Aphids damage plants either directly or indirectly. Aphids are one of the major agricultural pests. There are only a few plants that are not susceptible to infestation by this destructive pest. They cause direct damage by sucking the sap of leaves, blocking photosynthesis which results in leaf distortion, gall production, discoloration, stunting, leaf curling, wilting, twisting and premature leaf falls. They are directly involved in transmission of plant viruses and indirectly by depositing honey dew that reduces photosynthetic activity and induces sooty mold production and premature leaf senescence.Methodology Hosts were wheat and maize. There was twenty varieties of National Uniform Wheat Yield Trials (NUWYT) Normal (N) of year 2004-05, and twelve varieties of (NUWYT) Rain Fed (R.F) of year 2004-05 while there were twenty-two varieties of maize of year 2005-06. All these varieties were evaluated against bird cherry oat aphid R. padi L pest. Evaluation for resistance was done by seedling bulk test and by comparing the results of components of resistance like antibiosis, antixenosis and tolerance tests. These experiments were performed under controlled environmental conditions. Experiments were of randomized complete design and replicated. The data obtained was statistically analyzed of variance (ANOVA) and the mean values were compared by Duncan’s new multiple range test (DMRT) at 5 percent level of significance (Steel and Torrie, 1980). Results Among the tested germplasm (one variety and 11 lines of wheat), the V-5 line was found resistant and the NRL-2017 line was found susceptible to Rhopalosiphum padi. The results of the Antixenosis Test indicated that two wheat lines, V-5 and PR-83 were least preferred and three lines viz., NRL-2017, V-00055 and V-00BT004 were highly preferred by the test insect. The results of the Antibiosis Test showed that PR-83 line was least fecund whereas NR-241 and V-00055 lines were highly fecund. The results of the Tolerance Test indicated that four varieties, PR-83, V-5, SN-128 and NR-241 were highly tolerant, while only one line, V-00BT004 was least tolerant. Conclusion To avoid harmful effects of this insect pest, only resistant, least preferred, least fecund and highly tolerant lines must be used in wheat breeding programs.

Evaluation of resistance in wheat against Rhopalosiphumpadi (L.) (Homoptera:Aphididae) Under laboratory Conditions

Aims and introduction All over the world aphids are pests of economic importance, affecting all varieties of plants like cereal crops, vegetables, ornamental plants and fruits. Aphids damage plants either directly or indirectly. Aphids are one of the major agricultural pests. There are only a few plants that are not susceptible to infestation by this destructive pest. They cause direct damage by sucking the sap of leaves, blocking photosynthesis which results in leaf distortion, gall production, discoloration, stunting, leaf curling, wilting, twisting and premature leaf falls. They are directly involved in transmission of plant viruses and indirectly by depositing honey dew that reduces photosynthetic activity and induces sooty mold production and premature leaf senescence.Methodology Hosts were wheat and maize. There was twenty varieties of National Uniform Wheat Yield Trials (NUWYT) Normal (N) of year 2004-05, and twelve varieties of (NUWYT) Rain Fed (R.F) of year 2004-05 while there were twenty-two varieties of maize of year 2005-06. All these varieties were evaluated against bird cherry oat aphid R. padi L pest. Evaluation for resistance was done by seedling bulk test and by comparing the results of components of resistance like antibiosis, antixenosis and tolerance tests. These experiments were performed under controlled environmental conditions. Experiments were of randomized complete design and replicated. The data obtained was statistically analyzed of variance (ANOVA) and the mean values were compared by Duncan’s new multiple range test (DMRT) at 5 percent level of significance (Steel and Torrie, 1980).ResultsAmong the tested germplasm (one variety and 11 lines of wheat), the V-5 line was found resistant and the NRL-2017 line was found susceptible to Rhopalosiphum padi. The results of the Antixenosis Test indicated that two wheat lines, V-5 and PR-83 were least preferred and three lines viz., NRL-2017, V-00055 and V-00BT004 were highly preferred by the test insect. The results of the Antibiosis Test showed that PR-83 line was least fecund whereas NR-241 and V-00055 lines were highly fecund. The results of the Tolerance Test indicated that four varieties, PR-83, V-5, SN-128 and NR-241 were highly tolerant, while only one line, V-00BT004 was least tolerant.ConclusionTo avoid harmful effects of this insect pest, only resistant, least preferred, least fecund and highly tolerant lines must be used in wheat breeding programs.

Gall production on hawthorns caused by Gymnosporangium spp. in Hatay province, Turkey

Three hawthorn and related rust diseases caused by Gymnosporangium confusum on Crataegus monogyna, Gymnosporangium clavariiforme on Crataegus orientalis and Gymnosporangium sabinae on Pyrus communis were detected in Hatay province, Turkey. G. confusum was also found causing telial galls on Juniperus communis. G. confusum and G. clavariiforme produced aecial horns on overwintered galls on hawthorn twigs from May to June. The production of galls caused by Gymnosporangium on the secondary host is unusual. Portions of the nuclear ITS and LSU rDNA were sequenced for all three species of Gymnosporangium for use as a species barcode; sequences were deposited in GenBank. Sequence data from G. clavariiforme and G. sabinae matched those in GenBank; however, this is the first study to deposit sequence data from G. confusum to GenBank. The life cycles of G. confusum and G. clavariiforme are discussed along with implications for disease control.

Developmental plasticity and reduced susceptibility to natural enemies following host plant defoliation in a specialized herbivore

Host-specific phytophagous insects that are short lived and reliant on ephemeral plant tissues provide an excellent system in which to investigate the consequences of disruption in the timing of resource availability on consumer populations and their subsequent interactions with higher tropic levels. The specialist herbivore, Belonocnema treatae (Hymenoptera: Cynipidae) induces galls on only newly flushed leaves of live oak, Quercus fusiformis. In central Texas (USA) episodic defoliation of the host creates variation in the timing of resource availability and results in heterogeneous populations of B. treatae that initiate development at different times. We manipulated the timing of leaf flush in live oak via artificial defoliation to test the hypothesis that a 6- to 8-week delay in the availability of resources alters the timing of this gall former's life cycle events, performance and survivorship on its host, and susceptibility to natural enemies. B. treatae exhibits plasticity in development time, as the interval from egg to emergence was significantly reduced when gallers oviposited into the delayed leaf flush. As a consequence, the phenologies of gall maturation and adult emergence remain synchronized in spite of variation in the timing of resource availability. Per capita gall production and gall-former performance are not significantly affected by the timing of resource availability. The timing of resource availability and natural enemies interact, however, to produce strong effects on survivorship: when exposed to natural enemies, B. treatae developing in galls initiated by delayed oviposition exhibited an order-of-magnitude increase in survivorship. Developmental plasticity allows this gall former to circumvent disruptions in resource availability, maintain synchrony of life cycle events, and results in reduced vulnerability to natural enemies following defoliation of the host plant.

Why does Dasineura dielsi‐induced galling of Acacia cyclops not impede vegetative growth?

Summary Conventionally, agent host specificity has been the major concern in the selection of prospective agents for biological control of weeds. However, subtle interactions between agent and host plant that could influence the outcome of the biological control programme also need to be identified and assessed when selecting potential agents. A gall‐forming cecidomyiid Dasineura dielsi was introduced into South Africa for biological control of an invasive tree species, Acacia cyclops. Galls of D. dielsi form on flowers and prevent seed production, the intended aim of the biological control programme. Possible indirect effects of gall induction on vegetative growth of A. cyclops were investigated. The carbon costs of producing and maintaining galls and pods were compared by measuring their gas exchange characteristics, and those of subtending phyllodes. Relocation of 14C from phyllodes to galls and pods, and nutrient composition of galls and pods, were compared. Insecticide was used to exclude D. dielsi from trees, enabling comparison of growth rates of predominantly gall‐bearing and predominantly podded branches. Removal of galls, but not of pods, elevated photosynthetic rates of subtending phyllodes, indicating greater photosynthate demand by galls than pods. In light, the photosynthetic rates of expanded pods exceeded respiration rates. In contrast, there was a net release of CO2 from all age classes of galls in both light and dark. 14C allocation to mature galls was approximately three times as high as it was to young galls or immature pods. Pod production required more mineral nutrient than gall production, with N, P and Ca contents of mature pods (including seeds) being nine‐fold those of mature galls. Increases in stem diameters (i.e. vegetative growth rates) were similar for predominantly gall and predominantly pod bearing trees. Synthesis and applications. Although nutrient costs were lower for galls than pods, this advantage was offset by higher carbon costs of gall production and the influence on plant growth was neutral. These findings illustrate that subtle physiological effects of herbivorous insects may influence the ecology of their hosts and should be considered during screening of potential agents for biological control.

Female production within the gall and male production on leaves by individual alates of a social aphid

The social aphid Astegopteryx spinocephala forms a banana-bunch shaped gall, consisting of several subgalls, on Styrax benzoides in northern Thailand. The aphid’s life cycle is non-host alternating. Alates (sexuparae) containing both male and female embryos appear near the end of the dry season, when many sexuals and eggs are found in subgalls guarded by sterile soldiers. Our experiments revealed that these alates give birth to almost all (99%) females within the natal subgall before flying but most (73–86%) males on leaves of the host tree after flying, and that these first-instar males intrude into live subgalls for mating. The fact that some (14–27%) males are deposited in the natal subgall indicates the occurrence of both outbreeding and inbreeding, or some level of local mate competition (LMC), in this mating system. However, the primary (investment) sex ratio was estimated to be near 0.5. This suggests that factors other than LMC, a candidate for which is local resource competition, might also affect the sex ratio in A. spinocephala.