Plant Galls Research Articles

Molecular mechanisms of tannin accumulation in Rhus galls and genes involved in plant-insect interactions

For galling aphids and their hosts, tannins are crucial for plant-insect interactions and for protecting the host plant from herbivory. Due to their peculiar chemical characteristics, tannins from plant galls have been used for medical and chemical purposes for more than 2000 years. In this study, hydrolyzable tannin concentrations in galls increased from gall initiation (38.34% on June 21) to maturation (74.79% on August 8), then decreased gradually thereafter (58.83% on October 12). We identified a total of 81 genes (named as GTS1-81) with putative roles in gallotannin biosynthesis and 22 genes (TS1-22) in condensed tannin biosynthesis. We determined the expression profiles of these genes by real-time PCR over the course of gall development. Multiple genes encoding 1-beta-D-glucosyl transferases were identified, which may play a vital role in gallotannin accumulation in plant galls. This study is the first attempt to examine the molecular basis for the regulation of tannin accumulation in insect gallnuts. The differentially expressed genes we identified may play important roles in both tannin biosynthesis and plant-insect interactions.

New insights on the biology and larval morphology of Neotropical Mesostoinae (Hymenoptera, Braconidae): Hydrangeocola llaollin sp. nov. an endoparasitoid of Centrodiplosis crassipes (Diptera, Cecidomyiidae)

The Southern Hemisphere subfamily Mesostoinae (Hymenoptera: Braconidae) includes, in most cases, species associated with plant galls, although the details regarding their biological traits are largely unknown. In this contribution, Hydrangeocola llaollin sp. nov. is described based on specimens that develop as larval endoparasitoids of Centrodiplosis crassipes (Diptera: Cecidomyiidae) in stem galls on Lycium chilense (Solanaceae). The mature larva of a Neotropical mesostoine wasp is described here for the first time and is compared with the only known larva from Australia. Larval morphology is entirely congruent with features typical of endoparasitoid species, which together with male genital features clearly relates Hydrangeocola with the South American genus Andesipolis, but separates it from the Australian phytophagous genus Mesostoa. These findings reveal the relevance of larval and male genital characters for our comprehension of the relationships among representatives of this poorly known braconid subfamily.

Quantitative differences detected in the histology of galls induced by the same aphid species in different varieties of the same host.

Plant galls are abnormal growths caused by an inducer that determines their morphology and anatomy. We qualitatively and quantitatively compared the histological anatomy of five aphid species (Paracletus cimiciformis, Forda marginata, Forda formicaria, Baizongia pistaciae and Geoica wertheimae) that induce galls in Pistacia terebinthus shrubs growing in Israel. We also quantitatively compared these galls to those that the aphids create on the same host in Spain. Histological study was conducted following methods described previously by the authors. Quantitative differences among the galls were found in five of 12 common anatomical traits: gall thickness, stomatal number in the epidermis-air, size of vascular bundles, distance of phloem ducts from the lumen and number of intraphloematic schizogenous ducts. Other structures were particular to one or some species: number of cracks in the epidermis-lumen, a sclereid layer, trichomes and microcrystal inclusions. Fisher's tests of combined probabilities showed that the galls induced in Israel were statistically different from those in Spain. In particular, the number of intraphloematic schizogenous ducts was higher in the galls induced in P.terebinthus in Israel. Such differences were also found in other traits related to defence of the gall inhabitant. In conclusion, while the gall shape and size are determined mainly by the cecidogenic insect, it seems that the host plant also plays an important role in determining the number/size of quantitative traits, in this case mainly protective structures.

Use of organic waste as biofumigant for controlling root knot nematodes (Meloidogyne spp.) on potato

Root knot nematode (Meloidogyne spp.) is one of the important pathogens that causes big impact on potato crop yields. One of the control strategies for controlling this nematode is the use of biofumigants. Biofumigants are volatile toxic compound derived from plants, and have biocide properties against insects and plant pathogens. Organic waste such as Brassicaceae, Leguminoceae, and Solanaceae can be used as biofumigant sources. This research was conducted to determine the effectiveness of Brassicaceae, Leguminoceae, and Solanaceae as biofumigants against Meloidogyne spp. The experiment was set in a completely randomized design (CRD) with the treatments were organic wastes including Brassicaceae, Leguminoceae, and Solanaceae, both single and combinations, and 2 controls (positive and negative controls) with 3 replications. Each of the biofumigant treatments was prepared and stored for 2 weeks. Potato tubers were transplanted 15 days after germination into polybag inoculated with 1,000 Meloidogyne spp. J2s. The results showed that Brassicaceae + Solanaceae were effective in decreasing the number of galls in potato plants, however only Solanaceae improved plant growth.

Gall wasp biocontrol of invasive Acacia longifolia: implications of strong bottom‐up effects

AbstractThe population dynamics of insect herbivore biocontrol agents is central to the successful control of invasive weeds. Although the importance of agent population dynamics is recognized, it is rarely considered in assessments of the biocontrol potential of herbivore agents. Herbivore insect population dynamics are influenced by a combination of top‐down effects from natural enemies, bottom‐up effects from plant resource availability (resource quality and quantity), and potential interactions between these effects. To better understand the tri‐trophic interactions that are likely to determine biocontrol success in a host plant–gall wasp–parasitoid system, the relative importance of top‐down and bottom‐up effects for the survival of a herbivore biocontrol agent (Trichilogaster acaciaelongifoliae), on two Acacia host plants in their native range, was estimated using path analysis. On both host plants, there was a strong positive relationship between gall mass per chamber and gall wasp survival and a strong negative relationship between gall mass per chamber and gall parasitism, with parasitoids being less common in large than small galls. There was, however, no significant correlation between parasitism and gall wasp survival and, therefore, no evidence for top‐down effects in this system. Strong bottom‐up effects of host plant resources on both gall wasp survival and gall parasitism have implications for the spatio‐temporal variability of biocontrol success. Such variation should be considered in pre‐release assessments and post‐release monitoring of gall wasps used as herbivore biocontrol agents.

Subtropical Interactions: Comparing Galling Insect and Host Plant Diversity in Southern Brazil and Florida.

Gall-inducing insects seem to have a diversity pattern distinct from the usual latitudinal decrease in species, with more species occurring in xeric environments instead. Many questions regarding galler diversity over geographical scales remain unanswered: for example, little is known about beta diversity, and the role super host plants play in local/regional richness. Our aim was to compare galling insect and host plant diversity in different biogeographical regions, but under similar environmental conditions. We sampled short stature coastal woodlands on sandy soils of the Atlantic coast in both USA (Florida) and Brazil (Rio Grande do Sul, RS), between 25° and 30° latitude. Little-used 200-m long trails were searched during 90min for galls; there were four trails in USA and five in Brazil. Gall functional traits (galled plant organ, gall shape and colour) proportions were not different between Florida and RS. Local galling and host plant species richness also did not differ, and neither did regional galling diversity. The beta diversity pattern, however, was distinct: sites in Florida have more similar galling faunas than sites in RS. Common diversity patterns indicate common environmental biotic (plant diversity, vegetation structure) and abiotic (climate, soil) factors might be contributing to these similar responses. As Brazilian sites are in the Atlantic forest hotspot, a high galling insect beta diversity might be caused by a higher heterogeneity at larger scales-sample-based rarefaction curves were ascending for Brazil, but not for USA. Myrtaceans were super hosts in Brazil, but not in Florida, where oaks take up this role.

Влияние фитонцидных свойств дубовых насаждений на рост и развитие дубовых орехотворок порослевых дубрав зеленой зоны г. Воронежа

The article is devoted to research on the effect of phytoncide properties of oak grown in plantations of forest and park area of Voronezh on the growth and development of oak gallflies. The aim is to study the oak pests - oak gallflies - small flying insects. The female of gall wasps makes injection on an oak leaf using the ovipositor and lays eggs in the wound, which is beginning to develop, and the next underlying cells and tissues begin to form sheet "nut" or plant gall. Soon the larva hatches from the egg and begins to work its jaws. All larval development occurs in the gall. It turns out that from the time of laying the egg and then the larva during all the time of its development are in close proximity to the plant tissues and phytoncides. So, oak leaf tissue is not toxic to the larvae of gallflies. Meanwhile, it is well known that volatile phytoncides of oak leaves are poisonous to many microorganisms including the very resistant, for example, for the dysentery bacillus. When laying eggs in the leaf tissue insects necessarily hurt it. Namely wound leaf increases the "production" of phytoncides, but it remains without consequences for the insect to adapt to phytoncides of oak leaves. This adaptation of some insects to poisonous phytoncides affects equally scientists. One of the major reasons of sanitary and hygienic influence of the forest is the antimicrobial effect of the volatile, which secrete plant organizations as they play an important role in chemical interaction of plants in phytocenoses, that was proved by the works of N. G. Kholodny, A. L.Kholodny, A. L. Chesovennaya (1987) – the number of phytoncides and their activity in one and the same species varies with conditions of oak forest location

Rathayibacter toxicus, Other Rathayibacter Species Inducing Bacterial Head Blight of Grasses, and the Potential for Livestock Poisonings.

Rathayibacter toxicus, a Select Agent in the United States, is one of six recognized species in the genus Rathayibacter and the best known due to its association with annual ryegrass toxicity, which occurs only in parts of Australia. The Rathayibacter species are unusual among phytopathogenic bacteria in that they are transmitted by anguinid seed gall nematodes and produce extracellular polysaccharides in infected plants resulting in bacteriosis diseases with common names such as yellow slime and bacterial head blight. R. toxicus is distinguished from the other species by producing corynetoxins in infected plants; toxin production is associated with infection by a bacteriophage. These toxins cause grazing animals feeding on infected plants to develop convulsions and abnormal gate, which is referred to as "staggers," and often results in death of affected animals. R. toxicus is the only recognized Rathayibacter species to produce toxin, although reports of livestock deaths in the United States suggest a closely related toxigenic species may be present. A closely related but undescribed species, Rathayibacter sp. EV, originally isolated from Ehrharta villosa var. villosa in South Africa, is suspected of producing toxin. Many of the diseases caused by Rathayibacter species occur in arid areas and the extracellular polysaccharide they produce is believed to aid in their survival between crops. For example, R. "agropyri" was isolated from infected plant material after being stored for 50 years in a herbarium. Similarly, the anguinid vectors associated with these bacteria form seed galls in infected plants and are capable of surviving for very long periods of time under dry conditions. The addition of R. toxicus to the list of Select Agents has raised concern over its potential introduction and a realization that current diagnostic methods are inadequate to distinguish among Rathayibacter species. In addition, little is known about the Rathayibacter species and their seed gall nematode vectors present in the United States.

Weevils belonging to the Genus Smicronyx Schönherr, 1843 (Coleoptera, Curculionidae) affecting dodders (Cuscuta Linnaeus, 1753) in the Russian Far East

Two species of dodder are widespread in the Russian Far East—alien species Cuscuta campestris Yunck and native C. japonica Choisy (Cuscutaceae Dum.). For the first time we have identified individual species of Smicronyx genus in relation to specific dodder species as there was no such a research done in the Far East before. Smicronyx rubricatus Kono, 1930 was found on Cuscuta japonica Choisy, but plant galls were not detected. The insects fed on dodder sap and mate during the flower bud formation and flowering stages. Smicronyx madaranus Kono, 1930 was found to affect Cuscuta campestris Yunck.; its larvae form stem galls.

Endophytic yeasts in leaf galls

Yeast abundance and species diversity of endophytic complexes in galls (cecidia) formed on the leaves of Salix fragilis, Salix caprea, Quercus robur, Tilia cordata, and Ulmus laevis and the epiphytic yeast communities of undamaged leaves of these plants were studied. Dynamics of yeast abundance in the galls was significantly different from that of the epiphytic yeast communities. Maximum numbers of endophytic yeast cells in the galls (up to 104 CFU/g) were comparable to abundance of epiphytic yeasts. A total of 14 species of endophytic yeasts were isolated from galls of different plants. Ascomycetous yeasts were found to predominate in the insect galls on willows and oak, while basidiomycetous yeasts dominated in mite galls on linden and elm, as well as on plant leaves. These results indicate that gall formation may be considered not only as a bidirectional pathological process of the interaction between plants and invertebrates, but also as a process in which the endophytic microbial population of the galls plays an important role.

Expression analysis of defence related genes and histopathological changes in direct seeded rice genotypes (Oryza sativa L.) against root-knot nematode (Meloidogyne graminicola)

The root-knot nematodes, Meloidogyne spp. are one of the most important diseases causing organisms in direct seeded rice. In order to gain insight of differential response of susceptible and resistant rice cultivars upon nematode infection, expression of OsEDS1, OsPAD4 and OsWRKY genes involved in plant innate immunity was investigated. The expression analysis showed that EDS1-and PAD4mediated SA-upstream signaling triggered the induced defense at an the early stage of infection i.e., 2dpi and 6dpi in the resistant rice variety NDR-97, while it was negatively regulated in the susceptible genotype PB-1121. The histopathological studies of root galls of susceptible and resistant plants showed significant differences in the development of females, giant cells and egg production. The fecundity of the nematode was suppressed in the resistant cultivars.

Coupling of MIC-3 overexpression with the chromosomes 11 and 14 root-knot nematode (RKN) (Meloidogyne incognita) resistance QTLs provides insights into the regulation of the RKN resistance response in Upland cotton (Gossypium hirsutum)

Genetic analysis of MIC-3 transgene with RKN resistance QTLs provides insight into the resistance regulatory mechanism and provides a framework for testing additional hypotheses. Resistance to root-knot nematode (RKN) (Meloidogyne incognita) in Upland cotton (Gossypium hirsutum) is mediated by two major quantitative trait loci (QTL) located on chromosomes 11 and 14. The MIC-3 (Meloidogyne Induced Cotton3) protein accumulates specifically within the immature galls of RKN-resistant plants that possess these QTLs. Recently, we showed that MIC-3 overexpression in an RKN-susceptible cotton genotype suppressed RKN egg production but not RKN-induced root galling. In this study, the MIC-3 overexpression construct T-DNA in the single-copy transgenic line '14-7-1' was converted into a codominant molecular marker that allowed the marker assisted selection of F2:3 cotton lines, derived from a cross between 14-7-1 and M-240 RNR, having all possible combinations of the chromosomes 11 and 14 QTLs with and without the MIC-3 overexpression construct. Root-knot nematode reproduction (eggs g(-1) root) and severity of RKN-induced root galling were assessed in these lines. We discovered that the addition of MIC-3 overexpression suppressed RKN reproduction in lines lacking both resistance QTLs and in lines having only the chromosome 14 QTL, suggesting an additive effect of the MIC-3 construct with this QTL. In contrast, MIC-3 overexpression did not improve resistance in lines having the single chromosome 11 QTL or in lines having both resistance QTLs, suggesting an epistatic interaction between the chromosome 11 QTL and the MIC-3 construct. Overexpression of MIC-3 did not affect the severity of RKN-induced root galling regardless of QTL genotype. These data provide new insights into the relative order of action of the chromosomes 11 and 14 QTLs and their potential roles in regulating MIC-3 expression as part of the RKN resistance response.

Revision on Palaearctic species of Periclistus Förster with description of a new species and its host plant gall (Hymenoptera, Cynipidae).

Palaearctic species of Periclistus Förster has been systematically described, but a new inquiline gall-wasp, Periclistus qinghainensis sp. n., is described from China. This species was obtained from an unknown stem gall induced on Rosa sp. Diagnosis, distribution and biology of the new species are described in this paper. After examining the types of Periclistus idoneus Belizin, 1973 and Periclistus capillatus Belizin, 1968, it is concluded that Periclistus idoneus belongs to genus Aulacidea, and Periclistus capillatus is a valid species of Periclistus. A key to the Palaearctic Periclistus species is also given.

Caterpillar mimicry by plant galls as a visual defense against herbivores

Plant galls, induced by arthropods and various other organisms have an intimate relationship with host plants, and gall-inducers have limited mobility. In addition to their own photosynthesis, galls are resource sinks rich with nutrients, with neighboring plant organs commonly serving as external photosynthate sources. Galls, if not well defended, may therefore be attractive food sources for herbivores. Galls produced by some aphids, jumping plant lice, thrips, and gall midges in Japan, Palearctic region and in the Middle East visually resemble lepidopteran caterpillars. I propose that such visual resemblance may reduce herbivory of galls and surrounding plant tissues, resulting in an increase in galler survival due to reduced gall damage and in enhanced galler growth due to improved nutrient inflow to the galls, when herbivores avoid colonizing or consuming plant parts that look as if they have been occupied by other herbivores. Potential predators and parasitoids of caterpillars may be attracted to the caterpillar-like galls and then attack real caterpillars and other invertebrate herbivores, which would also be beneficial for both gallers and their hosts.

Galling problems – the Fergusobia nematode/Fergusonina fly mutualism on myrtaceous hosts

Fergusobia (Sphaerularioidea, Tylenchida) is the only known nematode to have a dicyclic life cycle with a generation in a plant (a myrtaceous host) followed by one in an insect (a Fergusonina fly: Diptera, Fergusoninidae). The nematode and fly have a mutualistic association, with the nematode inducing a plant gall on which the fly feeds and develops, and the fly providing transport for the nematode. The life cycle, specificity, diversity and distribution of the nematode are described, and the nematode phylogeny is discussed. Fergusobia is monophyletic but its origins are unclear. This paper raises questions about Fergusobia, including: what model best accounts for evolution of the known diversity of the nematode/fly mutualism?; how are the nematode/fly life cycles coordinated?; how do the nematodes avoid resistance mechanisms of both flies and plants?; what cecidogenic processes does the nematode use?; and what is the form of parthenogenesis occurring in Fergusobia and how does it relate to the inheritance of variability? Given the models of genomes and transcriptomes now available for other plant-parasitic nematodes and the availability of technologies to examine Fergusobia, it should be possible to answer some of these questions and begin to understand how Fergusobia nematodes might have evolved.

Parasitoids, Hyperparasitoids, and Inquilines Associated With the Sexual and Asexual Generations of the Gall Former,Belonocnema treatae(Hymenoptera: Cynipidae)

Insect-induced plant galls are thought to provide gall-forming insects protection from predation and parasitism, yet many gall formers experience high levels of mortality inflicted by a species-rich community of insect natural enemies. Many gall-forming cynipid wasp species also display heterogony, wherein sexual (gamic) and asexual (agamic) generations may form galls on different plant tissues or plant species. Despite broad interest in using these systems to study parasitism, enemy escape, and community assembly, few studies have provided complete characterizations of the natural enemy diversity associated with gall-forming wasp species, and fewer still have done so for both alternating generations. Here, we characterize the parasitoids, inquilines, and hyperparasitoids associated with the alternating sexual and asexual generations of the cynipid gall former, Belonocnema treatae Mayr in Texas, USA . We find 24 species associated with the asexual generation in leaf galls and four species associated with the sexual generation in root galls. We provide photographs and mitochondrial sequences for most species, discuss implications of these findings for hypotheses that consider heterogony as an adaptation for escape from natural enemies, and contemplate the relative incidence of specialized versus generalist feeding habits among gall former natural enemies.

Avirulence gene mapping in the Hessian fly (Mayetiola destructor) reveals a protein phosphatase 2C effector gene family

The genetic tractability of the Hessian fly (HF, Mayetiola destructor) provides an opportunity to investigate the mechanisms insects use to induce plant gall formation. Here we demonstrate that capacity using the newly sequenced HF genome by identifying the gene (vH24) that elicits effector-triggered immunity in wheat (Triticum spp.) seedlings carrying HF resistance gene H24. vH24 was mapped within a 230-kb genomic fragment near the telomere of HF chromosome X1. That fragment contains only 21 putative genes. The best candidate vH24 gene in this region encodes a protein containing a secretion signal and a type-2 serine/threonine protein phosphatase (PP2C) domain. This gene has an H24-virulence associated insertion in its promoter that appears to silence transcription of the gene in H24-virulent larvae. Candidate vH24 is a member of a small family of genes that encode secretion signals and PP2C domains. It belongs to the fraction of genes in the HF genome previously predicted to encode effector proteins. Because PP2C proteins are not normally secreted, our results suggest that these are PP2C effectors that HF larvae inject into wheat cells to redirect, or interfere, with wheat signal transduction pathways.

A Massive Expansion of Effector Genes Underlies Gall-Formation in the Wheat Pest Mayetiola destructor

Gall-forming arthropods are highly specialized herbivores that, in combination with their hosts, produce extended phenotypes with unique morphologies [1]. Many are economically important, and others have improved our understanding of ecology and adaptive radiation [2]. However, the mechanisms that these arthropods use to induce plant galls are poorly understood. We sequenced the genome of the Hessian fly (Mayetiola destructor; Diptera: Cecidomyiidae), a plant parasitic gall midge and a pest of wheat (Triticum spp.), with the aim of identifying genic modifications that contribute to its plant-parasitic lifestyle. Among several adaptive modifications, we discovered an expansive reservoir of potential effector proteins. Nearly 5% of the 20,163 predicted gene models matched putative effector gene transcripts present in the M. destructor larval salivary gland. Another 466 putative effectors were discovered among the genes that have no sequence similarities in other organisms. The largest known arthropod gene family (family SSGP-71) was also discovered within the effector reservoir. SSGP-71 proteins lack sequence homologies to other proteins, but their structures resemble both ubiquitin E3 ligases in plants and E3-ligase-mimicking effectors in plant pathogenic bacteria. SSGP-71 proteins and wheat Skp proteins interact in vivo. Mutations in different SSGP-71 genes avoid the effector-triggered immunity that is directed by the wheat resistance genes H6 and H9. Results point to effectors as the agents responsible for arthropod-induced plant gall formation.

Gradients of metabolite accumulation and redifferentiation of nutritive cells associated with vascular tissues in galls induced by sucking insects.

Plant cells respond to abiotic and biotic stimuli, which generate adaptive phenotypes in plant organs. In the case of plant galls, cell phenotypes are adaptive for the gall inducer and assume characteristics mainly linked to its protection and nutrition. Herein, the cytological development and histochemical profile of Nothotrioza cattleiani galls, a sucking insect, on the leaves of Psidium cattleianum are compared with those of other galls, especially N. myrtoidis galls, searching for conserved and divergent alterations in cell fates and cycles. Leaf cell fates are completely changed within galls, except for epidermal cells, but the comparison between Nothotrioza spp. galls shows conserved fates. Nevertheless, cytological development of N. cattleiani galls is different from the standby-redifferentiation of N. myrtoidis galls. Starch and lignins, and reducing sugars form centrifugal and centripetal gradients of accumulation, respectively. Proteins, total phenolics, terpenoids, proanthocyanidins and reactive oxygen species are detected in bidirectional gradients, i.e. weak or undetectable reaction in the median cortical cells that is gradually more intense in the cell layers towards the inner and outer surfaces of the gall. True nutritive cells associated with vascular tissues, together with the bidirectional gradients of metabolite accumulation, are herein reported for the first time in insect galls. The globoid galls of N. cattleiani, though macro-morphologically similar to the galls of N. myrtoidis, are distinct and unique among insect galls, as far as the cellular, subcellular and histochemical traits are concerned. Thus, the traits of the galls on P. cattleianum studied herein represent the extended phenotypes of their inducers.

Structure and development of 'witches' broom' galls in reproductive organs of Byrsonima sericea (Malpighiaceae) and their effects on host plants.

Galls are anomalies in plant development of parasitic origin that affect the cellular differentiation or growth and represent a remarkable plant-parasite interaction. Byrsonima sericea DC. (Malpighiaceae) is a super host of several different types of gall in both vegetative and reproductive organs. The existence of galls in reproductive organs and their effects on the host plant are seldom described in the literature. In this paper, we present a novel study of galls in plants of the Neotropical region: the 'witches' broom' galls developed in floral structures of B.sericea. The unaffected inflorescences are characterised by a single indeterminate main axis with spirally arranged flower buds. The flower buds developed five unaffected brownish hairy sepals and five pairs of elliptical yellow elaiophores, five yellow fringed petals, 10 stamens and a pistil with superior tricarpellar and trilocular ovary. The affected inflorescences showed changes in architecture, with branches arising from the main axis and flower buds. The flower buds exhibited several morphological and anatomical changes. The sepals, petals and carpels converted into leaf-like structures after differentiation. Stamens exhibited degeneration of the sporogenous tissue and structures containing hyphae and spores. The gynoecium did not develop, forming a central meristematic region, from which emerges the new inflorescence. In this work, we discuss the several changes in development of reproductive structures caused by witches' broom galls and their effects on reproductive success of the host plants.