Effects of single and dual species herbivory on the behavioral responses of three thrips species to cotton seedlings

This study investigated the olfactory responses of 3 thrips species [Frankliniella schultzei Trybom, F. occidentalis Pergrande and Thrips tabaci Lindeman (Thysanoptera: Thripidae)] to cotton seedlings [Gossypium hirsutum L. (Malvales: Malvaceae)] simultaneously damaged by different combinations of herbivores. Cotton seedlings were damaged by foliar feeding Tetranychus urticae Koch (Trombidiforms: Tetranychidae), Helicoverpa armigera Hübner (Lepidoptera: Noctuidae), Aphis gossypii Glover (Hemiptera: Aphididae) or root feeding Tenebrio molitor L. (Coleoptera: Tenebrionidae). Thrips responses to plants simultaneously damaged by 2 species of herbivore were additive and equivalent to the sum of the responses of thrips to plants damaged by single herbivore species feeding alone. For example, F. occidentalis was attracted to T. urticae damaged plants but more attracted to undamaged plants than to plants damaged by H. armigera. Plants simultaneously damaged by low densities of T. urticae and H. armigera repelled F. occidentalis but as T. urticae density increased relative to H. armigera density, F. occidentalis attraction to coinfested plants increased proportionally. Thrips tabaci did not discriminate between undamaged plants and plants damaged by H. armigera but were attracted to plants damaged by T. urticae alone or simultaneously damaged by T. urticae and H. armigera. Olfactometer assays showed that simultaneous feeding by 2 herbivores on a plant can affect predator–prey interactions. Attraction of F. occidentalis to plants damaged by its T. urticae prey was reduced when the plant was simultaneously damaged by H. armigera, T. molitor, or A. gossypii and F. schultzei was more attracted to plants simultaneously damaged by T. urticae and H. armigera than to plants damaged by T. urticae alone. We conclude that plant responses to feeding by 1 species of herbivore are affected by responses to feeding by other herbivores. These plant‐mediated interactions between herbivore complexes affect the behavioral responses of thrips which vary between species and are highly context dependent.     

Nematophagous Fungi Associated with Root Galls of Rice Caused by Meloidogyne graminicola and its Control by Arthrobotrys dactyloides and Dactylaria brochopaga

Root galls of rice caused by Meloidogyne graminicola were examined for natural colonization by nematophagous fungi from four fields with different nematode infestations. Old galls from severely infested fields had a higher frequency of Monacrosporium eudermatum and Stylopaga hadra than young galls. The frequency of Arthrobotrys oligospora, Arthrobotrys dactyloides, Dactylaria brochopaga and Monacrosporium gephyropagum was lower. A greater proportion (%) of root galls were colonized by nematophagous fungi in those fields in which rice roots had a greater root gall index. This indicated that disease severity supported the colonization of galls by nematophagous fungi. In vitro predacity tests of four fungi showed that A. dactyloides was most effective in capturing and killing J₂ of Mel. graminicola followed by D. brochopaga and Mon. eudermatum. Application of inocula of A. dactyloides and D. brochopaga in soil infested with Mel. graminicola, respectively, reduced the number of root galls by 86% and of females by 94%, and eggs and juveniles by 94%. The application of these fungi to soil increased plant growth: shoot length by 42.7% and 39.8%, root length by 45.5% and 48.9%, fresh weight of shoot by 59.9% and 56.7% and fresh weight of root by 20.3% and 25.1%, respectively, compared to these parameters for plants grown in nematode‐infested soil.     

A Role for Pectinase and Protease Inhibitors in Fungal Rot Development in Tomato Fruits

B. cinerea and C. atramentarium rotted wound-inoculated green tomato fruits and wounded or intact ripe fruits while G. cingulata developed rots only in ripe fruits. Pectic en-zymes were extracted from the fruit tissue rotted by B. cinerea and C. atramentarium but no pectic enzymes attributable to the fungus were detected in ripe fruits rotted by G. cingulata. G. cingulata produced endo-PG and endo-PL in vitro, C. atramentarium produced endo-PL in vitro and in vivo and B. cinerea produced exo-PG in vitro and in green fruits but endo-PG and endo-PL in ripe fruits. Well ripened tomato fruits contained high levels of endogenous PG. All three fungi produced proteolytic enzymes in vitro and in vivo. Proteases produced by G. cingulata and C. atramentarium had optimum activity at pH 9 to 10 and were not trypsin-like or chymotrypsin-like in nature. Protease produced by B. cinerea had optimum activity at pH 7 and showed both trypsin and chymotrypsin-like activity. Proteins extracted from the cell walls of tomato fruits inhibited both the endo-PG and endo-PL produced by G. cingulata and the endo-PL produced by B. cinerea but did not in-hibit the activity of PGs produced by B. cinerea, the endo-PL produced by C. atramentarium or the endogenous PG from tomato fruits. The cell wall proteins also contained trypsin and chymotrypsin inhibitor activity which inhibited 70 % of the activity of the protease produced by B. cinerea, but had little effect on the proteases produced by G. cingulata, C. atramentarium or the tomato endogenous protease. Enzymes produced in vitro by G. cingulata macerated green tomato tissue more slowly than enzymes produced in vitro by C. atramentarium and B. cinerea and the rate of mation was further reduced in the presence of added cell wall proteins. Excess inhibitor of the little effect on the rate of maceration by the enzymes produced by C. atramentarium of the cinerea.     

Origin of the main class of repetitive DNA within selected Pennisetum species

In an attempt to identify relationships among genomes of the allotetraploid Pennisetum purpureum Schumach and closely related Pennisetum species with which it can be successfully hybridized, repetitive DNA sequences were examined. Digestion with KpnI revealed two highly repetitive fragments of 140 by and 160 bp. The possibility that these sequences could be used as genome markers was investigated. Average sequences were determined for the 140 by and 160 by KpnI families from P. purpureum and P. squamulatum Fresen. Average sequences (based upon four or five repeats) were determined for the P. glaucum (L.) R. Br. 140 by KpnI family and the diploid P. hohenackeri Hochst. ex Steud. 160 bp KpnI family. The average sequences of the 160 by KpnI families in P. purpureum and P. squamulatum differ by only nine bases. The 140 by KpnI families of the three related species, P. purpureum, P. squamulantum, and P. glaucum are nearly identical, and thus likely represent a recent divergence from a common progenitor or a common genome. Each repetitive sequence may contain internal duplications, which probably diverged following amplification of the original sequence. The 140 by KpnI repeat probably evolved from the 160 by KpnI repeat since the missing 18 by segment is part of the internal duplication that is otherwise conserved in the subrepeats. Tandemly arrayed repetitive sequences in plants are likely to be composed of subrepeats which have been duplicated and amplified.Florida Aqricultural Experiment Station series #R-02758     

Comparison of Six Isoenzymes from 10 Species of Crithidia1

ABSTRACT. The electrophoretic mobility of six isoenzymes from 10 species of Crithidia from insects were compared. Five zymogram patterns emerged. Pattern I was presented by C. acanthocephali and Crithidia sp. from Euryophthalmus davisi; pattern II by C. hutneri and C. luciliae thermophila; pattern III by C. arili; pattern IV by C. luciliae luciliae, Crithidia sp. from Aedes solicitans, C. harmosa, and C. fasciculata; pattern V by C. oncopelti.     

Co-limitation of potato growth by Potato Cyst Nematode (Globodera rostochiensis) and Rhizoctonia solani

Globodera rostochiensis and Rhizoctonia solani are the most important growth limiting factors influencing potato production in Iran. The effects of inoculation with Potato Cyst Nematodes (PCN) (0, 50, 75 and 100 cysts/3.5?kg soil) and R. solani (with or without inoculation) on potato growth and development were investigated in cultivars Santé and Marfona. Inoculation with R. solani induced severe damage, especially when inoculation was accompanied with high density of PCN. The damage caused by R. solani tended to increase with an increase in PCN density, especially in Marfona. In Santé, number of stems or branches per plant significantly increased by inoculation with R. solani, while in Marfona it was significantly affected either by R. solani inoculation or PCN density. In Santé, number of stolons per plant was significantly increased by PCN, but not by R. solani. In Marfona, however, the number of stolons per plant was significantly affected either by R. solani inoculation or by presence of PCN, but not affected by PCN density. The general effect of R. solani or PCN inoculation treatments on shoot, below-ground and total dry weight of potato was significant, but strongly affected by cultivar. In general, our study supports the synergistic interaction between R. solani and PCN and its moderation by the use of a resistant cultivar such as Santé.     

Direct effect of biocontrol agents on wilt and root-rot diseases of sesame

In Egypt, sesame cultivation is subject to attack by wilt and root-rot diseases caused by Fusarium oxysporum f.sp. sesami (Zap) Cast. and Macrophomina phaseolina (Maubl) Ashby causing losses in quality and quantity of sesame seed yield. Bacillus subtilis and Trichoderma viride isolates which were isolated from sesame rhizosphere were the most effective to antagonise fungal pathogens, causing high reduction of hyphal fungal growth. Trichoderma viride was found to be mycoparasitic on Fusarium oxysporum f.sp. sesami and M. phaseolina causing morphological atternation of fungal cells and sclerotial formation. In general, Bacillus subtilis, T. viride, avirulent Fusarium oxysporum isolate and Glomus spp. (Amycorrhizae) significantly reduced wilt and root-rot incidence of sesame plants at artificially infested potted soil by each one or two pathogens. Data obtained indicate that Glomus spp significantly reduced wilt and disease severity development on sesame plants followed by T. viride. Meanwhile, avirulent Fusarium oxysporum isolate followed by Glomus spp. were effective against root-rot disease incidence caused by M. phaseolina. Glomus spp. followed by B. subtilis significantly reduced wilt and root-rot disease of sesame plants. All biotic agents significantly reduced F. oxysporum f.sp. sesami and M. phaseolina counts in sesame rhizosphere at the lowest level. Glomus spp. and the avirulent isolate of F. oxysporum eliminated M. phaseolina in sesame rhizosphere. Meanwhile T. viride was the best agent at reducing F. oxysporum at a lower level than other treatments. Application of VA mycorrhizae (Glomus spp.) in fields naturally infested by pathogens significantly reduced wilt and root-rot incidence and it significantly colonised sesame root systems and rhizospheres compared to untreated sesame transplantings.     

Reviews of publications

Book reviewed in this article: A World Like Our Own—Man and Nature in Madagascar, by Alison Jolly. Vertebrate Limb Regeneration, by H. Wallace. Statistical Methods in Biology, by N. T.J. Bailey Conservation and Evolution, by O. H. Frankel & M. E. Soule Evolution in Age-structured Populations by B. Charlesworth Essential Biology, by Herbert T. Hendrickson Flora Suzakiensis, edited by Biological Laboratory, Imperial Household Phylogenetic Patterns and the Evolutionary Process, by N. Eldredge & J. Cracraft Excursion Flora of the British Isles, by A. R. Clapham, T. G. Tutin & E. F. Warburg Whales, by W. N. Bonner Les Chevaux, Fossiles et Actuels, by V. Eisenmann Freshwater Snails of Africa and their Medical Importance, by David S. Brown Symbiosis in Cell Evolution, by Lynn Margulis Vegetation Dynamics, by J. Miles     

Relative consumption of three aphid species by the lacewing, Chrysoperla rufilabris, and effects on its development and survival

Relative consumption of three aphid species, Aphis gossypii Glover, Myzus persicae (Sulzer) and Lipaphis erysimi (Kaltenbach) (Homoptera: Aphididae), by larvae of the lacewing, Chrysoperla rufilabris (Burmeister) (Neuroptera: Chrysopidae), was determined in the laboratory, together with effects on lacewing development and survival. Percentages of survival of C. rufilabris from first instar to adult eclosion were significantly different among lacewing larvae fed different aphid species. When larvae were fed A. gossypii and M. persicae, all larvae developed to adulthood. All larvae died prematurely when they were fed L. erysimi. Developmental duration of C. rufilabris larvae was significantly shorter when larvae were fed A. gossypii (18.0 d) than when larvae were fed M. persicae (19.2 d). The number of fourth instar aphids consumed during development by C. rufilabris larvae differed significantly among individuals fed different aphid species. Chrysoperla rufilabris consumed an average of 168 M. persicae, followed by 141.6 A. gossypii, and only 26.6 L. erysimi. The percentage of these total number of aphids consumed by each larval stadium of C. rufilabris varied significantly among aphid species. The percentage of A. gossypii consumed by each larval stadium was similar to that for M. persicae, 12.1 and 11.4% by the first instar, 15.7 and 13.1% by the second instar, and 72.2 and 75.5% by the third instar, respectively; whereas in the case of L. erysimi, 23.3% of the total number of aphids were consumed by the first instar, 30.1% by the second instar, and 46.6% by the third instar.     

Mass production and utilization ofTrichogramma: 10. Control of the codling mothCydia pomonella and the summer fruit tortrix mothAdoxophyes orana [Lep.: Tortricidae]

The effectiveness ofTrichogramma dendrolimi, Trichogramma embryophagum, Trichogramma sp. strain 45 andTrichogramma sp. strain 48 to control the codling mothCydia pomonella L. and the summer fruit tortrix mothAdoxophyes orana F.R. was tested in 4 field trials (1984–1986). Four to sixTrichogramma treatments (depending on the temperature) each at 400 (pillar trees) to 9,000 (round tops) parasites per tree were carried out between June and August to insure the continuous presence ofTrichogramma in the plots. The monitoring was done by examining 3,000 to 10,000 apple fruits per plot. T. dendrolimi reduced the damage ofC. pomonella by 61.35%, ofA. orana by 72.85%.T. embryophagum reduced the damage ofC. pomonella by 50.06%, ofA. orana by 50.8%.Trichogramma strain 45 reduced the damage ofC. pomonella by 41.6% and ofA. orana by 87.9%,Trichogramma strain 48 by 57.2% and 51.2% respectively. The reduction of 67.1% in the number of apple fruits damaged byC. pomonella andA. orana obtained by the inundative releases ofT. dendrolimi in these experiments is considered economically and the use of this species in practice is recommended.      

Neutrophil activation by Candida glabrata but not Candida albicans promotes fungal uptake by monocytes

Candida albicans and Candida glabrata account for the majority of candidiasis cases worldwide. Although both species are in the same genus, they differ in key virulence attributes. Within this work, live cell imaging was used to examine the dynamics of neutrophil activation after confrontation with either C. albicans or C. glabrata. Analyses revealed higher phagocytosis rates of C. albicans than C. glabrata that resulted in stronger PMN (polymorphonuclear cells) activation by C. albicans. Furthermore, we observed differences in the secretion of chemokines, indicating chemotactic differences in PMN signalling towards recruitment of further immune cells upon confrontation with Candida spp. Supernatants from co‐incubations of neutrophils with C. glabrata primarily attracted monocytes and increased the phagocytosis of C. glabrata by monocytes. In contrast, PMN activation by C. albicans resulted in recruitment of more neutrophils. Two complex infection models confirmed distinct targeting of immune cell populations by the two Candida spp.: In a human whole blood infection model, C. glabrata was more effectively taken up by monocytes than C. albicans and histopathological analyses of murine model infections confirmed primarily monocytic infiltrates in C. glabrata kidney infection in contrast to PMN‐dominated infiltrates in C. albicans infection. Taken together, our data demonstrate that the human opportunistic fungi C. albicans and C. glabrata are differentially recognized by neutrophils and one outcome of this differential recognition is the preferential uptake of C. glabrata by monocytes.     

Arbuscular mycorrhizal fungi on adjacent semi-natural grasslands with different vegetation in Japan

Arbuscular mycorrhizal (AM) fungi on Japanese semi-natural grasslands were investigated at three adjacent sites with different vegetation. The predominant grasses at the three sites were 1)Pleioblastus chino, 2)Miscanthus sinensis andArundinella hirta (M. sinensis/A. hirta), and 3)Zoysia japonica, respectively. The degree of colonization was higher inM. sinensis/A. hirta than inP. chino andZ. japonica. AM fungi were recovered by spore extraction and by pot cultures started from soil inoculum or from transplanting of field plants. Total spore number obtained by the spore extraction method was highest in the rhizosphere ofM. sinensis/A. hirta and lowest in that ofP. chino. AGlomus sp. resemblingG. geosporum predominated in association withM. sinensis/A. hirta andP. chino. FromZ. japonica, three species,Acaulospora gerdemannii, Glomus leptotichum, and a species resemblingG. clarum, were isolated by pot culture from soil and two species,A. longula andScutellospora cerradensis, by pot culture from transplanting ofZ. japonica. FromM. sinensis/A. hirta, one species,A. longula, was found by pot culture from soil. FromP. chino, no AM fungus was detected by either method. Single-spore culture confirmed thatG. leptotichum andA. gerdemannii are conspecific.     

Reviews of publications

Book reviewed in this article: Reproduction of Marine Invertebrates. Vol. VI. Echinoderms and Lophophorates, edited by A. C. Giese, J. S. Pearse and V. B. Pearse. Pacific Grove, California, U.S.A. The Butterflies of Kenya and their Natural History, by T. B. Larsen. The Land and Freshwater Molluscs of Suffolk, by I. J. Killeen. Ipswich, U.K. Flycatcher. Memoirs of an Amateur Entomologist by K. A. Spencer. Ecosystems of the World 24. Intertidal and Littoral Ecosystems, edited by A. C. Mathieson and P. H. Nienhuis. Revision of the Northeast Atlantic and Mediterranean Stylasteridae (Cnidaria: Hydrozoa), by Helmut Zibrowius and Stephen D. Cairns. Paris: Mémoires du Musée Nationale d'Histoire Naturellee, 1992. Animals and Disease. An Introduction to the History of Comparative Medicine, by L. Wilkinson. The Inevitable Bond. Examining Scientist-Animal Interactions, edited by H. Davis and D. Balfour. Martin Lister's English Spiders (1678), edited by J. Parker and B. Harley (translated by M. Davies and B. Harley)). The Ecology of Fishes on Coral Reefs, edited by P. F. Sale. San Diego, USA: The Lepidoptera: Form, Function and Diversity, by M. J. Scoble. Bats. A Community Perspective, by J. S. Findley. The Insects of Australia. A textbook for students and research workers, Commonwealth Scientific and Industrial Research Organisation. Second Edition. Botanical monkeys, by E. J. H. Corner. The Biology of Millipedes, by S. P. Hopkin and H. J. Read. Mammals in the Palaearctic Desert: Status and Trends in the Sahara-Gobian Region, edited by J. A. McNeely and V. M. Neronov. Coelenterate Biology: Recent Research on Cnidaria and Ctenophora, edited by R. B. Williams, P. F. S. Cornelius, R. G. Hughes and E. A. Robson. Dordrecht, The Netherlands: Kluwer Academic Publishers, 1991. Animal Behaviour, 4th ed., by A. Manning and M. S. Dawkins. Weevils, Naturalists' Handbook 16, by M. G. Morris. Insects on Cabbage and Oilseed Rape. Naturalists' Handbooks 18, by W. D. J. Kirk.     

Suppression by Zygorrhynchus moelleri of Growth and Sclerotium Production by Rhizoctonia solani and Sclerotinia sclerotiorum

As indicated by reduced cellulolysis, Zygorrhynchus moelleri suppressed mycelial growth in Rhizoctonia solani and Sclerotinia sclerotiorum. Sclerotium production by both pathogenic fungi was also reduced by Z. moelleri in dual sand-oatmeal cultures. The viability of sclerotia produced by S. sclerotiorum, but not those produced by R. solani, was greatly reduced. Sclerotium production by S. sclerotiorum on celery and tomato segments was reduced to a much greater extent when Z. moelleri was applied to the plant tissue 24 h before the pathogen than when applied at the same time or 24 h after the pathogen.     

Enhanced hydrogen production from glucose by metabolically engineered <Emphasis Type="Italic">Escherichia coli</Emphasis>

To utilize fermentative bacteria for producing the alternative fuel hydrogen, we performed successive rounds of P1 transduction from the Keio Escherichia coli K-12 library to introduce multiple, stable mutations into a single bacterium to direct the metabolic flux toward hydrogen production. E. coli cells convert glucose to various organic acids (such as succinate, pyruvate, lactate, formate, and acetate) to synthesize energy and hydrogen from formate by the formate hydrogen-lyase (FHL) system that consists of hydrogenase 3 and formate dehydrogenase-H. We altered the regulation of FHL by inactivating the repressor encoded by hycA and by overexpressing the activator encoded by fhlA, removed hydrogen uptake activity by deleting hyaB (hydrogenase 1) and hybC (hydrogenase 2), redirected glucose metabolism to formate by using the fdnG, fdoG, narG, focA, focB, poxB, and aceE mutations, and inactivated the succinate and lactate synthesis pathways by deleting frdC and ldhA, respectively. The best of the metabolically engineered strains, BW25113 hyaB hybC hycA fdoG frdC ldhA aceE, increased hydrogen production 4.6-fold from glucose and increased the hydrogen yield twofold from 0.65 to 1.3 mol H₂/mol glucose (maximum, 2 mol H₂/mol glucose).     

Growth phase-differential quorum sensing regulation of anthranilate metabolism in <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis>

Pseudomonas quinolone signal (PQS) plays a role in the regulation of virulence genes and it is intertwined in the las/rhl quorum sensing (QS) circuits of Pseudomonas aeruginosa. PQS is synthesized from anthranilate by pqsA-D and pqsH whose expression is influenced by the las/rhl systems. Since anthranilate can be degraded by functions of antABC and catBCA, PQS synthesis might be regulated by the balance between the expression of the pqsA-D/phnAB, pqsH, antABC, and catBCA gene loci. antA and catA are repressed by LasR during log phase and activated by RhlR in late stationary phase, whereas pqsA-E/phnAB is activated by LasR in log phase and repressed by RhlR. QscR represses both but each repression occurs in a different growth phase. This growth phase-differential regulation appears to be accomplished by the antagonistic interplay of LasR, RhlR, and QscR, mediated by two intermediate regulators, AntR and PqsR, and their cofactors, anthranilate and PQS, where the expressions of antR and pqsR and the production of anthranilate and PQS are growth phase-differentially regulated by QS systems. Especially, the anthranilate level increases in an RhlR-dependent manner at late stationary phase. From these results, we suggest that RhlR and LasR regulate the anthranilate metabolism in a mutually antagonistic and growth phase-differential manner by affecting both the expressions and activities of AntR and PqsR, and that QscR also phase-differentially represses both LasR and RhlR functions in this regulation.     

Characterization of aStaphylococcus aureusTransposon, Tn5405,Located within Tn5404and Carrying the Aminoglycoside Resistance Genes,aphA-3andaadE

A new staphylococcal composite transposon, designated Tn5405,carrying the genesaphA-3andaadE,which encode resistance to aminoglycosides, was partially characterized. The transposon is 12 kb long and is flanked by inverted repeated sequences displaying the characteristic features of an insertion sequence, named IS1182.This insertion sequence is 1864 bp long and has 23/33-bp imperfect inverted repeats at its ends. One of the IS1182copies delimiting Tn5405contains a copy of IS1181flanked by 8-bp direct repeats. Tn5405was found in the chromosome of MRSA clinical isolate BM3121, within a Tn552-related transposon, Tn5404.Tn5404was previously characterized following its transposition onto a β-lactamase plasmid harbored by BM3121. Two forms of the recombinant β-lactamase-encoding plasmid generated by the inversion of Tn5405within Tn5404were detected. IS1182was not detected in the DNA of 4 of the 17 tested MRSA isolates containingaphA-3and resistant to streptomycin. Thus,aphA-3andaadEgenes are not disseminated only by Tn5405or related transposons delimited by IS1182.     

Transmission of <Emphasis Type="Italic">Methylobacterium mesophilicum</Emphasis> by <Emphasis Type="Italic">Bucephalogonia xanthophis</Emphasis> for paratransgenic control strategy of Citrus variegated chlorosis

Methylobacterium mesophilicum, originally isolated as an endophytic bacterium from citrus plants, was genetically transformed to express green fluorescent protein (GFP). The GFP-labeled strain of M. mesophilicum was inoculated into Catharanthus roseus (model plant) seedlings and further observed colonizing its xylem vessels. The transmission of this endophyte by Bucephalogonia xanthophis, one of the insect vectors that transmit Xylella fastidiosa subsp. pauca, was verified by insects feeding from fluids containing the GFP bacterium followed by transmission to plants and isolating the endophyte from C. roseus plants. Forty-five days after inoculation, the plants exhibited endophytic colonization by M. mesophilicum, confirming this bacterium as a nonpathogenic, xylem-associated endophyte. Our data demonstrate that M. mesophilicum not only occupy the same niche of X. fastidiosa subsp. pauca inside plants but also may be transmitted by B. xanthophis. The transmission, colonization, and genetic manipulation of M. mesophilicum is a prerequisite to examining the potential use of symbiotic control to interrupt the transmission of X. fastidiosa subsp. pauca, the bacterial pathogen causing Citrus variegated chlorosis by insect vectors.