Herbivory by Western Flower Thrips (Frankliniella occidentalis Pergande) (WFT) and drought-stress due to limited water availability are currently two major factors that can severely impact cotton (Gossypium hirsutum L.) production. This dissertation examines the effects of drought-stress on cotton and host-plant resistance (HPR) to WFT in laboratory conditions, and seeks to identify the physiological and morphological mechanisms that underlie drought-tolerance and HPR. A life-history systems-approach was developed that provides a new level of detail for understanding how environmental variation impacts adult female WFT. The approach was illustrated by investigating the combined effects of cotton genotype, periodic drought-stress, and prey availability on the adult female omnivorous thrips using a factorial design. Three treatment conditions were significantly different, none of which were predicted based on prevailing ecological-hypotheses. At the same time, the approach produced three novel insights about WFT life-history and reproductive strategy. The roles of negative photo-taxis and leaf biomechanical properties were investigated as potential mechanisms that influence WFT foraging-decisions on individual cotyledons. Results showed that WFT foraging-decisions could be considered adaptive, but there was limited support for either of the mechanisms investigated. The physiological responses to drought stress and drought recovery were investigated for three transgenic cotton cultivars and an untransformed wild-type (WT). At peak drought, ABA levels, stomatal area, and stomatal apertures in the transgenic isolone, AtRAV1-1 were 48% lower, 27.7%, and 16.3% smaller than WT. These results suggest that AtRAV1-1 was the most drought-tolerant and support the hypothesis that changes in stomatal morphology may have functionally contributed to drought-tolerance. Lastly, I investigated whether changes in phytohormone concentrations associated with periodic-drought stress in four cotton cultivars (three transgenic and WT) were correlated with WFT feeding, fitness and state-dependent reproductive responses (i.e., the relationship between initial weight and reproduction). Results showed that JA-Ile and JA were positively correlated with state-dependent egg viability and fecundity, respectively, and negatively correlated with total egg viability and fecundity, respectively, supporting the hypothesis that JA and JA-Ile underlie the negative effects on WFT reproduction and the associated shift to state-dependent reproduction.

Visando avaliar os efeitos do tempo e da temperatura de armazenamento de grãos de feijoeiro, Phaseolus vulgaris L., sobre a manifestação da resistência ao caruncho Acanthoscelides obtectus (Say, 1831), realizaram-se ensaios com e sem chance de escolha sob condições de laboratório. Em casa-de-vegetação avaliou-se a preferência para oviposição e os danos causados pelo caruncho em vagens e grãos. Os genótipos utilizados nos ensaios foram Arc.1S, Arc.3S, Arc.5S, Carioca Pitoco, Ipa 6, Porrillo 70, Onix, Arc.1, Arc.2, Arc.3 e Arc.4. Em teste com chance de escolha utilizando-se grãos de diferentes idades, observou-se que os genótipos selvagens Arc.1S e Arc.5S expressaram antibiose e/ou não-preferência para alimentação como mecanismos de resistência a A. obtectus; os genótipos Arc.1 e Arc.2 apresentaram somente antibiose; já Arc.3S expressou não-preferência para oviposição e baixos níveis de antibiose. Em teste sem chance de escolha, os genótipos Arc.1S, Arc.3S, Arc.5S, Arc.1 e Arc.2 expressaram antibiose. Em teste onde avaliou-se a influência do tamanho de grãos na manifestação da resistência, os genótipos selvagens Arc.1S, Arc.3S e Arc.5S expressaram antibiose e/ou não-preferência para alimentação; Arc.1 e Arc.2 expressaram antibiose. No estudo com grãos armazenados sob diferentes temperaturas observou-se antibiose em grãos de Arc.1S e Arc.2, independentemente da temperatura em que estiveram confinados; já com Arc.1, notou-se que os efeitos antibióticos de seus grãos foram reduzidos à medida que a temperatura de armazenamento se elevou. Constatou-se também que 25°C não é a melhor temperatura para discriminar genótipos em estudos de resistência, comparativamente à 20°C e 30°C. Em casa-de-vegetação observou-se que as vagens e grãos do genótipo Arc.4 foram mais preferidos para oviposição e alimentação por A. obtectus em relação aos demais materiais; por sua vez Arc.1, Arc.5S, Ipa 6, Arc.3S e Porrillo 70 revelaram-se menos preferidos para oviposição e alimentação pelo caruncho. / Aiming to evaluate the effects of the time and temperatures of storage bean grains Phaseolus vulgaris L. on the expression of the resistance to the bean weevil Acanthoscelides obtectus (Say, 1831), free and no choice tests were accomplished under laboratory conditions. The preference for oviposition and damages caused by the weevil in pods and grains were evaluated under greenhouse conditions. The genotypes used in the assays were Arc.1S, Arc.3S, Arc.5S, Carioca Pitoco, Ipa 6, Porrillo 70, Onix, Arc.1, Arc.2, Arc.3 and Arc.4. In free choice test using grains of different ages, the wild genotypes Arc.1S and Arc.5S expressed antibiosis and/or no-preference for feeding as resistance mechanisms to A. obtectus; the genotypes Arc.1 and Arc.2 presented only antibiosis; Arc.3S expressed no-preference for oviposition and low antibiosis levels. In no-choice test, the genotypes Arc.1S, Arc.3S, Arc.5S, Arc.1 and Arc.2 expressed antibiosis. In test where the influence of the size of grains was evaluated in the expression of resistance, the wild genotypes Arc.1S, Arc.3S and Arc.5S expressed antibiosis and/or no-preference for feeding; Arc.1 and Arc.2 expressed antibiosis. In the study with grains stored under different temperatures, antibiosis was observed in grains of Arc.1S and Arc.2, independently of the confinement temperature; in Arc.1, it was observed that the antibiotic effects of its grains were reduced as the storage temperature increased. It was also verified that 25°C was not the best temperature to discriminate genotypes in studies of resistance, comparatively to 20°C and 30°C. In greenhouse the pods and grains of Arc.4 were the most preferred for oviposition and feeding by A. obtectus, comparing to the other materials; Arc.1, Arc.5S, Ipa 6, Arc.3S and Porrillo 70 were the least preferred for oviposition and feeding by the bean weevil.

During post-alighting behaviour gravid female turnip root fly, D.jloralis, select a plant for oviposition predominantly during the initial landing phase; the cabbage root fly, D.radicum, also utilise the leaf resting phase. The post-alighting behaviour exhibited by D.radicum and D.floralis infers that oviposition site selection is primarily based upon positive stimuli present on the leaf surface. Ranking of four genotypes of plants for antixenotic resistance to oviposition by D.radicum and D.jloralis was found to be the same for both fly species, tested in the laboratory (swede cv Doon Major, most susceptible; kale cv Fribor, most resistant) and varied x80 (D.floralis) and x5 (D.radicum). Field experiments showed that oviposition (which was dominated by D.radicum) varied x2 between plant genotypes (swede cv Doon Major, most susceptible; swede cv GRL aga, most resistant). Testing of Brassica leaf surface extracts, applied to surrogate plants, indicated that leaf surface chemicals strongly influence the site of oviposition of D.floralis. Methanol soluble polar compounds are the most stimulatory element for D.floralis and a fraction which contained aliphatic glucosinolates stimulated oviposition strongly although glucosinolates were not the primary oviposition stimulant. Collaborative experiments indicate that "CIF" (cabbage identification factor) is probably present in this fraction. The concentrations of Brassica root sugars are generally reduced by the damage of both D.radicum and D.floralis and appear to influence larval development. The percentages of plant fibre and lignin in the roots of Brassicas rise following the damage of D.floralis. The concentrations of individual glucosinolates in Brassica roots arc radically altered by the damage of D.floralis and D.radicum. D.floralis damage resulted in a rise in the concentration of aromatic glucosinolates and a fall in the concentration of aliphatic glucosinolates. D.radicum damage generally resulted in an elevated concentration of both aliphatic and aromatic glucosinolates. There was no clear evidence that glucosinolatc profiles were associated with different levels of antibiotic resistance to D.radicum and D.floralis. GRL aga (SCRI breeding line) was consistently resistant to the oviposition and larval feeding of D.radicum and D.floralis both in the laboratory and in the field. It was shown that the use of end-of-season chemical analysis to assess the influence of plant chemistry on insect development or host plant resistance in field experiments and the use of damage indexes based on the percentage of a plant root damaged by D.radicum may be flawed.

The purpose of the present study was to investigate how plant spatial patterns and insect behavior interact to influence the population dynamics of insects using the plants. The study included three phases: l) field experiments using collards (Brassica oleracea) and the crucifer insect fauna; 2) simulation models representing the population dynamics of an insect herbivore as functions of insect dispersal behavior and host plant patch size; and 3) model-field syntheses integrating model predictions and field variability estimates to choose an appropriate spatial scale for future field experiments or applications. In field experiments on surrounding plant type, collards were planted with 1) other collards; 2) collards treated with a systemic insecticide; 3) broccoli, a related host; and 4) tomatoes, an unrelated host whose odor may repel crucifer pests. In three such experiments, eggs and larvae of the imported cabbageworm (Pieris rapae (L.)) were most abundant an collards surrounded by tomatoes. These results were contrary to those from previous experiments with other crucifer pests, but can perhaps be explained by P. rapae's preference for ovipositing on isolated host plants. In three patch size experiments, P. rapae eggs and larvae were more abundant on collards in small patches; in one of these experiments, the diamondback moth (Plutella xylostella (Linn.)) was more abundant in large patches. The results for P. rapae were consistent with previous studies showing more oviposition on plants in smaller patches and on plants at the edge of a patch. The simulation models predicted mean level and variability of an insect herbivore population based on interactions between insect behavior and host plant patch size. Features of insect behavior modeled were: 1) an inverse relationship between distance and dispersal; 2) preferences for host vs. nonhost plants, which differ for generalist and for specialist herbivores; and 3) preference of specialists for larger areas of host plants. Aspects of plant pattern studied were size and number of host plant patches in a background of nonhost vegetation. Constant, exponential and logistic growth of insect populations in the nonhost background and in the host patches were used. The models were designed to provide a theoretical framework for studying interactions between insect behavior and plant pattern, not to duplicate the dynamics of the field system. However, for the model-field syntheses, parameters of one model were fit to field data to establish a correspondence between expected differences in population levels predicted by the model and variability estimates obtained in the field experiments. The fitted model was used to construct a graph of differences in population levels versus patch size. Field variability estimates were used to calculate the least difference in population levels, for a given number of replicates and subsamples, that could be detected in field experiments. The least difference was compared with the differences predicted b y the fitted model to determine what patch sizes will produce significant effects of patch size on insect populations. This method was used to assess feasibility of future field experiments and to select appropriate patch sizes. The method can also be used to evaluate crop field size in agroecosystems as a component of pest management.

Baccharis halimifolia is host to many species of insect herbivore, including myrmecophilous aphids. Previous studies with B. halimifolia have revealed strong effects of competition by an early-feeding beetle, Trirhabda bacharidis, and nitrogen enrichment. The effects of ant mutualists, however, have not been evaluated for their potential influence on interspecific interactions among insects on the host plant. I have employed a series of experiments aimed at answering the following general questions. (1) How does the density of aphid-tending ants affect common insects on the host plant? (2) What are the relative effects of (a) competition from T. bacharidis, (b) nutrient enrichment, and (c) ant presence on common insects of the host plant? (3) How do the effects of exotic ants differ from those of native ants? The density of aphid-tending ants had positive effects on myrmecophilous aphids and aphid predators. However, given a choice between tended and untended aphid populations, aphid predators preferred to forage in the absence of ants. The density of aphid-tending ants also increased predation on leaf miners although this did not necessarily translate into reduced densities of leaf miners. Competition by early-season feeding of T. bacharidis negatively affected later-feeding herbivores but the effects of competition were unaffected by nutrient enrichment. Nutrient enrichment had positive effects on some herbivores, often only in the absence of early season herbivory. Trirhabda bacharidis larvae showed evidence of nitrogen and phosphorus limitation and suffered no predation by aphid-tending ants. Ant presence increased host plant survivorship from stemborer damage in 2004. Ant species identity was an important factor determining the densities of myrmecophiles and non-myrmecophiles on the host plant in addition to affecting the responses of herbivores to increases in host plant quality. Aphids were more abundant in the presence of the exotic Linepithema humile (Hymenoptera: Dolichoderinae) versus the native Camponotus floridanus (Hymenoptera: Formicinae). Aphid predators also had higher densities in the presence of L. humile versus C. floridanus. Only L. humile acted as predator on leaf mines although predation did not always translate into reduced seasonal abundances for both species of leaf miner.

No description available.

Made available in DSpace on 2014-06-11T19:35:45Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-03-22Bitstream added on 2014-06-13T18:47:16Z : No. of bitstreams: 1 pereira_jm_dr_botfca.pdf: 1295918 bytes, checksum: f68afd1f3561ee4b65e51e0137d4d990 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Desde sua introdução no Brasil, em 2003, o psilídeo-de-concha Glycaspis brimblecombei Moore (Hemiptera: Psyllidae) vem ocasionando sérios danos ao eucalipto, principalmente através de desfolha, desenvolvimento de fumagina e secamento de ponteiros. Como estratégia no controle deste inseto, o uso de genótipos resistentes pode ser uma ferramenta valiosa. Neste trabalho, avaliou-se a resistência das espécies Eucalyptus camaldulensis (VM e IPEF), E. grandis e E. urophylla e dos híbridos de E. grandis x E. camaldulensis – gracam ‘HGC’ (3025 e 1277), de E. urophylla x E. camaldulensis – urocam ‘HUC’ (VM-1), de E. urophylla x E. grandis – urograndis ‘HUG’ (H-13, I-144, C-219 e GG-100) e de E. grandis (EG-01, EG-02 e EG-03) a G. brimblecombei, através de testes de atratividade, preferência para oviposição e preferência para alimentação e/ou antibiose sob condições de laboratório e campo. Foram realizados testes preliminares, a fim de verificar a ocorrência de condicionamento pré-imaginal, além de ajustar a melhor densidade para infestação com adultos para testes de atratividade e a melhor posição nas mudas para avaliações de preferência para oviposição. Em laboratório, verificou-se que os adultos de G. brimblecombei não apresentaram condicionamento pré-imaginal, independentemente do hospedeiro de criação ser o híbrido 3025 ou E. camaldulensis IPEF. As densidades de 10 e 15 adultos de psilídeo-de-concha por muda de eucalipto proporcionaram maior número de ovos. As folhas próximas ao ápice foram preferidas para oviposição, sendo que o número de ovos decresceu do ápice para a base. No teste com chance de escolha, os genótipos E. grandis, E. urophylla, C-219 e H-13 foram menos atrativos ao psilídeo-de-concha, expressando não-preferência. Em teste com chance de escolha, o número de ovos depositados nas folhas dos genótipos H-13, E. grandis... / Since its introduction in Brazil in 2003, the red gum lerp psyllid Glycaspis brimblecombei Moore (Hemiptera: Psyllidae) has been causing serious damages in eucalyptus trees, especially through defoliation, development of sooty mold and dieback. The use of resistant genotypes as a strategy to control this insect may be a valuable tool. In this study, the resistance of species Eucalyptus camaldulensis (VM e IPEF), E. grandis and E. urophylla and hybrids E. grandis x E. camaldulensis - gracam ‘HGC’ (3025 and 1277), E. urophylla x E. camaldulensis - urocam ‘HUC’ (VM-1), E. urophylla x E. grandis – urograndis ‘HUG’ (H-13, I-144, C-219 and GG-100) and E. grandis (EG-01, EG-02 and EG-03) on G. brimblecombei, through attractiveness, oviposition preference and feeding preference and/or antibiosis tests under laboratory and field conditions evaluated. Initially preliminary tests were carried out, using eucalyptus seedlings, in order to verify the occurrence of preimaginal conditioning, and also adjust the best density for adult infestation for attractiveness tests and the best position in the seedlings for the evaluation of oviposition preference. In laboratory conditions, that G. brimblecombei adults did not present preimaginal conditioning, despite the fact that the rearing host was a 3025 hybrid or E. camaldulensis IPEF. The densities of 10 and 15 psyllid adults per eucalyptus seedlings showed a higher number of eggs. The insects showed preference for the leaves close the apex for oviposition, being that the number of eggs decreased from the apex to the basis. In the choice test concerning attractiveness, genotypes E. grandis, E. urophylla, C-219 and H-13 were less attractive to psyllid, showing non-preference. In a choice test, the number of eggs oviposited in leaves of genotypes H-13, E. grandis and E. urophylla were lower when compared... (Complete abstract click electronic access below)

Made available in DSpace on 2014-06-11T19:25:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2002-06-25Bitstream added on 2014-06-13T18:23:48Z : No. of bitstreams: 1 maia_oma_me_jabo.pdf: 901159 bytes, checksum: e78a92958b754c82d637ebb566194d6e (MD5) / No Brasil, Brevipalpus phoenicis (Geijskes, 1939) é vetor da leprose na cultura dos citros, doença responsável por significativa redução na produtividade. Objetivou-se avaliar, a capacidade de colonização de B. phoenicis sobre cercas-vivas, quebra-ventos e plantas daninhas, e a potencialidade destas como hospedeiras do vírus da leprose. Realizou-se a colonização das plantas com ácaros procedentes de uma criação-estoque sobre frutos de citros Pêra-rio, para as seguintes plantas hospedeiras intermediárias: Hibiscus sp., Malvaviscus mollis, Grevillea robusta, Mimosa caesalpiniaefolia, Bixa orellana, Euphorbia splendens, Bidens pilosa, Commelina benghalensis, Sida cordifolia, Ageratum conyzoides e Citrus sinensis. Constatou-se que a exceção de E. splendens, todas comportaram-se como hospedeiras do ácaro. Ácaros contaminados, procedentes da criação-estoque, após serem transferidos e confinados em arenas delimitadas nas plantas hospedeiras intermediárias, por um período de 7 dias, não perderam a capacidade de transmitir o vírus para mudas cítricas de Valência e Natal. Ácaros não contaminados que tiveram acesso alimentar por 3 dias nessas mesmas arenas, somente se contaminaram e transmitiram o vírus para mudas de citros, aqueles que se alimentaram sobre: C. benghalensis, S. cordifolia, A. conyzoides, B. pilosa, B. orellana e C. sinensis. Resultados semelhantes foram conseguidos com ácaros criados, por um período de 90 dias, sobre as mesmas plantas hospedeiras intermediárias, inicialmente infestadas com ácaros contaminados também procedentes da criação-estoque. / In Brazil, Brevipalpus phoenicis (Geijskes, 1939) is a vector of the leprosis in the culture of citrus, a disease that causes significant reduction in the productivity. In this work it was evaluated the B. phoenicis capacity of settling on common fence-lives, windbreaks and weeds, and their potentiality as hosts to the leprosis virus. The colonization of the plants was carried out with mites coming from a stock creation on fruits of Pêra-rio citrus, for the following intermediate host plants: Hibiscus sp., Malvaviscus mollis, Grevillea robust, Mimosa caesalpiniaefolia, Bixa orellana, Euphorbia splendens, Bidens pilosa, Commelina benghalensis, Sida cordifolia, Ageratum conyzoides and Citrus sinensis. It was verified that, except for the E. splendens, all species showed to be favorable to the B. phoenicis population growth. Infected mites, coming from the stock creation, that were transferred and confined in delimited arenas in the intermediate host plants for a period of 7 days, did not lose their capacity to transmit the virus for citric seedlings of Valência and Natal. Non infected mites, that had access to feed for 3 days in the same arenas, became only infected and transmitted the virus for citrus seedlings that fed on: C. benghalensis, S. cordifolia, A. conyzoides, B. pilosa, B. orellana and C. sinensis. Similar results were obtained using mites created, for a period of 90 days, on the same intermediate host plants that were initially infested with infected mites coming from the same stock creation.

Made available in DSpace on 2014-06-11T19:25:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-07-27Bitstream added on 2014-06-13T20:53:00Z : No. of bitstreams: 1 jesus_fg_me_jabo.pdf: 365325 bytes, checksum: 4e8f173032ee930a6c8031cefe478e23 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Avaliou-se o comportamento de genótipos de feijoeiro dos tipos de grãos carioca e preto nas épocas de cultivo “das águas”, “da seca” e “de inverno” e grãos dos tipos especiais na época “da seca” sob a infestação de Bemisia tabaci (Genn.) biótipo B e Caliothrips phaseoli (Hood.) e a associação de genótipos e inseticidas no controle destas pragas em condições de campo. Utilizaram-se os genótipos IAC-Carioca Tybatã, IAC Una, FT-Nobre, Pérola, Gen 96A98-15-3-32-1, Gen 96A45-3-51-52-1, IAC Alvorada, IAC Diplomata, Gen 96A3-P1-1-1, LP 98-122, LP 02- 130, LP 01-38, LP 9979, BRS-Pontal, BRS-Requinte, BRS-Triunfo, BRS-Grafite, CV-48, Z-28 para os tipos carioca e preto e IAPAR 31, Rosinha G2, Jalo precoce, Pérola, IAC Harmonia, Gen 99TGR110, Gen 99TG2868, Gen 99TGR3416, Gen 99TG3450, Gen 99TG823, Gen 99TGR609, IAC Jaraguá, Gen 95A10061531, Gen 99TGR3114 e Gen 96A1473153V2 para os grãos dos tipos especiais. Com relação ao comportamento dos genótipos dos tipos carioca e preto, os menos ovipositados pela B. tabaci biótipo B foram IAC Una, LP 98-122, BRS-Pontal, Pérola, Gen 96A45 3-51-52-1 e BRS-Triunfo. As menores presenças de ninfas de mosca branca foram observadas em LP 01-38 e IAC Alvorada e maiores em Z - 28. C. phaseoli foi encontrado em menor número em BRS-Triunfo, LP 9979, LP 98-122 e BRS-Requinte e maior número nos genótipos LP 02-130, BRS-Grafite, IAC Alvorada e IAC Diplomata. Para os grãos dos tipos especiais, os genótipos menos ovipositados pela B. tabaci biótipo B foram IAC Harmonia, Pérola, Gen TG3114 e Gen 95A10061531, enquanto os mais ovipositados destacaram IAC Jaraguá e Gen 99TG3450; as menores infestações de ninfas de B. tabaci biótipo B foram observadas em Pérola e IAC Harmonia e maior em IAC Jaraguá; e, todos os genótipos foram suscetível ao C. phaseoli... / The comportment of bean genotypes carioca and black grain was evaluated on field conditions on the water, dry and winter season and bean genotypes special type grains on dry season and under the infestation of Bemisia tabaci (Genn.) biotype B and Caliothrips phaseoli (Hood) and of common beans genotypes associated or not the insecticides use this pest in field conditions. The genotypes used were: IACCarioca Tybatã, IAC-Una, FT-Nobre, Pérola, Gen 96A98-15-3-32-1, Gen 96A45-3-51- 52-1, IAC Alvorada, IAC Diplomata, Gen 96A3-P1-1-1, LP 98-122, LP 02-130, LP 01-38, LP 9979, BRS-Pontal, BRS-Requinte, BRS-Triunfo, BRS-Grafite, CV-48, Z-28 for the type carioca and black grains and IAPAR 31, Rosinha G2, Jalo precoce, Pérola, IAC Harmonia, Gen 99TGR110, Gen 99TG2868, Gen 99TGR3416, Gen 99TG3450, Gen 99TG823, Gen 99TGR609, IAC Jaragua, Gen 95A10061531, Gen 99TGR3114 e Gen 96A1473153V2 for the type special grain. With relation at comportment carioca and black grain, the less oviposition genotypes by B. tabaci biotype B were IAC Una, LP 98- 122, BRS-Pontal and Perola, while the most oviposited were Gen 96A45 3-51-52-1 and BRS-Triunfo. The less presence of nymphs of whitefly were observed on LP 01-38 and IAC Alvorada and the most at Z-28. C. phaesoli was found in less number on BRSTriunfo, LP 9979, LP 98-122 and BRS-Requinte and more on the LP 02-130, BRSGrafite, IAC Alvorada and IAC Diplomata genotypes. For the type special grain, the less oviposition genotypes by B. tabaci biotype B were IAC Harmonia, Pérola, Gen TG3114 e Gen 95A10061531, while the most oviposited were IAC Jaraguá and Gen 99TG3450; the less presence of nymphs of whitefly was observed on Pérola and IAC Harmonia and the most at IAC Jaraguá; every genotypes were susceptible to attack of C. phaseoli; when associated insectised with genotypes, less oviposition genotypes by B. tabaci biotype B were LP 9979 and IAC Jaragua,... (Complete abstract, click electronic access below)

Master of Science / Entomology / Ming-Shun Chen / Robert "Jeff" J. Whitworth / MicroRNA (miRNA) plays a role in nearly all the biological pathways and therefore may provide opportunities to develop new means to combat the Hessian fly, Mayetiola destructor, a destructive pest of wheat. This study presents a comprehensive analysis of miRNA species via deep-sequencing samples from Hessian fly second instar larvae, pupae and adults. A total of 921 unique miRNA species were identified from approximately 30 million sequence reads. Among the 921 miRNA species, only 22 were conserved among Hessian fly and other insect species, and 242 miRNA species were unique to Hessian fly, the remaining 657 share certain sequence similarities with pre-miRNA genes identified from various insect species. The abundance of the 921 miRNA species based on sequence reads varies greatly among the three analyzed stages, with 20 exclusively expressed in adults, two exclusively expressed in pupae and two exclusively expressed in second instar larvae. For miRNA species expressed in all stages, 722 were with reads lower than 10. The abundance of the remaining 199 miRNA species varied from zero to more than eight-fold differences among different stages. Putative miRNA-encoding genes were analyzed for each miRNA species. A single putative gene was identified for 594 miRNA species. Two putative genes were identified for 138 miRNA species. Three or more putative genes were identified for 86 miRNA species. The three largest families had 14, 23 and 34 putative coding genes, respectively. No gene was identified for the remaining 103 miRNA species. In addition, 1516 putative target genes were identified for 490 miRNA species based on known criteria for miRNA targets. The putative target genes are involved in a wide range of processes from nutrient metabolism to encoding effector proteins. Analysis of the expression patterns of miRNA and pre-miRNA for the miRNA family PC-5p-67443, which contains 91 genes, revealed that miRNA and pre-miRNA were expressed differently in different developmental stages, suggesting that different isogenes are regulated by different mechanisms, or pre-miRNAs had other functions in addition to as an intermediate for miRNA biogenesis. The large set of miRNA species identified here provides a foundation for future research on miRNA functions in Hessian fly and for comparative studies in other species. The differential expression patterns between a pre-miRNA and its encoded mature miRNA in a multigene family is an initial step toward understanding the functional significance of isogenes in dramatically expanded miRNA families.