All plants are exposed to abiotic and biotic stresses and have developed intricate signalling responses to survive. They respond to cell-structure disruption caused by herbivore probing and feeding by the formation of callose. Callose is a linear homopolymer made up of β-1,3-linked glucose residues with some β-1,6-branches. Plant responses to abiotic or biotic stress share events such as phosphorylation, membrane depolarization, calcium influx and the release of reactive oxygen species such as hydrogen peroxide. These events lead to the up-regulation of several pathways leading to biosynthesis of signalling molecules such as salicylic acid, jasmonate, abscisic acid and ethylene pathways. The aim of this study was to determine the most suitable proteomic approach for identifying proteins and signalling pathways involved in cereal response to aphid infestation. An in silico approach was first evaluated in which the 5ʹ upstream regulatory region of proteins belonging to the family of callose synthases was scanned for cis-regulatory elements in order to identify which callose synthases are possibly expressed in plants during biotic or abiotic stresses. Bioinformatics tools were used in the identification of twelve Arabidopsis and ten rice callose synthase coding regions. Genome sequences for rice and Arabidopsis were scanned for the 2000 bp 5ʹ region upstream of the start codon of each callose synthase coding region. PlantCare, PLACE and Athena software were used to identify putative cis-regulatory elements present in the 2000 bp 5ʹ upstream sequences. The majority of cis-acting elements identified were involved in drought and high temperature responses and only one cis-acting element was involved in wound stress. These results therefore indicated a probable role for plant callose synthases in drought stress responses rather than in biotic stress responses. Genevestigator analysis of Arabidopsis results of micro-array experiments indicated that AtGSL10 is highly up-regulated, with AtGSL1, 3, 5, 6, 7, 8, 11 and 12 showing medium up-regulation and AtGSL2, 4 and 9 no up-regulation during aphid infestation of Arabidopsis plants, implicating a possible role for AtGSL10 in the plant response to aphid infestation. An LC/MS/MS approach was used to identify specific signalling pathways involved in wheat resistance or stress response to aphid infestation. Eight proteins were identified as being up-regulated during aphid feeding in wheat, and 11 proteins were identified as possibly involved in the wheat resistance mechanism against aphid infestation. Several proteins were also identified as constitutively expressed proteins, during normal conditions and aphid infestation. Most pathways identified with proteins up-regulated in the resistance mechanisms of TugelaDN plants, were related to energy metabolism and located in the chloroplast. Evaluation of two dimensional gel electrophoresis to identify phosphoproteins differentially regulated in wheat during aphid infestation, revealed the up-regulation of three proteins namely photosystem II oxygen-evolving complex protein 2, HVUNKNOWN from Hordeum vulgare subsp vulgare and HSKERAT9 NID from Homo sapiens. Additional 57 proteins were partially identified as involved in the stress response but due to low protein levels, the percentage of matching peptides to these proteins was below the required confidence level. Although these protein identifications were below the confidence level, it is interesting to note that several of the proteins are known stress response proteins, and therefore could serve as potential targets for future investigations. In conclusion, the down and up-regulation of wheat proteins after aphid feeding reported in this study suggest that several signalling pathways are involved in the cereal stress response to aphid feeding. In silico approaches require knowledge or identification of potential proteins whereas 2D and LC/MS can identify numerous proteins still unknown to be involved in specific stress responses. The 2D approach is also limited in that the proteins of interest may be in low abundance and therefore not detected in the gels due to the presence of high abundant proteins. Therefore the best approach to identify proteins and signalling pathways involved in the stress response of wheat to aphid infestation, is the LC/MS/MS approach, as this proved to be the most sensitive and robust, identifying the most proteins with a high degree of confidence.

The rice stink bug, Oebalus pugnax (F.), is an important late season pest of rice that is noted for causing grain yield and quality reductions in the United States. This study investigated rice injury using field cages in two rice cultivars (‘Cocodrie’ and ‘Wells’) at bloom, milk, and soft dough stages and O. pugnax ecology in the Delta Region of Mississippi. Specific objectives were: 1) to determine the impact of adult O. pugnax infestation on rice yield and grain quality at bloom, milk, and soft dough stages of rice development; 2) to determine the impact of adult O. pugnax gender and infestation duration on rice yield and grain quality at the milk stage of panicle development; 3) to identify and examine the seasonal abundance and phenology of O. pugnax on non-cultivated host grasses; and 4) to evaluate feeding preference and development of O. pugnax on host grasses. Rice injury increased as O. pugnax density increased. The bloom and milk stages were the most vulnerable to blank and discolored kernels, respectively. O. pugnax feeding injury was significant after 3 d of infestation duration during the milk stage of panicle development. Female O. pugnax caused a greater percentage of blank kernels compared to males. A survey of O. pugnax hosts indicated that Italian ryegrass, Lolium perenne L. ssp. multiflorum and winter wheat, Triticum aestivum L., were important hosts during spring and early summer. Junglerice, Echinochloa colona (L.) Link; crabgrass spp., Digitaria spp. Haller; southwestern cupgrass, Eriochloa acuminata (J. Presl) Kunth; and praire cupgrass, Eriochloa contracta (Hitchc.), were important hosts for O. pugnax during early to mid-summer. Browntop millet, Urochloa ramosa, and broadleaf signalgrass, Urochloa platyphylla, supported adult O. pugnax prior to overwintering. In a choice test of wild host grasses, junglerice was the most preferred over 10 other host grasses. In the no-choice test, mean development time was shorter and survival was greater for O. pugnax nymphs reared on rice, Oryza sativa L., compared to dallisgrass, Paspalum dilatatum Poir and junglerice. These results provide biological and ecological information on which new O. pugnax integrated pest management practices can be developed.

Experiments were conducted to determine the impact of water management strategies on populations of rice water weevil, Lissorhoptrus oryzophilus Kuschel. One experiment was conducted at the Delta Research and Extension Center during 2017 and 2018. The performance of chlorantraniliprole and thiamethoxam was evaluated in combination with flood removal of a field as a cultural control tactic for rice water weevil. Seed treatments significantly reduced rice water weevil populations at the prelood sample timing, only chlorantraniliprole reduced populations at the post-drainage sample timing. Overall, flood removal had little impact on rice water weevil management. An experiment was also conducted to determine the spatial and temporal distribution of rice water weevil larvae within a furrow irrigated rice production system. This experiment was established across eleven grower fields in major rice producing counties across the Mississippi Delta from 2017 to 2018. Fields were divided into three zones based on free standing water within that portion of the field between irrigation events. Rice water weevil larval populations were reduced in portions of the field that did not remain at two of the three sample timings. An experiment was conducted at the Delta Research and Extension Center during 2017 to determine the impact of various water management strategies and insecticide seed treatments on rice water weevil populations. The –10 cm free standing water management strategy significantly reduced rice water weevil populations from the untreated control. Chlorantraniliprole had significantly higher yields across all water management strategies compared to other seed treatments and the untreated control.

Urea is the predominant ammonium-forming nitrogen (N) source applied in delayed-flood rice because of its high N content (46%) and relatively low cost. Nitrogen applied prior to flooding can be lost by multiple mechanisms such as ammonia volatilization or nitrification/denitrification. In recent years, technological advancements have provided alternative enhanced efficiency fertilizer additives with potential to be incorporated in rice production to reduce N losses. Research was conducted at the Mississippi State University Delta Research and Extension Center from 2018 to 2020 to determine the effects of broadcast applications of nitrapyrin at two specific growth stages to enhance fertilizer-N recovery efficiency, determine optimal application methods of nitrapyrin with urea, determine the effects of nitrapyrin mixed with different herbicides for weed control, and to evaluate nitrapyrin efficacy alone and in conjunction with N-(n-butyl) thiophosphoric triamide (NBPT) to reduce ammonia volatilization. In the current research, there was no effect on grain yield responses from the addition of nitrapyrin regardless of soil textures or application timing. Broadcast applications of nitrapyrin did not improve fertilizer-N recovery efficiency regardless of soil texture or application timing. Differences in rice grain yield were not observed with respect to nitrapyrin application method or NBPT combination for clay and silt loam textures. Barnyardgrass control was unaffected with nitrapyrin applied with different herbicides. Lastly, nitrapyrin was ineffective at reducing ammonia volatilization and resulted in a similar trend to urea alone. Efficacy from nitrapyrin plus NBPT was not different from NBPT alone at reducing N losses. Nitrapyrin efficacy can be influenced by soil texture, application timing, or application method. Implementing nitrapyrin as an enhanced efficiency fertilizer additive to mitigate N losses is inconsistent, and rice grain yields will vary based on environmental and soil conditions.

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Thesis (Ph.D.) -- University of Western Sydney, Hawkesbury, 2001. / A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy, Faculty of Science, Technology and Environment, University of Western Sydney, Hawkesbury Campus, 2001. Bibliography : leaves 205-244.

Thesis (B. Sci. (Hons.))--University of Adelaide, Faculty Agricultural Science,1955. / Typewritten copy. Includes bibliographical references.

Thesis (Ph. D.)--Miami University, Dept. of Botany, 2008. / Title from second page of PDF document. Includes bibliographical references (p. 115-131).

Thesis (doctoral)--Landbouwhogeschool te Wageningen, 1983. / Summary in Dutch and Spanish. Vita. Includes bibliographical references (p. 227-237).