Browsing by Author "Burke, John J."
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Item A hydroponic approach to evaluate salt tolerance in cotton(2011-08) Castillo, Natalia; Auld, Dick L.; Dever, Jane G. K.; Abidi, Noureddine; Burke, John J.; Zhang, HongInterests in developing salt tolerant cultivars have intensified as the result of an increasing population and environmental constraints that limit crop productivity. New agronomic models have been designed to address the new challenges. Some include the development of a salt tolerant crop by evaluation and selection of tolerant germplasm, hybridization with selected germplasm, and development of inbred lines through pedigree selection or backcross, and testing of selected inbred lines. Many wild accessions in cotton have been found in many areas in the world and made accessible for research. Plant breeders are trying to produce new cotton varieties that can withstand the excessive salt concentrations found in the soil and in the water since salinity has become a limiting factor in crop agriculture. For farmers the abiotic stress due to salinity limits yield by inhibiting germination, flowering, and the development of vegetative branches and fruiting branches. Other concerns of plant breeders are abscission of cotton bolls, a reduction in cellulose deposition, and that both photosynthesis and stoma conductance are affected during the breakdown and conversion into carbohydrates. Preliminary studies conducted in 2006, 2007, 2008, and 2009 show one wild accession, TX 307 to be significantly more tolerant than others when plants were treated with NaCl. Since 2010, the focus of this research has been to use the hydroponic system as a screening method to evaluate and compare responses among cotton genotypes for salt tolerance characteristics to salinity stress. The wild cotton accession TX 307 was used as a control line to compare to three commercial cultivars ‘FM 989’ (PI603956, PVP9800259), ‘DP 491’ (PI618609, PVP 200100159, US2003/0229928AI), and ‘Coker 312’ (PI529278, PVP7200100); and two transgenic lines Avp68 and Avp86. Coker 312 was the cultivar used for the transformation and regeneration of Avp68 and Avp86 transgenic lines. Responses were evaluated at different salt concentrations (dose response) and at the same concentrations over time. The study was conducted under greenhouse conditions at the AgriLife Research and Extension Center in Lubbock, Texas. Experimental design was a randomized split block with four replications, four treatments, and ten plants/treatment sampling error. Significant differences (p < 0.05) were found during the dose response screening study, however, no significant response genotype interactions over time was observed. The hydroponic system was perhaps not the best method for evaluating response differences at later plant development stages because of possible premature plant death, but it was an effective screening method to isolate individual plants with respect to morphological and physiological responses to salinity stress. The system could also be used as an assessment tool to identify contrasting phenotypes at high salt concentrations early in plant development.Item Genetic interactions between RNA interference and abscisic acid response(2012-08) Jia, Fan; Rock, Christopher D.; Zhang, Hong; Shi, Huazhong; Burke, John J.; Xie, ZhixinRNA-interference is a conserved process in eukaryotes in which 21-24nt small RNAs (sRNAs) direct cleavage or translational inhibition of target mRNAs by Watson-Crick complementarity. MicroRNAs are a subclass of sRNAs processed from hairpin-forming, non-coding RNA-PolymeraseII transcripts which play crucial roles in development and stress responses. Abscisic acid (ABA) is a hormone associated with flowering, nutrient signaling, and post-transcriptional processes including miRNAs, but unlike auxin its molecular interactions with siRNAs are unknown. We show that At-MIR842 and At-MIR846 are transcribed as a cistron repressed by ABA and subject to alternative splicing. One target of miR846, At5g28520 encoding a jacalin-lectin, is highly up-regulated by ABA in roots. Cleavage of its transcript is directed by miR846, the major species produced by alternative At-MIR842-846 transcript splicing, but only in the absence of exogenous ABA. Mutants of ABA HYPERSENSITIVE1/CAP-BINDING-PROTEIN80 affect splicing, ABA signaling and the biogenesis of miRNAs. We show that double mutants of ABA hypersensitive1 and suppressor of gene silencing3, which encodes a zinc-finger protein required for RNAi, manifest novel phenotypes including early flowering, fused cotyledons, altered inflorescence phyllotaxy, bent siliques, poor pollen adherence to the stigma, reduced seed set, and resistance to fungal infection. A custom microarray was designed to probe the molecular bases of these phenotypes. Results confirmed documented effects of abh1on MIRNA expression and identified miRNA precursors and targets (e.g. pre-MIR168a, pre-MIR395c, pre-MIR824, pre-MIR2936,LACCASE12) induced by ABA and/or elevated in abh1 sgs3 double mutant (pre-MIR156ac, pre-MIR164b, pre-MIR166a,At5g15845/CONSTANS-LIKE1-cis-NAT-RNA). miR156 targets SQUAMOSA-PROMOTER-BINDING-PROTEIN-LIKE genes that spawn siRNAs and control flowering time; miR164 targets CUP-SHAPED-COTYLEDON1 and -2 genes; miR166 methylates target PHABULOSA gDNA in trans; miR168 targets ARGONAUTE1; miR2936 is pollen-specific. We also found abh1 or sgs3 by ABA interactions (e.g.At4g35770/SENESCENCE-ASSOCIATED1, At1g11260/SUGAR-TRANSPORTER1). We have uncovered new nodes in regulatory networks linking ABA and nutrient signaling, flowering, mRNA processing and RNAi.Item High throughput phenotyping of cotton in multiple irrigation environments(2014-05) Sharma, Bablu; Ritchie, Glen L.; Hequet, Eric F.; Maas, Stephan J.; Burke, John J.; Mulligan, Kevin R.; McMichael, Bobbie L.Rapid screening of plant growth can improve selection of cotton (Gossypium hirsutum L.) in breeding and productivity analysis. We tested several automated phenotyping methods, including measurements of plant height, ground cover fraction (GCF), Normalized Difference Vegetation Index (NDVI), and canopy temperature using a ground-based platform mounted on a research sprayer. In addition, we tested the effects of ten irrigation levels on crop growth, in-season stress indicators, final boll distribution, and fiber quality. The system was evaluated on sixteen cotton cultivars grown during the 2011, 2012, and 2013 seasons in Lubbock, Texas. All measurement parameters showed differences among irrigation levels during the study years. Rainfall and weather conditions during the 2013 season resulted in taller plants and higher yields, but fewer differences among irrigation treatments. Lint yield was positively correlated with each in-season growth parameter during the 2012 and 2013 seasons. The results support the following statements: ground based near remote sensing system can be used to phenotype multiple traits rapidly and precisely over multiple irrigation levels to screen cultivar and irrigation to maximize yield; ground cover estimation can be performed using a visible vegetation index; canopy architecture can be differentiated using canopy sensors; boll distribution can be tied to irrigation level over a variety of environmental conditions; and fiber quality has both a genetic and environmental component.Item Overexpression and interactions of Arabidopsis thaliana RAV1 (Related to Abscisic Acid Insensitive 3/ Viviparous 1), RAV2, RAV2-Like and ABI5 in transgenic cotton (Gossypium hirsutum): Effects on drought avoidance and fiber quality(2012-12) Mittal, Amandeep; Rock, Christopher D.; Burke, John J.; Zhang, Hong; Shi, Huazhong; Xie, ZhixinPlants have evolved complex overlapping response pathways for stresses such as drought, salt, cold, as well as hormonal cues such as abscisic acid (ABA). In this study, reverse genetics (knockout mutants) and overexpression of RAV (B3 domain) transcription factors suggested they could function as positive effectors of ABA response in seeds, roots, and leaves and delay flowering time. RAVs are highly induced at the transcript level by drought treatment, and AtRAV overexpression studies in cotton resulted in drought resistance due to biomass accumulation in lateral roots, more leaf area, delayed flowering, and higher water use efficiency under deficit irrigation in the field. Transgenic cotton plants had longer internodes and more stem weight. Unexpectedly, overexpression of RAVs leads to significant increases in fiber length. Repression of Gh Flowering Locus T by RAVs resulted in node positions 10-12 contributing to greater mass of cotton fibers than in wild type Coker 312 plants. Longer, more mature and finer fiber of RAVs transgenics resulted in better yarn production that has more tensile strength and has significantly fewer imperfections per unit length. ABI5 a basic leucine zipper TF (bZIP) functions in seeds and seedlings as a core component of ABA signaling. ABI5 transgenic cotton had more lateral root biomass that improved the water uptake and in conjunction with decreased stomatal conductance resulted in improved water use efficiency. ABI5 overexpression lines had significantly higher gin turn out in two independent lines under deficit and well-watered conditions on all the node positions studied. Stacking the B3 RAV and bZIP ABI5 TFS by crossing single transgenic lines of RAV1 or RAV2 plus ABI5 had additive or synergistic effects on late flowering, longer internode length, more fruit weight, and more root biomass. I interpret these results in the context of a “less stressed phenotype”. To test this hypothesis at the molecular level, I assayed drought- and reactive oxygen species (ROS)-inducible marker gene expression which provided evidence in support of the less stressed phenotypes.Item Selection for seedling cold vigor in grain sorghum(2017-05) Sanchez, Jacobo; Ritchie, Glen L.; Burke, John J.; Emendack, Yves Y.Sorghum is the fifth most widely grown cereal grown in the world, but one limitation to sorghum production is the restriction of cool temperatures on crop growth and development. The primary objective of the current study was to validate five previously identified markers of cold tolerance in sorghum by deriving a recombinant inbred line population from a cross between BTx623, a warm season elite sorghum line, and Hong Ke Zi, a Chinese sorghum landrace with increased cold tolerance. We conducted controlled environment screening testing of 307 recombinant inbred lines (RILs), followed by field-based phenotypic testing early-planted sorghum for 31 selected lines. Genotyping of the 31 F4 RILS using the KASP genotyping technology indicated that only two of the five markers tested showed segregation for the HKZ, BTx623, and the heterozygous genotype. Using the genotype data obtained, the genotype of each of the 31 RILS was compared to the various growth parameters measured by performing a one-way ANOVA analysis. Significant separation of the three genotypic groups (homozygous for HKZ allele, homozygous for BTx623 allele, and heterozygous for both alleles) was seen with the root biomass per plot (RBM/plot) phenotype only. That is, RILS that contained the homozygous HKZ (cold-tolerant) allele had significantly more root biomass than did RILS that were homozygous for the BTx623 allele or heterozygous for both alleles (Table 3.2). This result indicates that the two markers tested could be potential candidates in selecting for the seedling cold vigor trait using marker assisted selection (MAS). Though this result is promising, the markers need to be tested against a larger pool of diverse individuals to observe if the markers are truly viable as a selection tool.Item Toward development of peanut varieties with drought and heat tolerance(2005-08) Wallace, Jennifer Rae; Burow, Mark D.; Allen, Randy D.; Burke, John J.; Bronson, Kevin F.Depletion of groundwater requires greater efficiency in future water use for all crops. Efforts are currently being made in peanut productions to develop peanut cultivars that are drought and heat tolerant. The dry climate in west Texas creates the need for irrigation of crops due to the low annual rainfall (less than 18 inches). Peanuts cannot be grown under dryland conditions, but creating a variety that can be grown under reduced irrigation (drought conditions), withstand the heat, and still provide an adequate yield will help in using water efficiently. Improved resistance to abiotic and biotic stress is crucial for the long-term viability of peanut production and is necessary for efficient use of water. To determine components of tolerance to abiotic stress, twenty runner and four Spanish/Valencia accessions were planted in a replicated experiment in 2002 and increased to twenty-four runners and twelve Spanish accessions in 2003. Accessions were evaluated under drought (50% ET replacement) and irrigation (75% ET replacement). Significant differences were seen in flowering, harvest index, paraheliotropism, chlorophyll content, and root mass among genotypes. Heat stress was studied alongside drought, because they are closely related. Greenhouses were used to create high temperature stress to be tested for fluorescence determination for heat tolerance or susceptibility. A long-term program has been initiated to integrate modern physiological and molecular methods with plant breeding, to develop peanut varieties that can efficiently be grown under reduced water inputs and high heat stress. Suitable parents have been selected for and crosses are underway to develop F2 seeds that can be tested for drought and heat tolerance.