Naveen Puppala

Physiology and proteomics of the water-deficit stress response in three contrasting peanut genotypes.

Peanut genotypes from the US mini-core collection were analysed for changes in leaf proteins during reproductive stage growth under water-deficit stress. One- and two-dimensional gel electrophoresis (1- and 2-DGE) was performed on soluble protein extracts of selected tolerant and susceptible genotypes. A total of 102 protein bands/spots were analysed by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS) and by quadrupole time-of-flight tandem mass spectrometry (Q-TOF MS/MS) analysis. Forty-nine non-redundant proteins were identified, implicating a variety of stress response mechanisms in peanut. Lipoxygenase and 1l-myo-inositol-1-phosphate synthase, which aid in inter- and intracellular stress signalling, were more abundant in tolerant genotypes under water-deficit stress. Acetyl-CoA carboxylase, a key enzyme of lipid biosynthesis, increased in relative abundance along with a corresponding increase in epicuticular wax content in the tolerant genotype, suggesting an additional mechanism for water conservation and stress tolerance. Additionally, there was a marked decrease in the abundance of several photosynthetic proteins in the tolerant genotype, along with a concomitant decrease in net photosynthesis in response to water-deficit stress. Differential regulation of leaf proteins involved in a variety of cellular functions (e.g. cell wall strengthening, signal transduction, energy metabolism, cellular detoxification and gene regulation) indicates that these molecules could affect the molecular mechanism of water-deficit stress tolerance in peanut.

Gene expression profiling in peanut using high density oligonucleotide microarrays

BackgroundTranscriptome expression analysis in peanut to date has been limited to a relatively small set of genes and only recently has a significant number of ESTs been released into the public domain. Utilization of these ESTs for oligonucleotide microarrays provides a means to investigate large-scale transcript responses to a variety of developmental and environmental signals, ultimately improving our understanding of plant biology.ResultsWe have developed a high-density oligonucleotide microarray for peanut using 49,205 publicly available ESTs and tested the utility of this array for expression profiling in a variety of peanut tissues. To identify putatively tissue-specific genes and demonstrate the utility of this array for expression profiling in a variety of peanut tissues, we compared transcript levels in pod, peg, leaf, stem, and root tissues. Results from this experiment showed 108 putatively pod-specific/abundant genes, as well as transcripts whose expression was low or undetected in pod compared to peg, leaf, stem, or root. The transcripts significantly over-represented in pod include genes responsible for seed storage proteins and desiccation (e.g., late-embryogenesis abundant proteins, aquaporins, legumin B), oil production, and cellular defense. Additionally, almost half of the pod-abundant genes represent unknown genes allowing for the possibility of associating putative function to these previously uncharacterized genes.ConclusionThe peanut oligonucleotide array represents the majority of publicly available peanut ESTs and can be used as a tool for expression profiling studies in diverse tissues.

Genotypic variability and genotype by environment interactions in oil and fatty acids in high, intermediate, and low oleic acid peanut genotypes.

Variability of genotype and genotype x environment (G x E) interactions for fatty acids are important to develop high-oleic types in peanut varietal improvement programs. The objective of this study was to determine the variation in fatty acid composition among peanut genotypes and G x E interactions of fatty acids in three groups of genotypes with high, intermediate, and low-oleic acid. Twenty-one genotypes were tested in three environments consisting of two rainy seasons and one dry season. The results indicated that G x E interactions were significant for biomass, pod yield, and harvest index and also for oleic, linoleic acids, and O/L ratio. G x E interactions were less important than genotypic main effect. For oleic acid, significant interactions were found in the intermediate and low-oleic groups only. Therefore, selection for high-oleic trait in peanut breeding programs should be effective.

Lesquerella seed pretreatment to improve germination

Abstract Lesquerella fendleri is a potential oilseed crop. Seed dormancy, including light requirement, is common in many small-seeded species native to arid and semiarid environments, and may be a major contributor to stand establishment difficulties in Lesquerella. Gibberellic acid (GA3) and potassium nitrate (KNO3) in solutions of water have been shown to be effective moistening agents for improving germination and reducing light requirement of some Lesquerella species. The objectives of this study were to evaluate seed treatments for reducing or eliminating the light requirement of L. fendleri seed and developing methods for effectively applying these treatments. Three different experiments were conducted in a laboratory incubator with controlled photoperiod and temperature. The treatments evaluated included soaking seed for either 4 or 8 h in water, ethanol, methanol, or acetone with and without 100 mg GA3 l−1 or 1–2 g KNO3 l−1, and quick dipping seed in solutions of acetone or methanol with and without 0.1% Tween 20 and GA3. Presoaking the seed in an aqueous solution of 100 mg GA3 l−1 H2O followed by complete drying improved germination in light and appeared to satisfy light requirement when treated seeds were germinated in the dark. Soaking seeds in water alone appeared to satisfy the light requirement under dark conditions suggesting that presoaking in water alone was sufficient to leach out or deactivate the light requiring dormancy factor. Soaking the seeds for 4 h was just as effective as 8 h. Only methanol as a carrier solvent for GA3 in a quick-dip treatment at a concentration of 1000 mg GA3 l−1 showed promise for improving seed germination of L. fendleri in the dark. Additional studies are needed to evaluate the promising seed treatments under field conditions and to test other adjuvants and coatings for applying GA3 to Lesquerella seed for improving seed germination.

Identification of Peanut Hybrids Using Microsatellite Markers and Horizontal Polyacrylamide Gel Electrophoresis

In peanut hybridization, distinguishing inadvertent selfs from the true hybrids may be difficult. In this study, to differentiate between selfs and hybrids, DNA was extracted from leaf tissue of F1 or F2 plants, and SSR markers were amplified and bands separated by a novel submarine horizontal polyacrylamide gel electrophoresis (H-PAGE). By comparing the resulting banding patterns to those of the parents, 70% of the putative hybrids were shown to be true hybrids on the basis of possessing a marker allele from the male parent. The H-PAGE gels gave better band separation and differentiation of selfed progenies than agarose gels, and were compatible with the common horizontal agarose gel units. This method provides a quick assay to distinguish hybrids from inadvertent selfs, and should result in greater efficiency and more effective use of resources in peanut breeding programs.

Performance of direct-seeded and transplanted guayule

Abstract The commercialization of guayule (Parthenium argentatum, Gray) depends on economical plant production. Direct seeding has been successful and can reduce establishment costs when compared with seedling transplanting. Most economic and yield analyses have been based on transplants. The performance of direct-seeded and transplanted shrubs grown under the same field conditions has never been compared. The objective of this study was to evaluate various production parameters (biomass, rubber and resin content, rubber and resin yield) of five guayule lines established by direct seeding and transplanting. An experiment was initiated on a Delnorte very gravelly loam on 17 and 18 May 1994 at the Texas Agricultural Experiment Station near Fort Stockton, TX. Guayule selections AZ-R2, AZ-R3, 11 605, CAL-6, and UC-101 were direct-seeded and transplanted on raised beds spaced 1 m apart. Six plants from each line/replication were harvested on 6 March 1996 and 11 March 1997. Each plant was divided into branch (clipped 10 cm above the soil surface) and root (10 cm of lower branches plus approximately 15 cm of roots) sections. Guayule branch biomass was greater than root biomass at both harvests. Direct-seeded branch, root and total biomass was significantly lower than transplanted biomass in 1996. After 34 months at the 1997 harvest, no significant differences were observed between direct-seeded and transplanted shrubs. Resin and rubber content (%), and resin and rubber yield (kg/ha) were significantly greater in transplants versus direct-seeded shrubs in 1996, but not in 1997. Thus, direct seeding would be a viable system for commercially establishing guayule stands. Line AZ-R3 exhibited the least potential of the five lines to overcome the initial growth advantage of the transplants. Lines AZ-R2, 11 605, and CAL-6 are recommended for cultivation in west Texas and southern New Mexico.

The Peanut Genome

This book presents the current state of the art in peanut genomics, focusing particularly on the latest genomic findings, tools and strategies employed in genome sequencing, transcriptomes and analysis, availability of public and private genomic resources, and ways to maximize the use of this information in peanut breeding programs. Further, it demonstrates how advances in plant genomics can be used to improve crop breeding. The peanut or groundnut (Arachis hypogaea L. Millsp) is a globally important grain legume and oilseed crop, cultivated in over 100 countries and consumed in the form of roasted seeds, oil and confectionary in nearly every country on Earth. The peanut contributes towards achieving food and nutritional security, in addition to financial security through income generation; as such, it is also vital to the livelihood of the poor in the developing world. There have been significant advances in peanut research, especially in the last five years, including sequencing the genome of both diploid progenitors, and the availability of tremendous transcriptome resources, large-scale genomic variations that can be used as genetic markers, genetic populations (bi- and multiparent populations and germplasm sets), marker-trait associations and molecular breeding products. The immediate availability of the genome sequence for tetraploid cultivated peanuts is the most essential genomic resource for achieving a deeper understanding of peanut traits and their use in breeding programs.

Parallel-plate capacitance sensor for nondestructive measurement of moisture content of different types of wheat

A simple, low cost instrument that measures impedance and phase angle was used along with a parallel-plate capacitance system to estimate the moisture content (MC) of six types of wheat. Moisture content of grain is important and is measured at various stages of their processing and storage. A sample of about 150 g of wheat was placed separately between a set of parallel plate electrodes and the impedance and phase angle of the system were measured at frequencies 1 and 5 MHz. A semi-empirical equation was developed using the measured impedance and phase angle values, and the computed capacitance, and the MC values obtained by standard air-oven method. Multi Linear Regression (MLR) method was used for the empirical equation development using statistical software. In the present work, a low-cost impedance analyzer designed and assembled in our laboratory was used to measure the impedance and phase angles. MC values of wheat samples in the moisture range of 9% to 25%, not used in the calibration, were predicted by the equations and compared with their standard air-oven values. For over 97% of the samples tested from the six varieties of wheat, the predicted MC values were within 1% of the air-oven values. This method, being nondestructive and rapid, will have considerable application in the drying and storage processes of wheat and similar field crops.

Types of gene effects governing the inheritance of oleic and linoleic acids in peanut ( Arachis hypogaea L.)

Oleic and linoleic acids are major fatty acids in peanut determining the quality and shelf-life of peanut products. A better understanding on the inheritance of these characters is an important for high-oleic breeding programs. The objective of this research was to determine the gene actions for oleic acid, linoleic acid, the ratio of oleic to linoleic acids (O/L ratio) and percentage oil (% oil) in peanut. Georgia-02C, SunOleic 97R (high-oleic genotypes) and KKU 1 (low-oleic genotypes) were used as parents to generate P 1 , P 2 , F 2 , F 3 , BC 11 S and BC 12 S. The entries were planted in a randomized complete block design with four replications in the rainy season (2008) and the dry season (2008/2009). Gas liquid chromatography (GLC) was used to analyze fatty acid compositions. The data were used in generation means analysis to understand gene effects. The differences in season, generation and generation X season interactions were significant for oleic acid in the crosses Georgia-02C X KKU 1 and SunOleic 97R X KKU 1. Additive, dominance and epistasis gene effects were significant for oleic acid, linoleic acid, O/L ratio and % oil. Initial selection can be carried out in early segregating population, and final selection in late generations. Keywords: Breeding, gene actions, generation mean analysis, groundnut, oil quality

Reduced trigonelline accumulation due to rhizobial activity improves grain yield in peanut (Arachis hypogaea L.)

Abstract Crop improvement for drought tolerance is critical for the future of crop production. The objectives were to examine the relationship between trigonelline (TRG) accumulation and yield traits in 10 peanut (Arachis hypogaea L.) genotypes inoculated with two commonly used nitrogen-fixing Rhizobium spp., and to evaluate a role of TRG on growth traits. TRG increased as a defensive metabolite in response to water deficit, but resulted in the reduction of the number of nodules and yield. Symbiotic rhizobial activity helped plants to improve yield particularly in a fully irrigated field rather than under reduced irrigation. TRG concentrations in genotypes (7 out of 10) increased under reduced irrigation as compared with those under full irrigation in two years. Mean number of nodules at maturity (120 days after planting) across genotypes under reduced irrigation were 89 in the control, 111 in Lift, and 161 in Histick treatments, among which Histick was significant (p < 0.05) for nodulation. Mean pod yields in the control, Histick, and Lift treatments were 1.69, 2.34 and 1.87 Mg ha-1, respectively, under reduced irrigation. Under full irrigation, pod yields were 3.35 in the control, 4.50 in Histick and 3.41 Mg ha-1 in Lift treatments, but were more significantly improved as treated with Histick than other treatments. Genotype ICGS-76 produced the highest pod yield (5.13 Mg ha-1) as treated with Histick. All genotypes treated with Histick and Lift biosynthesized less TRG (decreased from 5.8 to 65.3% relative to the control) but produced larger numbers of pods (increased from 9.2 to 80.4% relative to the control), which resulted in substantially higher pod yields.