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Open Access Publications from the University of California

Department of Plant Sciences

UC Davis

Department of Plant Sciences

There are 1269 publications in this collection, published between 1976 and 2021.
Open Access Policy Deposits (932)

Developmental and Metabolic Plasticity of White-Skinned Grape Berries in Response to Botrytis cinerea during Noble Rot.

Noble rot results from exceptional infections of ripe grape (Vitis vinifera) berries by Botrytis cinerea. Unlike bunch rot, noble rot promotes favorable changes in grape berries and the accumulation of secondary metabolites that enhance wine grape composition. Noble rot-infected berries of cv Sémillon, a white-skinned variety, were collected over 3 years from a commercial vineyard at the same time that fruit were harvested for botrytized wine production. Using an integrated transcriptomics and metabolomics approach, we demonstrate that noble rot alters the metabolism of cv Sémillon berries by inducing biotic and abiotic stress responses as well as ripening processes. During noble rot, B. cinerea induced the expression of key regulators of ripening-associated pathways, some of which are distinctive to the normal ripening of red-skinned cultivars. Enhancement of phenylpropanoid metabolism, characterized by a restricted flux in white-skinned berries, was a common outcome of noble rot and red-skinned berry ripening. Transcript and metabolite analyses together with enzymatic assays determined that the biosynthesis of anthocyanins is a consistent hallmark of noble rot in cv Sémillon berries. The biosynthesis of terpenes and fatty acid aroma precursors also increased during noble rot. We finally characterized the impact of noble rot in botrytized wines. Altogether, the results of this work demonstrated that noble rot causes a major reprogramming of berry development and metabolism. This desirable interaction between a fruit and a fungus stimulates pathways otherwise inactive in white-skinned berries, leading to a greater accumulation of compounds involved in the unique flavor and aroma of botrytized wines.

On measuring the response of mesophyll conductance to carbon dioxide with the variable J method.

The response of mesophyll conductance to CO(2) (g(m)) to environmental variation is a challenging parameter to measure with current methods. The 'variable J' technique, used in the majority of studies of g(m), assumes a one-to-one relationship between photosystem II (PSII) fluorescence and photosynthesis under non-photorespiratory conditions. When calibrating this relationship for Populus trichocarpa, it was found that calibration relationships produced using variation in light and CO(2) were not equivalent, and in all cases the relationships were non-linear-something not accounted for in previous studies. Detailed analyses were performed of whether different calibration procedures affect the observed g(m) response to CO(2). Past linear and assumed calibration methods resulted in systematic biases in the fluorescence estimates of electron transport. A sensitivity analysis on modelled data (where g(m) was held constant) demonstrated that biases in the estimation of electron transport as small as 2% (∼0.5 μmol m(-2) s(-1)) resulted in apparent changes in the relationship of g(m) to CO(2) of similar shape and magnitude to those observed with past calibration techniques. This sensitivity to biases introduced during calibrations leads to results where g(m) artefactually decreases with CO(2), assuming that g(m) is constant; if g(m) responds to CO(2), then biases associated with past calibration methods would lead to overestimates of the slope of the relationship. Non-linear calibrations were evaluated; these removed the bias present in past calibrations, but the method remained sensitive to measurement errors. Thus measurement errors, calibration non-linearities leading to bias, and the sensitivity of variable J g(m) hinders its use under conditions of varying CO(2) or light.

The chromosome region including the earliness per se locus Eps-Am1 affects the duration of early developmental phases and spikelet number in diploid wheat.

Earliness per se genes are those that regulate flowering time independently of vernalization and photoperiod, and are important for the fine tuning of flowering time and for the wide adaptation of wheat to different environments. The earliness per se locus Eps-A(m)1 was recently mapped within a 0.8 cM interval on chromosome 1A(m)L of diploid wheat Triticum monococcum L., and it was shown that its effect was modulated by temperature. In this study, this precise mapping information was used to characterize the effect of the Eps-A(m)1 region on both duration of different developmental phases and spikelet number. Near isogenic lines (NILs) carrying the Eps-A(m)1-l allele from the cultivated accession DV92 had significantly longer vegetative and spike development phases (P<0.0001) than NILs carrying the Eps-A(m)1-e allele from the wild accession G3116. These differences were paralleled by a significant increase in the number of spikelets per spike, in both greenhouse and field experiments (P<0.0001). Significant interactions between temperature and Eps-A(m)1 alleles were detected for heading time (P<0.0001) but not for spikelet number (P=0.67). Experiments using NILs homozygous for chromosomes with recombination events within the 0.8 cM Eps-A(m)1 region showed that the differences in number of spikelets per spike were linked to the differences in heading time controlled by the Eps-A(m)1 locus. These results indicate that the differences in these two traits are either pleiotropic effects of a single gene or the effect of closely linked genes. A similar effect on spikelet number was detected in the distal region of chromosome 1AL in common wheat (T. aestivum L.).

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The Proceedings of the International Plant Nutrition Colloquium XVI (344)

Distribution of water extractable heavy metals (Cd, Co, Mn and Mo) in the topsoil of Osijek-Baranja County (Eastern Croatia)

Based on the pedological map of Osijek-Baranja County in eastern Croatia 74 soil samples were collected and analyzed for water extractable heavy metals (Cd, Co, Mn and Mo). By using GIS technique (ArcView software), different set of maps showing the water extractable metals were created. The maps indicate the correlation of water extractable fraction of heavy metals with soil pH, further statistical analysis will be preformed to confirm these assumptions. In addition analysis of variance was conducted to examine the influence of land use and different soil types on water extractable metals. Land use has shown significance for Cd, Co and Mn while soil type for Mo. These results also seem to be pH dependent, as land use and soil type differ in pH which is the factor causing the difference in the concentration of water extractable metals.

Effect of continuous cropping on changes in crop productivity nutrient budgets and soil properties with and without FYM under pearl millet - mustard – cowpea cropping sequence

Long-term field studies are important to generate information on nutrients dynamics which help in understanding nutrients management strategies for sustainable crop productivity. Keeping this in view, the present investigation (2002-07) was carried out in an on-going long term field experiment (started in 1980) to evaluate the effect of continuous cropping on changes in crop productivity, nutrient budget and soil properties with (F1) and without farmyard manure (FYM, F0) under pearl millet- mustard-cowpea (Fodder) cropping sequence. The FYM was applied at 10 t ha-1 once in a year to the kharif pearl millet (F1). Different fertility levels were applied to both FYM treatments: 0 (control, FL0), 50% (FL1), 100% (FL2), and 150% (FL3) of the recommended dose of NP fertilizers (RDF).

The FYM and fertilizer (NP) application increased crops yield over control; however, there was a continuous decline in the productivity of the crops over the years. The overall productivity of pearl millet and mustard grain decreased by 66 and 38%, respectively, in five years over the corresponding yields of 26 and 13.8 q ha-1 in 2002-03 without FYM. A similar decline in crops productivity was also noticed under FL treatments as well as in the control. The inorganic and organic N and P fractions showed depletion over the time in control only. In case of K, all the K fractions showed depletion irrespective of the treatments over the years. The depletion in total K was by 11 and 15 per cent in control and FL2, respectively during five years of cropping over their corresponding content of 7199 and 7964 mg kg-1 in 2002-03. The alone NP fertilization without FYM showed more adverse effect on availability of K, S and micronutrients viz., Zn, Fe and Mn than with FYM treatments.

The study suggested that supplementation of limiting nutrients to provide balanced nutrition to the crops is essential for sustainable higher productivity under intensive cropping on low to medium fertility light textured soils. The use of FYM and inclusion of leguminous crop like cowpea (fodder) in a cropping sequence was found advantageous to utilize soil nutrients more efficiently and to sustain soil fertility and productivity under intensive cropping.

Non-invasive imaging and characterization of absorption, transport and accumulation of cadmium in an intact rice plant

The absorption, transport and accumulation of cadmium (Cd) in rice (Oryza sativa L. cv. Nipponbare) were visualized and characterized quantitatively using the positron-emitting tracer imaging system (PETIS). We developed a method to produce a positron-emitting Cd-107 (half-life: 6.5 hr) tracer by ion-beam bombardment and chemical purification. The tracer was fed to the hydroponic culture and serial images of Cd distribution in the intact rice plants at vegetative stage and grain-filling stage were obtained by PETIS in every four minutes for 36 hours. The images showed that Cd moved up through the root and leaf sheath (vegetative stage) and through the culm to panicles (grain-filling stage) with velocities of a few cm/h. The most characteristic feature of the Cd dynamics was intensive accumulation in the nodes both at vegetative and grain-filling stages. It was found Cd moved from the shoot base into crown roots at vegetative stage. In contrast, no Cd was detected in the leaf blades. These results suggest that xylem-to-phloem transfer is a pivotal step in long-distance transport of Cd from the soil to the grains and the nodes are the most likely organ where the transfer takes place.

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