Assessment of Drought Tolerance of Miscanthus Genotypes through Dry-Down Treatment and Fixed-Soil-Moisture-Content Techniques

Miscanthus, a high-yielding, warm-season C4 grass, shows promise as a potential bioenergy crop in temperate regions. However, drought may restrain productivity of most genotypes. In this study, total 29 Miscanthus genotypes of East-Asian origin were screened for drought tolerance with two methods, a dry-down treatment in two locations and a system where soil moisture content (SMC) was maintained at fixed levels using an automatic irrigation system in one location. One genotype, Miscanthus sinensis PMS-285, showed relatively high drought-tolerance capacity under moderate drought stress. Miscanthus sinensis PMS-285, aligned with the M. sinensis ‘Yangtze-Qinling’ genetic cluster, had relatively high principal component analysis ranking values in both two locations experiments, Hokkaido University and Brigham Young University. Genotypes derived from the ‘Yangtze-Qinling’ genetic cluster showed relatively greater photosynthetic performance than other genetic clusters, suggesting germplasm from this group could be a potential source of drought-tolerant plant material. Diploid genotypes showed stronger drought tolerance than tetraploid genotypes, suggesting ploidy could be an influential factor for this trait. Of the two methods, the dry-down treatment appears more suitable for selecting drought-tolerant genotypes given that it reflects water-stress conditions in the field. However, the fixed-SMC experiment may be good for understanding the physiological responses of plants to relatively constant water-stress levels.

Volatile Components of Fermented Feedstuffs – Correcting Dry Matter and Energy Estimation

Fermentedfeedstuffs contain a number of volatile compounds such as organic acids, alcohols,ammonia and others that are lost in the oven dry-down process used to estimatefeed dry matter.  By not accounting forthese components, errors in the estimation of moisture, caloric content andcrude protein content of the feed will occur. This paper addresses the volatile components of major concern. 

Developing a Stabilizing Formulation of a Live Chimeric Dengue Virus Vaccine Dry Coated on a High-Density Microarray Patch

Alternative delivery systems such as the high-density microarray patch (HD-MAP) are being widely explored due to the variety of benefits they offer over traditional vaccine delivery methods. As vaccines are dry coated onto the HD-MAP, there is a need to ensure the stability of the vaccine in a solid state upon dry down. Other challenges faced are the structural stability during storage as a dried vaccine and during reconstitution upon application into the skin. Using a novel live chimeric virus vaccine candidate, BinJ/DENV2-prME, we explored a panel of pharmaceutical excipients to mitigate vaccine loss during the drying and storage process. This screening identified human serum albumin (HSA) as the lead stabilizing excipient. When bDENV2-coated HD-MAPs were stored at 4 °C for a month, we found complete retention of vaccine potency as assessed by the generation of potent virus-neutralizing antibody responses in mice. We also demonstrated that HD-MAP wear time did not influence vaccine deposition into the skin or the corresponding immunological outcomes. The final candidate formulation with HSA maintained ~100% percentage recovery after 6 months of storage at 4 °C.

Phenotypic and transcriptomic responses of cultivated sunflower seedlings (Helianthus annuus L.) to four abiotic stresses

Plants encounter and respond to numerous abiotic stresses during their lifetimes. These stresses are often related and could therefore elicit related responses. There are, however, relatively few detailed comparisons between multiple different stresses at the molecular level. Here, we investigated the phenotypic and transcriptomic response of cultivated sunflower (Helianthus annuus L.) seedlings to three water-related stresses (i.e., dry-down, an osmotic challenge with polyethylene glycol 6000 [PEG], and salt stress), as well as a generalized low-nutrient stress. Our goal was to identify commonalities in the response to the three water-related stresses and compare them to a distinct low-nutrient stress. All four stresses negatively impacted seedling growth, with the low-nutrient stress having a more divergent response from control as compared to the water-related stresses. Observed phenotypic responses were consistent with expectation for growth in low-resource environments, including increased (i.e., less negative) carbon fractionation values and leaf C:N ratios, as well as increased belowground biomass allocation. Analysis of the leaf and root transcriptome under each stress scenario revealed that most genes were differentially expressed in response to multiple stresses. The number of differentially expressed genes (DEGs) under stress was greater in leaf tissue, but roots exhibited a higher proportion of DEGs unique to individual stresses. Overall, the three water-related stresses had a more similar transcriptomic response to each other vs. low-nutrient stress, though this pattern was more pronounced in root tissue than in leaf tissue. In contrast with the results of our differential expression analysis, co-expression network analysis revealed that the response to each of the four stresses in our study were generally non-overlapping and there was little indication of a shared co-expression response despite the majority of DEGs being shared between multiple stresses. Importantly, PEG stress, which is often used to simulate drought stress in experimental settings, had little transcriptomic resemblance to true water limitation (i.e., dry-down) in our study calling into question its utility as a means for simulating drought.

Irrigated trap crops impact key hemipteran pests in organic pistachio orchard

Using sown groundcovers as trap crops to protect a cash crop is a traditional pest management tool. Pistachio is a major crop in California’s Central Valley, where high summer temperatures and little to no precipitation between May and November lead to summer dry-down of annual groundcover. Hemipteran pests that consist of ‘small bugs’ and ‘large bugs’ are a major contributor to nut damage, especially in organic production. In this 2-year field study, we tested the use of irrigated trap crop mixtures, sown between tree rows, to reduce those hemipteran pests’ abundance or damage. Biweekly beat samples of the tree canopy and sweep samples of the sown groundcovers in trap crop plots and resident weedy vegetation in control plots were taken over two consecutive growing seasons. Arthropod richness and abundance were highest in the groundcover and tree canopy in the trap crop plots. Small and large bug pest populations were higher and lower, respectively, in the tree canopy in trap crop plots, indicating a mixed response of these hemipterans to the presence of the trap crops. Additionally, natural enemy populations were more abundant in the tree canopy in trap crop plots than in control plots. There was no difference in nut damage between plots with and without the trap crop. These findings suggest that populations of hemipteran pests and beneficials can be manipulated successfully with irrigated trap crops, but future studies will need to focus on doing so in a way that decreases hemipteran pistachio damage.

Differing Fine-Scale Responses of Vegetation and Bare Soil to Moisture Variation in a Pinyon-Juniper Woodland Underlie Landscape-Scale Responses Observed from Remote Sensing

Pinyon juniper woodlands in the American southwest face an uncertain ecological future with regard to climate altered precipitation. Although satellite remote sensing will be relied upon to assess the overall health of these plant communities more fine scaled information is needed to elucidate the mechanisms shaping the broader scaled regional assessments. We conducted a study to assess the NDVI response at the plant canopy level (insitu sensors placed over the canopies) of three tree and one shrub species to changes in precipitation, reference evapotranspiration and soil volumetric water content. Landsat data was used to compare stand integrated and satellite NDVI values. We also provided supplemental water in the amount of 10.85 cm over the study period to additional trees and shrubs which also had insitu NDVI sensors placed over their canopies. NDVI at the canopy level separated statistically by species and when contrasted with bare soil (p<0.001). Spring early summer dry down events were inversely related to increasing ETref-precipitation with a steeper dry down slope in the first year associated with no rainfall occurring in May and June. All three-tree species did not show any significant difference in canopy NDVI based on supplemental water, however the shrub species did reveal a significant response to water (p<0.001). Although all of the three-tree species revealed a one-month period in which they responded to precipitation in July of the first year after 11.2 cm of precipitation, no immediate (day of or next day) response was observed to precipitation or supplemental water events. Snowberry was unique in its NDVI response during the spring green up period in the second year revealing a highly linear shift over a 40-day period with a clear separation between treatments (p<0.001) with those plants receiving supplemental water having a higher more positive slope. Landsat NDVI values revealed an inverse sinusoidal relationship with ETref-precipitation (R2=0.59 p=0.012). Landsat values (0.19+/- 0.01) were found to have no significant difference with bare soil NDVI (0.17+/- 0.01) but were significantly different from all four tree and shrub species. Integrated NDVI based on sensor weighted % cover estimates (0.37+/-0.03) were nearly double Landsat values (0.19+/-0.01). Both NDVI values of pinyon pine and Utah juniper were found to be linear correlated with Landsat NDVI in the second Year (R2>0.75, p<0.001). Multiple regression analysis revealed that 95% of the variation in Landsat NDVI in the second year could be accounted for based on bare soil NDVI and pinyon pine NDVI (p<0.001). et al., NDVI interspace (bare soil) of pinyon juniper woodlands dominated the nature of the Landsat curve. Our results demonstrate the value of ground sensors to help fill the gap between what can be inferred at the forest canopy level and what is occurring at the plant level.

Physiological changes in advanced hybrid chestnuts do not alter blight resistance under co-occurring drought

Chestnut breeding programs have been using a backcross breeding technique to produce trees with a predominantly American chestnut (<i>Castanea dentata</i>) genome and chestnut blight disease resistance from Chinese chestnut (<i>Castanea mollissima</i>). The potential for other physiological changes caused by breeding has yet to be widely studied. We quantify chestnut (American, Chinese, and BC₃F₃ hybrids) responses to water-stress and measure how co-occurring drought influences disease severity. The experiment was completed using 172 bare-root seedlings organized into a completely randomized factorial design in an outdoor rain-out shelter for one growing season. BC₃F₃ hybrid gas exchange (A_sat, g_s) rates were more similar to Chinese than American chestnuts over a 20-day dry-down period, and hybrid turgor loss point showed a more intermediate (between Chinese and American) response. The relationship of stomatal conductance to mid-day leaf water potential (Ψ_md) also exhibited both American and Chinese characteristics in the hybrid trees. There was no effect of drought on the disease severity for any of the chestnut groups. We find evidence that drought physiology has been altered in some BC₃F₃ hybrids, but do not find changes in disease severity when chestnuts are under co-occurring drought.