Research Note: Bird-Resistant Pollination Bags for Sorghum Breeding and Germplasm Maintenance

Bird damage is a problem in sorghum breeding and germplasm maintenance operations. Paper pollination bags are damaged by rain and provide only a minimal deterrent to birds. To overcome these limitations we fabricated pollination bags from spun polyethylene fiber sheeting. No seed yield difference was found between plants bagged with either spun polyethylene or paper. Seed loss by bird damage was nearly eliminated under the polyethylene bags. In areas where bird damage is problematic bird resistant pollination bags can allow for a reduction in the plot size required for breeding and germplasm maintenance operations, increase the productivity of such operations as genetic diversity per unit land area, and make direct measurement of seed yield possible in agronomic field experiments.

Evaluation of a Wireless Solar Powered Personal Weather Station

We are evaluating dryland cotton production in Martin County, Texas, measuring cotton lint yield per unit of rainfall. Our goal is to collect rainfall data per 250 - 400 ha. Upon selection of a rainfall gauge, we realized that the cost of using, for example, a tipping bucket-type rain gauge would be too expensive and thus searched for an alternative method. We selected an all-in-one commercially available weather station;hereafter, referred to as a Personal Weather Station (PWS) that is both wireless and solar powered. Our objective was to evaluate average measurements of rainfall obtained with the PWS and to compare these to measurements obtained with an automatic weather station (AWS). For this purpose, we installed four PWS deployed within 20 m of the Plant Stress and Water Conservation Meteorological Tower that was used as our AWS, located at USDA-ARS Cropping Systems Research Laboratory, Lubbock, TX. In addition, we measured and compared hourly average values of short-wave irradiance (Rg), air temperature (Tair) and relative humidity (RH), and wind speed (WS), and calculated values of dewpoint temperature (Tdew). This comparison was done over a 242-day period (1 October 2022-31 May 2023) and results indicated that there was no statistical difference in measurements of rainfall between the PWS and AWS. Hourly average values of Rg measured with the PWS and AWS agreed on clear days, but PWS measurements were higher on cloudy days. There was no statistical difference between PWS and AWS hourly average measurements of Tair, RH, and calculated Tdew. Hourly average measurements of Rg and WS were more variable. We concluded that the PWS we selected will provide adequate values of rainfall and other weather variables to meet our goal of evaluating dryland cotton lint yield per unit rainfall.

Irrigation Termination Thermal Time and Amount on Cotton Lint Yield and Fiber Quality

Cotton irrigation in the Texas High Plains (THP) is often dictated by the well capacity and not by the water needs of the crop. The source of irrigation-water is the Ogallala aquifer and in many areas of the THP, the water table has declined to well capacities that deliver 1.3 to >7.6 mm/d. There is plenty of information on cotton responses to irrigation frequency and amount;however, information on when to terminate irrigation and its effect on cotton lint yield and fiber quality is scarce. Our objective was to evaluate over a 4-year period three irrigation termination thermal times corresponding to cumulative daily heat units (∑HU) of 890 °C, 1000 °C and 1110 °C from crop emergence, and three levels of irrigation (2.5, 5.1 and 7.6 mm/d) on cotton lint yield and fiber quality. Irrigation was applied with a sprinkler system on a 3-day frequency in Lubbock, TX. Results showed that on average the 7.6 mm/d level produced the most cotton lint yield regardless of the irrigation termination thermal time. Terminating cotton at 1000- °C ∑HU resulted in water savings of 25 to 50 mm for the 2.5 and 5.1 mm/d levels without significantly affecting lint yield. For the 7.6 mm/d and terminating at 890- °C ∑HU resulted in water savings of 100 to 115 mm. Average fiber length statistically increased with termination thermal time and level. This effect was most significant in years with the least rain and warmer air temperature. Micronaire increased with the termination thermal time in years with >500 mm of rain. Average fiber length uniformity and fiber strength were minimally affected by termination thermal time. As irrigation level increased, the average micronaire decreased, and fiber strength increased for the 5.1 and 7.6 mm/d irrigation. We concluded that in the THP for well capacities that deliver 2.5 - 5.1 mm/d irrigation can be terminated when the ∑HU reaches about 1000 °C from emergence without impacting cotton lint yield.

Review Paper: Challenges and Limitations in Studying the Shrink-Swell and Crack Dynamics of Vertisol Soils

The need to study the shrink-swell and crack properties of vertic soils has long been recognized given their dynamics in time and space, which modifies the physical properties that impact water and air movement in the soil, flow of water into the subsoil and ground water, and generally alter the hydrology of vertic soils. Measurement of crack properties has been made by numerous researchers with the purpose to understand and quantify the spatial and temporal dynamics of shrinking and swelling and the associated formation of cracks. These crack properties, which are important in modifying hydrology of soils are: width, length, depth and orientation of soil’s cracks. To better understand the hydrology of vertic soils and incorporate crack properties into hydrologic simulation models, several techniques have been developed to measure crack properties. However, little attention is given to evaluate both the advantages and the limitations associated with these techniques. Thus, the purpose of this review is to highlight challenges and limitations that have been used or might be used to measure cracking in vertic soils.

Effect of Ambient UV-B on Stomatal Density, Conductance and Isotope Discrimination in Four Field Grown Soybean [<i>Glycine max</i>(L.) Merr.] Isolines

An experiment was designed to test whether ambient levels of UV-B radiation affect stomatal development, decrease stomatal density, and lead to increased water-use efficiency (WUE). Soybean [Glycine max (L.) Merr.] isolines with different stomatal distribution and flavonol expression patterns were field grown under shelters that either transmitted or blocked solar UV-B. All isolines exposed to solar UV-B accumulated higher concentrations of UV-screening phenolic pigments but other responses were isoline dependent. Solar UV-B decreased stomatal density and conductance in isolines expressing a unique branched kaempferol triglycoside. Decreased stomatal density was associated with increased season-long WUE and decreased internal CO2 concentration of leaf (estimated by δ13C discrimination). We concluded that photomorphogenic responses to UV-B affected stomatal density and WUE in field grown soybean;but that the magnitude and direction of these response were associated with isogenic pleiotropic differences in stomatal distribution and pigment expression. UV-B radiation had no effect on biomass accumulation or yield in a cultivar expressing only trace levels of kaempferol suggesting that flavonol expression is not prerequisite to UV-B tolerance.

Continuously Monitored Canopy Temperature as a Proxy for Plant Water Status

Water deficits are major limiters of crop yield worldwide. The detection of water deficits can be difficult. Measurements of the aerial and soil environment are often used to infer the water status and detect water deficits. Since crop yield accumulates incrementally and cumulatively over seasonal time scales, continuous direct monitoring of the water status of the crop may provide needed insight into plant/environment interactions. Canopy temperature can be measured near continuously on seasonal scales in the field. Cotton was grown under 11 irrigation regimes in 2009 and 2010 with water deficits from 26% to 86% of crop evapotranspiration. Yield varied accordingly from ~500 kg·ha-1 to ~2600 kg·ha-1. Canopy temperature was measured on a 15-minute interval for ~65 days in each year. Yield was described by a linear function of total water (irrigation + rain) for each year with similar slopes and different intercepts. When canopy temperature was used as a surrogate for total water, yield was linearly related to daytime leaf-to-air VPD, mean seasonal canopy temperature, mean seasonal daytime canopy temperature, and cumulative seasonal daytime canopy temperature. Limiting the analysis to daytime periods improved the ability to account for yield variation. Mean daytime seasonal canopy temperature and cumulative seasonal daytime temperature were most effective in accounting for yield variation across the seasons with a single regression line for both years.

Canopy Light Interception of a Conventional and an Erect Leafed Sorghum

Two sorghum lines, an erect leafed mutant sorghum and the wild type from which the mutant was generated, were field grown in rectilinear arrays at low (10 plants m-2) and high (23 plants m-2) population densities. Canopy light interception, biomass accretion and yield were measured. Photosynthetically active radiation under the canopy at ground level and midway through the canopy were higher in the erect leafed line, as compared to the normal leafed line. Planting density had less effect on mean grain yield and biomass in the erect leaf line than in the wild type. Though not conclusive, when taken together, the results suggested that optimal planting densities are higher for the erect leaf line and that the erect leaf trait could be useful for incorporation into breeding programs.

Phosphate Sorption in Water by Several Cationic Polymer Flocculants

Although inorganic phosphate is an essential plant nutrient, elevated levels in surface waters lead to adverse effects in the environment. These effects are attributed to runoff from rain or irrigation events that may cause the sorbed phosphate to be transported from the application sites and to move into neighboring watersheds. Increased phosphate concentration in watersheds may lead to a variety of environmental problems including increased algal blooms, bacterial contamination, and in some cases eutrophication. To overcome these effects, polymer flocculants have been shown to reduce the phosphate concentration in water by removing suspended solids and thereby removing the phosphate sorbed to the solids. The purpose of this study is to determine the amount, if any, of phosphate removed by several commercial polymers. The polymers chosen include the polyacrylamides Magnifloc 494C, Magnifloc 985N and Poly (diallyldimethyl ammonium chloride) (Poly (DADMAC)). Using these polymers, it is discovered that the positive charge density of the polymers affects the amount of phosphate removed from solution with Poly (DADMAC) (having 100% positive charge density) removing 40% of the phosphate from a solution containing 10 ppm phosphate.

System for High Throughput Water Extraction from Soil Material for Stable Isotope Analysis of Water

A major limitation in the use of stable isotope of water in ecological studies is the time that is required to extract water from soil and plant samples. Using vacuum distillation the extraction time can be less than one hour per sample. Therefore, assembling a distillation system that can process multiple samples simultaneously is advantageous and necessary for ecological or hydrological investigations. Presented here is a vacuum distillation apparatus, having six ports, that can process up to 30 samples per day. The distillation system coupled with the Los Gatos Research DLT-100 Liquid Water Isotope Analyzer is capable of analyzing all of the samples that are generated by vacuum distillation. These two systems allow larger sampling rates making investigations into water movement through an ecological system possible at higher temporal and spatial resolution.

Relating Xylem Cavitation to Gas Exchange in Cotton

Acoustic emissions (AEs) from xylem cavitation events are characteristic of transpiration processes. Though a body of work exists describing AEs and limited stem hydraulic conductivity under water stress, there is limited information about the effects of AEs on stomatal aperture and limitation on carbon assimilation. The objective of this work was to relate AEs to drought stress in cotton. Cotton was grown in mini-lysimeters in the greenhouse and instrumented with a portable photosynthesis system and ultrasonic transducers connected to a digital signal-processing unit. Whole plant transpiration, leaf level gas exchange and ultrasonic AEs were measured. Xylem cavitation events temporally associated with the onset of drought stress. The results are consistent with stomatal closure in response to reduced hydraulic conductance from xylem cavitation events. Clear direct empirical evidence of a reduction in carbon assimilation associated with xylem cavitation resulting from water stress is presented.

CO₂and Chamber Effects on Epidermal Development in Field-Grown Peanut (<i>Arachis hypogaea</i>L.)

Peanut, (Arachis hypogaea L.) cvar. C76-16, was grown either in the field, or in open gas exchange chambers under elevated or ambient CO2 concentrations. Stomatal density and other selected epidermal parameters associated with leaf development and gas exchange were measured on recently fully expanded canopy leaves. It was hypothesized that exclusion of solar UV by chambers would affect stomatal density, but no clear statistically significant chamber effect on stomatal density was found. However, elevated [CO2] did lead to a reduction in both adaxial and abaxial stomatal developmental initiation and in stomatal density. Since each stomate was bounded by companion cells resulting from developmental events, non-random stomatal spacing as the “one cell spacing rule” appears to result from ontogeny rather than a long hypothesized chemical signal inhibiting adjacent meristemoid differentiation into guard cells. A method of visualizing epidermal patterns is also described.

Short Communication: Analysis of Grain Size Distribution through Image Analysis

Herein we describe an approach to measure the volume and to characterize the volume distribution of large numbers of individual small regularly shaped seeds. The results of a preliminary investigation into the distribution of seed size of a multi-seeded sorghum mutant, as compared to the wild type from which it was developed are also reported, and are used as an example of the method’s utility.

Genetic Diversity in the Environmental Conditioning of <i>Gossypium hirsutum</i>and <i>Gossypium barbadense</i>Cultivars

Enzyme adaptations to temperature occur constantly as temperature patterns modulate diurnally and seasonally. These adaptations entail qualitative and/or quantitative metabolic changes that often provide a competitive advantage, impact adjustment to new environments, and effect the survival of the species. Changes in isozymes or allozymes, changes in enzyme concentration, modification by substrate and effectors, and metabolic regulation of enzyme function without changing enzyme composition are all possible strategies for adaptation to changes in temperature. The degree of adaptation among cotton cultivars to a specific thermal regime may be difficult to determine from phenotypic responses of the plants. The present study evaluated the thermal sensitivity of Gossypium hirsutum L. and Gossypium barbadense L. cultivars following growth under distinct thermal environments. The metabolic fitness of Gossypium hirsutum L. and Gossypium barbadense L. cultivars showed that the Gossypium hirsutum L. cultivars grown in a 28&deg;C/20&deg;C day/night cycle tended to be better equipped to cope with a 16 h - 38&deg;C treatment than the same cultivars grown in a 38&deg;C/32&deg;C day/night cycle. The Gossypium barbadense L. cultivars, on the other hand, grown in a 38&deg;C/32&deg;C day/night cycle tended to be equipped to cope with a 16 h - 38&deg;C treatment than the same cultivars grown in a 28&deg;C/20&deg;C day/night cycle. The Gossypium hirsutum L. line TX 303 is an exception to these general trends as its responses were similar to the Gossypium barbadense L. St. Vincent and Pima S-7 cottons.

Description of a Novel Allelic “Thick Leafed” Mutant of Sorghum

An allelic sorghum [Sorghum bicolor (L.) Moench] mutant with thick and narrow erect leaves (Thl) and reduced adaxial stomatal density was isolated from the Annotated Individually pedigreed Mutagenized Sorghum mutant library developed at the Plant Stress and Germplasm Development Unit at Lubbock TX. The mutant, Thl, was isolated from a pedigreed M3 family generated by ethyl methanesulfonate mutagenization from an elite inbred sorghum line, BTx623, which had been used to sequence the sorghum genome. The mutant has been backcrossed to the wild-type BTx623 confirming that the trait results derive from a stable recessive nuclear gene mutation. Herein, we briefly described morphological and selected physiological characteristics of this mutant sorghum.

Systematic Errors Introduced into Sorghum Grain Yield Data: Does the Multiseed (<i>msd</i>) Trait Increase Sorghum Seed Yield?

Multiseed (msd) mutant sorghum [Sorghum bicolor (L.) Moench] lines with greatly increased seed numbers were developed. It was originally thought that the msd trait could increase grain yield several times in comparison with the wild type from which the mutant was derived. However, in a small plot trial, msd seed yield decreased when compared to the parent line. Herein we report results that msd seed yield remained either unchanged or slightly increased in comparison to the parent line. We suggest that attempts to measure msd sorghum seed yield were complicated due to systematic errors associated with the post-harvest processing methods, including threshing and pneumatic winnowing equipment that was used for harvest. That is, seed recovery and seed loss from individual panicles were affected by the post-harvest processing. When evaluating sorghum grain yield of types with different seed sizes, threshing and seed cleaning harvesting methods should be optimized for each sorghum line.

Evaluation of a Metabolic Cotton Seedling Emergence Model

A model for cotton seedling emergence (MaGi) based on malate synthase kinetics was evaluated. Cotton seeds were planted through the early spring and into typical planting times for the areas. Soil temperatures at seed depth were used as inputs into MaGi and a commonly used seedling emergence model based on heat unit accumulation (DD60). Time to 50% emergence was calculated and compared with predicted emergence using MaGi and DD60. MaGi yielded predictive capability without the need to resort to lengthy experimentation required by traditional methods. The results suggest that a physiological or semi-empirical approach incorporating both enzyme kinetics and whole plant temperature responses would be useful for rapidly constructing seedling emergence models.

Genetic Diversity in a Collection of Chinese Sorghum Landraces Assessed by Microsatellites

Genetic diversity was characterized in a collection of 159 sorghum (Sorghum bicolor L. Moench) landraces gathered from the colder region (primarily the northeastern region) of China. A set of 41 microsatellites or simple sequence repeat (SSR) markers distributed throughout the 10 chromosomes of sorghum was utilized in the analysis. Majority (40 out of 41 SSRs, 98%) of the SSR markers were polymorphic and highly informative with polymorphism information content (PIC) value ranging from 0.05 to 0.92. An estimation of genetic similarity coefficients (GSC, with values ranging from 0.42 to 0.96) revealed a range of variability in this collection of sorghum landraces. Eight clusters of accessions were identified at a cut off at 0.50 GSC and these groupings were supported by the analysis of subpopulations using Structure. This study provides evidence that Chinese landraces of sorghum exhibit moderate genetic diversity and results from cluster analysis may well aid in identification of diverse accessions that can serve as parental lines for efficient utilization and application of these germplasm into sorghum breeding programs.

Genetic Diversity in the Environmental Conditioning of Two Sorghum (<i>Sorghum bicolor</i>L.) Hybrids

Sorghum metabolism continually adapts to environmental temperature as thermal patterns modulate diurnally and seasonally. The degree of adaptation to any given temperature may be difficult to determine from phenotypic responses of the plants. The present study was designed to see if the efficiency of quantum yield of photosystem II could be used as a measure of how well leaf tissue metabolism was able to withstand a prolonged respiratory demand caused by elevated temperatures. The efficiency of quantum yield values of Pioneer 84G62 and Northrup King KS585 commercial sorghum hybrids showed that when the hybrids were grown in a 28&deg;C/20&deg;C day/night cycle in the greenhouse or the field, Pioneer hybrid 84G62 withstood subsequent elevated thermal challenges better than Northrup King KS585. The same hybrids grown in a 39&deg;C/32&deg;C day/night cycle showed similar efficiency of quantum yield values when thermally challenged. Water-deficit stress increased the heat resistance of the tissue raising the efficiency of quantum yield of both lines to the same level. Upon recovery from the water deficit stress the differential efficiency of quantum yield values between the two lines re-appeared. The data provided in this study suggest a metabolic advantage of Pioneer 84G62 to environmental thermal challenges compared with the Northrup King KS585.

Measurement of Cotton Transpiration

There are a few field methods available to directly measure water evapotranspiration (ET) along with its two components, evaporation from the soil (E) and from the crop (T). One such technique that measures T, uses sensors to calculate the sap flow (F) of water through the plant stem and is based on the conservation of mass and energy, i.e., the stem heat balance method. This instrument consists of a flexible heater that is wrapped around the plant stem with temperature sensors to measure the difference in temperature of F below and above the heater. This is a null method, where all inputs and outputs are known and the calculated F is a direct measure of T. This method has been used to measure T in a variety of crops, including cotton, grapes, olive trees, soybean, ornamental and horticultural crops. A new version of the EXO-SkinTM is the Stem Gauge Dual Channel Design (SGDCTM), which was commercially introduced and had a radically new design resulting in a different energy balance, compared to the original design, which needed experimental verification. An initial evaluation was done with potted cotton (Gossypium hirsutum, L.) plants in a greenhouse experiment showing that values of cotton-T measured with the new sensor were accurate;however, this comparison was limited to daily T T in the 2 - 7 mm/d range, representative of the semiarid Texas High Plains. For this purpose, cotton was planted on 12 June 2017 on a 1000 m2 plot in a soil classified in the Amarillo series at the facilities of the USDA-ARS, Lubbock, TX. For a period of 15 days, 2 to 16 Sep 2017, we measured hourly cotton-T with the new sensors and with portable growth chambers (0.75 m × 1 m cross-section, and 1 m height) where water vapor flux was measured at a 10 Hz frequency using an infrared gas analyzer. We used three chambers and, in each chamber, the new sensors were installed on four cotton plants. We used linear regression analysis to compare hourly and daily values of cotton-T measured with the sap flow gauges against T measured by the chambers. Using a t-test (p T for a wide range of environmental conditions.

Scaling Leaf Measurements to Estimate Whole Canopy Gas Exchanges of Cotton

Diurnal leaf and canopy gas exchanges of well-watered field grown cotton were measured. Our objective was to scale leaf-level values of transpiration and net assimilation to the whole canopy level using estimates of canopy leaf area. Single leaf gas exchange measurements were made with two portable photosynthesis systems and canopy measurements with four open Canopy Evapo-Transpiration and Assimilation (CETA) chamber systems. Canopy leaf area was measured at the end of the experiment and estimated during gas exchange by fitting values to a growth curve. Leaf level measurements were arithmetically scaled to estimate canopy level gas exchange based on canopy leaf area and then compared to the measured values. Scaled values of single leaf transpiration were very similar to canopy transpiration measurements, although both whole canopy transpiration and assimilation were overestimated around mid-day. We conclude that canopy cotton transpiration of well-watered field grown plants could be estimated within 5% throughout the day by scaling leaf level measurements to the whole canopy using measured canopy leaf area. Estimating canopy assimilation from leaf level measurements remains problematic.