2013 Annual Report
1a.Objectives (from AD-416):
The objectives of this study are to (i) advance and validate a tractor-based phenotyping method for canopy temperature, plant height, and vegetation indices (e.g., normalized difference vegetation index, NDVI), and (ii) conduct a time-related QTL analysis on these traits under supra-optimal temperatures and water-limited conditions.
1b.Approach (from AD-416):
In 2012, a genetic mapping population of 98 recombinant inbred lines (RILs), parents (NM24016 and TM1), and differential checks will be grown at Maricopa for a third consecutive year. Field evaluations at Maricopa will include well-watered and water-limited treatments with two replicates each. The water-limited treatment will be initially applied before first flower. Measurements of canopy temperature, plant height, and vegetation indices will be collected weekly from tractor-based observations throughout July-August, which coincides with the critical stage of peak flowering and boll development as well as the hot, humid monsoon season in central and western Arizona. These data will be compared to that of helicopter-based remote sensing of vegetation indices and land surface temperature, which is highly effective but expensive for remote sensing of crop fields. Other measured agronomic and physiological traits will include but are not limited to pollen sterility, specific leaf area, leaf thickness chlorophyll content, plant height, carbon isotope discrimination (an indirect measure of water use efficiency) as well as yield and fiber traits. Taken together, these data will be used in a time-related QTL analysis and analyzed together with phenotypic data from 2010 to test the role of physiological traits in cotton productivity under heat and water stress.
This Trust Agreement is in support of Objective 2 of the parent project- Develop improved germplasm resources for abiotic stress resistance and fiber quality in Gossypium barbadense and G. hirsutum utilizing and integrating classical and biotechnology-based methodologies, Subobjectives 2.a - Develop improved germplasm resources for abiotic stress resistance and fiber quality in G. hirsutum utilizing and integrating classical and biotechnology-based methodologies, and 2.b - Develop improved germplasm resources for abiotic stress resistance and fiber quality in G. barbadense utilizing and integrating classical and biotechnology-based methodologies. The present study was conducted to develop and implement a tractor-based, high-throughput phenotyping system for the simultaneously measurement of multiple traits related to heat and drought stress tolerance. In collaboration with an ARS scientists at Maricopa, AZ, converted a high-clearance modified sprayer into a field vehicle for proximal remote sensing of the crop canopy. By retrofitting a front-mounted boom with multiple sensors, the high-clearance modified sprayer could simultaneously measure plant height, canopy spectral reflectance, and canopy temperature in a four-row configuration. Proximal remote sensing data were collected from an interspecific cotton recombinant inbred line mapping population on weekly basis and multiple times within a day from peak flowering to end of flowering. In total, 25 scans of the experimental plots were completed for plant height, canopy temperature, and canopy spectral reflectance on 10 different dates.
Cotton developed for irrigated production in hot, arid environments such as Arizona tends to have relatively high stomatal conductance rates in the absence of water stress. In this “heat avoidance” mechanism, higher stomatal conductance promotes evaporative cooling of the canopy to temperatures that are dramatically less than ambient air. In a preliminary statistical analysis of canopy temperature data from a representative day, it was shown that drought stressed and well watered plots were statistically different for canopy temperature at both mid-morning and late afternoon. This research provides new high-throughput phenotyping tools for plant breeding and genetics research in the field. Progress performance has been monitored through discussion of project plans, reviewing program goals and accomplishments at ARS facilities, teleconference, e-mail, and quarterly reports.