Progress 07/01/21 to 02/28/22
Outputs
Target Audience:The market for PowerPollen® is the global agricultural seed industry. Within this market, the improvement of hybrid production systems enabled by pollen preservation technology can have applicability to almost any crop, but our focus for this SBIR project is on companies that sell wheat seed, which is our initial addressable market for this project--and into which we believe we can make major inroads. For currently proposed hybrid wheat production systems, the primary economic driver for adoption of a pollen-preservation technology such as PowerPollen® would be to solve the major problem of delivering viable pollen from male plants to female plants in a timely and efficient manner.Because our PowerPollen® technology does just that, it may enable cost-effective wheat hybridization for the first time, opening an entirely new hybrid wheat industry. Changes/Problems:No major problems encountered. Changes in technical personnel were required due to turnover. This did not affect the progress of the research program. What opportunities for training and professional development has the project provided?The project has provided opportunity for graduate student training for a company employee associated with the wheat project. How have the results been disseminated to communities of interest?Several press releases listed on the PowerPollen website News update on BASF AgSolutions US website Company presentations to collaborators, investors, and community groups. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Objective 1: Prove the feasibility of designing/constructing a scalable method for mechanically harvesting male wheat spikes containing mature viable pollen. Technical Metrics for Phase I: Mechanized spike-collection prototype obtains at least 50% of spikes per plant containing anthers with highly viable pollen. Collection techniques are compatible with anther-extraction protocols in Objective 2. Specific Accomplishments: Task 1: Construct prototype cutting and collecting machine. In Phase I the wheat team successfully developed a prototype mechanical device to harvest wheat spikes from field-grown plants. Field testing confirmed a single pass of the spike harvester routinely collected at least 60% of the available reproductive-stage spikes, often harvesting more than 90% of those bearing mature anthers, far exceeding the metric for scaling. Task 2: Determine factors that affect wheat spike collection efficiency. In Phase I, we evaluated a wide range of mechanical and biological factors to maximize collection of intact wheat spikes per unit time.We conducted these evaluations in cooperation with the BASF wheat breeding program under commercial field conditions. Mechanical factors evaluated included harvester speed over ground, height of harvester cutter bar, geometry/design of spike gathering and cutting systems, machine power requirements, and harvester carrying capacity. Biological and agronomic factors evaluated included plant stand count, amount of vegetative (flag leaf) material collected, plant row spacing, stage of plant reproductive maturity, and wind velocity. Task 3. Determine impact of variation in wheat spike morphology, tiller production, and spike maturation on collection efficiency. Using a combination of field and laboratory evaluations of pollen, anther, spike, and canopy development, we identified Zadocks 61 to 65 as the optimum range of wheat reproductive development to maximize mechanized anther collection for use in Objective 2. Objective 2: Construct a scalable prototype to validate the concept of separating anthers containing viable pollen from green plant material. Mechanical Metrics for Phase I: Collect at least 50% of all non-exserted anthers from processed wheat heads. System can be scaled to process at least 600 wheat spikes/min. Separation techniques are compatible with pollen- extraction protocols in Objective 3. Specific Accomplishments: Task 1: Construct a mechanical prototype for harvesting non-exserted anthers from wheat spikes. In Phase I, the engineering team designed and evaluated a number of novel mechanical approaches to separate and collect anthers from intact wheat spikes. By far the most efficient design was a roller mill thresher. With its unique geometry and threshing action, the thresher very efficiently separated floral spikelets from the rachis (reproductive stalk) AND liberated the anthers from other protective floral structures. The liberated anthers were then easily screened from the rest of the plant material for storage and/or pollen extraction in Objective 3. Task 2. Optimize efficiency of anther separation. We evaluated numerous characteristics of the roller mill structure and operation to optimize throughput and separation efficiency. Variables included roller geometry, absolute and differential roller speeds, roller spacings, and feed rate. The most efficient combination these variables for the small prototype mill extracted up to ~80% of the anthers per spike and easily processed 60 spikes per minute. Task 3. Determine impact of spike development, spikelet morphology, and time after spike harvest on anther collection efficiency. As in Objective 1 Task 3, supporting laboratory documentation of pollen, anther, spikelet, and spike development identified Zadocks 61 to 65 as the optimum range of reproductive development to optimize mechanized anther collection for use in Objective 3. Based on these positive outcomes, we designed and constructed a prototype anther harvester (spike collector + anther extractor) for scaled anther collection in a commercial hybrid wheat field in Phase II. Preliminary tests indicate the anther harvester increases efficiency of anther collection more than 10-fold over the two-step process of anther collection and extraction evaluated with our Phase I prototypes. The capacity of the anther harvester exceeds the Phase I metrics for volume and efficiency of anther collection of 600 spikes/min. Objective 3: Develop and prove an efficient method of liberating viable pollen grains from intact wheat anthers for subsequent conditioning and storage. Technical Metrics for Phase I: Collect 50% of viable pollen available in harvested anthers. Maintain pollen viability through spike collection, anther harvesting, and pollen extraction. Limit anther debris to 10% of pollen harvest. Specific Accomplishments: Task 1: Design and construct anther-pollen separator. In phase I, the wheat team successfully developed a novel disk mill to liberate intact viable pollen from the anthers isolated in Objective 2. The disk mill efficiently liberates pollen from anthers introduced in either a liquid or dry powder medium. As anthers enter the disk mill, parallel plates rotating in opposite directions shred the anthersvia frictional forces. Intact pollen is liberated into the surrounding liquid or powder medium, from which it can be transferred to storage or applied immediately in either system. Extracting pollen in a liquid matrix increased anther throughput, simplified pollen collection, and maintained pollen integrity and viability. Task 2: Separate viable pollen from anthers.Biological analysis of the pollen viability and fertility revealed dramatic changes during spike development. At Zadocks 61, most of the pollen is highly viable, but not capable of fertilization (di-nucleate). At Zadocks 65, most of the pollen is capable of fertilization (tri-nucleate), but much lower in viability. The later fact confirmed our earlier observation that pollen released from dehiscing anthers is typically very low in viability. We determined collecting pollen from anthers between stages Z61-65 was a practical compromise for commercial scale mechanical collection. Task 3: Quantify fraction of total production of pollen per plant collected. On average, about 1100 pollen grains were liberated from each shredded anther. This is more than 70% of the pollen typically produced by commercial wheat anthers. This mechanical procedure for collecting pollen from anthers is nearly 10X more efficient than collecting pollen from naturally dehiscing anthers, which provide only about ~150 grains per collection. Task 4: Quantify impact of mechanical isolation on pollen viability and vigor.Microscopic analysis and in-vitro tests confirmed the percentage of pollen grains physically damaged or ruptured during disk mill extraction was not significantly different from that of pollen naturally released from anthers. In summary, in Phase I we met or exceeded all metrics for success developing prototype mechanical systems to collect large volumes of wheat anthers rapidly and efficiently without sacrificing pollen integrity and viability relative to naturally shed pollen. The proprietary liquid matrix developed to extract pollen, preserve, and apply wheat pollen derived from anthers greatly facilitates scaling under commercial field conditions in Phase II.
Publications
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