Location: Water Management and Conservation Research
Project Number: 2020-13660-009-011-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2024
End Date: Aug 31, 2026
Objective:
This proposal evaluates direct-seeded guayule, a shrub used to produce rubber, including new guayule germplasm, under various irrigation practices to optimize cut heights, irrigation levels, and temperature conditions for maximum rubber yield. Additionally, it aims to increase genetic diversity by integrating material from guayule's center of genetic diversity in Mexico. The study relates to CRIS 2020-21410-008-000D, Developing Biofuels and New Industrial Crops for Sustainable Semi-arid Agricultural Systems, Objective 1, Conduct research to identify alleles, candidate genes, and molecular markers for drought and/or heat tolerance of oilseed and biomass crops in semi-arid field conditions and determine association of abiotic stress tolerance with agronomic performance and biofuel traits such as biomass yield and conversion, by introducing high-performance germplasm and selecting stress-tolerant lines. The study is conducted at the University of Arizona Maricopa Agricultural Center.
The main objective is to determine the relationship between cut heights, temperature, and irrigation levels in the multiple harvest protocol for direct-seeded guayule, line AZ2, and select the best regrowers. This involves evaluating the impact of different cut heights and irrigation regimes on the regrowth and rubber production of guayule. Specific objectives are: (1) to cause guayule to make more rubber by removing previously synthesized rubber particles from physiological notice by the plants using severe, non-lethal water stress as a management tool; (2) to direct seed advanced lines of guayule not yet in the public domain and follow performance under different irrigation regimes for 2-3 years; (3) to increase the genetic diversity of guayule in the US with the goal of increasing rubber yield by screening plants established from seed legally collected from the Mexican center of diversity.
Approach:
To test multiple harvests of direct-seeded crops at different cut heights and times grown under different irrigation levels. The experiment will be conducted at the University of Arizona Maricopa Agricultural Center (MAC), Maricopa, Arizona in two fields: a 4-acre field and a 1.3-acre field. Guayule will be harvested at various heights (e.g., 4”, 8” and 12”) at monthly intervals while being irrigated at 50%, 80%, and 100% of their water requirements. Data on crop yield, regrowth rate, and biomass will be collected, and statistical analysis will be conducted to determine optimal conditions for vigorous regrowth. For the drought stress experiment, direct-seeded guayule will be subjected to drought stress to reduce bark water content by 50%, followed by rewatering at different levels (50% and, 80% and 100%) and allow the recovered plants to pass through the main rubber production season (winter 2024/25), and compared with plants in the control plots. Infrared spectroradiometric quantification models will be generated to measure bark water and rubber content, and latex and rubber quantities will be assessed post-dormancy in spring 2025. Advanced lines of guayule will be directly seeded and grown under varying irrigation regimes to evaluate their long-term performance over 2-3 years. 20,000 guayule seeds collected from Mexico under a CIQA agreement will be planted in a 1.3-acre field at MAC under optimal irrigation conditions. These plants will be selected based on vigorous growth and rapid latex and rubber accumulation using near-infrared spectroradiometry. The best performing plants from these different experiments and trials will be further propagated for genetic evaluation and performance testing.
