Evaluating Pistachio Rootstock Tolerance to Phytophthora Root and Crown Rot

Area of Science:

• Plant Pathology
• Horticulture
• Agronomy

Background:

• Phytophthora root and crown rot is a significant disease affecting pistachio cultivation in California.
• The industry-standard UCBI rootstock exhibits high susceptibility to this disease.
• Sustainable management strategies are needed to mitigate disease impact on pistachio orchards.

Purpose of the Study:

• To evaluate the relative tolerance of three commercial pistachio rootstocks (UCBI, PGI, Platinum) to key Phytophthora species.
• To identify rootstock resistance levels against Phytophthora niederhauserii, P. mediterranea, and P. taxon walnut.

Main Methods:

• Conducted stem and soil inoculation experiments on UCBI, PGI, and Platinum rootstocks.
• Assessed lesion lengths, root loss percentage, and crown rot development to determine susceptibility.
• Utilized Phytophthora niederhauserii, P. mediterranea, and P. taxon walnut as causal agents.

Main Results:

• Platinum rootstock demonstrated significantly smaller lesion lengths and lower root loss compared to UCBI and PGI.
• UCBI and PGI rootstocks were confirmed highly susceptible to Phytophthora root and crown rot.
• Platinum exhibited minimal to no crown rot development across all experimental conditions.

Conclusions:

• Significant differences in rootstock tolerance to Phytophthora root and crown rot were observed.
• Platinum rootstocks offer enhanced resistance and are recommended for areas with Phytophthora infections.
• Findings support the adoption of Platinum rootstocks for sustainable pistachio management.