When citrus growers think about viruses and viroids, symptoms above ground — such as tree decline, leaf issues and poor fruit production — often receive the most attention. A new study shows that what happens below the soil surface may also provide important clues about how citrus rootstocks respond to these pathogens.
The study, “Root Traits Responses of Citrus Rootstocks to Virus and Viroid Graft-Induced Infection,” was published in HortScience. Marissa Gonzalez, Madhurababu Kunta, Mamoudou Sétamou, John da Graça and Joel Reyes-Cabrera from Texas A&M University-Kingsville conducted the study.
WHAT WAS EXAMINED
Researchers evaluated how different citrus rootstocks responded after being graft-inoculated with several important citrus pathogens, including citrus tristeza virus (CTV), citrus tatter leaf virus, citrus exocortis viroid and hop stunt viroid. The team focused on root characteristics because healthy roots are critical for water uptake, nutrient absorption and long-term tree performance.
The study examined three commercially important rootstocks: sour orange, trifoliate orange and US-942. Researchers collected root samples from trees about 2.5 years old and analyzed traits such as root length, diameter, surface area and root density.
KEY FINDINGS
One important finding was that virus and viroid infections did not cause major changes in most root traits measured. However, the pathogens did affect specific root length, a measurement that helps describe how efficiently a plant develops fine roots for resource capture.
The researchers found differences among rootstocks. US-942 produced strong root characteristics, including greater root length and root length density, while also showing tolerance to citrus tristeza virus. Sour orange had larger root diameter and greater root dry weight. Trifoliate orange generally showed lower values for several root measurements.
STUDY SIGNIFICANCE
For citrus growers, the findings highlight the importance of selecting rootstocks based not only on above-ground performance, but also on how root systems respond to disease pressure. A strong root system can help trees better withstand stress and maintain productivity over time.
The researchers say evaluating root traits during nursery production could become a useful tool for breeding programs and rootstock selection. Identifying rootstocks with desirable characteristics may help growers prepare for future disease challenges and reduce reliance on rootstocks that are vulnerable to certain pathogens.
This research adds valuable information about the relationship between root health and citrus disease response. As growers continue dealing with challenges such as HLB, CTV and other graft-transmitted pathogens, understanding rootstock performance will remain an important part of building resilient citrus production systems.
Read the full research article here.
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