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ARS Home » Pacific West Area » Parlier, California » San Joaquin Valley Agricultural Sciences Center » Crop Diseases, Pests and Genetics Research » Research » Publications at this Location » Publication #422371
Research Project: Identifying Vulnerabilities in Vector-host-pathogen Interactions of Grapevine and Citrus Pathosystems to Advance Sustainable Management Strategies

Location: Crop Diseases, Pests and Genetics Research

Title: A T30 genotype of CTV causes quick decline of citrus on sour orange rootstocks in California

Author
item Yokomi, Raymond
item HAJERI, SUBHAS - Alliance Of Pest Control Districts
item HARPER, SCOTT - Washington State University
item Sun, Yongduo

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/23/2025
Publication Date: 3/16/2025
Citation: Yokomi, R.K., Hajeri, S., Harper, S., Sun, Y. 2025. A T30 genotype of CTV causes quick decline of citrus on sour orange rootstocks in California. Meeting Abstract. Presented at the International Organization of Citrus Virologist XX111 Conference in Mildura, Victoria, Australia from March 16-20, 2025.

Interpretive Summary:

Technical Abstract: Citrus tristeza virus (CTV)- induced Quick Decline (QD) of citrus has been the foremost challenge for citrus production on sour orange rootstock early century. In the 1930s-50s in southern California, the CTV-QD epidemic forced the industry to move to Central California and switch to CTV-tolerant rootstocks such as trifoliate and its hybrid rootstocks. T36 is a well-studied genotype of CTV, and it was reported to induce QD in Florida. However, despite several decades of CTV surveys in California, T36 was never detected in QD trees. In recent years, next-generation sequencing (NGS) streamlined deciphering full-length genome sequences. Over the past three years, 19 QD samples representing five properties in Tulare County were subjected to broad-spectrum and MCA13 ELISA and strain-specific RT-qPCR. Fourteen samples from QD trees were subjected to NGS. After removing host sequences, 16.8M reads were obtained, and de-novo assembly resulted in 13K contigs of 100bp or longer. With direct mapping of small RNAs against the representative sequences of the CTV genotypes, we obtained complete genome coverage for T30 (T385) alone, while the coverage for other genotypes was scattered across 3’ genes but not enough coverage to reconstruct the complete genome. QD-sampled trees typically exhibited classic CTV-QD symptoms of budunion necrosis with some honeycomb pitting on the sour rootstock. Therefore, we conclude that our T30 strain (Accession PQ603092 not released yet) obtained from dying QD trees causes CTV-QD in California. Further examination of biological stresses along with molecular studies are needed to determine which gene sequences are involved in QD induction by generating hybrid infectious CTV clones with gene knockouts or substitutions and examining the phenotype of inoculated sweet orange on sour orange rootstock.