Submitted to: Phytopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/15/1999
Publication Date: 4/1/2000
Citation: Brown, K.J., Ostrow, K.M., Idris, A.M., Stenger, D.C. 2000. Chino del tomate virus:relationships to other geminivuruses and the identification of two a component loci that interact to modulate symptoms. Phytopathology. Interpretive Summary: Chino del tomate virus (CdTV) and tomato leaf crumple virus (TLCrV) are two geminiviruses isolated from tomatoes in the Sonoran Desert. Comparison of DNA sequences indicate that these two viruses are closely related strains of the same virus. Because CdTV was described first, TLCrV is designated here as the leaf crumple strain of CdTV (CdTV-LCr). While chino del tomate e(CdT) disease has been observed in tomato plantings since the 1970's, demonstration that a single virus could cause CdT disease was lacking. Through the analysis of full-length infectious clones of the CdTV DNA A and B components, we demonstrate that CdTV alone is sufficient to cause CdT disease. Minor nucleotide substitutions present in naturally occuring variants of CdTV DNA A have significant effects on the type and severity of symptoms produced in tomato. Inoculation of CdTV DNA A components bearing different combinations of nucleotide substitutions at two positions in the genome indicate that it is the interaction of symptom determinants encoded by the two CdTV A components that dictate the type of symptoms produced.
Technical Abstract: Phylogenetic and distance analyses place chino del tomate virus (CdTV) in the abutilon mosaic virus clade of New World begomoviruses, and indicate that CdTV and tomato leaf crumple virus (TLCrV) are closely related strains of the same virus. Because CdTV was described first, TLCrV is designated here as the leaf crumple strain of CdTV (CdTV-LCr). One CdTV A component (pCdTV-H6) was poorly infectious when inoculated to tomato with the B component (pCdTV-B52), and produced only mild leaf curling and veinal chlorosis. Another CdTV A component (pCdTV-H8) was highly infectious when coinoculated to tomato with the B component, and produced moderate leaf curling and veinal chlorosis very similar to that reported by others for TLCrV. Co-inoculation of both CdTV A components and the B component to tomato produced wild type chino del tomate (CdT) disease symptoms consisting of severe leaf curling, veinal chlorosis, and stunting. The two oCdTV A components were nearly identical, except at nucleotide (nt) positions 1722 and 2324. The polymorphism at nt 1722 resulted in a change at amino acid (aa) 261 of Rep. The second polymorphism at nt 2324 resulted in changes at Rep aa60 and AC4 aa10. Two chimeric A components constructed by reciprocal exchange of a fragment bearing the polymorphic site at nt 1722 were evaluated for symptom phenotype. One chimeric A component (pCdTV-H86) produced wild type CdT symptoms when co-inoculated to tomato with the B component. The reciprocal chimeric A component (pCdTV-H68), when co-inoculated to tomato with the B component, also produced severe leaf curling, veinal chlorosis, and stunting similar to wild type CdTV, but in addition induced novel chlorotic spots and interveinal chlorosis. The symptom determinant loci at nts 1722 and interact to modulate symptoms.