TABLE 1.

Infectivity of chimeric TYMV genomes and symptom appearance in Chinese cabbage plants^a

TYMC genome	Properties of cloned progenitor genomeb		Properties of plant-adapted progeny virusc				Properties of cloned progeny genomesd
	Time to initial symptoms in plants (dpi)	Infectivity: no. symptomatic/ no. inoculated	Vein clearing (dpi)	Chlorotic spots, mosaic (dpi)	Mature symptoms (dpi)	Infectivity: no. symptomatic/ no. inoculated	Vein clearing (dpi)	Chlorotic spots, mosaic (dpi)	Mature symptoms (dpi)	Infectivity: no. symptomatic/ no. inoculated
WT	7–8	6/6					8.6	10.6	15.1	12/12
WT			7.7	9.1	14.4	12/12
-TYV	43	1/6
-XXe			7.9	8.6	15.1	10/10
-XX1f							9.1	10.9	16.4	10/10
-TYV-BP	45	1/6
-YYe			8.9	10.1	16.0	13/13
-YY1g							10.3	12.0	18.5	6/6
-YY1/U6150h							9.1	10.6	18.1	6/6
-ELV	18–61	5/6
-Hi			8.7	10.3	15.3	10/10
-H1j							9.1	10.6	15.4	10/10
-EMVk	16–31	2/5
-El			9.2	ND	ND	15/15
-Metm	14	2/5
-Mn			8	ND	ND	10/10

^aSymptom appearance in noninoculated leaves. Note that at early times of symptom appearance, symptom intensity was less for all chimeric genomes than for TYMC. WT, wild type. ND, not done. 

^bData taken from references 9 and 18 for initial cloned chimeric or mutant constructs. dpi, days postinfection. 

^cProperties of virus sequentially passaged until high infectivity was attained (all inoculated plants visibly infected within 2 days of symptom appearance on plants inoculated with the wild type) except TYMC (progeny of TYMC transcripts, amplified in Chinese cabbage); inoculations with 1 μg of virus. 

^dProperties of cloned chimeric TYMC genomes reconstructed by incorporating 3′ mutations identified in plant-adapted viral RNAs; inoculations with 5 μg of 5′-capped genomic transcripts. Values are the averages for all the plants whose infectivities are reported in the rightmost column. 

^ePlant-adapted viruses (9). 

^fProduct of cloning the 3′ sequence of TYMC-XX RNA shown in Fig. 1 in place of the TYMV TLS; differs from TYMC-TYV RNA by the U98→C TLS mutation. 

^gProduct of cloning the 3′ sequence of TYMC-YY RNA shown in Fig. 1 in place of the TYMV TLS; differs from TYMC-TYV-BP RNA by the U88→C TLS mutation and the addition of C2. 

^hDiffers from TYMC-YY1 by inclusion of the C6150→U substitution present in TYMC-YY, a silent mutation in the coat protein coding region. 

ⁱPlant-adapted virus described in (9); note the presence of the previously missed additional mutation acquired in planta, C6→U, in the TLS. 

^jProduct of cloning the 3′-sequence of TYMC-H RNA shown in Fig. 1 in place of the TYMV TLS; differs from TYMC-ELV RNA by the C6→U TLS mutation and the deletion of a C adjacent to the 3′-A. 

^kThe sequence shown in Fig. 1 for the heterologous EMV-derived RNA has been corrected from that reported (18): the sequence joining the TYMV and EMV sequences is slightly different (5′-UAAUU and not 5′-UUAG as previously stated), and the native EMV U43 is present, not A43 as previously reported. The reported properties of TYMC-EMV RNA (18) are correct. 

^lPlant-adapted virus resulting from 6 sequential passages in Chinese cabbage, using sap inoculum for the first 4 passages and 5 μg of virus for the latter two; 5/5 infectivity was reached after 4 passages. No sequence changes were found in the EMV-derived TLS. 

^mPreviously named TYMC-U55/C54/A53(L1=UU) (7). 

ⁿPlant-adapted virus resulting from 2 sequential passages in Chinese cabbage, using sap inoculum; 5/5 infectivity was reached after first passage. No sequence changes were found in the 3′-untranslated region.