A mutual titer-enhancing relationship and similar localization patterns between Citrus exocortis viroid and Hop stunt viroid co-infecting two citrus cultivars

Table 1 Significance of correlation coefficients for titers of Citrus exocortis viroid (CEVd) and Hop stunt viroid (HSVd) in four tissues of two citrus cultivars from the field and greenhouse

Correlation coefficients
		CEVd and HSVd
Numbers of citrus plants	Tissues	Nonparametric methods^a
17 citrus plants	All	++^b
7 citrus plants^d	All	++
11 Blood oranges	Roots	-^c
	Rootstock bark	++
	Twig bark	-
	Leaves	++
6 Murcott mandarins	Roots	++
	Rootstock bark	++
	Twig bark	-
	Leaves	-
Double infections^e	Roots	++
	Rootstock bark	++
	Twig bark	++
	Leaves	++
12 citrus plants^f (Sets in greenhouse)	All	++

^aThree nonparametric methods are Spearman’s nonparametric correlation coefficient, Kendall tau rank correlation coefficient and Hoeffding’s inequality
^bcorrelation coefficients marked with “++” are statistically significant by all three methods; those marked with “+” are statistically significant by two of three methods
^cindicates no significant difference
^dThere were no underdetermined values in this data set including 3 Blood oranges and 4 Murcott mandarins
^eincludes 5 Blood oranges and 4 Murcott mandarins
^fArtificially double inoculated plants include 6 Blood oranges and 6 Murcott mandarins