Table 2. Structures and ages of LTR-retrotransposons identified in orthologous regions of indica and japonica.

Structures of LTR-retrotransposons	Number of LTR-retrotransposons	Age,* mya
		Range	Average
Present in indica only
Solo LTR	9
Intact element	4	0.12-0.31	0.22
Present in japonica only
Solo LTR	8
Intact element	7	0.00-0.31	0.16
Present in indica and japonica†
Solo LTR	13 and 12
Intact element	1 and 2	0.69-2.04	1.37

^*Ages of LTR-retrotransposons were estimated by employing a substitution rate of 1.3 × 10^-8 mutations per site per year.

^†Thirteen and 12 of 14 conserved LTR-retrotransposons between indica and japonica have undergone unequal homologous recombination, respectively.