Hi I know from a file that Havana#501 is the first Havana variant how have Resistante against "wildfire" and it's a Cross between T.L#106 and Havana#211(comes up 1966), Havana#503 is a cross between Havana#501 and Burley#21.. I have from the start of my hobby growing of tobacco Havana#503B in my garden.. My question is wat means whit the B after Havana 503 one my tobacco??