Trees that are selected will be further screened for tolerance in two different ways, via chemical fingerprinting and directly through controlled inoculations.
Bydd coed sy'n cael eu dewis yn cael eu sgrinio ymhellach ar gyfer goddefiant mewn dwy ffordd wahanol, drwy olion bysedd cemegol ac yn uniongyrchol drwy inocwleiddiadau a reolir.