phloem necrosis meaning in Hindi

Owing to the " U . wallichiana " in its ancestry, young specimens of'Lobel'proved particularly susceptible to elm yellows ( phloem necrosis ) in trials in Italy.
The presence of " U . wallichiana " in the ancestry of poses the risk of susceptibility to elm yellows ( phloem necrosis ), which seriously damaged its Dutch stablemate'Lobel'used as a control in the Italian elm breeding programme.