Genetic Variation of Paulownia Provenances Resistance against Paulownia witches'Broom

Paulownia witches'Broom is one of the most severe diseases affecting the growth of Paulownia trees. In P. tomentosa, the MLO occurs in all provenances except for those in Pingliang (Gansu), even heavily in Nanjing (Jiangsu), Shiyan and Huanggang (Hubei), Shang county (Shanxi) and Dalian (Liaoning), where disease index was over 30%. In P. fortuneii, the incidence of diseases was low, and MOL didn't occur in the southern provenances but was heavy in the north where distribution of P. fortuneii and P. tomentosa overlap. Provenance trails showed that MOL was generally severe in P. tomentosa, the severity tended to increase with the longitude of provenance origins from the western provenances to eastern provenances. Contrastingly, the MLO incidence in P. fortuneii was independent from the longitude of provenance origins, but significantly correlated with the latitude. The higher the latitude of provenance origin, the lower the incidence of diseases was and the smaller the infection index was. There were also significant differences in incidence of diseases and infection index among different Paulownia clones, so it is feasible to select clones with high resistance to the Paulownia witches 'Broom.