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By using ITS - nrDNA-RELP, ITS sequencing, and RAPD molecular marker, this paper studied the genetic diversity of 11 isolates in 5 races of Melampsora larici-populina from different regions. The results indicated that the genetic differentiation of M. larici-populina was correlated to its geographical distribution, which could be grouped into northern and western geographic populations, and the latter could be grouped into high-mountain forest ecologic type (HMF) and western plain ecologic type (WPL). The genetic differentiation of the race was not always corresponded with the pathogenic one. T test manifested that the genetic diversity of the 5 races had no statistic difference in RAPD markers, and the diversity index of HMF was 0.5172, being slightly higher than that of WPL (0.5089). The ITS sequence of ribosome DNA was strictly conservative, and not suitable for the genetic diversity study of M. larici-populina intra-species populations.

This paper studied the effect of insect pest on the activities of protective enzymes SOD and CAT and the contents of H2O2 and O2*- in lanceolate leaves of Populus euphratica under different soil water conditions. The results showed that soil water deficiency did not increase SOD and CAT activities and H2O2 and O2*- contents in lanceolate leaves, but under this condition, insect pest increased them. When soil water was abundance, insect pest couldn't increase the activities of SOD and CAT and the contents of H2O2 and O2*- in lanceolate leaves. It's concluded that insect pest had an important role in death of Populus euphratica under soil water deficiency.

The study showed that the insect-resistance of transgenic hybrid poplar 741 was closely related with temperature. The total mortality and accumulative mortality of Gypsy moth (Lmantriadispar L.) larvae increased with increasing temperature, and the sensitivity of larvae to the clones of transgenic hybrid poplar 741 and temperature decreased gradually with the increasing instars. Temperature had a promotion to the development of larvae fed on CK. When the temperature was high, the development of larvae quickened, the development period shortened, and the weight increasing rate and the frass increasing quantity quickened, but the development rate of larvae fed on transgenic hybrid poplar 741 was not obvious with varied temperature. The regressive equation of temperature and Clostera anachoreta (Fabricius) mortality during 1998-2000 year indicated that high resistant and medium resistant clones' temperature-insect mortality curve presented an obvious regressive relation.