The tolerance of Pennisetum americanum (L.) K Schum (P. americanum) to the herbicide atrazine, as well as the atrazine accumulation in exposed plants, was investigated in this study. The germination of P. americanum seeds was not significantly inhibited by exposure to atrazine at concentrations below 100 mg.L-1. The roots of the seedlings were much more sensitive to atrazine than the shoots were, as shown by observations that shoot and root elongation were significantly inhibited by treatment with 100 and 50 mg.kg(-1) of atrazine, respectively. In addition, significant differences were found in the dry weights of the seedling shoots and roots after exposure to 50 and 20 mg.kg(-1 )of atrazine, respectively. Atrazine accumulated readily in the roots of exposed seedlings, and the root ultrastructure was visibly damaged by exposure to lower levels of atrazine compared to the ultrastructure of the shoot. The contents of chlorophyll a and chlorophyll b and the transcription of psbA were inhibited by exposure to atrazine at concentrations above 20 mg.kg(-1). Finally, the tolerance threshold of P. americanum to atrazine was about 20 mg.kg(-1), indicating that the test plant exhibited some atrazine tolerance.

Calcium (Ca) has been reported to lessen oxidative damages in plants by upregulating the activities of antioxidant enzymes. However, atrazine mediated reactive oxygen species (ROS) reduction by Ca is limited. This study therefore investigated the effect of exogenously applied Ca on ROS, antioxidants activity and gene transcripts, the D1 protein (psbA gene), and chlorophyll contents in Pennisetum seedlings pre-treated with atrazine. Atrazine toxicity increased ROS production and enzyme activities (ascorbate peroxidase APX, peroxidase POD, Superoxide dismutase SOD, glutathione-S-transferase GST); but decreased antioxidants (APX, POD, and Cu/Zn SOD) and psbA gene transcripts. Atrazine also decreased the chlorophyll contents, but increased chlorophyll (a/b) ratio. Contrarily, Ca application to atrazine pre-treated seedlings lowered the harmful effects of atrazine by reducing ROS levels, but enhancing the accumulation of total chlorophyll contents. Ca-protected seedlings in the presence of atrazine manifested reduced APX and POD activity, whereas SOD and GST activity was further increased with Ca application. Antioxidant gene transcripts that were down-regulated by atrazine toxicity were up-regulated with the application of Ca. Calcium application also resulted in up-regulation of the D1 protein. In conclusion, ability of calcium to reverse atrazine-induced oxidative damage and calcium regulatory role on GST in Pennisetum was presented.

The change of lignin content in wild soybeans inoculated with P. sojae was studied in this paper. The results showed that there was no significant difference between the resistant and susceptible wild soybeans in the content of the lignin before inoculated with P. sojae. The lignin content in stems of resistant wild soybeans increased compared with the control at most of the pathogenicity stages,and the increase rate was also higher than that of susceptible soybean varieties. The lignin content of resistant and susceptible wild soybeans decreased compared with the control at most of the pathogenicity stages in leaves.

Pathogenesis-related(PR)proteins were originally discovered to accumulate in plants that were infected by pathogens,but were later found to accumulate in plants in response to a variety of biotic and abiotic stresses.PR proteins were the most crucial component of plant defense responses.Currently,PR proteins have been classified into 17 families on the basis of structural differences,serological relationships and biological activity.PR10 proteins are typically described as small,acidic,intracellular proteins of 15-19 kDa.Many PR10 proteins including CaPR10,LaPR10,SPE16,AhPR10,pea PR10.1,and maize ZmPR10 exhibit ribonuclease activity.The RNase activity of PR10 proteins suggests a potential role in defenses against pathogenic infections.Some studies showed PR10 proteins played important roles in plant defense system,having widespread applied prospect.The genetic structures of PR10s,expression patterns,ribonuclease activities,resistance mechanism and the application in transgenic plants were reviewed to provide a basis for disease resistant breeding.

Phytophthora root and stem rot caused by Phytophthora sojae is a world wide destructive soybean disease,it may attack plants at any growth stage,causing root and stem rot.The principle of POD activity changes in roots,stems and leaves of soybean varieties with different resistance to Phytophthora sojae and the effect of POD on resistance to this disease were researched.The results showed that the POD activities of leaves in resistant soybean varieties increased compared with the susceptible soybean varieties at most of the pathogenicity stages,and it was also higher than that of control.The reaction of POD in roots and stems increased at most of the pathogenicity stages,however,the change extent was relatively low.

Phytophthora root and stem rot of soybean [Glycine max(L.) Merril] caused by Phytophthora sojae Kaufmann & Gerdemann is a destructive disease which can harm soybean in any growth period.Polyphenol is an important composition of phytoalexin and it has closely relation with plant resistance.The change of total polyphenol content in wild soyeban inoculated with P.sojae was preliminarily studied in this paper.The results showed that total polyphenol activity in roots,stems,and leaves of both resistant and susceptible wild soybean materials were increased compared with those of control at most stages of pathogenetic process.Overall,the variation of total polyphenol in resistant wild soybean(30%,55%,-40%,-100%) was higher than susceptible ones(20%,35%,50%,90%).

The ultrastructures of hypocotyls of resistant and susceptible wild soybeans infected with zoospores of Phytophthora sojae from 3 to 72 h after inoculation were observed using transmission electron microscopy in this paper.The results showed that the cell structures of the susceptible wild soybean were seriously destroyed with the inoculation time from 3 to 36 h,but those of the resistant one were almost intact.The sediments on the cell wall of the resistant soybean could be seen at 48 h after inoculation,but no sediments could be seen for the susceptible one and its cell wall began to degrade to some extent.Although there was plasmolysis at 72 h after inoculation,the cell structures were almost intact for the resistant wild soybean.However,there were nearly no intact cell structures for the susceptible ones.The results could provide theoretical basis on cytology for clarification of pathogenic mechanism of P.sojae to wild soybeans.

Phytophthora root and stem rot caused by Phytophthora sojae is a destructive disease in soybean production regions all around the world.Some protective enzymes begin to be active when soybean is infected by P.sojae.Of the enzymes,phenylalanine ammonia-lyase(PAL)is a key and rate-limiting enzyme in phenyl propane metabolize pathway which could produce kinds of antimicrobial products.There is abundant wild soybean in China,but there are few reports on the relationship about PAL and resistance of wild soybean to P.sojae.In this paper,4 resistant wild soybeans and 4 susceptible wild soybeans were inoculated with zoospores of P.sojae race 1 as treatment and those inoculated with water as control.The PAL activity in roots,stems,and leaves were measured after inoculation of 0,12,24,36,48,60,and 72 h in the treatment and control respectively.The results indicated that the PAL activity in roots and stems of resistant wild soybeans was higher than that of the control at most of the stages of pathogenetic process,but was lower than that of control for susceptible wild soybean.The change range of PAL activity in leaves of both susceptible and resistant wild soybeans were relatively low compared with that of control.

Phytophthora root and stem rot of soybean(Phytophthora sojae) is one of destructive diseases endangering soybean production,but there have been few reports on gene expression after inoculated with pathogen.In this study,SSH cDNA library of resistance soybean variety Suinong 10 inoculated with race 1 of P.sojae was constructed successfully,and 2 067 positive clones were screened.The length of most of the insert fragments was focused on 100-800 bp.375 functional ESTs have been gotten,and they dealt with the effect of inhibition pathogen growth,cell self-protection,signal transduction,system acquired resistance,protein synthesis and respiration,etc.after compared with sequences in unigene database of GeneBank with BLASTn and BLASTx algorithm.

Change of phenylalanine ammonia-lyase (PAL) activities among different resistance soybean varieties treated with pathotoxin from Phytophthora sojae was preliminarily studied in this paper.The results showed that the optimum concentration of pathotoxin (0.0897mg/mL) led to higher PAL activities in resistant varieties than those of control variety during most stages of disease processing.Contrarily,susceptible varieties were possessed of medium high levels of PAL activities with a rapid declination only during few limited stages of the disease processing.However,treatment with high concentration of pathotoxin (0.1794mg/mL) caused low levels of PAL activities in both resistance varieties and susceptible ones compared with treatment of the optimum concentration.

The roots of different soybean varieties with different concentration pathotoxin were treated to study the effect of pathotoxin on the cell ultrastructure of soybean root.The results showed that the inner structure of the root cells of both resistant and susceptible varieties were destroyed apparently when they were treated with high concentration(0.1794 mg·mL-1) pathotoxin.However,when they were treated with the optimum concentration(0.0897 mg·mL-1),the inner structures of resistant varieties were mainly complete,but the susceptible varieties were changed largely and their mitochondria were mainly destroyed.It was concluded that only treated with the optimum concentration of pathotoxin could distinguish soybean varieties between resistant and susceptible to Phytophthora sojae.The research lays a fundation for revealing the pathologic and antitoxin mechanism on the cell level.

60 strains of Phytophthora sojae have been isolated from 262 infected plants collected from Jiansanjiang Farm,Jiamusi,Heihe,Jixi,Shuangyashan,Binxian,Shuangcheng,Acheng,Bayan,Ningan,Hailun,Suihua,Baoqing,Yanshou in Heilongjiang Province.Race1,3,5 and 17 have been identified.The total number of virulence types was 16,and there are 12 intermediate virulence types among them,which showed that these strains were very complex in virulence.60% of all collected plants were infected by race 1 which appeares as the dominant race in Heilongjiang Province.Race 15 was reported for the first time in China.

Phytophthora root and stem rot caused by Phytophthora sojae is a destructive disease in soybean production regions all around the world.Utilization of resistant variety is the most economical and environmentally safe method for controlling the disease,and it is the basement for resistance breeding.536 soybean germplasms(including 280 native soybean varieties)from Heilongjiang,Jilin,Henan,Liaoning,Hubei,Sichuan,Hebei,Shannxi,Chinese Academy of Agricultural Sciences were inoculated with race 1 of Phytophthora sojae,which is the superiority race in Heilongjiang Province.The results showed the resistant,intermediate and susceptible ones were 152,135 and 249,and accounted for 28.3%,25.2% and 46.5%,respectively.Among the 280 native soybean varieties,eighty-nine(accounted for 32%)were resistant.The results suggest that native soybean varieties are more resistant to Phytophthora sojae,and there is more resistance germplasm in soybean with yellow hilum or brown seed coat.

Phytophthora root rot caused by P.sojae was a destructive disease in soybean production regions all around the world.Utilization of resistant varieties was the most economical and environmentally safe method for controlling the disease.And it was base in fastness resource filtration.415 wild soybean accessions from 19 province in China were identified for their reaction to race 1 of P.sojae from Heilongjiang and using the hypocotyls inoculation technique.The results indicated that there were 96 lines resistant to Phytophthora sojae,and 152 lines intermediate responsed to P.sojae and 167 susceptible to P.sojae.Their proportion was 23.1%,36.6% and 40.2% respectively among the tested lines.The results indicated that the distribution of wild soybeans resistant to race 1 of Phytophthora was extensive in China.

The internal transcribed spacer (ITS) region (ITS1, ITS2 and 5.8S rDNA) of the nuclear ribosomal DNA (nrDNA) was amplified via the PCR method in seventeen different isolates of Phytophthora sojae using the common primers of the ITS of fungi. Around 800 bp-1,000 bp fragments were obtained based on the DL2000 marker and the sequences of the PCR products were tested. Taking isolate USA as outgroup, the phylogenetic tree was constructed by means of maximum parsimony analysis, and the genetic evolution among isolates was analyzed. The results showed that there is a great difference between the base constitution of ITS1 and ITS2 among various isolates. The seventeen isolates are classified into three groups, and the isolates from the same region belong to the same group, which shows the variation in geography.