Physiological And Biochemical Characteristics Of Masson Pine Clone Pre- And Post-inoculation With Bursaphelenchus Xylophilus

Masson pine(Pinus massoniana)is one of the main timber species in the southern China.Due to its strong adaptability,easy propagation,rapid growth and wide distribution,Masson pine is an important economic species.In recent years,however,the invasion of pine wood nematode caused a lot of Masson pine trees died off.Bursaphelenchus xylophilus is one of the most dangerous invasive species in China,which can cause pine wilt disease(PWD).The PWD is the fatal disease of pine forests.Studies on PWD at home and abroad are mostly concentrated in Bursaphelenchus xylophilus and mucronatus species identification,life history,host,pine wood nematode insect vectors,transmission,pathogenesis,prevention and treatment measures,but so far few studies has been conducted on which is an effective method to protect this pine wilt disease.This study focusd on the PWD-resistent Masson Pine Clones selected by the Forestry Research Institute of Anhui Province.Based on the different resistent clones,we conducted once more inoculation experiment to reveal the differences in physiological and biochemical characteristics amongst these clones before and after the inoculation and analyze their correlation with the resistance of Masson pine.The results obtained are as follows.(1)The net photosynthetic rate(Pn),stomatal conductance,and transpiration rate(Tr)of needles of the different PWD-resistent Masson pine clones showed a bipeak pattern before inoculation(in July)with an obvious "noon-break" phenomenon.The main controlling factors are photosynthetically active radiation and relative air humidity.After inoculation,the diurnal patterns of above-mentioed parameters showed monopeak in September and November.Intercellular CO2 concentrations were generally decreased at first and then increased both before and after inoculation.(2)The light saturation point and light compensation point were higher before inoculation than after inoculation for the different PWD-resistent Masson pine clones,indicating a strong adaptability to high light intensity for this pine species with great photosynthetic potential in summer.(3)The effects of inoculation of pine wood nematode on chlorophyll content was not significant.However,the contents of chlorophyll a and ratio of chlorophyll a to b were significant different among the different PWD-resistent clones.The changes of chlorophyll fluorescence parameters such as Fo,Fo'/Fm' and ETR were significant differences among the different PWD-resistent clones after inoculation.This suggests that pine wood nematode inoculation had a significant impact on the initial fluorescence,effec tive photochemical quantum yield and electron transfer rate.The three parameters can be used as physiological indices for evaluating whether the tree infected wood nematode.(4)There were significant differences in proline contents of needles among the different PWD-resistent clones,with the highest content in the mid-resistent clone and lowest in the low-resistent clone.The inoculation had a significant effect on the proline content.(5)The activities of SOD and POD were not significant difference between the different resistent clones,while the activity of CAT was significantly different.This result indicated that the inoculation had significant effect on the activities of SOD and POD.