Field Distribution And Biological Characteristics Of Two Species Of Wheat Cereal Cyst Nematode In Henan Province

Cereal Cyst Nematode（CCN）is one of the most serious disease on wheat，happened in the world and got spreading widely in China. By the present, there’s noeffective measure for controlling this disease. The comprehensive understanding of itsbiological characteristics is the basis of the management of CCN and also the hot spotof research at home and abroad. Because of the differences in the adaptability of CCNin different area, the biological characteristics, including the field distribution,hatching and infection time and the generations are different from each other. In thisstudy, the horizontal and vertical distribution, infection dynamics and the factorsrelated the hatching of the two species of CCN，Heterodera avenae and Heteroderafilipjevi in Henan province were studied, and the results are as follows:The investigation on vertical distribution of the two species of CCN found thatthe number of the cysts tend to increase first and decrease later with the increasementof soil depth，most cysts exist in the soil with the depth from5to30cm．with theincrease of soil depth under30cm，the number of cysts and average eggs in per cystdecreased dramatically．The investigation on horizontal distribution of the two species of CCN found thatcysts exist in every investigation plots，but the quantity in each unit varied with eachother，some reach to38in100mL soil，and some less than5．It is apparent that thewhole field is infected completely．A study has been conducted under field conditions on the infection dynamics ofthe two species of cereal cyst nematode，H．avenae and H．filipjevi．The resultindicates that the wheat roots were infected by the second stage juveniles two weeksafter planting，and the first infection peak of the second stage juveniles comes6weeksafter the planting，at the same time a few of the fourth stage juveniles appear．With thetemperature gets lower after planting60days in the winter，the number of the larva ofdifferent stages remains stable．120days after planting，with the temperature rising inthe spring，the number of the second stage juveniles starts to increase and reaches to the second peak in the late March and early April，but the number of juveniles whichinvade the wheat roots in the second peak is apparently less than the first one．Afterthat the larva gradually developed into white females and cysts．The infectiondynamics of two CCN species is approximately same，but the third stage，fourth stageof the larva and the white female of the H．filipjevi appear one week early thanH．avenae．These results provide the important theoretical basis for the control ofcereal cyst nematode of wheat．In order to ascert the influence of the temperature on the hatching of the twospecies of the CCN，a indoor study is conducted on the cyst collected in the field ofXuchang and Xingyang in the middle of August．The results show that larva ofh．avenae can emerge under5°C，10°C，15°C，20°C and25°C，the larva of H．filipjevian emerge under5°C，10°C and15°C，but it can be hardly found under20°C and25°C．the larva start to emerge about20days later．The hatching peak come about50-60days after the first day．There are more larvas of H．filipjevi than that ofH．avenae during the early days．Obviously，the two species have hatching peak under10°C and15°C and the period of hatching can last around75days，there is not thepeak under5°C，and the period of hatching can reach to100days．The largest amountof larva can emerge under15°C．the number of the larva in the cyst of H. avenae canreach to200under5°C，10°C and15°C，while for the H．filipjevi，it is close to150under5°C，10°C and15°C．Changing the temperature can increase the number of the larva dramatically，andthe hatching rate is above83%．Put the cysts in the water under5°C for some times，then transfer them to thecondition under15°C，the peak of the hatching can come early，and the hatchingquantity increased obviously，the larva can emerge during a short term，and the theincubation period become shorter．Put the cysts which were collected in different time in the incubator under15°C，it can be found that the hatching quantity and the rate is not the same，the hatchingrate of the H．avenae which is collected in june is just4%，and for H．filipjevi，it is22%．the hatching rate increase if the cysts were collected in july. August andSeptember are the best time for cyst sampling with the larger hatching rate．The hatching of the cysts under15°C is observed when they have been in therefrigerator for different weeks，the results show that the time in the condition under4°C have little impact on the hatching rate of the two species of cysts，the rate can remain above50%even the cysts were conserved in the refrigerator for more than24weeks．While，the hatching peak comes a little early．...