Study Occurrence, Damage, And Control Of Cereal Cyst Nematode On Wheat And Barley In Qinghai

Cereal cyst nematode (CCN) is a new disease on wheat and barley in Qinghai Province.In past years, this disease was ignored for symptom similar to that of other wheat foliardiseases at the early stage in Qinghai. However, in decade years, CCN has been spreadextensively to thirteen wheat-producing provinces, and caused high yield loss in China sincethe occurrence of CCN was firstly reported in Hubei in1989. Therefore, the objective of thisstudy were (1) to investigate pathogenic species, distribution of CCN on wheat and barley,and yield loss of wheat and barley caused by CCN,(2) to screen wheat and barley cultivarsresistant to CCN, and (3) to acquire approaches to control CCN in Qinghai province in orderto provide technical support to solve the problem of the cereal cyst nematode influence thecrop safe production. The results as follows：1．64soil samples were collected from wheat and barley fields from21different regionsin Qinghai province, and were identified by using morphological and molecular biologymethods. The results showed that Heterodera avenae Wollen weber is main pathogenicspeices of CCN on wheat and barley in Qinghai, and Heterodera filipjevi was detected onlyone soil sample from Huangyuan county.2. Through investigations on CCN in1434wheat and barley fields in102villages andtowns,23counties belonging to7different regions in Qinghai province, the current status ofoccurrence, distribution of CCN on wheat and barley in Qinghai province were acquired. Theresults indicated that CCN on wheat and barley were commonly detected in21countiesbelonging to7different areas including Xining, the eastern Qinghai, Haibeizhou, Hainanzhou,Haixizhou, Huanghaizhou, Yushuzhou. Number of serious CCN-infected regions accounts for19.05percent in total of investigated ones, the moderates accounts for66.67percent, and theslights accounts for14.28percent. Simultaneously, CCN were found in different altitudes,different ecological areas, and different soil types during the field investigations. Differenceof the population density of CCN occurred in different altitudes was insignificant, butsignificant in different ecological zones and soil types. At the same time, the fieldinvestigations also demonstrated that CCN mainly infected wheat and barley in soil with1-20 cm in depth underneath soil surface. The number of CCN in such a soil layer accounts for70-95.32percent in the total number of CCN.3. The relationship between population density of CCN and yield loss were determinedin greenhouse and field. The results showed that CCN influenced the root development toresult in root producing root nodes and branches, which can’t absorb water and nutrients fromsoil to cause reduction of agronomic characters, such as height, tillering, growth potential,spikelets,1000-grain weight, and yield. Based on our analyses, the losses of agronomiccharacteristic were not significant and the yield losses were less than ten percent whenpopulation density of CCN was less than (5±1.5) eggs/(g·soil). When the losses weresignificant and the yield losses were between15.52%and55.01%when the density of CCNwas more than (10±2) eggs/(g·soil). The yield loss was various under different cultivars, soils,cultivation and management conditions.4. The resistance level of144wheat and184barley germplasm resources were identifiedthrough field experiment, and indoor experiment using artificial inoculation. The resultssuggested that144wheat germplasm resources were susceptible to CCN, which showingremarkable difference of resistance to CCN. Of184tested barley germplasm to CCN, only6showing moderately resistant to CCN, which average number of CCN cysts on single plantroots was5.1-10.0.16were moderately susceptible to CCN with10.1-20.0CCN cysts onsingle plant roots. The other tested barley germplasm were highly susceptible with20.1-53.00CCN cysts on single plant roots on average.5. Efforts were made to test control effect to CCN by different crop rotations andfertilizers in four counties including Huangyuan, Huangzhong, Xunhua, and Hualong ofQinghai province. The results indicated that the wheat-potato, wheat-broad bean andwheat-rape rotation s can take good effect on controlling CCN. Compared with successivewheat field, the rate of CCN population densities in these fields was obviously decline up to45.41%～51.64%, and the yield was increased to18.84%～23.71%. There was no significantdifference between organic fertilizer-applied filed and chemical fertilizers-applied field.However, application of organic fertilizer can improve growth potential, and resistance tostress, and even can reduce yield loss of15.50-20.58percent.6. Based on tests of nematicides to CCN in field, a series of nematicides includingFosthiazate, Phosphorus, Aldicarb etc. were showed obvious control effect to CCN, whichreaches up to40-60%. However, these nematicides have negative influences to environmentand soil, such as strong toxicity, high residual, and high-cost. Therefore, the nematicides werehard for extensively application in fact. However, Seed-coating nematicide No.1developedby Gansu agricultural university, which has advantages of low-cost, low residual, and low dosage, was an ideal nematicide for manage of CCN with control effect of greater than70%.It should be feasible for controlling CCN by further development in the future.