【作者】 郭玉霞；

【导师】 南志标； 沈禹颖；

【作者基本信息】 甘肃农业大学 ， 草业科学， 2003， 硕士

【摘要】 本项目以甘肃庆阳黄土高原地区草田轮作系统中苜蓿和小麦为研究材料，在2002年整个生长季内，分别于拔节期(分枝期)、开花期、成熟期和幼苗期(第三茬分枝期)取样，分离、鉴定了两种作物的根部入侵真菌，实验室内测定了分离所得根部入侵真菌对其寄主作物及另一种作物的致病力，并探讨了施肥、休闲时期对根部入侵真菌的影响。结果表明： 在试验区内共分离到27种根部入侵真菌，包括自小麦根系分离到26种，苜蓿侧根分离到23种。其中22种为苜蓿和小麦共同的根部入侵真菌，包括：细交链孢(Alternaria alternata)、多主枝孢(Cladosporium herbarum)、柱孢(Cylindrocarpon destructuns)、锐顶镰孢(Fusarium acuminatum)、燕麦镰孢(F.avenaceum)、多隔镰孢(F.decemcellulare)、尖镰孢(F.oxysporum)、半裸镰孢(F.semitectum)、腐皮镰孢(F.solani)、镰刀菌(Fusarium sp.)、壳梭孢(Fusicoccum sp.)、胶帚霉(Gliocladium sp.)、粉红胶帚霉(G.roseum)、毛霉(Mucor sp.)、青霉(Penicillium sp.)、丝葚霉(Papulaspora sp.)、茎点霉(Phoma medicaginis)、丝核菌(Rhizoctonia sp.)、大孢肉座菌(Selinia sp.)、圆孢霉(Staphylotrichum sp.)、匐柄霉(Stemphylium botryosum)、轮枝菌(Verticillium sp.)。4种真菌仅从小麦根系上分离到，包括根腐离蠕孢(Bipolaris sorokiniana)、叶志菌(Melasmia sp.)、黑团孢(Periconia sp.)及疫霉(Phytophthora sp.)；1种仅从苜蓿上分离到，即蒲头霉(Mycotypha sp。)。 两种作物根部主要的入侵真菌种有明显的不同。苜蓿根部最主要的5种入侵真菌按分离率的高低依次为尖镰孢17.0％、大孢肉座菌15.4％、茎点霉9.5％、腐皮镰孢6.7％及柱孢6.6％；而小麦根部5种最主要的入侵真菌按分离率的高低依次为黑团孢15.0％、丝葚霉12.1％、多主枝孢5.4％、丝核菌4.0％及尖镰孢3.9％；总的真菌分离率亦是苜蓿高于小麦。 苜蓿与小麦的根段带菌率均有随生长季的延长而增高的特征。苜蓿春季分枝期的根段带菌率为49.1％，显著低于成熟期(p＜0.05)，而开花期、种子成熟期和第三茬再生草的分枝期的根段带菌率依次为70.3％、81.9％与76.3％，三者无显著差异(p>0.05)。 小麦春季拔节期、开花期与成熟期根段带菌率分别为43.1%、71.0%与94.8%，11月份当年播种的处于苗期的根段带菌率为30.9%，各生育期的根段带菌率均差异显著(p<0.05)o 在试验条件下，参试的首蓓、小麦根部入侵真菌对首蓓和小麦均有一定的致病力，但对首楷种子和幼苗的致病力强于对小麦种子和幼苗的致病力。 根据测定的各项指标一相对发芽率、烂种率、相对苗长、相对根长及病情指数的综合评定，自首蓓侧根分离到的大抱肉座菌、尖镰抱、腐皮镰抱、多隔镰抱、甸柄霉、多主枝抱、燕麦镰抱及茎点霉等对首蓓种子与幼苗致病力较强，烂种率为21.0%一32.0%，种子相对发芽率降低幅度达23.0%一57.0%，病情指数为63.8一89.5。而尖镰抱和旬柄霉对小麦幼苗致病性较强，病情指数分别为89.5和63.8，其中尖镰抱使小麦种子相对发芽率降低31.0%。 自小麦根部分离到的锐顶镰抱、尖镰抱、燕麦镰抱、一种腐皮镰抱、一种未定_名的镰刀菌、黑团饱及丝甚霉等对首楷种子与幼苗致病力较强，烂种率为2().0%一41.0%，种子相对发芽率降低幅度达8.0%一56.0%，病情指数为67.7一88.2。而镰刀菌和根腐离蠕饱对小麦幼苗致病性较强，病情指数分别为99.1和88.8，其中根腐离蠕抱使小麦种子相对发芽率降低11 .0%。更多还原

【Abstract】 Root-invading fungi of lucerne (Medicago saliva) and winter wheat (Triticum aestivum)were studied under the forage legume-cereals rotation systems in the Loess Plateau of eastern Gansu province, China. Roots of wheat and lucerne were sampled at spring jointing (spring branching) , flowering, maturity and seedling or regrowth stage in 2002. Fungi were isolated from lucerne rootlet and wheat root system. Pathogenicity of these root-invading fungi to lucerne and wheat were determined in the laboratory. In addition, effects of fertilizer and fallow period on root-invading fungi of wheat were investigated.The results showed that 27 fungal species were isolated and identified from the field plots. Of which 26 fungi were isolated from wheat root and 23 fungi isolated from lucerne rootlet. Among the fungi isolated 22 species were shared by lucerne and wheat. They were Altemaria alternata, Cladosporium herbarum, Cylindrocarpon destructiuns, Fusarium acuminatum, F. avenaceum, F. decent, F. oxysporum, F. semitectum, F. solan j, Fusarium sp., Fusicoccum aesculi, Giiocladium sp., G. roseun, Mucor sp., Penicillium sp., Papulaspora sp., Phoma medicagmis, Rhizoctonia sp., Selinia sp., Staphylotrichum sp., Stemphylium botryosum and Verticillium sp.. Four fungi including Bipolaris sorokiniana, Melasmia sp., Periconia sp. and Phytophthora sp. were only found in wheat root, whereas only one fungal species isolated from lucerne rootlet and not isolated from wheat i.e. Mycotypha sp.However, the major root-invading fungi in lucerne and wheat were differed. The most common fungal species from lucerne, in order of decrease frequency of isolation, were F. oxvsporum (17.0%), Selinia sp. (15.4%), P. medicaginis (9.5%), F. solani (6.7%) and Cy. Destructuns (6.6%). The five most common fungi isolated form wheat were Periconia sp.(l5.0%), Populospora sp. (12.1%), C. herbarum (5.4%), Rhizoctonia sp. (4.0%) and F. oxysporum (3.9%). The total percentage of fungal isolation obtained from lucerne was higher than mat from wheat.As lucerne growing from Spring to Autumn, the percentage of fungal isolation from rootlet were increased. The percentage of fungal isolation at early growth stage in Spring was 49.1%, which was significantly lower than that at maturity (p<0.05) . However, rootlet inviading fungi incidence of lucerne at flowering, maturity and at regrowth stage after 3rd cut was 70.3%, 8J.9% and 76.3%, respectively. There were no significantly differences among these percentages (p>0.05) .Incidence of fungal isolation from wheat at jointing, flowering and maturity was 43.1%, 71.0% and 94.8%, respectively, And was 30.9% at seedling stage in Autumn after sowing. All of these were differed significantly between one and another (p<0.05).The pathogenicity test results showed that all the fungi tested under the laboratory conditions had pathogenic effects to lucerne and wheat in some extent. In general, all the fungi tested have more severe pathogenicity to seed and seedling of lucerne than to that of wheat.Accorging to integrated accessment of measurement including relative germination, decayed seed percentage, relative shoot length, relative root length and disease index, fungi isolated from lucerne rootlet including Selinia sp., F. oxysporum, F. solani, F. decem, S. botrysum, C. herbarum, F. avenaceum and P. medicaginis were pathogenic to lucerne seed and seedling. Compared to the no inoculated control, decayed seed percentages in inoculated treatments were 21.0%~32.0%,relative germination was decreased by 23.0%~57.0%, disease index was 63.8?9.5. Whereasonly F. oxysporum and Stemphylium botrysum showed pathogenicity to wheat seedling, disease index was 89.5 and 63.8, respectively. The relative germination was decreased by 31.0% by F. oxysporum.Fungi isolated from wheat including F. acuminatum, F. oxysporum, F. avenaceum, F. solani, Fusarium sp., Periconia sp. and Papulospora sp. showed pathogenicity to seed and seedling of lucerne. Compared to the no inoculated control, the inoculation treatements had 20.0%~4更多还原