利用12C6+重离子辐射和尖孢镰刀菌毒素筛选杂交兰抗茎腐病突变体

为创建抗茎腐病杂交兰资源,本研究以玉女兰类原球茎为材料,采用¹²C⁶⁺重离子辐射技术结合尖孢镰刀菌(Fusarium oxysporum)粗毒素筛选抗茎腐病突变体。结果表明,经不同剂量¹²C⁶⁺重离子辐射后,玉女兰类原球茎的死亡率差异显著,辐射剂量为50 Gy时,死亡率为54.66%;尖孢镰刀菌粗毒素对玉女兰类原球茎存活率影响显著,当粗毒素滤液浓度为80%时,玉女兰类原球茎存活率为41.98%。采用逐步筛选法对经50 Gy¹²C⁶⁺辐射后的玉女兰类原球茎进行抗茎腐病筛选,获得14个抗性系类原球茎,筛选率为4.67%;对抗性系类原球茎进行分化、生根壮苗和移栽,获得3个抗性系Z50Gt₁、Z50Gt₂和Z50Gt₃。在含80%粗毒素滤液的培养基上抗性系类原球茎的超氧化物歧化酶(SOD)和过氧化物酶(POD)的活性均高于对照,POD活性峰值比对照提高了867.67 U·g^-1·h^-1;丙二醛(MDA)含量呈现先高于对照,随着毒素胁迫时间的延长,转变为低于对照的趋势。对3个抗性系试管苗和小苗进行人工接种鉴定,结果表明,抗性系Z50Gt₂和Z50Gt₃的再生植株具有稳定的茎腐病抗性,2个抗病株系7个月大的盆栽植株病情指数分别为20.00%和19.33%,均为抗性级别。本研究结果为采用重离子辐射技术选育抗茎腐病杂交兰新品种奠定了基础。

Screening Mutants Resistant to Stem Rot Using 12C6+Heavy Ion Beam Irradiation and Crude Toxin of Fusarium oxysporum in Hybrid Cymbidium

In order to create germplasm resources resistant to stem rot in hybrid Cymbidium, protocorm-like bodies (PLBs) of Cymbidium Yunv were employed to establish the method of screening the mutants resistant to stem rot using heavy ion beam irradiation and crude toxin leachate of Fusarium oxysporum. The results showed that the mortality rates of PLBs irradiated by various irradiation dosage of ¹²C⁶⁺heavy ion beam were significantly different, and the mortality rate was 54.32% when the irradiation dosage was 50 Gy. Crude toxin leachate of Fusarium oxysporum had significant inhibitory effect on survival rate of PLBs in Cym. Yunv, and the survival rate was 41.98% when the concentration of crude toxin leachate was 80%. After the PLBs of Cym. Yunv were irradiated by ¹²C⁶⁺heavy ion beam with 50 Gy, 14 lines resistant to stem rot were obtained by stepwise selection method with the screening rate being 4.67%, and eventually, three lines, Z50Gt₁, Z50Gt₂ and Z50Gt₃, were gained after differentiation, rooting and strong seedling culture, and transplanting in turn. The activity of SOD and POD in PLBs of resistant lines was higher than that of in control, and the peak value of the POD increased by 826.67 U·g^-1·h^-1compared with the control, while the content of MDA in PLBs of resistant lines was higher within 36 h and lower after that compared to the control. The test-tube seedlings of Z50Gt₂ and Z50Gt₃ showed the resistance to stem rot by artificial inoculation, and the disease indices of seven-month-old pot plants of the two lines were significantly lower than that of control, and the resistant level reached resistant rank. The results laid a foundation of creating new cultivars with resistance to stem rot by heavy iron beam irradiation breeding in hybrid Cymbidium.