象耳豆根结线虫对抗病番茄品种VFNT的致病性研究

 象耳豆根结线虫是近年在我国发现的一种扩散迅速、寄主广泛、致病性强的根结线虫。为探究象耳豆根结线虫的强致病性原因,本研究用象耳豆根结线虫和南方根结线虫分别接种抗线虫番茄品种VFNT和感病番茄品种Rutgers,30 d后象耳豆根结线虫对VFNT和Rutgers的累计侵入率分别为14.1%和19.2%、虫瘿率为62.5%和81.6%,而此时南方根结线虫累计侵入率为0%和18.8%、虫瘿率为0%和68.5%,象耳豆根结线虫的侵染力和致病力显著强于南方根结线虫;通过侵染抗病番茄品种VFNT的病理切片以及根尖侵染早期胼胝质、活性氧染色发现象耳豆根结线虫的侵染不会激活Mi-1基因诱导的特异性抗性,在侵染早期南方根结线虫引起的胼胝质沉积量在72 h最大,是象耳豆根结线虫的2.0倍;体外H₂O₂应激测试发现,H₂O₂浓度为10～80 μmol·L^-1象耳豆根结线虫对H₂O₂的耐受性显著强于南方根结线虫。象耳豆根结线虫具有强致病性的原因可能是:具有更强的侵染力和活性氧耐受力;侵染不会激活Mi-1基因诱导的特异性抗性且侵染引起的胼胝质的积累量较低。

Pathogenicity of Meloidogyne enterolobii on the resistant tomato variety VFNT

Meloidogyne enterolobii is a type of root-knot nematode, recently found in China. It is known to spread rapid, infecting a wide host range and has strong pathogenicity as well. In order to explore the pathogenicity of M. enterolobii, we used M. enterolobii and M. incognita to inoculate VFNT and Rutgers as nematode-resistant and susceptible tomato varieties, respectively. After 30 days, the cumulative invasion rates of VFNT and Rutgers by M. enterolobii were 14.1 % and 19.2 %, while the percentage of gall was 62.5 % and 81.6 %, respectively. At the same time, the cumulative invasion rates of M. incognita to VFNT and Rutgers were 0 and 18.8 %, while the percentage of gall was 0 and 64.5 %, respectively. These results indicated that the infection and pathogenicity of M. enterolobii were remarkably stronger than that of M. incognita. Through the root tissue staining and pathological section of the resistant VFNT as well as the early callose and reactive oxygen species staining of the infected root tip, it was revealed that the specific resistance induced by Mi-1 gene was not activated by the infection of the M. enterolobii. Furthermore, at the early stage of infection, the amount of callosum deposition caused by M. incognita infection was the largest at 72 h, which was 2.0 times that of M. enterolobii infection. In addition, in vitro H₂O₂ stress test displayed that M. enterolobii was more tolerant to H₂O₂ with the 10-80 μmol·L^-1 concentration range than M. incognita. The results of the study indicated that the strong pathogenicity of M. enterolobii might be attributed to its stronger infectivity and tolerance to reactive oxygen species. Additionally, its infection does not activate the specific resistance induced by Mi-1 gene and causes a lower accumulation of callose.