南方根瘤線蟲複合感染對番茄青枯病病徵表現及土壤中病原族群消長之影響

Abstract

以供試之責枯病感病蕃茄品種農友301號及抗病品種臺中亞蔬四號，分別接種不同濃度的青枯病菌，不論先接種南方根瘤線蟲後接種胃枯病菌 (N+B)、先接種青枯病菌後接種南方根瘤線蟲 (B+N)、單獨接種南方根瘤線蟲 (N)、或兩者同時接種 (N+B) 等處理，其根瘤指數 (galling index) 與單獨接種根瘤線蟲處理比較均無明顯差異。而在青枯病發病程度方面，則當有南方根瘤線蟲存在時，不論抗或感病番茄品種其均有使發病程度提高的現象。 而以不同濃度南方根瘤線蟲 [500、1000 、500、及 10000 隻二齡幼蟲 (second juvenile, J2)]， 依上述不同的接種次序處理接種青枯病抗感病番茄品種時，則發現其不僅根瘤指數隨著接種濃度的增加而提高，青枯病發病指數也隨著南方根瘤線蟲接種濃度的提高而升高。 以 1000 隻南方根瘤線蟲二齡幼蟲及 IX10 �� cfu/g dry soil 青枯病菌菌量為接種濃度， 接種後分別於第 0、14、28、42、56 、及 70 天調查植株根圈附近青枯病菌與南方根瘤線蟲族群之消長，結果顯示單獨接種南方根瘤線蟲的處理 (N)，土壤中所含之線蟲數較同時接種兩種病原 (NB) 的處理為多，而每克土壤所含之細菌菌量則以兩病原同時接種的處理 (NB) 較單獨接種青枯病菌的處理 (B) 為多。由上述複合感染過程中南方根瘤線蟲與青枯病原細菌族群變化及病徵表現關係，顯示南方根瘤線蟲之為害不但對青枯病菌於蕃茄作物之為害其有明顯之協力作用 (synergism)，且可明顯降低抗病品種對青枯病之抗病性，而青枯病之為害則對南方根瘤線蟲之為害並無顯著之影響。 Bacterial wilt-susceptible and -resistant tomato cultivars were inoculated with the southern root knot nematode (Meloidogyne incognita, second juvenile stage, 1,000/pot) and different concentrations of Ralstonia solanacearum . No significant difference in galling index of the plants was observed among treatments. On the contrary, the disease index increased consistently with the inoculation of M. incognita for both tomato cultivars. In the second experiment, inoculation with different concentrations of M. incognita (500, 1,000, 5,000, and 10,000 per pot) along with R. solanacemm (10 �� cfu/g dry soil) resulted in increased disease and galling indexes of the tomato cultivars with increased inoculation concentrations of the nematode. Investigation of the nematode and pathogen populations in the rhizosphere was conducted at 0, 14, 24, 42, 56 and 70 days after the inoculation of 1,000 M. incognita per pot and R. solanacenim (105 cfu/g dry soil). The nematode population was lower for the complex-inoculation treatments as compared to that for treatment inoculated only with the nematode; whereas the bacterial population was higher for the complex-inoculation treatments. The results indicated the synergistic effect of the nematode on the bacterial wilt disease, and hence increased the susceptibility of the disease-resistance cultivar to R. solanacenim. On the other hand, the presence of R. solanacenim exhibited no significant effect on the infection of the nematode in the tomato plants.