Screening On Resistance Variety Of Luohanguo To Meloidogyne Incognita And Preliminary Explore On The Resistance Mechanism

Mature females, males, juveniles and eggs of root-knot nematode were isolated fromthe infected roots and rhizosphere of Luohanguo (Siraitia grosvenorii) which colletedfrom Louzhou, Guilin, Nanning of Guangxi. Two species were identified as Meloidogyneincognita and Meloidogyne javanica based on morphological characters, M. incognitawas the dominant specie.Condition optimization assay for inoculation of M. incognita on host Luohanguowere conducted at greenhouse. Results indicated that the optimal quantity of M.incognita was 1000 second-stage juveniles (J2)/plant, or 1000 eggs/plant, or 2000 mLinfected soil/plant(contained 41 J2 in 100 mL soil), the optimal inoculation period wassix-leaf stage of Luohanguo seedling, the optimal monthly mean temperature for diseaseinfection was 25.5～30.5℃.12 Luohanguo varieties were evaluated on resistance to M. incognita in the field. 11varieties were moderate varietie and 1 variety was slightly susceptibility to M. incognita;21 Luohanguo varieties were evaluated on resistance to M. incognita at greenhouse, 5varieties were moderate resistance, 10 varieties were slightly susceptibility and 6varieties were moderate susceptibility to M. incognita.POD activity of Luohanguo after inoculation of M. incognita was determined. PODactivity of susceptible variety Yeshengqingpiguo was increased by 4.22 unit, PODactivity of resistant variety Yeshenghongmaoguo was increased by 11.17 unit, PODactivity of resistant variety Changtanguo was increased by 25.17 unit. Results indicatedthat POD activity of resistant variety increased more than that of susceptible variety.Effects of root exudates of Luohanguo on eggs hatch of M. incognita weredeterminated by experiment in vitro. On fourth day after treatment of root exudates, mean eggs hatching quantity was 37.3, 24.3, and 11.7 for variety cd-7 (with moderatesusceptibility), variety Yeshenghongmaoguo (with moderate resistance), and distilledwater respectively. Hatching peak of the eggs was on 6th day, 8th day, and 8th day aftertreatment of root exudates for variety cd-7, variety Yeshenghongmaoguo, and distilledwater respectively. Results indicated that root exudates enhanced the eggs hatch indifferent degree.