ارزیابی عکس ‌العمل 14 رقم توتون نسبت به نماتد ریشه‌گرهی Meloidogyne javanica در شرایط گلخانه

Root- knot nematodes (Meloidogyne spp.) limit the cultivation of various crops including tobacco. Due to the biological hazards resulting from the use of nematicides, today the cultivation of resistant hosts has been considered as one of the safest and most efficient methods in the management of root- knot nematodes. In this study, we evaluated the reaction of 14 tobacco cultivars including Ch-Mutant, Harison Special, Mac nair 944, Coker 176, Tirtash 19, Bel 61-10, Virginia E1, Coker 48, S-392-36, Tl33, Speight 626, Vega 2, Hicks 55 and Virginia 115 to root- knot nematode, M. javanica, with 3000 second stage juveniles (2J2s/g soil) in the pots with 9 cm diameter and 1.5 kg of sterile soil (equal proportions of soil, sand and vermiculite) in 5 replicates in a completely randomized design for 90 days in the greenhouse at 28°C and 50% relative humidity. Eventually, after separating the plants from soil the nematode reproductive indices such as the number of galls and egg masses/g root and total root, eggs/egg mass, eggs/root, J2s /soil and final nematode population were calculated. The means were compared based on LSD and they were analyzed by using Minitab 17 software. In this study, two evaluation systems were used to determine the level of resistance, one system was based on the reproduction index (RI) and the other was based on the gall index (GI) and reproduction factor (RF). The results showed that all cultivars are very susceptible based on RI. However, based on another evaluation system, it was determined that all cultivars (with RF>1 and GI>2) are susceptible to root-knot nematode. Comparisons of the average of the nematode reproductive traits showed that Virginia E1, Speight 626, Bel 61-10 and Virginia 115 cultivars with the highest number of galls, egg masses, eggs, J2/soil and consequently the highest nematode population had higher sensitivity to root-knot nematode than other cultivars. Also, other cultivars with lower population were at a similar level. Totally, the results of this study demonstrated that none of the cultivars had enough resistance to root-knot nematode, M. javanica.