Temperature Effects on Development of Meloidogyne enterolobii and M. floridensis

Meloidogyne enterolobii and M. floridensis are virulent species that can overcome root-knot nematode resistance in economically important crops. Our objectives were to determine the effects of temperature on the infectivity of second-stage juveniles (J2) of these two species and determine differences in duration and thermal-time requirements (degree-days [DD]) to complete their developmental cycle. Florida isolates of M. enterolobii and M. floridensis were compared to M. incognita race 3. Tomato cv. BHN 589 seedlings following inoculation were placed in growth chambers set at constant temperatures of 25 degrees C, and 30 degrees C, and alternating temperatures of 30 degrees C to 25 degrees C (day-night). Root infection by the three nematode species was higher at 30 degrees C than at 25 degrees C, and intermediate at 30 degrees C to 25 degrees C, with 33%, 15%, and 24% infection rates, respectively. There was no difference, however, in the percentages of J2 that infected roots among species at each temperature. Developmental time from infective J2 to reproductive stage for the three species was shorter at 30 degrees C than at 25 degrees C, and 30 degrees C to 25 degrees C. The shortest time and DD to egg production for the three species were 13 days after inoculation (DAI) and 285.7 DD, respectively. During the experimental timeframe of 29 d, a single generation was completed at 30 degrees C for all three species, whereas only M. floridensis completed a generation at 30 degrees C to 25 degrees C. The number of days and accumulated DD for completing the life cycle (from J2 to J2) were 23 d and 506.9 DD for M. enterolobii, and 25 d and 552.3 DD for M. floridensis and M. incognita, respectively. Exposure to lower (25 degrees C) and intermediate temperatures (30 degrees C to 25 degrees C) decreased root penetration and slowed the developmental cycle of M. enterolobii and M. floridensis compared with 30 degrees C.