REACTION OF 10 CULTIVARS OF WATERMELON (CITRULLUS-LANATUS) TO A PUERTO-RICAN POPULATION OF MELOIDOGYNE-INCOGNITA

Ten cultivars of watermelon were evaluated for their response to a Pue rto Rican population of Meloidogyne incognita under greenhouse conditi ons in a 2-year study (1989 and 1990). Ten-day-old seedlings were plan ted in steam-sterilized soil in 15-cm-d plastic pots. The nematode ino culum consisted of 10,000 eggs and (or) second-stage juveniles (J2)/pl ant. The cultivars were Sugar Baby, Charleston Gray, Seedless, Prince Charles, Charleston 76, Jubilee, Florida Giant, Royal Charleston, Roya l Sweet, and Royal Jubilee, with tomato cv. Rutgers included as a susc eptible check. A completely randomized design with 10 replications was used. Fifty-five days after soil infestation, root-gall indices, numb ers of nematode eggs per root system, and J2 per 250 cm(3) of soil wer e recorded. All cultivars were susceptible. Sugar Baby had the lowest root-gall index, egg and J2 numbers, and a reproductive factor (Rf) of 2.89. Rf differed (P less than or equal to 0.05) among cultivars and ranged up to 7.36. Sugar Baby, Seedless, and Florida Giant showed the lowest susceptibility to M. incognita, whereas Charleston 76 and Charl eston Gray were the most susceptible.