Differential reproduction of Meloidogyne incognita and M. javanica in watermelon cultivars and cucurbit rootstocks

The suitability of watermelon cultivars and cucurbit rootstocks as hosts to Meloidogyne incognita and M. javanica was determined in pot and field experiments. Meloidogyne incognita showed higher reproduction than did M. javanica on watermelon and cucurbit rootstocks. The watermelon cultivars did not differ in host status when challenged with these two species and supported lower nematode reproduction than the cucurbit rootstocks. Rootstocks Lagenaria siceraria cv. Pelops and Cucurbita pepo AK15 supported lower reproduction than did the squash hybrid rootstocks (C. maxima 9 C. moschata). Egg production increased (P < 0.05) with a rising initial inoculum level (Pi) in the non-grafted Sugar Baby but the reproduction factor Rf (eggs per plant/Pi) was similar at two Pi levels. The total egg production in the plants grafted onto squash hybrids RS841 and Titan was greater (P < 0.05) at the higher Pi, but the Rf values were lower. The development of field-grown non-grafted watermelon plants was significantly stunted in plots where nematodes were detected at planting. However, no differences were observed in plots with grafted plants. In plots with nematodes, non-grafted and Titan-grafted plants had similar yields that were higher than that of RS841-grafted plants. In the commercial plastic houses with grafted watermelon, the average Rf value was 42-fold, confirming the high susceptibility of squash hybrids as rootstocks for grafted watermelon. The Titan-Sugar Baby combination was tolerant to M. javanica.