Several studies were carried out to determine (i) thermal requirements for development, egg production and emergence of juveniles, and completion of the life cycle of Meloidogyne incognita and Meloidogyne javanica on cucumber, (ii) the maximum multiplication rate and the equilibrium density of root-knot nematodes on cucumber and yield losses in pot and plastic greenhouse experiments, and (iii) the relationships between relative leaf chlorophyll content (RLCC) and relative cucumber dry top weight biomass (RDTWB) in relation to increasing nematode densities at planting (P-i) in pot experiments. Thermal requirements of M.incognita and M.javanica on cucumber did not differ, irrespective of the biological stage. In the pot experiments, M.javanica completed one generation. The maximum multiplication rate (a) was 833, and the equilibrium density (E) varied according to the effective inoculum densities. The relationship between RDTWB and P-i fitted the Seinhorst damage function model. The RLCC value at 40 or 50days post-inoculation also fitted the damage model and was related to RDTWB. In greenhouse experiments, conducted from 2009 to 2012, M.incognita completed three generations. The values for a and E were 1147 and 625second stage juveniles (J2) per 250cm(3) soil, respectively. The tolerance limit was below zero, and the minimum relative yield ranged from 012 to 034.Postprint (published version

The present research was undertaken to evaluate the effects of soil temperature on the life cycle of root-knot nematodes (RKN) on zucchini-squash in growth chambers and to assess the relationship between Meloidogyne incognita soil population densities at planting (Pi), its multiplication rate, and crop losses of zucchini in field conditions. Thermal requirements for M. incognita and M. javanica were determined by cultivating zucchini plants in pots inoculated with 200 second stage juveniles (J2) of each Meloidogyne species at constant temperatures of 17, 21, 25, and 28 A degrees C. Number of days from nematode inoculation until appearance of egg laying females and until egg hatching were separately recorded. For life cycle completion, base temperatures (Tb) of 12 A(0)C and 10.8 A(0)C and accumulated degree-days above Tb (S) of 456 and 526, were estimated for M. incognita and M. javanica, respectively. The relationship between fruit weight and M. incognita Pi fits the Seinhorst damage function, but differed accordingly to the cropping season, spring or autumn. Tolerance limits for M. incognita on zucchini were 8.1 J2 per 250 cm(3) of soil in spring and 1.5 in autumn cropping cycles, and the minimum relative yields were 0.61 in spring and 0.69 in autumn. Zucchini-squash was a poorer host for M. incognita in spring than in autumn, since maximum multiplication rates (a) and equilibrium densities (E) were lower in spring (a = 16-96; E = 274-484) than in autumn (a = 270-2307; E = 787-1227).Postprint (published version

The relationship between the initial (P i ) and final (P f ) population densities of Meloidogyne javanica and yield of watermelon, Citrullus lanatus, cv. Sugar Baby were determined in pot and field experiments. In the pots, the maximum reproduction rate of the nematode was 14, and the equilibrium density was 49 400 eggs/100 cm 3 of soil. Yield data represented as fresh top weight fitted the Seinhorst damage function (P < 0.001, R 2 = 0.7), and the minimum relative yield (m) was 0.65 at P i ≥ 3200 eggs/100 cm 3 of soil and the tolerance limit (T) 74 eggs/100 cm 3 . In the field experiments (2011 and 2012), the maximum reproduction rate was 73 and 70, and the equilibrium density 32 and 35 second-stage juveniles (J2)/100 cm 3 soil. Yield data represented as fruit weight fitted the Seinhorst damage function in 2011 (P < 0.001, R 2 = 0.92) and the mand T-values were 0.63 and 20 J2/100 cm 3 of soil, respectively. Meloidogyne incognita and M. javanica needed similar length of time for development to egg-laying females and life cycle completion at 24.4 ∘ C.

Pot experiments were carried out to characterize the response of two Cucumis metuliferus accessions (BGV11135 and BGV10762) against Mi1.2 gene (a)virulent Meloidogyne arenaria, M. incognita and M. javanica isolates and to determine the compatibility and the effect on physicochemical properties of fruit melons. In addition, histopathological studies were conducted. One week after transplanting, plants were inoculated with one J2 cm−3 of sterilized sand (200 cm3 pots) and maintained in a growth chamber at 25 °C for 40 days. The susceptible cucumber cv. Dasher II or melon cv. Paloma were included for comparison. The number of egg masses and number of eggs per plant were assessed, and the reproduction index (RI) was calculated as the percentage of eggs produced on the C. metuliferus accessions compared to those produced on the susceptible cultivars. The compatibility and fruit quality were assessed by grafting three scions, two of Charentais type and one of type piel de sapo, under commercial greenhouse conditions. The resistance level of both C. metuliferus accessions ranged from highly resistant (RI < 1%) to resistant (1% ≤ RI ≤ 10%) irrespective of Meloidogyne isolates. Melon plants grafted onto C. metuliferus accession BGV11135 grew as self‐grafted plants without negatively impacting fruit quality traits. Giant cells induced by Meloidogyne spp. on C. metuliferus were in general poorly developed compared to those on cucumber. Furthermore, necrotic areas surrounding the nematode were observed. Cucumis metuliferus accession BGV11135 could be a promising melon rootstock to manage Meloidogyne spp., irrespective of their Mi1.2 (a)virulence, without melon fruit quality reduction.

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 < 0Á05) 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 < 0Á05) 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.