Resistance genes in response to root-knot nematode (Meloidogyne javanica) infection suppress one or more of several critical steps in nematode parasitism and their reproduction rate. The reaction of seven commercial tomato genotypes to M. javanica infection was investigated under greenhouse conditions. Current results classified these genotypes as: three resistant (Jampakt, Malika and Nema Guard), one moderately resistant (Fayrouz), and three susceptible (Castle Rock, Super Marmande and Super Strain B). Except Nema Guard, nematode infection significantly reduced plant height, fresh and dry weights of shoots of the other tomato genotypes. Leaf area was significantly reduced for all examined tomato genotypes except Malika and Nema Guard. Total chlorophyll was reduced in all tested tomato genotypes except Jampakt. Infection parameters of M. javanica and their population were significantly reduced on all nematode-resistant tomato genotypes compared to the susceptible genotypes. Also, the maturation rate of M. javanica was suppressed in the resistant genotypes compared to the susceptible genotypes. These results were confirmed by histological study that illustrated a delay in nematode development and their maturation. Total phenolic content significantly increased in nematode infected roots of both resistant and susceptible genotypes except Malika. Among non-infected roots, Malika showed the highest level of total phenols while after M. javanica infection, Nema Guard revealed the highest level of total phenols. Among infected roots, the highest level of total phenols was recorded in Castle Rock. These results suggested that using nematode-resistant tomato genotypes could provide an efficient and nonpolluting method to control root-knot nematodes.

Hylocereus undatus flower is commonly used as food or for medicinal purposes in south China. To study its antioxidant activity and mechanism we used antioxidant and chemical assays to compare two commercial samples from different locations (Shenjing, Qixing). The difference in antioxidant levels corresponded with differences in chemical content (including total phenolics, total flavonoids, kaempferol and quercetin) between Shenjing and Qixing. The antioxidant ability of H. undatus flower seems attributable to total phenolics (mainly total flavonoids). Kaempferol is one of the main bioactive components. H. undatus flower exerts its antioxidant effects through metal chelation and radical scavenging via hydrogen atom (H•) and electron (e) donation.