New strategies for the control of plant-parasitic nematodes

The Hs1(pro-1) locus confers resistance to the beet cyst nematode (Heterodera schachtii Schmidt), a major pest in the cultivation of sugar beet (Beta vulgaris L.). The Hs1(pro-1) gene was cloned with the use of genome-specific satellite markers and chromosomal break-point analysis. Expression of the corresponding complementary DNA in a susceptible sugar beet conferred resistance to infection with the beet cyst nematode. The native Hs1(pro-1) gene, expressed in roots, encodes a 282-amino acid protein with imperfect leucine-rich repeats and a putative membrane-spanning segment, features similar to those of disease resistance genes previously cloned from higher plants.

ABSTRACT Nematicidal activity of essential oils extracted from 27 spices and aromatic plants were evaluated in vitro and in pot experiments. Twelve of the twenty-seven essential oils immobilized more than 80% of juveniles of the root-knot nematode Meloidogyne javanica at a concentration of 1,000 mul/liter. At this concentration, most of these oils also inhibited nematode hatching. Essential oils of Carum carvi, Foeniculum vulgare, Mentha rotundifolia, and Mentha spicata showed the highest nematicidal activity among the in vitro tested oils. These oils and those from Origanum vulgare, O. syriacum, and Coridothymus capitatus mixed in sandy soil at concentrations of 100 and 200 mg/kg reduced the root galling of cucumber seedlings in pot experiments. The main components of these essential oils were tested for their nematicidal activity. Carvacrol, t-anethole, thymol, and (+)-carvone immobilized the juveniles and inhibited hatching at >125 mul/liter in vitro. Most of these components mixed in sandy soil at concentrations of 75 and 150 mg/kg reduced root galling of cucumber seedlings. In 3-liter pot experiments, nematicidal activity of the essential oils and their components was confirmed at 200 and 150 mg/kg, respectively. The results suggest that the essential oils and their main components may serve as nematicides.