No abstract

Transfer of resistance toHeterodera avenae, the cereal cyst nematode (CCN), by a "stepping-stone" procedure from the wild grassAegilops ventricosa to hexaploid wheat has been demonstrated. The number of nematodes per plant was lower, and reached a plateau much earlier, in the resistant introgression line H93-8 (1-2 nematodes per plant) than in the recipient H10-15 wheat (14-16 nematodes per plant). Necrosis (hypersensitive reaction) near the nematode, little cell fusion, and few, often degraded syncytia were observed in infested H93-8 roots, while abundant, well-formed syncytia were present in the susceptible H10-15 wheat. Line H93-8 was highly resistant to the two Spanish populations tested, as well as the four French races (Fr1-Fr4), and the British pathotype Hall, but was susceptible to the Swedish pathotypes HgI and HgIII. Resistance was inherited as though determined by a single quasi-dominant factor in the F2 generations resulting from crosses of H93-8 with H10-15 and with Loros, a resistant wheat carrying the geneCre1 (syn.Ccn1). The resistance gene in H93-8 (Cre2 orCcn2) is not allelic with respect to that in Loros. RFLPs and other markers, together with the cytogenetical evidence, indicate that theCre2 gene has been integrated into a wheat chromosome without affecting its meiotic pairing ability. Introduction ofCre2 by backcrossing into a commercial wheat backgroud increases grain yield when under challenge by the nematode and is not detrimental in the absence of infestation.

Summary• The response of the resistant wheat / Aegilops ventricosa introgression line, H-93-8, to a Spanish population of the cereal cyst nematode, Heterodera avenae , was studied in order to determine changes in gene expression correlated with resistance.• Roots of susceptible ( Triticum aestivum cv. Anza) and resistant wheat seedlings were analysed using histological (electron microscopy), cytochemical (at tissue and cytological level) and biochemical (isoelectrofocusing) techniques.• Infection of resistant wheat lines with H. avenae resulted in a hypersensitive reaction, with syncytial cells deteriorating in a few days. Following nematode infection, peroxidase, esterase and superoxide dismutase activities were increased in H-93-8 roots compared with the susceptible wheat. Syncytial cells in roots of resistant lines were highly reactive to diaminobenzidine and homovanillic acid oxidase, the latter associated with plasma and nuclear membranes and vacuoles. The same syncytial cells showed early positive reaction to phloroglucinol, indicating lignification.• The Cre2 resistance gene in H-93-8 inhibited reproduction of H. avenae. Peroxidases, esterases and superoxide dismutase might represent products of genes whose expression is correlated with the resistance response to this nematode.

Several preparations were obtained from the aerial parts of predomesticated Lavandula luisieri, including the essential oil and ethanolic, hexane, and ethyl acetate extractives. Additionally, pilot plant vapor pressure extraction was carried out at a pressure range of 0.5-1.0 bar to give a vapor pressure oil and an aqueous residue. A chemical study of the hexane extract led to the isolation of six necrodane derivatives (1, 2, and 4-7), with four of these (1, 2, 5, and 7) being new, as well as camphor, a cadinane sesquiterpene (9), tormentic acid, and ursolic acid. The EtOAc and EtOH extracts contained a mixture of phenolic compounds with rosmarinic acid being the major component. Workup of the aqueous residue resulted in the isolation of the necrodane 3 and (1R*,2S*,4R*)-p-menth-5-ene-1,2,8-triol (8), both new natural compounds. The structures of the new compounds were established based on their spectroscopic data. The phytotoxic and nematicidal activities of these compounds were evaluated.