The role of salicylic acid (SA) was investigated in basal defence and induced resistance to powdery mildew ( Oidium neolycopersici ) and grey mould ( Botrytis cinerea ) in tomato ( Lycopersicon esculentum ) and tobacco ( Nicotiana tabacum ). A comparison of NahG transgenic tomato and tobacco (unable to accumulate SA) to their respective wild types revealed that in tomato, SA was not involved in basal defence against O. neolycopersici but NahG tobacco showed an enhanced susceptibility to O. neolycopersici infection, the effect becoming more obvious as the plants grew older. In contrast, SA played no role in the basal defence of tobacco against B. cinerea , but seemed to contribute to basal defence of tomato against B. cinerea. Activation of the SA-dependent defence pathway via benzothiadiazole (BTH) resulted in induced resistance against O. neolycopersici in tobacco but not in tomato. Microscopic analysis revealed that BTH treatment could prevent penetration of the Oidium germ tube through tobacco leaves, whereas penetration was successful on tomato leaves irrespective of BTH treatment. In contrast, soil or leaf treatment with BTH induced resistance against B. cinerea in tomato but not in tobacco. It is concluded that the SA-dependent defence pathway is effective against different pathogens in tomato and tobacco. 相似文献
AIM: To investigate a possible interaction between lolitrem B and ergovaline by comparing the incidence and severity of ryegrass staggers in sheep grazing ryegrass (Lolium perenne) containing lolitrem B or ryegrass containing both lolitrem B and ergovaline.
METHODS: Ninety lambs, aged approximately 6 months, were grazed on plots of perennial ryegrass infected with either AR98 endophyte (containing lolitrem B), standard endophyte (containing lolitrem B and ergovaline) or no endophyte, for up to 42 days from 2 February 2010. Ten lambs were grazed on three replicate plots per cultivar. Herbage samples were collected for alkaloid analysis and lambs were scored for ryegrass staggers (scores from 0–5) weekly during the study. Any animal which was scored ≥4 was removed from the study.
RESULTS: Concentrations of lolitrem B did not differ between AR98 and standard endophyte-infected pastures during the study period (p=0.26), and ergovaline was present only in standard endophyte pastures. Ryegrass staggers was observed in sheep grazing both the AR98 and standard endophyte plots, with median scores increasing in the third week of the study. Prior to the end of the 42-day grazing period, 22 and 17 animals were removed from the standard endophyte and AR98 plots, respectively, because their staggers scores were ≥4. The cumulative probability of lambs having scores ≥4 did not differ between animals grazing the two pasture types (p=0.41).
CONCLUSIONS AND CLINICAL RELEVANCE: There was no evidence for ergovaline increasing the severity of ryegrass staggers induced by lolitrem B. In situations where the severity of ryegrass staggers appears to be greater than that predicted on the basis of concentrations of lolitrem B, the presence of other tremorgenic alkaloids should be investigated. 相似文献
Under Mediterranean conditions, drought affects cereals production principally through a limitation of grain filling. In this study, the respective role of post‐anthesis photosynthesis and carbon remobilization and the contribution of flag leaf, stem, chaff and awns to grain filling were evaluated under Mediterranean conditions in durum wheat (Triticum turgidum var. durum) cultivars. For the purpose, we examined the effects of shading and excision of different parts of the plant and compared carbon isotope discrimination (Δ) in dry matter of flag leaf, stem, chaff, awns and grain at maturity and in sap of stem, flag leaf, chaff and awns, this last measurement providing information on photosynthesis during a short period preceding sampling. Source–sink manipulations and isotopic imprints of different organs on final isotope composition of the grain confirmed the high contribution of both carbons assimilated by ears and remobilized from stems to grain filling, and the relatively low contribution of leaves to grain filling. Grain Δ was highly and significantly associated with grain yield across treatments, suggesting the utilization of this trait as an indicator of source–sink manipulations effects on grain yield. Chaff and awns Δ were better correlated with grain Δ than stem and leaf Δ, indicating that chaff were more involved in grain filling than other organs. Moreover, in chaff, sap Δ was highly significantly correlated with dry matter Δ. These results suggest the use of Δ for a rapid and non‐destructive estimation of the variation in the contribution of different organs to grain filling. 相似文献