Quantitative resistance affects the speed of frequency increase but not the diversity of the virulence alleles overcoming a major resistance gene to Leptosphaeria maculans in oilseed rape.

Quantitative resistance mediated by multiple genetic factors has been shown to increase the potential for durability of major resistance genes. This was demonstrated in the Leptosphaeria maculans/Brassica napus pathosystem in a 5year recurrent selection field experiment on lines harboring the qualitative resistance gene Rlm6 combined or not with quantitative resistance. The quantitative resistance limited the size of the virulent isolate population. In this study we continued this recurrent selection experiment in the same way to examine whether the pathogen population could adapt and render the major gene ineffective in the longer term. The cultivars Eurol, with a susceptible background, and Darmor, with quantitative resistance, were used. We confirmed that the combination of qualitative and quantitative resistance is an effective approach for controlling the pathogen epidemics over time. This combination did not prevent isolates virulent against the major gene from amplifying in the long term but the quantitative resistance significantly delayed for 5years the loss of effectiveness of the qualitative resistance and disease severity was maintained at a low level on the genotype with both types of resistance after the fungus population had adapted to the major gene. We also showed that diversity of AvrLm6 virulence alleles was comparable in isolates recovered after the recurrent selection on lines carrying either the major gene alone or in combination with quantitative resistance: a single repeat-induced point mutation and deletion events were observed in both situations. Breeding varieties which combine qualitative and quantitative resistance can effectively contribute to disease control by increasing the potential for durability of major resistance genes.

Alteration of pathogenicity-linked life-history traits by resistance of its host Solanum tuberosum impacts sexual reproduction of the plant pathogenic oomycete Phytophthora infestans.

Although sexual reproduction implies a cost, it represents an evolutionary advantage for the adaptation and survival of facultative sexual pathogens. Understanding the maintenance of sex in pathogens requires to analyse how host resistance will impact their sexual reproduction through the alteration of their life-history traits. We explored this experimentally using potato (Solanum tuberosum) and one of its pathogens, the heterothallic oomycete Phytophthora infestans. Sexual reproduction was highest on hosts favouring asexual multiplication of the pathogen, suggesting similar nutritional requirements for both sexual and asexual sporulation. Sexual reproduction was also highest on hosts decreasing the latent period, probably because of a trade-off between growth and reproduction. Distinguishing host effects on each pathogenic trait remains however uneasy, as most life-history traits linked to pathogenicity were not independent of each other. We argue that sexual reproduction of P. infestans is an adaptation to survive when the host is susceptible and rapidly destroyed.

A new simple method to perform pressure-volume curves obtained under quasi-static conditions during mechanical ventilation.

OBJECTIVE: To describe a fast, simple method to acquire pressure-volume curves of the respiratory system and to compare this with a classic method in terms of reliability of the data and speed. DESIGN: Acquisition of pressure-volume curves by low flow inflation technique (P-Vlf) versus the occlusion technique (P-Vst) using the standard equipment of a Cesar ventilator. SETTING: General ICU - Aix en Provence Hospital. PATIENTS: Ten sedated, curarized patients undergoing mechanical ventilation. INTERVENTIONS: P-Vlf curves were acquired by setting the ventilator parameters at f = 5 c./min, duty time Ti/Ttot = 80 %, VT = 1100 ml, pause time = 0. The pressure and volume data were collected directly on the ventilator screen. P-Vst curves were acquired using an airway occlusion technique. The pressures obtained for the same inflation volumes and times necessary for performance of the two techniques were compared. RESULTS: The time needed to acquire a P-Vlf curve was 3 min versus 38 min for P-Vst curve. Concordance analysis between the two methods showed a 95 % confidence interval of (-0.5 cm H2O, + 1.8 cm H2O) for pressure. CONCLUSIONS: P-Vlf curves are close to P-Vst curves, are much less time-consuming, easy to acquire with Cesar ventilator equipment, and may be used in clinical routine to assess the elastic properties of the respiratory system.

[Analgesia with intra-articular injection of buprenorphine after surgery of the shoulder]. / Analgésie par injection intra-articulaire de buprénorphine après chirurgie de l'épaule.

The effect of 10 ml of intra-articular buprenorphine (0.30 mg) or normal saline on postoperative pain after shoulder surgery was studied in a randomized, prospective, double-blind study in 30 ASA I-II patients receiving general anaesthesia. The pain scores (Five Point Scale ranging from "no pain" to "unbearable pain" and Visual Analog Pain Scale) 1, 2, 3, 4, 6 and 24 hours after surgery, time to first analgesic use and total 6-hours and 24-hours analgesic requirements were recorded. VAPS was significantly lower in the buprenorphine group compared with placebo-treated patients one hour after surgery (p < 0.05). The time to first analgesic use was longer and total 6-h opioid requirements were lower in the buprenorphine group when compared with the control group (p < 0.05). No significant differences were detected in total 24-h analgesic requirements between the two groups. These results indicate that intra-articular injection of buprenorphine after shoulder surgery provides short analgesia. This effect may be mediated by systemic absorption.