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Research Note, VITIS - Journal of Grapevine Research, Vol. 45 No. 1 (2006): Vitis

In rice, at least 40 genes conferring resistance to blast (caused by Magnaporthe grisea) have been described since 1985 (Sallaud et al, 2002), but only two were cloned (Pib [Wang et al 1999] andPita [Jia et al 2000]). These genes belong to the nucleotide-binding site-leucine-rich repeat) (NBSLRR) family of plant resistance genes. Direct molecular interaction between the protein encoded by Pita and the corresponding M. grisea avirulence gene product AVR-PITA (a small secreted protein) has been demonstrated (Jia et al 2000). Therefore, the recognition of fungal protein produced during the early stages of the infection process is the initial step in the resistance to blast controlled by Pita. Other known M. grisea avirulence genes encode for small proteins that are likely to be secreted during infection. They are involved in nonhost resistance either in weeping lovegrass or in rice.

International audience; Using a genomic clone encoding a rice lipid transfer protein, LTP1, we analysed the activity of the 5 region of the Ltp1 gene in transgenic rice (Oryza sativa L.) during plant development and under pathogen attack. The −1176/+13, −556/+13 and −284/+13 regions of the promoter were fused upstream from the uidA reporter gene and nos 3 polyadenylation signal, resulting in the p 1176Gus, p 556Gus and p 284Gus constructs which were transferred to rice by microprojectile bombardment. Histochemical and fluorometric GUS assays and in situ detection of uidA transcripts in transgenic homozygous lines harbouring the p 1176Gus construct demonstrated that the Ltp1 promoter is preferentially active in aerial vegetative and reproductive organs and that both specificity and level of expression are regulated during organ development. In leaf sheath, GUS activity which is initially strictly localized in the epidermis of growing tissue, becomes restricted to the vascular system in mature tissues. In expanded leaf blade, expression of the uidA gene was restricted to the cutting level suggesting inducibility by wounding. Strong activity was detected in lemma and palea, sterile glumes, and immature anther walls and microspores but not in female reproductive organs. No GUS activity was detected during seed embryo maturation whereas the uidA gene was strongly expressed at early stages of somatic embryogenesis in scutellum tissue. The Ltp1 transcripts were found to strongly accumulate in response to inoculation with the fungal agent of the blast disease, Magnaporthe grisea, in two rice cultivars exhibiting compatible or incompatible host-pathogen interactions. Analysis of p 1176Gus leaf samples inoculated with the blast fungus demonstrated that the Ltp1 promoter is induced in all cell types of tissues surrounding the lesion and notably in stomata guard cells. In plants harbouring the Ltp1 promoter deletion construct p 556Gus, activity was solely detected in the vascular system of mature leaves whereas no uidA gene expression was observed in p 284Gus plants. These observations are consistent with the proposed role of LTP1 in strenghtening of structural barriers and organ protection against mechanical disruption and pathogen attack.

International audience; We developed sequence characterized amplified region (SCAR) markers to monitor recombination and migration within Magnaporthe grisea populations. Twenty-two primer pairs were designed from random amplified polymorphic DNA (RAPD) markers or available gene sequences. Sixteen of these SCARs were polymorphic in M. grisea when tested on 232 isolates collected from worldwide origins.

This article 'Indica/japonica doubled haploid population as a model for mapping rice yellow mottle virus and blast resistance genes' appeared in the International Rice Research Notes series, created by the International Rice Research Institute (IRRI) to expedite communication among scientists concerned with the development of improved technology for rice and rice-based systems. The series is a mechanism to help scientists keep each other informed of current rice research findings. The concise scientific notes are meant to encourage rice scientists to communicate with one another to obtain details on the research reported.

This article 'Comparison of Xanthomonas oryzae pv. oryzae Strains From Africa, North America, and Asia By Restriction Fragment Length Polymorphism Analysis' appeared in the International Rice Research Notes series, created by the International Rice Research Institute (IRRI) to expedite communication among scientists concerned with the development of improved technology for rice and rice-based systems. The series is a mechanism to help scientists keep each other informed of current rice research findings. The concise scientific notes are meant to encourage rice scientists to communicate with one another to obtain details on the research reported.

This article 'Resistance of 99 Oryza glaberrima Steud. Varieties to Blast' appeared in the International Rice Research Newsletter series, created by the International Rice Research Institute (IRRI). The primary objective of this publication was to expedite communication among scientists concerned with the development of improved technology for rice and for rice based cropping systems. This publication will report what scientists are doing to increase the production of rice in as much as this crop feeds the most densely populated and land scarce nations in the world.

This article 'Isolation of Pseudomonas fuscovaginae with a Semiselective Medium (KBS)' appeared in the International Rice Research Newsletter series, created by the International Rice Research Institute (IRRI). The primary objective of this publication was to expedite communication among scientists concerned with the development of improved technology for rice and for rice based cropping systems. This publication will report what scientists are doing to increase the production of rice in as much as this crop feeds the most densely populated and land scarce nations in the world.

The mating type and female fertility isolates of Magnaporthe grisea populations from China and some other Asian countries were studied by crossing with standard hermaphroditic isolates. The genetic diversity of 143 isolates was analyzed with SCAR markers by using PCR amplification.

To develop a quantitative evaluation of grapevine resistance to powdery mildew and of pathogenicity of the causal agent (Erysiphe necator), a spot inoculation method was developed using detached leaves of potted plants. The percentage of inoculating spots leading to a colony and the mean diameter of colonies were determined to assess the host-pathogen relationships. Significant differences were found between host cultivars and their ranking was associated with that observed in the vineyard. There was a significant interaction between cultivar and replicate during the whole experiment indicating that the physiological state of detached leaves is important. Aging of tissues was accompanied by a gain in resistance that was considerably more marked in resistant cultivars. Only partly expanded leaves of resistant cultivars that stopped expansion on the agar medium supported the development of the fungus. Significant differences between E. necator isolates were also demonstrated, but these variations were less marked than those due to host cultivar and leaf position. Preliminary results obtained with different isolates from the two European genetic groups (A and B) indicate that, on average, group A is less pathogenic., VITIS - Journal of Grapevine Research, Vol. 45 No. 1 (2006): Vitis