Plant disease resistance

About: Plant disease resistance is a research topic. Over the lifetime, 12952 publications have been published within this topic receiving 381820 citations. The topic is also known as: plant innate immunity.

Association analysis of historical bread wheat germplasm using additive genetic covariance of relatives and population structure

Abstract: Linkage disequilibrium can be used for identifying associations between traits of interest and genetic markers. This study used mapped diversity array technology (DArT) markers to find associations with resistance to stem rust, leaf rust, yellow rust, and powdery mildew, plus grain yield in five historical wheat international multienvironment trials from the International Maize and Wheat Improvement Center (CIMMYT). Two linear mixed models were used to assess marker–trait associations incorporating information on population structure and covariance between relatives. An integrated map containing 813 DArT markers and 831 other markers was constructed. Several linkage disequilibrium clusters bearing multiple host plant resistance genes were found. Most of the associated markers were found in genomic regions where previous reports had found genes or quantitative trait loci (QTL) influencing the same traits, providing an independent validation of this approach. In addition, many new chromosome regions for disease resistance and grain yield were identified in the wheat genome. Phenotyping across up to 60 environments and years allowed modeling of genotype × environment interaction, thereby making possible the identification of markers contributing to both additive and additive × additive interaction effects of traits.

OsWRKY13 Mediates Rice Disease Resistance by Regulating Defense-Related Genes in Salicylate- and Jasmonate-Dependent Signaling

Abstract: Although 109 WRKY genes have been identified in the rice genome, the functions of most are unknown. Here, we show that OsWRKY13 plays a pivotal role in rice disease resistance. Overexpression of OsWRKY13 can enhance rice resistance to bacterial blight and fungal blast, two of the most devastating diseases of rice worldwide, at both the seedling and adult stages, and shows no influence on the fertility. This overexpression was accompanied by the activation of salicylic acid (SA) synthesis-related genes and SA-responsive genes and the suppression of jasmonic acid (JA) synthesis-related genes and JA-responsive genes. OsWRKY13 bound to the promoters of its own and at least three other genes in SA- and JA-dependent signaling pathways. Its DNA-binding activity was influenced by pathogen infection. These results suggest that OsWRKY13, as an activator of the SA-dependent pathway and a suppressor of JA-dependent pathways, mediates rice resistance by directly or indirectly regulating the expression of a subset of genes acting both upstream and downstream of SA and JA. Furthermore, OsWRKY13 will provide a transgenic tool for engineering wider-spectrum and whole-growth-stage resistance rice in breeding programs.

Disease resistance conferred by expression of a gene encoding H2O2-generating glucose oxidase in transgenic potato plants.

Abstract: Plant defense responses to pathogen infection involve the production of active oxygen species, including hydrogen peroxide (H2O2). We obtained transgenic potato plants expressing a fungal gene encoding glucose oxidase, which generates H2O2 when glucose is oxidized. H2O2 levels were elevated in both leaf and tuber tissues of these plants. Transgenic potato tubers exhibited strong resistance to a bacterial soft rot disease caused by Erwinia carotovora subsp carotovora, and disease resistance was sustained under both aerobic and anaerobic conditions of bacterial infection. This resistance to soft rot was apparently mediated by elevated levels of H2O2, because the resistance could be counteracted by exogenously added H2O2-degrading catalase. The transgenic plants with increased levels of H2O2 also exhibited enhanced resistance to potato late blight caused by Phytophthora infestans. The development of lesions resulting from infection by P. infestans was significantly delayed in leaves of these plants. Thus, the expression of an active oxygen species-generating enzyme in transgenic plants represents a novel approach for engineering broad-spectrum disease resistance in plants.

Ubiquitin ligase-associated protein SGT1 is required for host and nonhost disease resistance in plants.

Abstract: Homologues of the yeast ubiquitin ligase-associated protein SGT1 are required for disease resistance in plants mediated by nucleotide-binding site/leucine-rich repeat (NBS-LRR) proteins. Here, by silencing SGT1 in Nicotiana benthamiana, we extend these findings and demonstrate that SGT1 has an unexpectedly general role in disease resistance. It is required for resistance responses mediated by NBS-LRR and other R proteins in which pathogen-derived elicitors are recognized either inside or outside the host plant cell. A requirement also exists for SGT1 in nonhost resistance in which all known members of a host species are resistant against every characterized isolate of a pathogen. Our findings show that silencing SGT1 affects diverse types of disease resistance in plants and support the idea that R protein-mediated and nonhost resistance may involve similar mechanisms.

Will Stem Rust Destroy the World’s Wheat Crop

Abstract: Race Ug99, or TTKSK, of fungus Puccinia graminis tritici, causing stem or black rust disease on wheat (Triticum aestivum), first identified in Uganda in 1998 has been recognized as a major threat to wheat production. Its spread in 2006 to Yemen and Sudan and further spread towards North Africa, Middle East and West-South Asia is predicted -aided by predominant wind currents and large areas of wheat varieties that are susceptible and grown under environments favorable for survival and multiplication of the pathogen. This has raised serious concerns of major epidemics that could destroy the wheat crop in these primary risk areas. Detection in Kenya of a new variant TTKST in 2006 with virulence to gene Sr24, which caused severe epidemics in 2007 in some regions of Kenya and rendered about half of the previously known Ug99-resistant global wheat materials susceptible, has further increased the vulnerability globally. Rigorous screening since 2005 in Kenya and Ethiopia of wheat materials from 22 countries and International Centers has identified low frequency of resistant materials that have potential to replace susceptible cultivars. Diverse sources of resistance, both race-specific and adult-plant type, are now available in high-yielding wheat backgrounds and are being used in breeding. The proposed strategy is to deploy spring wheat varieties possessing durable, adult plant resistance in East Africa and other primary risk areas to reduce inoculum and selection of new virulences capable of overcoming undefeated race-specific resistance genes. Race-specific resistance genes can then be deployed in secondary risk areas preferably in combinations. We believe that Ug99 threat in most countries can be reduced to low levels by urgently identifying, releasing and providing seed of new high yielding, resistant varieties.