The diversity of head-scab resistance in Triticeae and their relation to ecological conditions
Abstract1507 accessions from 93 species of 18 genera in Triticeae were screened for resistance to initial infection and resistance to pathogen spread with multi-floret and single-floret injection inoculation methods respectively. The accessions with high resistance were mainly found in perennial genera: Roegneria, Hystrix, Agropyron, Kengyilia and Elymus. Based on differences in resistance, 18 genera screened in Triticeae could be classified into five groups. The species with high resistance were mainly distributed in humid ecological environments.
Genetic Resistance of Crops to Diseases
Management of crop diseases through disease resistance is acknowledged to be the most desirable and profitable approach. In order to develop cultivars with built-in resistance, the knowledge about the methods of assessing the levels of resistance to diseases caused by microbial pathogens and identifying resistance sources genes is essentially required. The genetic basis of resistance to various diseases affecting crop(s) of interest, availability of resistance in cultivars or wild hosts, natural variations in pathogen populations, nature of plant-pathogen interaction and markers for identifying genotypes lines possessing resistance genes can be studied by applying a range of molecular techniques. Use of molecular markers has been found to be very useful for selecting resistant plants rapidly even in seedling stage without waiting for the plants to reach the particular growth stage. In addition, the presence and contents of the pathogen DNA can be determined, using appropriate molecular technique well before the appearance of visible symptoms. The molecular bases of race-specific resistance, characterized by programmed cell death (PCD) and general resistance characterized by inducible defense responses exhibited in tissues far away from the infection site have to be clearly understood. The molecular methods have been successfully applied to understand various phenomena such as virulence and avirulence functions, role of elicitors, signaling systems induced in compatible and incompatible interactions, the posttranscriptional gene silencing and virus-induced gene silencing mechanisms, operating in plants and induction of various defense-related compounds and their action on microbial plant pathogens. The fungal, bacterial and viral pathogens have their own unique strategies to enhance their virulence and to overcome the host strategies to hamper their successful colonization of and establishment in plant tissues.
A NEW ELYMORDEUM HYBRID FROM ALASKA
A number of unusual grass plants were discovered in the fall of 1964 along Cottonwood Creek in the Cook Inlet area of south central Alaska. The occurrence, morphology, and sterility of these plants...