A review of Septoria diseases of wheat and barley

A laboratory technique for screening cereals for resistance to Septoria nodorum using detached seedling leaves

The development of Septoria nodorum in relation to host lignification was monitored following inoculation of unwounded primary leaves of 4 wheat varieties differing in resistance to this pathogen. Although no differences were observed in spore germination and appressorium formation, the growth of surface germ-tubes was slower on the more resistant varieties, notably Atlas 66 and Zorba, differences being observed prior to penetration. The majority of appressoria on all the varieties failed to initiate successful penetrations and failure was accompanied by the production of lignified papillae and haloes by the host. Successful penetrations, which occurred most frequently on the least resistant variety, Maris Ranger, resulted in rapid epidermal cell collapse and lignification. Those hyphae reaching the mesophyll continued to spread mainly via the intercellular spaces, the sparse mycelium initiating collapse and degeneration of surrounding host cells. This process was closely accompanied by the deposition of lignin in the degenerating cytoplasm and accumulating extracellular deposits, as well as in the cell walls. The pattern of events was similar in all the varieties although considerably delayed in the more resistant ones. Examination of wound inoculated leaves revealed identical rates of lignification for all varieties although differences in resistance were still apparent. Administration of cycloheximide or u.v. light to unwounded leaves prior to inoculation reduced varietal differences and made all the varieties more susceptible, indicating that defence mechanisms may be induced and/or dependent on protein synthesis. The results indicate that lignification functions in all varieties to reduce penetration and the rate of fungal colonization but that other mechanisms act to reduce fungal growth even further in the more resistant varieties, possibly allowing lignification to be more effective.

The resistance of wheat to Septoria nodorum: fungal development in relation to host lignification

Publisher Summary There are three recognized Septoria diseases of wheat, each characterized by its causal fungus. On a worldwide basis, the two most important are septoria nodorum blotch (SNB) and septoria tritici blotch (STB). The third, septoria avenae blotch, is found infrequently and is generally considered a minor disease. This chapter focuses on breeding for resistance to SNB and STB. The relative emphasis that different breeding programs place on resistance to SNB and STB typically depends on the importance of the diseases in the geographic area of interest. The need for Septoria resistance must be viewed in relation to other breeding objectives. Thus, in some breeding programs it may be sufficient to simply avoid extremely susceptible germplasm, whereas other programs may require a high level of resistance. The chapter discusses how resistance to SNB and STB has been identified, relevant features concerning pathogen variation, what is known about the genetics of resistance, and a reference list containing sources of resistance to SNB and STB.

Breeding Wheat for Resistance to Septoria nodorum and Septoria tritici

Studies on Seed Mycoflora of Certain Cereals

Varietal reaction of wheat to leaf infection by Leptosphaeria nodorum and Septoria tritici

The environment in which Leptosphaeria -infected seed germinates is shown to be of great importance with regard to the subsequent development of symptoms on the seedlings. When seed is sown in Vermiculite the effects of the disease are most severe in a temperature range of 10–20 °C when conditions are neither too dry nor too wet. When infected seed was sown in seven different agricultural soil types, symptoms were more marked in loams and considerably less evident on seedlings grown in chalky soil of high pH.

Celia J. Baker

Papers

Varietal reaction of wheat to leaf infection by Leptosphaeria nodorum and Septoria tritici

Influence of environmental factors on development of symptoms on wheat seedlings grown from seed infected with Leptosphaeria nodorum

Morphology of seedling infection by Leptosphaeria nodorum