Potential Sources of Resistance to Stripe Rust (Puccinia striiformis fsp. titici ).

In West Asia, Central Asia and the Caucasus (CAC), and North African (CWANA) countries, wheat is the main cultivated crop under irrigation, in higher rainfall and moderate rainfall agro-ecological areas. Cultivation of high yielding mega-varieties across many countries is rapidly replacing the traditional lower yielding landraces. In CWANA countries, wheat stripe (yellow) rust is a major diseases in irrigated and in the high rainfall areas. Annual yield losses have been recorded in one or more countries and in certain areas have reached epidemic levels. Since 1970’s yellow rust has become sporadic due the deployment of effective resistance genes or gene combinations. Durable resistance has been linked to a number of genes such Yr18 and some very effective major genes such as Yr 9, Yr27; Yr1 that were associated with good parental lines and hence were extensively used by breeding programs globally. Virulent race on Yr9 resistance gene occurred in East Africa and spread eastward affecting wheat production in Middle East, West and South East Asia. Resistance genes Yr27, Yr18, and other Yr-Genes have effectively reduced the impact of yellow rust for over a decade. Recently, virulence on Yr27 has been detected in many countries. The spread of this new virulence is a typical example of potential risk of wheat rusts. Major genes are implicitly vulnerable to pathogen plasticity, and their longevity can range from rapid vulnerability to relative (and often deceiving) durability. This paper discusses potential resistance sources to wheat stripe rust in new elite bread wheat genotypes.