ARS | Publication request: Identification of markers associated with genes for rust resistance in lens culinaris medik

Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 3, 2010
Publication Date: October 1, 2010
Citation: Saha, G., Sarker, A., Chen, W., Vandemark, G.J., Muehlbauer, F.J. 2010. Identification of markers associated with genes for rust resistance in lens culinaris medik. Euphytica. 175 (2):261-265.

Interpretive Summary: Leaf and stem rust is one of the major diseases of lentil (Lens culinaris Medik.) in south Asia and north and east Africa. Because lentils have a relatively low value on a per-acre basis, the application of fungicides for controlling this and other diseases caused by fungi is not an economically viable method for disease control. The control method most preferred by growers is the cultivation of improved varieties that have genetic resistance to a wide portfolio of different diseases. The development of varieties with improved disease resistance is greatly impacted by the ability of plant breeders to easily and accurately screen plants and identify resistant materials. A major difficulty in screening for resistance in lentils to rust is that the pathogen responsible for disease (Uromyces vicia-fabae) cannot be cultured in growth media, which requires the reliance on naturally occurring inoculum for initiating disease in screening nurseries. Years in which inoculum are not present in adequate levels result in an inability to accurately identify resistant materials. An alternative approach to directly screening for disease resistance would be to identify DNA markers associated with resistance and use these DNA markers for subsequent identification of resistant lines. Our objective was to identify molecular markers that were associated with rust resistance in lentil. A lentil population that exhibited differences among plants in disease resistance was screened in the field for two years. We identified one DNA marker (F7XEM4a) that was significantly associated with resistance in lentil to rust over both years. In the immediate future we will examine the utility of this marker for accelerating the development of improved lentil varieties and also try to identify more markers associated with rust resistance.

Technical Abstract: Lentil rust caused by Uromyces vicia-fabae (Pers.) Schroet is one of the most important diseases of lentil in South Asia, North Africa and East Africa. This disease is usually observed during late flowering and early podding stages. Early infection accompanied by favorable environmental conditions can result in complete crop failure and huge economic losses. Therefore, breeding for resistance against this pathogen is one of the major challenges for the breeders in those regions. It is important to identify resistance sources and to determine the location of the genes for resistance in the lentil genome. Since field screening is often difficult due to the unpredictable nature of the disease, selectable molecular markers can be useful tools to assist lentil breeding and complement field screening and selection for resistance. To map the genes for resistance, a recombinant inbred line (RILs) population composed of 220 RILs was developed from a cross between a rust resistant line, ILL-4605, and a susceptible line from Bangladesh, ILL-5888. Phenotyping of the RIL population was carried out during 2006-2007 and 2008-2009 cropping seasons at the Pulse Research Center, Ishurdi, Bangladesh. There was a lack of uniformity of disease pressure in the 2006-2007 cropping year causing inconsistencies between replicates. Nevertheless, we were able to choose clearly resistant and clearly susceptible RILs for selective genotyping using markers previously placed on our lentil genetic map. One of the 62 markers used for selective genotyping proved to be linked to the gene for resistance. The identified sequence related amplified polymorphism (SRAP) marker, F7XEM4a, was estimated to be 7.9 cM from the gene for resistance. The F7XEM4a marker could be used for marker assisted selection for resistance; however, additional markers closer to the resistance gene are needed.