Screening of apple germplasm of Kashmir Himalayas for scab resistance genes

Abstract

In India, apple (<i style="mso-bidi-font-style:normal">Malus × domestica</i>) is grown on a large scale in Kashmir province (valley) of the Jammu and Kashmir State. We surveyed several orchards of the valley in order to assess the germplasm. Apple scab was found to be the one of most important diseases, which is caused by the fungal pathogen, <i style="mso-bidi-font-style: normal">Venturia inaequalis. </i>For the present investigation, 80 cultivars were screened for the presence of known genes conferring disease resistance. Different cultivars of apple showed variable response to apple scab. Of the four resistant cultivars identified previously, namely two, Shireen and Firdous were found to harbour <i style="mso-bidi-font-style:normal">Vf </i><span style="mso-bidi-font-style:italic">(<i style="mso-bidi-font-style: normal">Rvi6</i><span style="mso-bidi-font-style:italic">)<i style="mso-bidi-font-style:normal"> </i>gene as the source of resistance. Other two resistant cultivars were found to lack this gene. Therefore, it appears that these cultivars may have either other known or novel scab resistance gene(s). Using specific primers, PCR technique was used to amplify <i style="mso-bidi-font-style:normal">Vf </i><span style="mso-bidi-font-style: italic">(<i style="mso-bidi-font-style:normal">Rvi6</i><span style="mso-bidi-font-style:italic">)<i style="mso-bidi-font-style:normal"> </i>specific fragments, which were later cloned, sequenced and further characterized by using bioinformatics tools. These clones showed similarity with different clones of <i style="mso-bidi-font-style:normal">Vf </i>gene isolated from <i style="mso-bidi-font-style:normal">M. floribunda</i> by earlier workers. Bioinformatics analysis showed some similarity of cloned sequences with serine-threonine kinases that help the plant to overcome various stresses. However, further work is needed to confirm this observation.

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