Thumbnail Image

Thesis

Browse

20141
Reset filters
Subject: Biotechnology × Author: Elkot, Ahmed Fawzy Abdelnaby × End date: 2014 × Start date: 2014 × Type: Thesis × Thesis Type: Ph.D ×
Reset filters

Search Results

Now showing 1 - 1 of 1
  • Thumbnail Image
    ThesisItemRestricted
    Marker assisted transfer of novel powdery mildew resistance gene(s) from Triticum boeoticum (Boiss.) to hexaploid wheat Triticum aestivum (L.)
    (PAU, 2014) Elkot, Ahmed Fawzy Abdelnaby; Singh, Kuldeep
    Powdery mildew (PM), caused by Blumeria graminis f. sp. tritici, is one of the most important wheat diseases in the world and development of resistant varieties is safest and most economical approach for containing this disease. Wild species are an important source for PM resistance genes. In a previous study, two PM resistance genes designated as PmTb7A and Pm1Tb were identified in T. boeoticum acc. Pau5088 and mapped on chromosome arm 7AL the two genes were approximately 48cM apart and two resistance genes analogue (RGA)-STS markers Ta7AL-4556232 and 7AL-4426363 were found to be linked to the PmTb7A and Pm1Tb, at a distance of 0.6cM and 6.0cM, respectively. In the present study the two genes were transferred from T. boeoticum to T. aestivum cvs PBW 343-IL and PBW 621using T. durum cv PBW114 as bridging species. As many as 12317 florets of F1 of the cross T. durum cv PBW114/T. boeoticum acc pau5088 were pollinated with T. aestivum cvs PBW343-IL and PBW621 to produce 61 and 65 seeds, respectively of three-way F1. The resulting F1s of the cross T. durum/T. boeoticum//T. aestivum, were screened with marker flanking both the PM resistance genes PmTb7A and Pm1Tb (foreground selection) using SSR and RGA-STS markers and selected plants were backcrossed to generate BC1F1. Marker assisted selection was carried in both BC1F1 an BC2F1 generations with the objective of transferring these genes with minimum of the linkage drag. In BC2F1, out of total 121 BC2F1 plants of cross PBW114 / T. boeoticum acc. pau 5088//3*PBW343-IL, 41 had only PmTb7A linked markers, 13 had Pm1Tb linked markers, six had introgression for markers linked to both the genes and 61 plants did not show any introgression. Likewise, out of 93 BC2F1 plants derived from cross of PBW114/T. boeoticum//3*PBW621, 21 had only PmTb7A linked markers, 16 had Pm1Tb linked markers, 14 had introgression for markers linked to both the genes and 42 plants did not show any introgression. Out of more than 110 plants showing introgression for markers linked to the two PM resistance genes, 40 agronomically desirable plants were selected for background selection for the carrier chromosome to identify the plants having minimum of the alien introgression. Introgression in different BC2F1 plants varied from 15.4 - 62.9 per cent with minimum introgression in plants CBT76-4 which had PmTb7A only but not Pm1Tb and CBT101-3 which showed introgression for Pm1Tb but not for PmTb7A. Most of the selected plants had yield component traits similar or better than the recurrent parents. Cytological analysis showed that most plants have chromosome number ranging from 40-42. BC2F2 plants homozygous for the two genes have been identified and these will be crossed to generate lines combining both the PM resistance genes but with minimal of the alien ntrogression. One of the PM resistance genes PmTb7A which is novel, maps in a region on 7AL where Sr22, a stem rust resistance gene effective against the race Ug99, also maps. Markers analysis with Sr22 linked gene showed introgression in 31 plants out of total 40 selected BC2F1plants. Thus in addition to PM, the line with PmTb7A should also be resistant to stem rust race Ug99. To the best of our knowledge, this is the first example of marker assisted transfer of a gene from wild species into cultivated wheat.