| Abstract: |
The present investigation was carried out at experimental Farm of El- Gemmeiza, Agricultural Research Station, Egypt during three winter seasons 2008/2009, 2009/2010 and 2010/2011 for obtaining F1 and F2 seeds and growing them with their parents under both Orobanche free and Orobanche infestation conditions. The molecular approach was carried out at Molecular and Microbial Genetics Laboratories, Genetics Department, Faculty of Agriculture, Zagazig University. The collected data from F1 and F2 generations were analyzed using Hayman approach for estimating the genetic nature and heritability of morphological characters, i.e. seeds yield and its attributes. Chemical criteria related to tolerance of Orobanche (osmotic pressure, potassium content and % total soluble phenols) were determined in parents and its hybrids of F1 generation. Trial to discover a molecular marker for Orobanche tolerance or susceptible by using Bulked Segregant Analysis (BSA) using RAPD and ISSR techniques. The F1 diallel results indicated that both additive and dominance effects play an important role in the genetic control of three Orobanche criteria, which related to Orobanche tolerance or susceptible by using Bulked Segregant Analysis Orobanche tolerance. The correlation coefficient between (Vr+Wr) and Yr indicated that the three Orobanche related tolerance criteria possessed a positive correlation coefficient (r),then the direction of dominance towards low values of three Orobanche tolerance criteria were dominant over high values. Therefore, the Orobanche tolerance genes were dominant over susceptible recessive genes. from the F1 graph, Misr-1 variety possessed most tolerance genes for Orobanche. The correlation coefficient confirmed the highly negative correlation between seed yield and its attributes with date of Orobanche emergence and no. of Orobanche spikes/ m2.The F2 diallel under infested field showed that date of Orobanche emergence and no. of Orobanche spikes/m2 possessed positive correlation coefficient (r) between (Vr + Wr) and Yr. These results were agree with the results in F1 diallel and conceded the importance of these relationships for selection of Orobanche tolerance in the field condition. The mean degree of dominance of days to 50 % flowering and no. of Orobanche spikes /m2 were decreased to half in F2 generation as compared to F1 generation.The line x tester analysis revealed the importance of both additive and non-additive gene actions for potassium content and % of total soluble phenols. On the other hand, the osmotic pressure was governed by additive gene action only; therefore, the selection of osmotic pressure as a highly related criterion with Orobanche tolerance can be done in early generation.The molecular genetic markers for Orobanche tolerance using Bulk Segregant Analysis with RAPD primers showed that primer B20 showed four positive molecular markers which were found only in the tolerant parent (x-1722), F1 and the tolerant F2 bulk, while, three negative molecular markers which were found only in the sensitive parent (Giza-40), F1 and the sensitive F2 bulk. One of these negative markers formed in primer B18 and the other negative markers in primer A09. The ISSR primers exhibited only one negative molecular marker in primer HB12.
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