Prediction of heterosis in wheat using coefficient of parentage and RFLP-based estimates of genetic relationship

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Abstract
Genetic relationship can be a useful predictor of the relative performance of hybrid combinations for a hybrid breeding program resulting in reduced time and cost of hybrid testing. Genetic relationships of 112 wheat (Triticum aestivum L. em. Thell.) lines were estimated using 41 DNA clones hybridizing to 273 DNA fragments and by calculating coefficient of parentage (COP). Heterosis was estimated for 722 hybrids grown in multiple locations, with 189 being tested in more than 1 year. The average RFLP (restriction fragment length polymorphism) based genetic distance index (DI) was 0.35. Midparent heterosis for grain yield ranged from −20 to 57% and high-parent heterosis from −22 to 47%. The correlation between RFLP-based estimates of genetic distance and COP was nonsignificant (−0.33). Coefficient of parentage was significantly correlated with heterosis for all traits in 1991 but not in other years. Genetic distance based on RFLPs scored in this study was not correlated with heterosis in any of the years tested. Further refinement of gene pools and new prediction methods will be required to facilitate the exploitation of genetic variability for hybrid wheat improvement. Key words : wheat, heterosis, genetic distance.