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  • Author or Editor: G. Sethi x
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The relative efficiency of in vitro and in vivo screening techniques for drought tolerance, comprising various parameters, namely germination (%), shoot length, root length, coleoptile length, root number, root/shoot ratio and seedling vigour index (SVI) under in vitro conditions and morpho-physiological and yield-contributing traits under in vivo conditions, was studied using 78 winter × spring wheat-derived doubled haploid lines of bread wheat along with 13 parental genotypes and two check varieties, HPW 155 and PBW 343. Analysis of variance for different in vitro parameters in control (0 MPa) and stress (−0.7 MPa) environments and various in vivo parameters under irrigated and rainfed environments indicated sufficient genetic variability and the differential response of the genotypes to the different stress levels for all the in vitro and in vivo parameters. Correlation studies revealed the significance of percentage germination, root number, coleoptile length and seedling vigour index under in vitro conditions and relative water content and excised leaf water loss under in vivo conditions as important selection criteria for drought tolerance, as these parameters were related with each other as well as with the drought susceptibility index (S). The significant positive rank correlation between the in vitro (−0.7 MPa) and in vivo (rainfed) stress conditions indicated that the performance of a genotype under field conditions is very similar to its performance under laboratory conditions. Hence, the selection precision for a crucial and complex trait like drought tolerance in wheat can be enhanced by exercising in vitro selection coupled with evaluation in the field. The drought susceptibility index ‘S’ should not be taken as the sole criterion to categorize genotypes as drought-tolerant or susceptible ones.

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Comparisons between androgenesis and maize-mediated haploid production efficiencies were made in six F1 genotypes each of winter × spring wheat and triticale × wheat crosses. The haploid status of the plantlets obtained was confirmed through cytological examination of the root tips. Much higher embryo formation (15.2%), haploid induction (8.7%) and doubled haploid production (8.3%) were obtained in the winter × spring wheat F1s through the wheat × maize system than by androgenesis (3.1%, 3.2 and 2.7%, respectively). Three of the triticale × wheat F1 genotypes failed to respond to androgenesis, while no haploids were recovered through the wheat × maize system in any of the six triticale × wheat F1s. Genotypic specificity, low callus induction and albinism reduced the efficiency of androgenesis both in winter × spring wheat and triticale × wheat hybrids. In all, the wheat × maize system proved to be better for winter × spring wheat hybrids and androgenesis for triticale × wheat hybrids.

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