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  • Author or Editor: H. Chaudhary x
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The success of winter × spring wheat hybridization programmes depends upon the ability of the genotypes of these two physiologically distinct ecotypes to combine well with each other. Hence the present investigation was undertaken to study the combining ability and nature of gene action for various morpho-physiological and yield-contributing traits in crosses involving winter and spring wheat genotypes. Five elite and diverse genotypes each of winter and spring wheat ecotypes and their F 1 (spring × spring, winter × winter and winter × spring) hybrids, generated in a diallel mating design excluding reciprocals, were evaluated in a random block design with three replications. Considerable variability was observed among the spring and winter wheat genotypes for all the traits under study. Furthermore, these traits were highly influenced by the winter and spring wheat genetic backgrounds, resulting in significant differences between the spring × spring, winter × winter and winter × spring wheat hybrids for some of the traits. The winter × spring wheat hybrids were observed to be the best with respect to yieldcontributing traits. On the basis of GCA effects, the spring wheat parents HPW 42, HPW 89, HW 3024, PW 552 and UP 2418 and the winter wheat parents Saptdhara, VWFW 452, W 10 and WW 24 were found to be good combiners for the majority of traits. These spring and winter wheat parents could be effectively utilized in future hybridization programmes for wheat improvement. Superior hybrid combinations for one or more traits were identified, all of which involved at least one good general combiner for one or more traits in their parentage, and can thus be exploited in successive generations to develop potential recombinants through various breeding strategies. Genetic studies revealed the preponderance of additive gene action for days to flowering, days to maturity and harvest index, and non-additive gene action for the remaining six traits.

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Seventy-eight doubled haploid (DH) lines, derived from 21 elite and diverse winter × spring wheat F 1 hybrids, following the wheat × maize system, were screened along with the parental genotypes under in vitro and in vivo conditions for cold tolerance. Under in vitro conditions, the 2,3,5-triphenyl tetrazolium chloride (TTC) test was used to characterize the genotypes for cold tolerance. Based on the TTC test, only one doubled haploid, DH 69, was characterized as cold-tolerant, seven DH and five winter wheat parents were moderately tolerant, while the rest were susceptible. Analysis of variance under in vivo conditions also indicated the presence of sufficient genetic variability among the genotypes (DH lines + parents) for all the yield-contributing traits under study. The correlation and path analysis studies underlined the importance of indirect selection for tillers per plant, harvest index and grains per spike in order to improve grain yield. It was also concluded that selection should not be practised for grain weight per spike as it would adversely affect the grain yield per plant. When comparing the field performance of the genotypes with the in vitro screening parameters, it was concluded that in addition to the TTC test, comprising a single parameter, other physiological and biochemical in vitro parameters should be identified, which clearly distinguish between cold-tolerant and susceptible genotypes and also correlate well with their performance under field conditions.

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Doubled haploidy breeding via wide hybridization has been used in durum wheat haploid production for creating homozygosity in the shortest possible time. Post pollination treatment with hormones is a key factor for inducing haploid embryos in durum wheat wide crosses. An intergeneric hybridization experiment was carried out in seven durum wheat genotypes using Imperata cylindrica and two composites of Maize viz., Bajaura Makka and Early Composite, as pollen sources. The pollinated spikes were injected with 2,4-Dichlorophenoxyacetic acid (2,4-D) in five different concentrations i.e., 100, 150, 200, 250 and 300 ppm, for three consecutive days at 24, 48 and 72 hrs after pollination. Analysis of variance revealed that the five concentrations of 2,4-D significantly differed in their ability to induce haploid embryos and 2,4-D at 250 ppm was found to be most effective in durum wheat haploid production through wide hybridization. The highest frequency of embryo carrying seeds was recorded to be 65.75 and 36.73 percent, at 250 ppm with I. cylindrica and Bajaura Makka, respectively in first cropping season. During second season, embryo formation frequency was observed to be maximum, 70.69, 32.84 and 27.59 percent, at 250 ppm 2,4-D with all three pollen sources, viz., I. cylindrica, Bajaura Makka and Early Composite, respectively.

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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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To identify an efficient pollen source for maize mediated system of chromosome elimination, wheat genotypes (10 F1s) were pollinated with eight diverse Himalayan maize genotypes. Among these, two were composite varieties Early Composite (Check) and Bajaura Makka (L 201) and rest six were locally grown traditional open pollinated maize varieties collected from diverse regions of North-west Himalaya. The data were recorded for three haploid induction parameters viz. pseudo seed formation, embryo formation and regeneration. In most of the crosses, haploid embryos were produced, asserting the potential of wheat × maize system as a genotype non-specific system as compared to androgenesis and bulbosum technique, where the genotype specificity limits the development of haploid plants. Frequencies of all the three haploid induction parameters in different crosses of wheat × maize clearly indicated that both wheat and maize genotypes were behaving differently for different crosses. The line × tester analysis also revealed significant influence of crosses, wheat, maize and their interaction on all the three haploid induction parameters. The results obtained suggest association of both additive and dominance gene action with all the haploid induction parameters. Over all proportional contribution of tester for embryo formation and regeneration parameters was found to be more, followed by line × tester interaction. On the basis of haploid formation efficiency (HFE) as well as general combining ability (GCA), Bajaura Makka has emerged to be the best general combiner among maize genotypes and also superior to the earlier identified variety, Early Composite. Also, HPW 155 × VL 852 and HPW 155 × HPW 211 were the top general combiners among wheat genotypes. Correlation between various haploid induction parameters revealed negative correlation between pseudo seed formation and embryo formation whereas embryo formation and regeneration were found to be significantly positively correlated; however the magnitude of correlation was not very high.

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An investigation to standardize the protocol for in vitro application of colchicine for enhancing the doubled haploid production in wheat was done. Two tetraploid (PDW-314 and A-9-30-1); and two hexaploid (DH-40 and C-306) wheat genotypes were used as maternal parents, whereas, the pollen sources involved Zea mays (cv. Bajaura Makka) and Imperata cylindrica. During the rabi seasons of years 2013–14 and 2014–15, wheat × maize and wheat × I. cylindrica hybridization was carried out followed by treatment of their haploids produced as a result of elimination of chromosomes of maize and I. cylindrica respectively, with varied doses of colchicine for different durations The various doses of colchicine were categorized into two groups: lower doses for longer durations (0.01, 0.025, 0.05% each for 5, 7, 9, 11 hrs) and higher doses for shorter durations (0.05, 0.075, 0.10, 0.15, 0.20, 0.25% each for 5, 4, 3, 2 hrs). The response of different concentrations of colchicine applied for varied durations revealed significant differences for various doubled haploidy parameters viz., per cent survived plants, per cent doubled haploid formation and per cent doubled haploid seed formation. In hexaploid and tetraploid wheats, colchicine doses of 0.075% for 4 hrs and 0.15% for 4 hrs, respectively were established as optimum for enhanced doubled haploid production.

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Pollen of two I. cylindrica genotypes, one having spike with brown anthers (Ic-Pbr) and other with yellow anthers (Ic-Pye) was collected from three collection environments (early, mid and late flowering) and preserved in sealed Petri dishes under three preservation regimes, P1 (4 °C temperature and 60% RH), P2 (–20 °C and 65% RH) and P3 (–80 °C temperature and 45% RH). The pollen viability and germination tests of the preserved pollen were conducted after every 15 days till complete loss of viability. The study revealed that Ic-Pbr was superior to Ic-Pye in terms of the mean absolute pollen viability (APV) under preservation conditions. Among the collection environments, pollen collected just after first anthesis, that is, early flowering was superior in terms of the preservation potential. The preservation regime, P2 was found to be best among the three for better preservation of I. cylindrica pollen. By utilizing the one month old preserved pollen for pollination of wheat spikes, pollen from P2 regime induced haploid embryos to the tune of 25.53%. The study concluded that by preserving I. cylindrica pollen at –20 °C, the period of DH production in wheat can be extended by at least one month. The preserved pollen will also open avenues for exploring the possibilities of inducing haploids in other cereals like rice and maize whose flowering does not coincide with I. cylindrica naturally.

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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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The Imperata cylindrica-mediated chromosome elimination approach has been identified as the most efficient system of doubled haploidy breeding in wheat (Triticum aestivum L.). The present investigation was carried out to assess the mean performance of diverse I. cylindrica genotypes (five) collected from different locations and wheat F1s (21) generated out of various elite winter and spring wheat ecotypes. Also, the proportional contribution of wheat F1s and I. cylindrica genotypes was evaluated to find out the relative contribution of maternal and paternal parents to haploid induction. The investigation revealed that the mean response of wheat and I. cylindrica to haploid induction parameters, viz. pseudoseed formation, embryo formation, haploid regeneration and haploid formation varies from wheat and I. cylindrica genotype to genotype. The I. cylindrica genotype, Ic-Aru from north east Himalayas and wheat genotype, DH 114 × KWS 29 exhibited highest mean performance to haploid embryo formation, the stage for which all the three contributors, that is, wheat F1s, I. cylindrica genotypes and wheat × I. cylindrica interaction were found to be similar for their proportional contribution (%) towards haploid induction. Thus, concluding that the haploid induction through preferential chromosome elimination approaches can be enhanced by using more efficient pollinators.

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Thirty diverse elite Indian wheat genotypes varying in their yield performance and drought tolerance were evaluated to examine differences for some drought tolerance characters and to determine relationship between these characters. Genotypes differed in their response for grain yield, days to heading, excised-leaf water loss and relative water content under both conditions over years. Under irrigated conditions differences in the genotypes for water retention traits were not clear. The varieties HPW251, Hindi 62, HPW184, VL 892 and VL 907 showed a good combination of drought resistance, water retention and high grain yield, whereas C 306, VL 421 and NI 5439 had high grain yield only under drought stress conditions and showed better water retention in the leaves. These genotypes may be used for exploitation of drought tolerance in wheat breeding programmes. Drought response index (DRI) appeared to be an important trait as the genotypes having high DRI values also had high grain yield, high water retention and low score of drought susceptibility index (DSI) under drought stress.

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