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  • Author or Editor: H.K. Chaudhary x
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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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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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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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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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Authors: Vijay Rana, Dhirendra Singh, R. Dhiman and H.K. Chaudhary

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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The present research endeavor was undertaken to depict the response of different generations viz., F1, F2, BC1F1, BC1F2, BC1F3, BC1F4 and BC1F5 of triticale × wheat and wheat × rye hybrids towards the different parameters of haploid induction. The experimental material included the different generations obtained utilizing five genotypes of triticale (DT-123, DT-126, TL-2900, TL-2908 and TL-9335), four genotypes of Himalayan rye (Karoki rye, shanoor rye, tino rye and triloki rye) with various elite bread wheat genotypes as parents in wide hybridization programme. The triticale × wheat and wheat × rye recombinants were further subjected to Imperata cylindrica-mediated chromosome elimination approach of doubled haploidy breeding. The variability in the haploid induction parameters was observed to be under genetic control for embryo formation and regeneration, while pseudoseed formation was only affected by auxin treatment. Among the different generations, the backcross generations viz., BC1F1 and BC1F2 were found to exhibit significant positive response towards haploid induction parameters in both triticale × wheat and wheat × rye hybridization. Knowledge of effective generation for haploid induction in triticale × wheat and wheat × rye hybridization not only saved the time and energy but also enhanced the efficiency of haploid induction.

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The investigation was undertaken at two different climatic regimens of NW Himalayas, to determine the response of diverse genotypes of triticale and wheat and environment on their crossability as well as to evaluate the efficiency of Imperata cylindrica-mediated chromosome elimination approach for haploid induction in triticale × wheat (Triticum aestivum) hybrids. The experimental material included three elite hexaploid triticale genotypes (DT123, DT126 and TL9335) and five bread wheat genotypes (DH40, HPW155, HS295, VL829 and C306). Significant genotypic and environmental variations were observed for seed setting at two agroclimatic zones. Among parental genotypes, DT126 (triticale) and C306, HPW155 and HS295 (wheat) responded significantly better for seed setting due to significant positive GCA effects at both locations. Maximum seed set of 39.53% and 45.37% was recorded at short day and long day climates, respectively, proving later as the better location for seed setting in most of the crosses. For all the three parameters of haploid induction, viz. pseudoseed formation, embryo formation and regeneration, significant differences were recorded in all the triticale × wheat hybrids depicting the potential of I. cylindrica-mediated approach for haploid induction. Triticale × wheat cross DT126 × HS295 followed by DT126 × HPW155 were found to be significantly more responsive towards embryo formation and regeneration.

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Pollen viability is among the critical factors, which determine the success of a doubled haploidy breeding programme, thus the present investigation was undertaken to assess the functional viability and relative longevity of the pollen from Zea mays and Imperata cylindrica for the chromosome elimination mediated approach of doubled haploidy breeding. Two wheat genotypes representing spring and winter ecotypes, namely DH 40 and Saptdhara were pollinated with freshly harvested pollen of two known potential haploid inducing sources, namely Z. mays (grown in polyhouse conditions) and I. cylindrica (wild grass) for 15 and 17 days, respectively, keeping five minutes interval between two subsequent pollinations. The results revealed a significant decrease in the viability of Z. mays pollen up to 95 percent in Saptdhara and 85 percent in DH 40 within one hour, whereas Imperata pollen was found to be functionally viable even at the end of experimentation period, showing high embryo formation in both the wheat parents. I. cylindrica exhibited higher frequencies for haploid induction parameters in both the wheat parents as compared to Z. mays. I. cylindrica pollen, being viable for relatively longer periods than Z. mays can hasten the haploid induction endeavours, thus may be a more efficient alternative to Z. mays for breeding programmes using doubled haploidy technique.

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