Reconsidering the direct cross approach for gene transfer from Aegilops tauschii to hexaploid wheat using diversified D
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ORIGINAL PAPER
Reconsidering the direct cross approach for gene transfer from Aegilops tauschii to hexaploid wheat using diversified D genome donors S. R. Cambay1,2 · N. S. Bains2 · S. K. Sandhu2 · Srivastava Puja2 Received: 17 December 2019 / Accepted: 4 September 2020 © Akadémiai Kiadó Zrt. 2020
Abstract The direct cross-hybridization approach between 16 Aegilops tauschii (AT) and 10 bread wheat (W) lines was carried out in reciprocal directions. W (♀) x AT (♂) yielded no embryo formation whereas embryo formation ranging from 34.09 to 43.33% was obtained in AT (♀) x W (♂) crosses in all 160 combinations. The major bottleneck of low plant regeneration in AT (♀) x W (♂) crosses was cleared by adopting detached tiller culture and embryo rescue medium adjuvants such as casein hydrolysate (200 mg/L) and activated charcoal (2 g/L). The regeneration frequency as a result of these two interventions increased from 3.61 to 19.29 per cent. Two innovative methods of chromosome doubling included in situ colchicine (0.05%) treatment with cotton swab method and pre-regeneration colchicine treatment (0.1 and 0.2%) to pollinated ovaries were found to be effective. The findings of the study make successful exploitation of direct cross approach (AT (♀) x W (♂)) possible in wheat improvement. Keywords Direct cross · Aegilops tauschii · Reciprocal cross · Embryo rescue
Introduction The identification and utilization of desirable genes and traits from wild relatives has long been realized an effective approach in improving common wheat (Fu and Somers 2009; Nevo 2014). Distant wild relatives, such as Dasypyrum villosum (Chen et al. 2013), Thinopyrum ponticum (Niu et al. 2014), and Agropyron cristatum (Luan et al. 2010; Ye et al. 2015; Zhang et al. 2015) as well as progenitor species such as Aegilops speltoides (Klindworth et al. 2012), have been utilized for the improvement of common wheat. Wild progenitors species, Ae. tauschii (AT) with wide spectrum of allelic variation and unhindered recombination Electronic supplementary material The online version of this article (https://doi.org/10.1007/s42976-020-00079-0) contains supplementary material, which is available to authorized users. * S. R. Cambay [email protected] 1
Present Address: Genetics Division, IARI, New Delhi 110012, India
Department of Plant Breeding and Genetics, PAU, Ludhiana 141004, India
2
with the structurally unaltered wheat D genome chromosomes represents a highly promising gene donor for hexaploidy wheat improvement (Kilian et al. 2011). Gene transfers from AT have mostly been through the production of synthetic hexaploid wheat (SHW) (tetraploid Wheat x AT) as a first step, which is then used as a “bridge” for transfer of genes from AT into common wheat (Miranda et al. 2007). This approach has led to several advanced backcross introgression lines (Pestsova et al. 2006; Kunert et al. 2007; Naz et al. 2008; Yu et al. 2014) representing successful introgression of numerous QTLs located on the D genome. Direct crosses between W x AT are an alternati
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