Abstract
Doubled haploid production via microspore culture is a technique known to accelerate crop breeding by shortening the breeding cycle through achieving homozygosity in one generation. Prior research observed that some embryogenic microspores aborted their development before reaching the embryoid stage. Such embryogenic abortion reduces embryoid yield, making microspore cultures less efficient. The present research aims at identifying stages during which microspore development is susceptible to embryogenic abortion. Information gained through delineation of the developmental dynamics of microspores in culture could be used to improve the efficiency of microspore culture. Embryogenic microspores were isolated from stress-treated wheat (Triticum aestivum L.) tillers and cultured in liquid medium. The development of embryogenic microspores was monitored over a 35 day period. At day 7, 10, 14, 21, 28, and 35, the developing microspores were counted and categorized into multicellular structures, pre-embryoids, immature embryoids and mature embryoids. The results showed that 44% - 62% of embryogenic microspores halted their development before the mature embryoid stage. Of these aborted embryogenic microspores, 21% - 33% terminated as multicellular structures, 16% - 19% arrested their development as pre-embryoids, and 7% - 10% halted development as immature embryoids. Identifying factors that are responsible for embryogenic abortion and finding remedy to the issue will help improve the efficiency of doubled haploid production.
Highlights
Triticum aestivum was once considered as a recalcitrant species for androgenesis—a process through whichHow to cite this paper: Zheng, M.Y., Bieren, K. and Griggs, R. (2015) Developmental Dynamics of Wheat (Triticum aestivum L.) Microspores under Culture
The results indicate that of the total number of microspores initially cultured, about 40% proceeded to the multicellular structure phase while the remaining 60% failed to divide or divide beyond the first two cell cycles (Figures 7-9)
Of the embryogenic microspores that proceeded to multicellular structures, 54% - 58% developed into mature embryoids for the genotypes studied
Summary
Triticum aestivum was once considered as a recalcitrant species for androgenesis—a process through whichHow to cite this paper: Zheng, M.Y., Bieren, K. and Griggs, R. (2015) Developmental Dynamics of Wheat (Triticum aestivum L.) Microspores under Culture. In vitro embryogenesis, called somatic embryogenesis, is the production of a pseudo-embryo (or embryoid) from a cell without involving fertilization. This embryoid so obtained is functionally equivalent to an embryo and able to germinate into a plant under adequate conditions. The most appropriate time to reprogram microspores for embryogenesis in cereal species is the mid to late uninucleate stage [4] [9]. During this period, microspores are not yet fully committed to their developmental fate and are susceptible to androgenic induction [8]. Once the first gametophytic mitosis occurs, the cytoplasm in immature pollen may be dominated with gametophytic cues, making it very difficult to reverse the development toward a male gametophyte [10] [11]
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