Abstract
The use of doubled haploids in onion breeding is limited due to the low gynogenesis efficiency of this species. Gynogenesis capacity from Spanish germplasm, including the sweet cultivar Fuentes de Ebro, the highly pungent landrace BGHZ1354 and the two Valenciana type commercial varieties Recas and Rita, was evaluated and optimized in this study. The OH-1 population, characterized by a high gynogenesis induction, was used as control. Growing conditions of the donor plants were tested with a one-step protocol and field plants produced a slightly higher percentage of embryogenesis induction than growth chamber plants. A one-step protocol was compared with a two-step protocol for embryogenesis induction. Spanish germplasm produced a 2–3 times higher percentage of embryogenesis with the two-step protocol, Recas showing the highest percentage (2.09%) and Fuentes de Ebro the lowest (0.53%). These percentages were significantly lower than those from the OH-1 population, with an average of 15% independently of the protocol used. The effect of different containers on plant regeneration was tested using both protocols. The highest percentage of acclimated plants was obtained with the two-step protocol in combination with Eco2box (70%), whereas the lowest percentage was observed with glass tubes in the two protocols (20–23%). Different amiprofos-methyl (APM) treatments were applied to embryos for chromosome doubling. A similar number of doubled haploid plants were recovered with 25 or 50 μM APM in liquid medium. However, the application of 25 μM in solid medium for 24 h produced the highest number of doubled haploid plants. Somatic regeneration from flower buds of haploid and mixoploid plants proved to be a successful approach for chromosome doubling, since diploid plants were obtained from the four regenerated lines. In this study, doubled haploid plants were produced from the four Spanish cultivars, however further improvements are needed to increase their gynogenesis efficiency.
Highlights
Onion (Allium cepa L.) is a valuable crop for food and medicinal purposes, ranking second after tomato in the list of vegetables cultivated worldwide, with production of over 90 million tons on 4.7 million ha (FAO, 2013)
OH-1 is a synthetic population specially designed for high gynogenesis induction, obtained with inbred lines B2923B and B0223B (Havey and Bohanec, 2007)
Effect of Donor Plant Growing Conditions on Gynogenesis Induction and Plant Production Bulbs from Fuentes de Ebro, Recas, and Rita were grown in the field and in a growth chamber
Summary
Onion (Allium cepa L.) is a valuable crop for food and medicinal purposes, ranking second after tomato in the list of vegetables cultivated worldwide, with production of over 90 million tons on 4.7 million ha (FAO, 2013). The onion production in Spain is over 1.2 million tons, ranking second among crop vegetables. Onion is an allogamous species and both open pollinated cultivars and hybrids are cultivated. Uniform highly inbred lines are needed for hybrid production, but they are difficult to obtain through conventional methods of plant breeding (between 10 and 12 years) due to severe inbreeding depression and their biennial cycle, (Jakše et al, 2010). Haploid onion plant production and subsequent chromosome doubling offers a time-saving approach to obtain pure inbred lines (Dunwell, 2010; Chen et al, 2011). Onion breeding programs based on DH are being conducted at different public institutions such as Cornell University (Hyde et al, 2012), Wisconsin University in collaboration with Ljubljana University (Duangjit et al, 2013), Texas A&M University (Walker et al, 2006), INTA (Dr Galmarini, personal communication), the Agricultural University of Kraków in collaboration with private companies (Adamus, personal communication), and Pamukale University (Alan et al, 2014; Celebi-Toprak et al, 2015)
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