Abstract
Objective The objective is to screen the optimal medium suitable for callus induction from unpollinated ovules of Camellia oleifera, and explore the origin and developmental process of callus by cytological observation, so as to provide data reference for haploid breeding of C. oleifera. Method C. oleifera ‘huajin’ was used as the test material to screen the optimal medium formula for inducing callus from unpollinated ovule, and to study the basic medium types MS, WPM, MT, 1/2MS, and B5, as well as effects of plant growth regulator concentration such as auxins NAA, IAA, IBA, and 2,4-D, and cytokinins 6-BA, KT, and TDZ on callus induction. Calluses with different external morphology were selected for paraffin section, and their origin and development process were studied according to the ploidy identification results of flow cytometry. Result MS was used as the basic medium, and the highest induction rate was 92.97% when 1.0 mg·L−1NAA+2.0 mg·L−1 TDZ+40 g·L−1 sucrose was added. NAA and TDZ had significant effects on the induction rate(P＜0.05), and the impact of TDZ was greater than that of NAA. The embryogenic callus was light green granular, with cytological characteristics of close arrangement, large nucleus, and ploidy identification of hexaploid. Conclusion The optimal medium for inducing embrygenic callus from unpollinated ovules of C. oleifera is MS+40 g·L−1sucrose +7 g·L−1 AGAR +1.0 mg·L−1 NAA+2.0 mg·L−1 TDZ. The callus is formed by dedifferentiation of outer integument cells. A relatively stable and efficient technical system for inducing embryogenic callus from unpollinated ovules of C. oleifera is obtained, providing a reference for further establishing a complete and efficient system for somatic embryogenesis and haploid breeding of C. oleifera. [Ch, 4 fig. 3 tab. 33 ref.]
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