Induction of Autotetraploids in Pummelo (Citrus grandis L. Osbeck) through Colchicine Treatment of Meristematically Active Seeds In Vitro

Divya Kainth, Jude W. Grosser

Abstract


Autotetraploids in pink/red-fleshed pummelo selections 5-1-99-2, C2-5-12, and UKP-1 (all derived from Hirado Buntan pink pummelo) were produced by treating the germinated seeds with different colchicine concentrations of control, 0.1%, 0.2%, and 0.3% for different treatment durations of 12 and 24 h. The seedlings emerged when put on rooting media under sterile conditions. The seedling ploidy was determined via flow cytometry at a stage when the seedlings had 1–2 expanded leaves. Higher colchicine concentrations and treatment durations decreased the survival rates of the seedlings compared with the lower concentrations and smaller treatment durations. The seeds that received higher concentrations and longer durations turned brown completely or had a dead meristematic bud. A similar trend was observed for the number of mutated shoots (tetraploids and mixoploids). Colchicine treatment decreased the growth rate of the affected seedlings. The frequency of autotetraploidy varied among the selections. Selections 5-1-99-2, C2- 5-12, and UKP-1 successfully produced 2, 1, and 3 autotetraploids and 1, 2, and 4 mixoploids, respectively. The most efficient colchicine concentration was 0.1%. Reversion of the tetraploids and mixoploids into diploids was also observed. The stable pink/red-fleshed tetraploid plants generated should be useful as breeding parents in grapefruit/pummelo improvement programs. Use of monoembryonic tetraploids in interploid citrus crosses eliminates the need for embryo rescue to recover seedless triploid progeny; until now, no pink or red-fleshed monoembryonic pummelo parents are available.

Keywords


Citrus paradisi, flow cytometry, interploidy crosses

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283