Abstract
Eucalyptus dunnii Maiden produces good quality cellulose pulp, showing good frost tolerance. However, in Uruguay, it needs more than six years to reach the reproductive stage. Genome duplication was proposed as a strategy to obtain useful variability. The application of mitosis inhibitors for chromosomal duplication, in explants growing in vitro, was evaluated. Two antimitotic agents were used: colchicine and oryzalin in different concentrations and exposure times, in two types of explants: explants growing in vitro and pre-germinated seeds. The number of chloroplasts was used as a rapid ploidy estimator and confirmed by flow cytometry. For chloroplast count, fluorescein diacetate (FDA) applied to in vitro leaves was used for staining. Oryzalin was effective for inducing plant duplication in E. dunnii from in vitro explants. In pre-germinated seeds, both antimitotic agents induced polyploids. The average number of chloroplasts was 5.5 in diploid control plants and more than 7 in tetraploids. Obtained plantlets were successfully cloned in the greenhouse. This is the first report on artificial polyploidy obtained in E. dunnii.
Highlights
The E. dunnii (Maiden) is a diploid species (2n=22) that belongs to the Myrtaceae family(1), originally from small populations in Queensland, Australia(2), and grows well in temperate climates, showing good tolerance to frost
Genome duplication is important for variability generation(1) since the change in the number of gene copies results in changes in the morphology, structure, and physiology of new individuals(8)(9)
Conditions of treatments T12, T13 and T14 were lethal for In vitro explants (IE) and in these treatments no individuals were recovered
Summary
The E. dunnii (Maiden) is a diploid species (2n=22) that belongs to the Myrtaceae family(1), originally from small populations in Queensland, Australia(2), and grows well in temperate climates, showing good tolerance to frost. Forest species have problems associated with the long period of juvenility until plants reach maturity and flowering; this is why a breeding program becomes slow, expensive, and complex(4). Considering the long reproduction cycle in these species, technologies have been developed to accelerate and shorten the breeding cycles; one of these technologies is polyploid induction. Polyploidy exists in nature and constitutes a way of generating new variability, mainly through the production of non-reduced gametes and interspecific hybridization(5), with the potential for almost instant reproductive isolation, in addition to being a proven source of novel adaptation(6)(7). Different methods have been used to generate polyploid trees, the application of colchicine is among the most used. This compound has shown great effectiveness in the results
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