Abstract
Changes in the chemical environment at the maturation stage in Pinus spp. somatic embryogenesis will be a determinant factor in the conversion of somatic embryos to plantlets. Furthermore, the study of biochemical and morphological aspects of the somatic embryos could enable the improvement of somatic embryogenesis in Pinus spp. In the present work, the influence of different amino acid combinations, carbohydrate sources, and concentrations at the maturation stage of Pinus radiata D. Don and Pinus halepensis Mill. was analyzed. In P. radiata, the maturation medium supplemented with 175 mM of sucrose and an increase in the amino acid mixture (1,100 mgL–1 of L-glutamine, 1,050 mgL–1 of L-asparagine, 350 mgL–1 of L-arginine, and 35 mgL–1 of L-proline) promoted bigger embryos, with a larger stem diameter and an increase in the number of roots in the germinated somatic embryos, improving the acclimatization success of this species. In P. halepensis, the maturation medium supplemented with 175 mM of maltose improved the germination of somatic embryos. The increase in the amount of amino acids in the maturation medium increased the levels of putrescine in the germinated somatic embryos of P. halepensis. We detected significant differences in the amounts of polyamines between somatic plantlets of P. radiata and P. halepensis; putrescine was less abundant in both species. For the first time, in P. radiata and P. halepensis somatic embryogenesis, we detected the presence of cadaverine, and its concentration changed according to the species.
Highlights
Somatic embryogenesis has been suggested as the most promising method for vegetative propagation for a large number of conifers (Gupta et al, 1993), and it can help to capture the greatest benefits from traditional breeding programs by multiplying trees with desirable characteristics for plantation forestry (Pullman and Bucalo, 2014).Pinus radiata D
Significant differences were observed when comparing the osmolality of MIX I with the media supplemented with MIX II and MIX III (Table 3)
Regarding the amino acid mixture used in the maturation media, statistically significant differences were found for all the parameters evaluated in P. radiata (NAE, LE, WE, germination of ses, and acclimatization of plantlets) except for the NNE and LE/WE ratio (Table 4)
Summary
Somatic embryogenesis has been suggested as the most promising method for vegetative propagation for a large number of conifers (Gupta et al, 1993), and it can help to capture the greatest benefits from traditional breeding programs by multiplying trees with desirable characteristics for plantation forestry (Pullman and Bucalo, 2014).Pinus radiata D. In previous experiments, we have focused on the optimization of somatic embryogenesis (SE) processes In this sense, the optimization of initiation and proliferation stages of SE in P. radiata (Montalbán et al, 2010, 2012) and P. halepensis (Montalbán et al, 2013) has been our objective in recent years. Some studies focused on promoting and improving the embryogenic process in terms of quality and quantity of somatic embryos (ses) obtained by reduction of water availability in P. radiata (Garcia-Mendiguren et al, 2016; Castander-Olarieta et al, 2020) and P. halepensis (Pereira et al, 2016, 2017; do Nascimento et al, 2020) have been carried out. The rate of germination (%) and the subsequent conversion into plantlets is sometimes low (do Nascimento et al, 2020), and additional research is needed to increase somatic plantlet regeneration (Montalbán and Moncaleán, 2019)
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