In preparation for a major GWAS (Genome Wide Association Study) of plant regeneration and transformation, a large number of factors were examined for their effects on indirect regeneration rate in diverse wild genotypes—seeking a high rate of regeneration, but also highly genetically variable and heritable treatments. Many of the factors examined have never before been reported on for their effects on callus, shoot, or root organogenesis in poplar (
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Abstract Populus ). Stems had the highest regeneration potential, followed by petioles and leaves, with greenhouse grown explant sources superior toin vitro growth explant sources. Changes of ± 50% to Murashige and Skoog (MS) basal medium salts and micronutrients had a minor effect on regeneration. Many popular treatments that were evaluated also had little to no useful effect at the levels studied, including activated charcoal, ascorbic acid, silver nitrate, melatonin, serotonin, sucrose concentration, and lipoic acid. As a result of this wide exploration, treatment combinations that substantially elevated regeneration in diverse genotypes were identified, enabling GWAS. -
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Summary Plants transition through juvenile and adult phases of vegetative development in a process known as vegetative phase change (VPC). In poplars (genus
Populus ) the differences between these stages are subtle, making it difficult to determine when this transition occurs. Previous studies of VPC in poplars have relied on plants propagatedin vitro , leaving the natural progression of this process unknown.We examined developmental morphology of seed‐grown and
in vitro derivedPopulus tremula × alba (clone 717‐1B4), and compared the phenotype of these to transgenics with manipulated miR156 expression, the master regulator of VPC.In seed‐grown plants, most traits changed from node‐to‐node during the first 3 months of development but remained constant after node 25. Many traits remained unchanged in clones over‐expressing miR156, or were enhanced when miR156 was lowered, demonstrating their natural progression is regulated by the miR156/SPL pathway. The characteristic leaf fluttering of
Populus is one of these miR156‐regulated traits.Vegetative development in plants grown from culture mirrored that of seed‐grown plants, allowing direct comparison between plants often used in research and those found in nature. These results provide a foundation for further research on the role of VPC in the ecology and evolution of this economically important genus.
