| Jujube(Ziziphus jujuba Mill.)is an economically important woody fruit tree that originated in China.Of the cultivated selections,‘Maya’ jujube(Ziziphus jujuba Mill.Maya zao)is among the most favored cultivars.The fruit of ‘Maya’ jujube has an attractive oval shape,thin peel,and is rich in nutrients and,thus,is popular among consumers.In the previous study,the research group used colchicine to induce2 n female gametes from ‘Maya’ in the field,and obtained a triploid germplasm after free pollination.In this study,the triploid germplasm was used as the material,and the paternal analysis was carried out.On this basis,by observing and comparing the characters of the triploid with its all-sibling diploid and its maternal parent,the variation of the growth characteristics of the triploid was understood.At the same time,a system of tissue culture and in vitro regeneration of the ’Maya’ and new triploid germplasm was established,and the process of in vitro regeneration of adventitious buds from leaves of the triploid germplasm was further observed in morphology and histology.The main test results are summarized as follows:(1)Through paternal analysis,the true paternal parent of the triploid germplasm was identified as wild jujube(Ziziphus jujuba Mill.var.spinosa(Bunge)Hu ex H.F.Chow),and four full-sib diploid plants were identified at the same time;according to the molecular marker allele configuration at the same site of the parent and the triploid,it was confirmed that the triploid germplasm is the result of doubling the chromosome of the female gamete.The triploid had more developed thorn,larger leaf area but lower leaf shape index.The triploid leaves were oval and the leaf margins were jagged,showing a clear difference from diploid.The length and width of stomata were significantly higher than that of diploid,but the density was lower.According to the observed leaf anatomy,it was found that the triploid leaves were thicker and more compact,with no significant changes in the number of cell layers but significant volume enlarged.Triploid plants also showed better photosynthetic and physiological traits.(2)The best initiation explants for ’Maya’ and triploid germplasm were stems with axillary buds;the best initiation medium was MS+6-BA 1.5 mg/L+IBA 0.2 mg/L+sucrose 30 g/L+agar 5.9 g/L,the axillary buds grew well.The best multiplication medium for tissue culture seedlings of triploid germplasm was MS+6-BA 1.0 mg/L +IBA 0.2 mg/L +TDZ 0.001 mg/ L+ sucrose 30 g/L+agar 5.9 g/L,the multiplication coefficient could reach 2.7.The meristerial buds had strong stems,dark green leaves and vigorous growth.The best rooting medium for triploid germplasm was 1/2MS+IBA 0.6 mg/L +NAA 0.4 mg/L+sucrose 20g/L+agar 5.9 g/L,the rooting rate,average root number and average root length reached 88.24%,5.47 and 0.52 cm,respectively.(3)’Maya’ semi-lignified stem with axillary buds had the best regeneration effect.The best induction medium was selected as MS+6-BA 1.5 mg/L+IBA 0.2 mg/L+TDZ 0.01 mg/L,the callus rate of stem segment could reach 100%,and the average number of buds per explant could reach 3.12.The buds and callus grow well.The best induction medium for the regeneration of adventitious buds from leaves of new triploid germplasm was WPM+TDZ 1.0 mg/L+IBA 0.3 mg/L+sucrose 30 g/L+agar 5.9 g/L,the adventitious bud induction rate reached 92.87%,and the number of adventitious bud regeneration per leaf could reach 3.6.Morphological and histological observations of the adventitious bud regeneration process found that the process is a direct regeneration method to obtain adventitious buds.The regenerated adventitious buds mainly originated from the parenchyma cells surrounding the leaf vein vascular bundles. |
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