Identification of Molecular Markers for Gender Determination in Populus ciliata Wall ex Royle

Abstract

newline ABSTRACT newlineThe Himalayan poplar, Populus ciliata Wall. ex Royle, is a large deciduous, dioecious newlineand native tree of the Himalayas. Sex chromosomes are not identified in this species and at newlinejuvenile stage male and female trees do not show any significant phenotypic differences like newlineother dioecious plants. However, at maturity male and female trees are differentiated from each newlineother on the basis of biomass, growth rate and habitat etc. Near human settlements, propagation newlineof female plants is not recommended because seed production causes many health problems newlinelike allergies, respiratory diseases, etc. Reliable and quick methods are, therefore, needed for newlinedetermination of sex in juvenile plants of P. ciliata. It has been hypothesised that in plants newlinewhere sex chromosomes are not identified, there may be a gene in a plant s genome that newlineinfluences its gender. newlineThe present study dealt with the development of RAPD and isozyme markers for newlinegender determination. The variation in leaf morphological characters was also studied on newlinemature trees. In addition monthly variation in the concentration of two phenolic glycosides newline(salicin and populin) and their role in flowering from the bark and buds of both sexes was also newlineinvestigated. Out of ten random primers used, OPK-20 gave significant difference between newlinemale and female trees and identified as female specific marker (OPK-20400, OPK-20500 and newlineOPK-20800). The isozyme analysis was conducted with seven enzyme systems namely newlineperoxidase, esterase, malate dehydrogenase, alcohol dehydrogenase, catalase, ribulose newlinebisphosphate carboxylase and acid phosphatases. Peroxidase and esterase enzymes newlinesuccessfully showed differentiation between male and female genotypes. Peroxidase produced newlineone female specific band at a RM value 0.29 whereas esterase produced one male and one newlinefemale specific band at Rm values 0.30 and 0.11 respectively; thus distinguishing the female newlineand male plants genetically. newlineQualitative traits like shape of leaf blade, tip of leaf blade, sinus with petiole, newlinepubescence on the lower surface of leaf lamina, leaf margin and colour of leaf blade were newlineanalysed. Female and male trees were distinguished by the shape of base of leaf blade, its sinus newlineand leaf margin. On the other hand all quantitative traits excepting shape factor, leaf area, newlineaverage value in percentage for the ratio of lamina length to lamina width (L/W %), average newlinevalue in percentage for the ratio of petiole to medial nerve (P/N %), perimeter of leaf, aspect newlinexiv newlineratio showed non-significant differences. Study of monthly variation of salicin and populin newlineshowed accumulation of phenolic glycosides during flowering season but did not indicate their newlinerole in flowering. This study concludes that qualitative differences exist between male and newlinefemale trees besides specific markers. However, for identification of gender at seedling stage newlinemolecular markers (RAPD and isozyme) are best suited. Gender determination would help in newlinedetermining sex of juvenile plants of P. ciliata for plantations and also in its non-flowering newlinetrees for clonal propagation.