Phenotypic diversity for natural populations of Juniperus rigida in the Helan Mountains of Ningxia

Key words: 
• forest tree breeding /
• Juniperus rigida /
• natural population /
• phenotypic diversity /
• Helan Mountains

Abstract: To determine the phenotypic variation for natural populations of Juniperus rigida and the relationship between phenotypic variation and different population distribution areas，six populations and 120 families were sampled in the Helan Mountain Nature Reserve of Ningxia. Twenty phenotypic traits were analyzed，including needles，cones，seeds，height，diameter at breast height（DBH），crown diameter，height-diameter ratio，crown-diameter ratio，density of primary branches，height of stem under branch，stem straightness，total number of primary branches and length，and diameter of primary branches using variance analysis，correlation analysis，and the Unweighted Pair Group Method with Arithmetic Mean（UPGMA）hierarchical cluster analysis. Results showed that significant differences （P ＜ 0.01） among populations for 11 characteristic indices，such as needle length/needle width，cone length，cone width，cone length/cone width，seed length，seed width，seed length/seed width，DBH，stem straightness，height-diameter ratio，crown-diameter ratio，total number of primary branches，diameter of primary branches，and height of stem under branch. Also within populations，seven characteristic indices were significantly different（P ＜ 0.01），such as needle length，needle width，needle length/needle width，cone length，cone width，seed width，and seed length/seed width. Variation among populations mainly contributed to phenotypic variation with a mean phenotypic differentiation coefficient（Vst） of 66.63%; whereas within populations，VST was 33.37%. For correlations between needle length and total number of primary branches，canopy density was positively and significantly（P ＜ 0.05）correlated; for needle width, altitude was significant（P ＜ 0.01）positive correlated；for height of stem under branch, gradient was significant（P ＜ 0.05） positive correlated；for needle width, slope direction was significant（P ＜ 0.05）negative correlated；In addition, six populations gathered into four groups by cluster analysis, which inconsistent with the geographic distribution and altitude gradient of Juniperus rigida in the Helan Mountains. There were significant differences in phenotypic variation among and within populations. Utilizing of variation within and among populations is important significance for genetic improvement of Juniperus rigida.［Ch, 1 fig. 7 tab. １９ ref.］