Researches On Clonal Propagation Technology Of Colorful Conifers

Due to the variety,rich color,long ornamental period and strong resistance characteristic,colorful conifers were excellent species in the northern cities.Colorful conifers mostly adopt clonal propagation technology.Whether using cutting or grafting propagation,there was the problem of how to control the quality and quantity of cuttings;in addition,the specific clonal propagation strategy should be established for different cultivars.This paper studies the technical measures which can improve the clonal propagation efficiency of different colorful conifer cultivars,including light conditions,pruning,cutting time and substrate,rootstock selection,etc.And then makes a continuous observation and comparison of grafted and cutting seedlings of some cultivars.This study provides theoretical guidance and technical support for the large-scale propagation of colorful conifers.The main findings are as follows:The five-year-old J.chinensis ‘Plumosa Aurea' and J.scopulorum ‘Blue Heaven' stock plants were treated with full light condition,30% of shading,and 50% of shading.Statistics and analysis of the differences in plant morphology,growth changes,and cutting yield were carried out.The cuttings under different treatments were cutting under full light,comprehensive evaluation of the effects of different light treatments on cutting quality was made combined with the rooting rate and rooting quality.The results showed that:(1)Photosynthetic capacity of J.chinensis ‘Plumosa Aurea' stock plants under 30% shading treatment was the strongest in the three groups.The yield of the stock plant was 8.65 per plant,the cutting rooting rate could reach to 76.3% due to the low degree lignification of cuttings.(2)The photosynthesis of the J.scopulorum ‘Blue Heaven' stock plants under 30% shading treatment was slightly lower than that of the full-light treatment group.The yield of the stock plant was 13.28 per plant.The phloem tissue was more developed than other groups,and the cutting rooting rate was 42.67%.The pruning methods of two partial crown cultivars were studied.the effect of cutting size on rooting quality was researched.The results showed that:(1)The germination ability of J.sabina ‘Tamaricifolia' and Juniperus×media ‘Pfitzeriana Aurea' were trimmed by 1/3 cut-back,the average cutting yield was 19.67 and 14.32,respectively.(2)The rooting rates of large and small cuttings of J.sabina ‘Tamaricifoli' were 96.67% and 93.33% respectively.And they were 65.33% and 76.67% respectively for Juniperus×media ‘Pfitzeriana Aure'.The cutting time and substrate for 9 cultivars were studied.The results showed that:(1)Callus rooting type were J.Chinensis ‘Saybrook Gold',J.scopulorum;and J.× Pfitzeriana ‘Gold Coas',they should choose pure perlite as the substrate for cutting in July.(2)Mixed(mainly callus-based)rooting type were J.scopulorum ‘Blue Heaven' and J.chinensis cv.Pyramidalis ‘Aurea',for these cultivars pure perlite should be selected as the substrate,and the appropriate propagation time was July.(3)Mixed(mainly rooting in the skin)rooting type were J.× media ‘Pfitzeriana Aurea',J.communis ‘Depressa Aurea',J.horizontalis ‘Blue Chip' and J.horizontalis ‘Prince of Wales',for these cultivars,using perlite: peat = 3: 1 or perlite: peat = 1: 1 as substrate in July and August can increase rooting rate.Researches on screening of rootstocks of different cultivars were made.The results showed that:(1)Ch.Pisifera ‘Filifera Aurea',J.chinensis cv.Pyramidalis ‘Aure' were compatibly with P.orientalis,S.chinensis and J.formosana;J.× Pfitzeriana ‘Gold Coast' was compatibly with J.formosana and P.orientalis;the remaining 7 cultivars were compatibly with one rootstock respectively.A comparative study of cutting and grafted seedlings of 4 cultivars were made.The results showed that:(1)The growth rhythm of the cuttings and the grafted seedlings was basically the same.The slow seedling period was from May to June,the fast growth period was from June to October,and then all seedlings gone to dormant.(2)The growth potential was stronger and the number of branches was more for grafted seedlings of Juniperus×media ‘Pfitzeriana Aurea',while which was greater for cutting seedlings of J.scopulorum ‘Blue Heaven'.There was no significant difference in between cutting and graft seedlings of J.horizontalis ‘Mother Lode'.(3)Grafting seedlings in Beijing area can survive without protection over winter,while cutting seedlings would have different degrees of freezing damage.