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白杨三倍体及其插穗生根特性的研究
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摘要
本论文主要针对毛白杨三倍体育种与生产中存在的生根困难、品种混杂等问题,开展了有关易生根三倍体选育、毛白杨三倍体特性及三倍体生根性与扦插繁殖的研究,取得了阶段性进展。
     (1)以银毛杨为母本,毛白杨为父本,选育出苗期表现优良的白杨杂种989号无性系。苗期测定表明,989号无性系具有生长快、抗性及生根力强等特点。年生长量苗高、胸径分别超过同类条件下毛白杨的34.02%和19.94%,和三倍体毛白杨生长量相当。在高温、干旱、低温条件下细胞原生质膜受害较轻,初具较强的耐逆性。在根原基、先期根数、诱导根数等生根性状上优于毛白杨及其三倍体,同亲本银毛杨差异不显著。经形态及显微结构观察比较,989的巨大性十分明显。染色体镜检表明其体细胞染色体数大于50条,是一个很有前途的三倍体无性系。
     (2)在详细观察测量各无性系形态器官的基础上,对毛白杨三倍体进行了苗期形态分类研究。将6个三倍体品种根据叶型分为两组,即花叶型和圆叶型。花叶型叶片大,叶形不规则,3—5深裂,分枝多。圆叶型叶较小,有规则的叶形,叶全缘,几不分枝。根据每个无性系的典型特征将其分别命名为:掌叶三毛杨(S1)、直脉三毛杨(S2)、多毛三毛杨(S3)、三角三毛杨(S4)、褐干三毛杨(S5)和皱叶三毛杨(S6),特征明显,易于识别。
     (3)6个三倍体毛白杨在生长和抗性上存在显著差异。总体上花叶型优于圆叶型。S1、S2、S3、和S4生长量大,S5和S6生长量小。抗旱性次序为S3> S2> S1>S4>毛白杨> S6> S5,抗寒性次序为S2>S1>S3>S4>S5>毛白杨>S6。综合各无性系抗性指标极差标准化均值表明,在抗旱能力上S1、S2、S3属同一类型,S5、S6属同一类型;在抗寒能力上,S1、S2属同一类型,S3、S4、S5属同一类型。
    (4)三倍体毛白杨生根力受品系、种条部位及人为处理因素影响较大。各无性系之间生根率存在很大的差异,变异范围在45.9%—73.1%之间,生根性状的重复力在0.75以上,从中选择易生根无性系会得到很好的选择效果。三倍体苗干基部插穗生根力最强,扦插成活率比梢部插穗高33%。石蜡处理可明显提高三倍体扦插成活率及扦插苗质量,处理较对照扦插成活率提高了29.4%,苗高提高了18.4%,胸径提高了17.4%。石蜡处理提高扦插成活率的原因是促进皮部生根,推迟抽枝展叶期,机理是改善了插穗的水分状况。生长素可促进皮部生根,但对愈伤组织生根作用不明显。生长素中低比例的细胞分裂素可明显促进愈伤组织根的形成,含量高则起反作用。论文通过流水浸条、石蜡处理、NAA+BA(2:1)(浓度250—750ppm)相结合的措施,将三倍体扦插成活率提高到65.4%的平均水平,最高达82.3%。
     (5)首次对杨树混系扦插繁殖条件下群体遗传结构及由此所导致的后果进行了探讨。在混系扦插繁殖时,各无性系由于生根率的差异产生不同的生根选择压,结果导致群体的基因型频率发生变化,易生根的基因型频率逐渐增大,趋近于1;难生根的基因型频率逐渐减小,趋近于0,并最终被淘汰;群体生根率逐渐提高。当优良性状与生根率负相关时,混系扦插繁殖会对遗传增益产生负效应;当优良性状与生根率正相关时,对用材树种而言可提高遗传增益,此时用生根选择压提高扦插成活率是可行的。三倍体毛白杨属这种情况。考虑到生物多样性的重要性,必须保持三倍体群体合理的基因组成,最有效的办法是建立采穗圃或采根圃。
Directed against the question of rooting difficulty and strain mixing etc on breeding and propagation, breeding of easy rooting triploid, characters and cutting propagation of the triploids Section Leuce were studied. The research results were as follows:
     1) The Section Leuce hybrid 989 clone, bred through P. alba×P. tomentosa crossing, appeared the obvious superiority in growth, resistance to adversity and rooting character at seedling stage. It's seedling height and breast diameter exceeded P.tomentosa 34.02%and 19.94% respectively under the same condition, and it was not obvious difference with triploid P. tomentosa. The cell plasma membrane was damaged little under high temperature, drought or low temperature condition. It was better than P. tomentosa and the triploid, and had no obvious difference with it's parent P. alba at the character of root primordia, primary root number and induced root number. The giant quality of 989 was very obvious through morphology and microscope observation. The chromosome of 989 was more than 50. 989 was a potential triploid.
     2) Based on detailed observation and measurement of the morphology organ of every clone, the 6 triploid clones were divided into two groups ——leaf-crack type and leaf-round type, the former's leaf was bigger, and its leaf shape was irregular and had 3-5 cracks, and it had more lateral branches. The later,'s leaf was smaller, and leaf shape was regular and had no cracks, and it had less lateral branches. According to the typical characteristic of every clone, we named them as palm-leaf triploid P.tomentosa(S1), vertical-verve triploid P.tomentosa (S2), more-down triploid P.tomentosa(S3), triangle-leaf P.tomentosa(S4), brown-stem triploid P.tomentosa(S5), and wrinkle-leaf triploid P.tomentosa (S6), whose characteristic were obvious and easy to be recognized.
     3) The 6 triploidS P. tomentosa had obvious difference in growth and resistance. Totally, the type of leaf-crack is better than that of leaf-round. The growth increment of S1, S2, S3and S4 were bigger than that of S5 and S6. The drought-resistance abilities of 6 clones from high to low were S3>S2>S1>P.tomentosa>S6>S5, the cold-resistance abilities order was S2>S2>S3>S4>S5> P.tomentosa >S6. The standardized index average of each resistance indexes of clones showed that S1, S2 and S3 belonged to same type on drought resistance, S5 and S6 belonged to same type, and on cold resistance S1 and S2 belonged to same type, and S3, S4 and S5 belonged to same type.
     4) The rooting ability of triploid P.tomentosa was affected extremely by variety, cutting's position and artificial factors. There was a great difference in rooting rate among 6 triploid clones. The variation range was from 45.9% to 73.1%, and the heritability of rooting characters was more than 0.75. So, selecting easy rooting clone from triploid population may be better. The cuttings at the base of triploid stem had a relative higher rooting ability compared with cuttings at the top, and the survival rate of cuttings at the base was higher 33% than that of the top. Treating cuttings with paraffin wax could increase the survival rate of cuttings and quality of seedlings remarkably. Compared with the contrast, the survival rate, height and breast diameter of seedlings were increased respectively 29.4%, 18.4% and 17.4%. The reason of wax increasing survival rate was that it can promote bark rooting, postpone the time sprouting, the mechanism is developing the cuttings water condition. Auxin can promote bark rooting but had no effect on callus rooting. A small amount of cytokinin added to auxin could result in stimulating the development of the callus and adventitious root formation from callus. Through wax and NAA+BA (2:1) (concentration 250-750ppm) treatment, the survival rate of cutting was increased average 65.4%, and the biggest is up to 82.3%.
     5) The variation of the population genetic structure and its effect under the condition of poplar mixed strain cutting propagation were pro
引文
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