香荚兰镰刀菌根腐病药剂毒力测定及幼根接种防治试验

在ＰＤＡ含毒介质上的试验表明,苯莱特（５０％ＷＰ）、多菌灵（５０％ＷＰ）、甲基托布津（７０％ＷＰ）抑菌效果最好,稀释３０万倍的药液对尖孢镰刀菌抑菌率分别为１００％、９１．９％、６７．９％,而粉锈灵（１５％ＷＰ）３０００倍液,抑菌率仅为７０．１％;苯莱特、粉锈灵１５００倍液对腐皮镰刀菌抑菌率仅为９４．４％和１４．０％。苯莱特和粉锈灵对尖孢镰刀菌的抑菌效果明显高于腐皮镰刀菌。抑菌圈法试验,多菌灵、苯莱特５００～１０００倍液对腐皮菌的防效又优于尖孢镰刀菌,而粉锈灵对２种镰刀菌均不产生抑菌圈。香荚兰幼根接种药效试验,粉锈灵对尖孢镰刀菌防效最好（５６．６％）,多菌灵、甲基托布津次之（５１．６％、５０．９％）,而苯莱特较差（４０．４％）。粉锈灵１０００倍液浸泡１ｈ和盆栽施药,均对香荚兰幼根产生药害。     

西双版纳香荚兰根腐病发病规律研究

通过系统观察,香荚兰根腐病周年发生,随种植时间延长而病情累积增高。新增病根发病率增高在高温季节,而在低温干旱季节降低。根腐病发病率＜５０％的调查样方有１９．７％的表现出蔓叶发黄;发病率＞６０％的,则有９０％以上的蔓叶发黄,可以把发病率＜４０％作为该病的控制指标。田间管理好,根系发达,生长良好的园地,病情较轻。离体幼根接种试验表明,根尖和根毛区是病原主要的入侵部位。有１５％的幼根不感病,大多数感病根,病斑扩展到一定程度即停止活动,仅有１２％的根病斑发展到全根死亡。病斑扩展期为２～７ｄ,扩展速度为０．２～８．４ｍｍ／ｄ。     

深耘断根对旱地高产小麦花后根系干重及产量的影响

在旱地大田条件下研究了深耘断根对旱地高产小麦花后根系干重及产量的影响,结果表明,４个处理中以冬前深耘断根最好,起身期深耘断根与对照（不断根）次之,冬前和起身期都深耘断根效果最差,冬前深耘断根可增加中,下层和根系的重量和比率,降低根系生长冗余性,控制最高总茎数,提高成穗数及成穗率,使子粒产量中各自花后光合率官输送的比例增加,从而使产量提高,因而在旱地高产麦田应推广冬前深耘断根。     

大麦剑叶形态生理性状的遗传分析

1986-1989年间,用8个大麦品种建立完全双列杂交,对剑叶长、宽、面积、开张角、叶基角和披垂度等形态生理性状进行遗传分析。对F#-1代的双列分析表明,除披垂度外,其余5个性状均符合加性一显性模型。其中,加性效应起着主要作用;叶基角以低值为部分显性,其余性状均以增值为部分显性;剑叶长的狭义遗传力较高,在80%左右,其余性状在50%-60%之间。各性状在F#-2群体中均表现出连续分布,测定值基本分布在双亲值的范围内,超亲优势不明显。剑叶长和宽均匀与面积呈极显著正相关,其中长与面积的关系更为密切;开张角、叶基角和披垂度之间呈极显著正相关,三者与叶长和叶宽分别呈极显著正相关和负相关。     

玉米自交系对镰刀菌茎腐病抗性的研究初报

玉米自交系对镰刀菌茎腐病的抗性存在着广泛的遗传变异(gcv=18.37%),并具有较高的遗传力(h~2=84.87%)。随着玉米年龄的增大,髓组织密度与髓组织含糖量间的相关系数的绝对值逐渐增大,在抽雄后19天和28天,正相关性达到了极显著水平。病害发展过程中各时期的髓组织密度对茎腐病级别的总效应和直接效应皆为负值;不同时期的髓组织     

Rooting ability of Leucaena leucocephala stem cuttings

Single-node leafy and leafless cuttings harvested from one-year-old, 1.3 to 1.5 m tall Leucaena leucocephala seedlings were successfully rooted in a non-mist propagator which is suitable for use in the rural tropics. Cuttings with a leaf attached rooted more successfully than those without a leaf (71% and 39% respectively) and clones differed significantly (43% to 71%). There was also a clear pattern in rooting ability of cuttings collected sequentially down the main stem. Cuttings rooted most successfully when taken from node five to 13, counting from the apex; this was the region where internodes were longest (64 to 109 mm) of moderate diameter (2.9 to 5.5 mm) and all cuttings had a leaf attached. This revised version was published online in June 2006 with corrections to the Cover Date.     

Distribution of ectomycorrhizas and ectomycorrhizal fungal inoculum with soil depth in a birch forest

The distributions of ectomycorrhizas and ectomycorrhizal fungal inoculum with soil depth (0–45 cm) were determined in a 40-year-oldBetula platyphylla var.japonica forest. Mycorrhizal and non-mycorrhizal fine roots were measured in each soil core sample that was collected at soil depths of 0–5, 5–10, 10–15, 15–20, 20–25, 30–35, and 40–45 cm. The ectomycorrhizas were mainly distributed (>50%) in the top soil (0–5 cm) of organic forest floor horizons. Below 5 cm the quantity of ectomycorrhizas decreased sharply. The percentage of fine roots which were ectomycorrhizal gradually declined with the depth of soil. The ectomycorrhizal fungal inoculum was evaluated by a bioassay method, measuring the lengths of the entire root system and of the ectomycorrhizal roots of birch seedlings planted in each soil sample. The soil samples were collected from 0–5, 10–15, 20–25, 30–35, and 40–45 cm depths of the soil profile. Ectomycorrhizal formation on birch seedling roots in the bioassay was high in both the soil depth intervals 0–5 cm and 10–15 cm, while the amount was lower in the soil depth interval from 20–45 cm. The results of these investigations show that the amount of the ectomycorrhizas in soil, and the ectomycorrhizal fungal inoculum potential as determined by bioassay, are not always consistent with each other.     

Field performance of containerized black spruce seedlings with root systems damaged by freezing or pruning

Roots of 2-year-old black spruce seedlings (Picea mariana [Mill.] B.S.P.) were exposed to freezing temperatures to destroy 20, 40, 60, and 80% of the root systems. For comparison, other root systems were pruned to eliminate the same proportions of roots. Treated and control seedlings were planted in spring 1992 at Forêt Montmorency (the Université Laval forest research station, 50 km north of Quebec City). From 1992 to 1995, survival, shoot height and stem diameter were measured. Mortality mainly occurred in 1993, the year after planting; pruned seedlings showed practically no mortality while seedlings with 20, 40, 60, and 80% of their root systems affected by frost showed mortality rates of 0, 6, 17, and 24%, respectively. Shoot height and stem diameter decreased with increasing root damage when compared to controls. After three years on the planting site, shoot height was reduced by 2, 8, 11, and 18% while stem diameter was reduced by 4, 21, 25, and 24% for 20, 40, 60, and 80% frost damage, respectively. For pruned seedlings, shoot height was increased by 3% at 20% damage and was decreased by 1, 3, and 13% for 40, 60, and 80% root damage while stem diameter was reduced by 1, 4, 8, 19% for 20, 40, 60, and 80% respectively. Use of damaged seedlings on the planting sites should be limited in order to reduce the cost of replacement planting.     

Analysis of genetic variability of aluminium tolerance response in triticale

Comparative analyses of genetic variability of aluminium tolerance response were made in a range of triticale genotypes of two sets, one consisting of six Australian cultivars (or lines), the other consisting of eight South African lines and an Australian check, by following solution culture and screening under controlled growth cabinet conditions. Results showed that Tahara, Tahara ‘S’ and Abacus were the most Al-tolerant triticales among the Australian genotypes in terms of root regrowth characteristics at 10 μg.g^-1 Al. The 19th ITSN 70-4, along with the standard cultivar Tahara was superior to all other South African genotypes; the eight South African genotypes spanned the range from Al-tolerant, moderately Al-tolerant to Al-sensitive. Regrown root length and percentage of seedlings with root regrowth were the two key indicators for screening and evaluating Al tolerance response. Considerable genetic variability of tolerance to Al stress among the two sets of tested genotypes was revealed by the estimates of genetic parameters. High heritability values were recorded for those two indicators, with associated high levels of relative genetic advance (RGA). Further improvement of varietal tolerance to Al stress in triticale could be anticipated through selection and breeding. This revised version was published online in July 2006 with corrections to the Cover Date.     

土壤水分对冬小麦初生根和次生根生长发育的影响

１９９３－１９９４年冬小麦管栽水分试验结果表明,初生根与次生根生长量、数量及分枝能力基本与土体水量呈正相关,胁迫程度愈深,受抑程度愈大。初生根特别是一、二次根及其分枝数人有很强抗逆能力。水量愈大,三,四次根数愈多。次生根尤其是其数量对对水土土水环境极为敏感。当土壤含水量低于田间持水量６０％时,受到严重抑制。胁迫后复水,使初一根三次根数量增加,根系活性延长,地次生根的激励作用更大,前期胁迫愈严重。促