Mycorrhizal infectivity of eroded soils

A method to assess the mycorrhizal inoculum infectivity of soils is described. Mature pasture soils in the North Island, New Zealand, had 6–19 mycorrhizal propagules g^?1 soil. Of 31 samples taken from extensive areas of eroded soil around Gisborne and Masterton 22 had fewer than 1.0 mycorrhizal propagule g^?1 soil, and 13 of these soils had less than 0.2 propagules g^?1. In a pot trial, mycorrhizal inoculation of white clover plants increased shoot growth in seven eroded soils, by 1–12-fold.     

Occurrence, isolation and biological activity of phytotoxic metabolites produced in vitro by Sphaeropsis sapinea, pathogenic fungus of Pinus radiata

Sphaeropsis sapinea was repeatedly isolated in Sardinia from symptomatic samples of the upper part of declining pine (Pinus radiata) plants. Observed symptoms mainly consisted of foliage chlorosis, drying of needles and cankers on branches. The S. sapinea strains were shown to produce phytotoxic metabolites in culture filtrates. Three metabolites were isolated for the first time from this fungus and identified by their spectroscopic and optical properties as R-(−)-mellein, (3R,4R)-4-hydroxymellein and (3R,4S)-4-hydroxymellein. When assayed for phytotoxic and antifungal activities on host and non-host plants and on some phytopathogenic fungi, the R-(−)-mellein showed significant activity, while the other two 3,4-dihydroisocoumarins showed only a synergic activity in both tests.     

Pepper resistance-breaking tobamoviruses: Can they co-exist in single pepper plants?

We previously reported a procedure for identifying pathotypes of the tobamoviruses infecting the L-resistant genotypes of pepper based on the polymerase chain reaction (PCR) (Tenllado et al., 1994). We have now used this method to assess pathotype incidence in virus isolates from field pepper samples representing three successive epidemic episodes in southeastern Spain, and to analyse the interaction of pathotypes during experimental infections in pepper plants. The majority of virus isolates corresponded to the P_1,2 pathotype, and only three out of twenty behaved as P_1,2,3 pathotypes. Interestingly, restriction enzyme analysis of the PCR-amplified products distinguished two restriction subgroups on each P_1,2 and P_1,2,3 pathotype, referred to as restrictopatterns I₁ and I₂ or II₁ and II₂, respectively. Experimental coinoculations of pepper plants with mixtures of two different pathotypes showed coexistence between them when inoculations proceeded simultaneously. However, reciprocal cross-protection was observed between P_1,2 and P_1,2,3 pathotypes when they were successively inoculated, while no cross-protection was observed between P₁ and either P_1,2 or P_1,2,3 pathotypes. The potential of the PCR-based method for detecting heterogeneity within P_1,2 and P_1,2,3 pathotypes, and the possibility of genetically engineered resistance to those viruses by genetic transformation with viral coat protein genes are briefly discussed.     

3个巴西橡胶树品种的死皮病调查

在现有割胶制度下对巴西橡胶树3个品种(热研8-79、热研7-33-97、PR107)的死皮病进行了调查。结果表明:这3个品种的幼龄树发病率和停割率从大到小依次为热研7-33-97(开割4年)PR107(开割6年)热研8-79(开割3年),中龄树发病率和停割率从大到小依次为PR107(开割15年)热研7-33-97(开割8年)热研8-79(开割14年)。3个品种的中龄橡胶树比幼龄橡胶树的死皮病发病率、停割率和病情指数都有所上升。总体来看,对于幼龄橡胶树而言,肥水条件较好的地块,年干胶株产量高,发病率和停割率低;而中龄树除热研7-33-97表现出幼龄树的趋势外,其它2个品种(热研8-79和PR107)则干胶株产量高,发病率和停割率也高。绝大多数死皮病属割面干涸类型,少部分为褐皮病;褐皮病有一部分是一开始就发生的,多数是由割面干涸发展而来的。在停割至少1年之后,能够恢复排胶的死皮树比例较小,很少超过10%。在3个橡胶树品种中,PR107品种恢复排胶的比例最高,幼龄树和中龄树恢复率分别达8.70%和6.20%。     

牛病毒性腹泻病毒一步 RT-LAMP快速检测方法的建立

[目的]建立一种快速、敏感、特异的检测牛病毒性腹泻病毒（BVDV）反转录环介导等温扩增（RT-LAMP）方法,为诊断与监测BVDV 提供准确可靠工具。[方法]根据GenBank公布的BVDV序列,在其保守序列区域设计了一套 LAMP引物,优化了反应时间与反应温度,建立了检测 BVDV的 RT-LAMP方法。[结果]该方法能在56℃等温条件下40分钟完成扩增,扩增结果可通过凝胶电泳梯形带判定。该方法具有良好的特异性和敏感性,最低能检测到3.74×100 copies/μl的病毒 RNA,而且与其他病毒无交叉反应。[结论]该方法能用于牛病毒性腹泻病毒的诊断与监测。     

益生菌SFU—9发酵工艺的确定

益生菌具有促进动物生长，提高机体免疫能力等生理功能，常用作微生态饲料添加剂。菌体SFU－9是一株蜡状芽杆菌，该菌株在不利环境下能够以孢子形式存在，具有耐高温，耐酸碱和耐挤压等优点，较乳酸菌，酵母菌等益生菌更能保持活菌状态，适合饲料加工业的需要。该研究以菌株SFU－9进行实验，研究发酵温度，接种量，培养基初始pH值，溶解氧等因素对菌株生长的影响，确定出最佳培养条件为：培养基初始pH值为6．0－6．5，接种量5％（相对摇瓶装液量），培养温度30－32℃，装液量28-33mL/250mL。发醇液中的活菌数可达10^11cfu/mL。在此基础上，采用单因子和正交实验相结合的方法，确定出最佳发酵培养基组成为：玉米淀粉2．0％，啤酒酵母1．5％，NaH2PO40.2%,Na2HPO40.2%,玉米浆2．0％。是以最佳培养基配方给菌体提供营养，在最佳培养条件下培养，可以使发酵液中的活菌数高达10^12cfu/mL.     

小麦 B 染色体组双端体旗叶 CO2 导度的研究

采用整套“中国春”Ｂ组双端体为材料，研究了田间条件下不同染色体臂缺失对叶片导度及净光合速率（Ｐｎ）的影响，结果表明：在旗叶一生中，气孔导度（ｇｓ）、叶肉导度（ｇｍ）和净光合速率（Ｐｎ）均于叶片全展达到最大值以后逐渐下降，胞间ＣＯ２体积比（Ｃｉ）自叶片全展后不断增加。各供试Ｂ染色体组双端体材料的叶片导度表现不同，染色体臂１ＢＬ、２ＢＬ、５ＢＬ、６ＢＬ、２ＢＳ和３ＢＳ对气孔导度（ｇｓ）有正效应，７ＢＬ     

马氏珍珠贝肉营养液的研制及营养评价

采用酶技术,利用珍珠养殖场开珠后的废弃物－－马氏珍珠贝肉,研制珍珠贝肉营养液。结果显示,采用枯草杆菌中性蛋白酶和风味酶Ｆｌａｖｏｕｒｙｚｍｅ联合水解马氏珍珠贝肉的效果最好,通过正交试验法确定了酶法水解的最佳工艺条件是：温度５０℃,时间５ｈ,ｐＨ６．５,枯草杆菌中性蛋白酶和Ｆｌａｖｏｕｒｙｚｍｅ的添加量分别为０．６％和０．２５％。对营养液的营养价值进行分析评价,营养液中蛋白质达到７３．６ｍｇ／ｍＬ,