Growth and development of Cuscuta chinensis Lam. and its impact on selected crops

The growth and development of Cuscuta chinensis Lam., and the effects of the holoparasite on the growth and yield of tomato ( Lycopersicon esculentum ), chilli ( Capsicum annuum ) and rice ( Oryza sativa ) were investigated in pot experiments under glasshouse conditions. 'Mature' and 'immature' seeds of C. chinensis showed 15 and 47% germination, respectively. The independent life duration of seedlings from 'immature' seeds was 6 days shorter than 'mature' seeds (19 days). Cuscuta chinensis formed haustoria on chilli and tomato, but not on rice seedlings. Infection with three C. chinensis seedlings per host plant reduced leaf area, dry weight, carbon and nitrogen content by 78–84% and 27–44% in tomato and chilli plants, respectively. Dry weight of C. chinensis was 0.63 g per pot in tomato, and 0.24 g per pot in chilli. Carbon and nitrogen content of C. chinensis was 0.189 and 0.028 g per pot, respectively, when grown with tomato. When it was grown with chilli, the carbon and nitrogen content of C. chinensis was 0.001 and 0.007 g per pot, respectively. Cuscuta chinensis reduced the fruit yield of tomato and chilli by 72 and 29%, respectively. The results indicated that tomato is a preferred host of C. chinensis compared with chilli, and rice is not preferred. In the host–parasite associations, C. chinensis suppressed growth and yield of chilli and tomato by diverting the elaborated products of metabolism of the hosts.     

Systemic spread of Plum pox virus (PPV) in Mariana plum GF 8-1 in relation to shoot growth

Infection of Prunus spp. by Plum pox virus (PPV) is characterized by an uneven distribution of the virus within the tree and branches. In order to gain a better understanding of this distribution, a method for modelling tree growth was used. PPV spread was followed within susceptible Mariana plum clone GF 8-1 shoots for 4 months after inoculation. Shoot growth was unaffected by the presence of the virus. Symptoms appeared on leaves produced in the most actively growing parts of the shoots, i.e. at the beginning of the season. PPV was detected in leaves other than those showing symptoms. The proportion of leaves with detectable virus decreased from the zone showing symptoms, with 100% ELISA-positive responses, to the shoot tip with no detectable virus in leaves produced between 111 and 127 days after inoculation. Furthermore, a higher proportion of positive ELISA results was obtained below the zone showing symptoms (77%) compared with 50% above. PPV was detected in 95% of the most vigorous shoots 71 days after inoculation compared with 37% of slower-growing, later-produced shoots.     

Effects of aqueous extracts and decomposition of Mikania micrantha H.B.K. debris on selected agronomic crops

Laboratory and greenhouse experiments were conducted to determine the effects of aqueous extract and the debris of Mile-a-Minute ( Mikania micrantha H.B.K.) on the germination and growth of four test species, viz. tomato ( Lycopersicon esculentum Mill.), Chinese cabbage ( Brassica chinensis L.), corn ( Zea mays L.) and long bean ( Vigna sesquipedalis L.). Germination percentage, radicle length and fresh weight of two crops, Chinese cabbage and tomato, decreased progressively when plants were exposed to increasing concentrations (12.5, 25, 37.5 and 50 g L⁻¹) of aqueous extract of Mikania , but did not affect those of corn and long bean seedlings. The emergence of tomato and Chinese cabbage was greatly reduced when Mikania debris was incorporated into the soil, irrespective of the amount of debris and the decomposition period. In contrast, the emergence of corn and long bean seedlings was not affected. The application of fertilizer (NPK 15 : 15 : 15) enhanced the fresh weight of all seedlings tested as compared with those not supplied with the fertilizer. Four compounds were identified in the leaf extract of Mikania , viz. caffeic acid, p -hydroxybenzaldehyde, resorcinol and vanillic acid.     

20%多效唑·甲哌 FEE7 微乳剂防止小麦倒伏和增产机理研究

冬小麦二棱期喷施植物生长调节剂20%多效唑·甲哌鎓微乳剂375 mL/hm2,可以显著抑制茎秆基部节间伸长,增加各节间充实度,其中赤霉素(Gas)和生长素(IAA)降低,可显著增强小麦抗倒伏能力和降低田间倒伏率.处理还协调了穗数、穗粒数和粒重的关系,增产幅度6.2%～28.6%.增产原因可能在于促进籽粒灌浆强,增加籽粒中内源Gas、IAA、细胞分裂素(CTKs)的水平,增强了籽粒库活性,同时促进茎叶中干物质向籽粒运转.     

1-(1-苯基-1,2,4-三氮唑-3-氧代乙酰氧基)烃基膦酸酯的合成与植物生长调节活性

合成了一系列新的1-(1-苯基-1, 2, 4-三氮唑-3-氧代乙酰氧基) 烃基膦酸酯, 并测定了它们对小麦和黄瓜的植物生长调节活性。结果表明, 在100 Lg/g 时, 所有化合物对小麦芽鞘的生长具有抑制作用, 而在10 Lg/g时化合物6a、6g 对黄瓜显示了较高的促生长活性。     

25％啶菌噁唑乳油防治番茄灰霉病药效试验

田间试验表明25%啶菌唑乳油对番茄灰霉病有良好的防治效果,53.3～106.7mL/667m23次药后防效79%以上。     

转 Bt基因抗虫棉对棉大卷叶螟抗性的研究

:转Bt基因抗虫棉对棉铃虫有很好的抗性,对棉大卷叶螟(SyleptaderogataFabricius)的抗性未见报道。作者研究表明,棉大卷叶螟在棉田为聚集分布型,低龄幼虫有集中为害习性;抗虫棉对其有很好的抗性,平均虫株率为2.2%,较常规棉中棉所12降低96.6%;百株虫量为133.8头,较常规棉降低88.4%。     

丛枝菌根真菌对芋组织培养苗生长的影响

 于温室盆栽条件下研究了丛枝菌根(AM) 真菌Gigaspora rosea、Glomus mosseae 和Glomus versi-forme 对芋(Colocasia esculenta) 组织培养苗移栽成活率、矿质营养、光合速率及生长的影响。结果表明, 接种AM真菌能提高芋组织培养幼苗移栽成活率和叶片光合速率, 降低气孔阻力; 其叶片和根内氮、磷、钾含量和生长量显著高于不接种对照。认为接种有效AM真菌是促进组织培养苗健康生长的重要技术。     

SSR技术及其在果树上的应用

SSR(Simple sequence repeat)技术以其丰富的多态性、共显性遗传、重复性好和操作简便等优点日益受到重视,已成为植物遗传和育种研究中不可缺少的分子标记。对SSR技术的原理和特点作了简要的介绍,较详细地分析了如何获得SSR引物,特别是综述了果树上SSR引物的研究现状,同时将其与其它几种主要的分子标记进行了比较分析,认为SSR标记检测的位点多态性水平明显高于RFLP,而且重复性优于RAPD;着重介绍了SSR技术在果树种质资源和构建果树遗传图谱及基因定位等研究中的应用现状;指出SSR技术将在果树科研上起到重要的作用。     

Occurrence of Mirafiori Lettuce Virus and Lettuce Big-vein Virus in Relation to Development of Big-vein Symptoms in Lettuce Crops

Big-vein disease (BV) of lettuce has been attributed to infection by Lettuce big-vein virus (LBVV), vectored by the soil fungus Olpidium brassicae. The finding of a second soil-borne virus in lettuce, Mirafiori lettuce virus (MiLV), led to a re-investigation of the role of LBVV in big-vein disease, with evidence emerging that both MiLV and LBVV are vectored by O. brassicae, and that MiLV, not LBVV, is the cause of BV (Lot et al. (2002), Phytopathology 92: 288–293). The two viruses have coat proteins of similar size but have different morphologies and are serologically unrelated. We tested individual lettuce plants in BV-prone fields and protected crops in France and Italy for the presence of the two viruses, using DAS-ELISA and antisera specific for each virus. Both MiLV and LBVV were found at high incidence, often together but sometimes separately. Symptoms were frequently found to be associated with MiLV alone or both viruses, but rarely LBVV alone. However, no absolute correlation emerged, because sometimes MiLV was present in the absence of symptoms, and vice versa. To clarify the situation, individual lettuce plants were examined over a period of time in two further surveys. In surveys of protected crops in France, plants with big-vein were always ELISA-positive for MiLV, or else symptomless plants positive for MiLV were later seen to develop big-vein symptoms. Presence or absence of LBVV appeared to have no effect on symptom development. In surveys of open fields in Italy, all combinations were found: presence of both viruses, apparent absence of both viruses, or presence of each one alone, in plants that developed BV. At the end of the observation period, nearly all plants had BV and contained both viruses.