Fisheries catches and the carrying capacity of marine ecosystems in southern Brazil

The carrying capacity of marine shelf ecosystems in southern Brazil for harvestable species is analyzed by (1) quantifying the amount of available primary production appropriated by fisheries catches, (2) evaluating the trend in the mean trophic level of fisheries, and (3) simulating the ecosystem effects of “fishing down the food web” in an intensively exploited shelf region. Fisheries utilize ca. 27 and 53% of total primary production in the southern and south-eastern shelf regions, respectively. Regional variation in the carrying capacity appropriated by fisheries results from differences in the primary production, catch volume and trophic transfer efficiencies. Overall, fisheries landings do not display a trend of decreasing trophic level with time due to the collapse of the sardine fishery and the recent increasing of offshore fishing for higher trophic level species, mainly tunas and sharks. However, the simulations show that fishing down the food web through fisheries that target small pelagic planktivorous fishes, while at first increasing catches in intensively exploited regions, has the potential of decreasing yields, by interrupting major energy pathways to exploited, high-trophic level species. The consequences of these results to the design of precautionary measures for future fishing policies are discussed.     

花芽分化期滴灌施肥频率对香蕉生长及产量构成的影响

以威廉斯B6为试材,设置3种施肥频率处理(分别于花芽分化期至现蕾期的57d内施6、12、18次水肥),研究该时期不同滴灌施肥频率对香蕉生长特性(株高、茎粗和青叶数)、抽蕾时间及其产量构成的影响。结果表明,在广西地区降雨量集中的5-7月份,增加滴灌施肥频率仍然可以显著提高蕉园管理质量,但对香蕉生物量和养分累积量影响不大。处理3d一次较其他处理提前抽蕾5~10d,现蕾更为集中,且果指数显著增加。水肥频次对香蕉果指数的影响主要体现在第一梳、第二梳与第五梳。     

香蕉粘胶纤维结构与吸湿性能研究

以香蕉粘胶纤维、普通粘胶纤维、Tencel纤维为原料,采用烘箱干燥法和回归模型分析法,对不同材料进行了吸湿、放湿测试与分析。结果表明：香蕉粘胶纤维具有良好的吸湿性和放湿性,香蕉菠萝粘胶纤维吸湿率20.5 %、放湿回潮率26.3 %;普通粘胶纤维吸湿率18.5 %、放湿回潮率24.6 %;Tencel纤维回潮率17.1 %、放湿回潮率23.4 %,香蕉粘胶纤维的吸湿速率略高于普通粘胶纤维,Tencel纤维最低;放湿速率香蕉粘胶纤维最高,Tencel纤维粘胶纤维居中,普通粘胶纤维最低。     

Understanding banana bunchy top disease epidemiology in Burundi for an enhanced and integrated management approach

This study on the epidemiology of banana bunchy top disease (BBTD) was carried out in the context of small‐scale farms in Burundi for an integrated management approach. Banana trials were established in farmers’ fields comparing different plot locations, while spatial and seasonal occurrence of aphid vectors was evaluated at three different altitudes. In addition, serological tests were performed on banana leaf samples to confirm the presence and titre of the virus. The results showed that BBTD incidence varied among banana cultivars and locations. Nine months after plot establishment, BBTD incidence ranged from 21·8% to 56·4% in plots within affected fields, while a range of 0–12·3% was reported in plots located between 5 and 30 m away from affected banana fields. Aphid numbers were highest in the dry season. These aphids were able to acquire and transmit the virus irrespective of altitude. A mean incubation period of 21 and 84 days was observed at low (780 m a.s.l.) and high (2090 m a.s.l.) altitude, respectively. Thus, a holistic approach, taking into account banana cultivar, plot location, disease‐free planting material and regular field sanitation, should be promoted for long‐term BBTD management.     

Systemicity of Xanthomonas campestris pv. musacearum and time to disease expression after inflorescence infection in East African highland and Pisang Awak bananas in Uganda

Banana xanthomonas wilt (XW) caused by Xanthomonas campestris pv. musacearum (Xcm) attacks all banana cultivars. Xcm in inflorescence‐infected Pisang Awak plants with wilting male bud bracts is restricted to the upper parts of the true stem; therefore, cutting these plants at the pseudostem base has been recommended to prevent further Xcm spread. In order to fine‐tune existing control strategies, this study examined the movement of Xcm into plants and mats, in relation to disease incubation period. Mature Pisang Awak and East African highland (AAA‐EA) plants were inoculated with Xcm through abscission wounds of female bracts, male bud bracts, male flowers, a combination of male bud bracts and flowers, and by cutting male buds with a contaminated machete. Thirty plants per genotype and treatment were monitored for 24 months for disease symptoms. An additional 68 AAA‐EA and 33 Pisang Awak plants were sampled weekly to assess the rate of Xcm spread within the plants. All floral entry points resulted in disease, with the highest incidence in combined male bract and male flower abscission wound inoculations. The study confirmed the systemicity of Xcm, with the pathogen able to live within the mat for long periods (5–16 months) without causing disease. Reliance on disease symptom expression to manage XW is therefore not sufficient. The long incubation period in lateral shoots may explain the current resurgence of the disease in locations where the disease was thought to have been successfully eradicated.     

海南香蕉产业发展存在的问题及前景思考

本文介绍了香蕉的特性,进而分析并列举了海南香蕉产业发展中存在的问题,最后结合海南的实际环境,提出了对海南香蕉产业发展前景的思考,以期给香蕉产业的从业者提供一些新的思路,在规避生产、销售过程中风险的同时,促进海南香蕉产业的健康、快速发展。     

香蕉皮果胶提取条件的优化

以香蕉皮作为原料,对果胶提取条件进行优化,分别探讨了提取时间、提取温度、pH、料液比等因素对香蕉皮中果胶提取的影响.然后通过正交试验得出,香蕉皮中果胶提取的最佳条件为提取时间90 min、提取温度85℃、pH 1.5、料液比1:3 (m/V,g:mL),影响果胶产率的因素为pH＞提取温度＞提取时间＞料液比.在此优化条件下,香蕉皮果胶产率可达到6.23％,提取的果胶含量为82.6％.     

木霉制剂对土壤微生物数量和香蕉枯萎病的影响

采用稀释分离法研究木霉菌在土壤中的定殖动态及木霉制剂对土壤微生物数量的影响情况.结果显示:在含有基质的情况下,木霉菌在土壤中的存活数量呈先上升后下降的趋势;并且木霉菌在灭菌土中的存活量明显高于自然土.蕉园施入木霉制剂后,香蕉根围土壤中真菌的数量显著提高,枯萎病的发病率明显降低,处理区最高防效达63.5％.     

海南香蕉叶脉坏死病病原检测

应用ELISA和PCR技术对香蕉叶脉坏死病病样进行病原检测。结果显示：病样在ELISA 反应中对BBTV 和CMV 表 现为阳性,对BSV 表现为阴性;而在PCR 反应中,对上述猿种病毒均表现为阳性。初步研究认为袁该病可能是由BBTV 和CMV 两种病毒复合侵染所致。     

我国香蕉标准体系研究及实施现状分析

香蕉是热带地区重要的水果,我国是世界第三大香蕉生产国。香蕉产业标准化程度的高低袁,不仅影响香蕉的产量和质量,而且对推进其他热带经济作物生产的标准化和产业化有重要的作用。通过对我国香蕉标准制修订、宣贯和实施现状的分析及其标准体系的研究,存在香蕉标准结构不合理、标龄老化、标准与生产结合不紧密等主要问题。同时,提出加强香蕉标准宣贯、及时修订标准,紧密结合香蕉产业等对策建议。