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The potential of nonpathogenic Fusarium oxysporum and other biological control organisms for suppressing fusarium wilt of banana 总被引:3,自引:0,他引:3
The aim of this study was to evaluate the ability of nonpathogenic F. oxysporum and Trichoderma isolates from suppressive soils in South Africa to suppress fusarium wilt of banana in the glasshouse. Several biological control agents and commercial biological control products were included in the study. The isolates were first screened in vitro on potato dextrose agar. In glasshouse evaluations, the fungal and bacterial isolates were established on banana roots before they were replanted in pathogen-infested soil, while the commercial biocontrol agents were applied as directed by the supplier. Banana plantlets were evaluated for disease development after 7 weeks. In vitro tests showed none of the nonpathogenic isolates suppressed Fusarium oxysporum f.sp. cubense ( Foc ), while slight suppression was observed with the two Trichoderma isolates. Results of the glasshouse evaluations revealed that two of the nonpathogenic F. oxysporum isolates, CAV 255 and CAV 241, reduced fusarium wilt incidence by 87·4 and 75·0%, respectively. The known biological control agent Fo47 did not suppress Foc significantly. Pseudomonas fluorescens strain WCS 417, known for its ability to suppress other fusarium wilt diseases (WCS 417), reduced disease incidence by 87·4%. These isolates should be further evaluated for potential application in the field, independently and in combination. 相似文献
44.
选用3头3月龄左右装有瘤胃瘘管的荷斯坦奶公犊,按3×3完全拉丁方试验设计,喂给3种日粮,日粮组成按精粗比分别表示为:Ⅰ组70∶30、Ⅱ组60∶40、Ⅲ组50∶50,研究不同日粮组成下高寒地区小黑麦的DM、CP以及NDF在断奶初期奶公犊瘤胃内动态降解。试验结果表明:精粗比为60∶40日粮时,其CP的消失率和降解参数明显低于精粗比为70∶30和50∶50的日粮,差异显著(P<0.05);其DM和NDF的消失率和降解参数明显高于精粗比为70∶30和50∶50的日粮,差异显著(P<0.05)。 相似文献
45.
To obtain the basic information on fruit set regulation, effects of several RNases including S-RNase on pollen tube growth and RNA degradation in the tube were studied in the pear. Purified S-RNase from the Japanese pear ‘Kosui’ (S4S5) predominantly inhibited the growth of ‘Kosui’ pollen tubes (self) in vitro at 0.28 unit μL−1, but it inhibited ‘Chojuro’ (S2S3) pollen (cross) only slightly. The same unit of RNase T1 (EC 3.1.27.3) clearly inhibited the pollen tube growth, but the action was significantly weaker than that of the S-RNase against the self-pollen. Inhibitory effect of RNase T2 (EC 3.1.27.1) and RNase A (EC 3.1.27.5) was only slight. The proteins other than the S-RNase extracted from pear style did not have any inhibitory action, though they possessed RNase activity 3.8 times higher than S-RNase. Thus, RNases tested here could not substitute for the S-RNase in specific inhibition against the self-pollen tube growth. Total RNA degradation by each RNase occurred in the pollen tubes as following order; S-RNase (self) ≥T1 > T2 ≥ A > S-RNase (cross). Degradation degree of 28S and 18S rRNA was as follows; S-RNase (self) > A > T1 > T2 > S-RNase (cross). The degradation of 5.8S and 5S rRNA was; S-RNase (self) > S-RNase (cross) > A > T2 > T1. The degree of rRNA degradation was, thus, not always in parallel with the degree of pollen growth inhibition. The S-RNase may degrade not only rRNA but also mRNA essential for pollen tube growth, and may be specifically adapted to inhibit the growth of self-pollen tubes. Therefore, controlling S-RNase amount in the style will produce self-thinning cultivars efficiently, which are unnecessary not only for hand-pollination but fruit-thinning practices in the pear. Practically, cultivar with weak self-incompatibility and small amount of S-RNase, such as ‘Okusankichi’, may be an expecting candidate for breeding self-thinning cultivars. 相似文献
46.
青藏高原草地退化原因述评 总被引:23,自引:11,他引:23
导致青藏高原草地退化的因子很多,主要有气候、野生动物和人类活动等。在气候因素中以气温和降水的影响为主,短期内气候的变化不会成为草地退化的主导因素,从长期来看,气候变化与草地退化之间的相互作用可引起草地生态系统的退化;野生动物因素中主要以植食性小哺乳动物的影响为主,其危害程度取决于其种群数量的高低,同时大型野生草食动物对草地退化的影响也不容忽视;人类活动因素中主要以家畜过度放牧为主,在一定程度上,家畜放牧强度的高低直接决定草地的退化程度;草地退化是多种因素综合作用的结果。不同地区导致草地退化的主要因素不尽相同,导致青藏高原草地退化最主要的因子是过度放牧和植食性小哺乳动物种群爆发。针对退化的原因,提出了青藏高原退化草地恢复与管理过程中应注意的事项。 相似文献
47.
通过对不同种植时间、不同种植基质的香根草Vetiveria zizanioides分株苗、组培苗根际丛枝菌根(AM菌)感染检测,探讨了香根草对AM菌的感染特性.结果表明,在消过毒的森林泥炭土中,组培苗种植12个月感染率只有20.0%,感染强度低;种植22个月只有53.3%,感染强度为中.分株苗种植在自然土壤中,3个月就有AM菌感染,其感染率为56.7%;种植22个月感染率达到最高峰,为80.0%,感染强度为中等;种植时间为33个月时,感染率不再增加,但感染强度进一步增高.说明香根草根际AM菌的感染率和感染强度可能与苗源无关,而与种植基质密切相关. 相似文献
48.
小麦根际pH,细菌数量,有机质变化研究 总被引:3,自引:0,他引:3
通过研究灰漠上和碱化灰漠上中小麦根际、非根际pH、细菌数量和有机质含量变化,发现两种土壤小麦根际上中细菌数量和有机质含量比非根际上中高。由于较低的pH值,因而灰漠土中小麦根际、非极际土中的有机质含量和细菌数量均高于碱化灰漠土中。 相似文献
49.
人类活动对晋西北地区生态环境影响的初步研究 总被引:9,自引:0,他引:9
苏志珠 《干旱区资源与环境》1998,12(4):127-132
晋西北地处我国北方生态环境脆弱的农牧交错带,同时又是资源富集,资源与环境的矛盾十分突出。人类不合理的经济活动加剧了该区以土壤风蚀沙化和水土流失为主的环境退化问题。因此,加强环境保护刻不容缓。 相似文献
50.
《Land Degradation \u0026amp; Development》2017,28(7):1891-1901
Hardpan is a major cause of land degradation that affects agricultural productivity in developing countries. However, relatively, little is known about the interaction of land degradation and hardpans. The objective of this study was, therefore, to investigate soil degradation and the formation of hardpans in crop/livestock‐mixed rainfed agriculture systems and to assess how changes in soil properties are related to the conversion of land from forest to agriculture. Two watersheds (Anjeni and Debre Mewi) were selected in the humid Ethiopian highlands. For both watersheds, 0–45 cm soil penetration resistance (SPR, n = 180) and soil physical properties (particle size, soil organic matter, pH, base ions, cation exchange capacity, silica content, bulk density and moisture content) were determined at 15 cm depth increments for three land uses: cultivated, pasture and forest. SPR of agricultural fields was significantly greater than that of forest lands. Dense layers with a critical SPR threshold of ≥2000 kPa were observed in the cultivated and pasture lands starting at a depth of 15–30 cm but did not occur in the undisturbed forest land. Compared with the original forest soils, agricultural fields were lower in organic matter, cation exchange capacity, and exchangeable base cations; more acidic; had a higher bulk density and more fine particles (clay and silt); and contained less soluble silica. Overall, our findings suggest that soil physical and chemical properties in agricultural lands are deteriorated, causing disintegration of soil aggregates, resulting in greater sediment concentration in infiltration water that clogged up macro‐pores, thereby disconnecting deep flow paths found in original forest soils. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献