芝麻菜品种对尖镰孢菌枯萎病的抗性评价

尖镰孢菌枯萎病是意大利西北部芝麻菜栽培品种(Eruca vesicaria)和野生品种(Diplotaxis spp．)上的重要病害之一,常引起严重的损失。为评价芝麻菜品种对尖镰孢菌枯萎病的抗性,2004年6～11月,选用了44个栽培及野生品种资源在玻璃温室进行抗性试验,使用浓度为1×10~6cfu/ mL的孢子悬浮液蘸根法人工接种30天苗龄的芝麻菜幼苗,以分离自芝麻菜两个不同野生品种的菌株Fus．Ruc．9A/02和Fus．Ruc．13/03,以及分离自栽培和野生品种的32个菌株混合(MIX),分别作为抗病试验接种体,每次接种试验设A、B、C三个重复。整个试验重复进行2次。调查病害引起的死苗率(%)和病情指数(DI),作为评价芝麻菜品种抗性差异的两项指标。研究结果显示,这两项指标间的相关性极显著(P＜0．01),即表明可采用其中一项指标评价芝麻菜品种对尖镰孢菌枯萎病的抗性。供试的44个栽培及野生芝麻菜品种中,多数品种抗尖镰孢茵茵株Fus．Ruc．13/ 03,而对菌株Fus．Ruc．9A/02及菌株混合MIX表现为易感性,而且这些易感品种在菌株Fus．Ruc．9A/02及菌株混合MIX两试验中的抗性表现较为一致,Fus．Ruc．9A/02和MIX的毒性也更强于Fus．Ruc．13/03菌株。芝麻菜品种12/03和品种20/03高抗菌株混合MIX,品种6/03和品种7/04高抗菌株Fus．Ruc．9A/02,而品种9/02、2/03、5/03、6/03、7/03、9/03、11/03、12/03、20/03、21/03、24/03、3/04、6/04、7/04和11/04高抗菌株Fus．Ruc．13/03。     

Evidence for an expanded host range ofFusarium oxysporum f.sp.raphani

The pathogenicity of four isolates ofFusarium oxysporum obtained from infected cultivated rocket (Eruca vesicaria) and wild (sand) rocket (Diplotaxis tenuifolia) was tested on the following cruciferous hosts: stock, radish, wild and cultivated rockets, and various species in the cabbage tribe: cabbage (Brassica oleracea var.sabauda), cauliflower (Brassica oleracea var.botrytis), Brussels sprouts (Brassica oleracea var.gemmifera), broccoli (Brassica oleracea var.italica), turnip (Brassica rapa var.rapa). The results indicated that isolates ofF. oxysporum from cultivated and wild rocket belong to theforma specialis raphani. The isolates from rocket were pathogenic on cabbage, Brussels sprouts, broccoli, turnip, radish and stock; isolates ofF. oxysporum conglutinans from cabbage and radish, and the isolate ofF. oxysporum f.sp.raphani from rape obtained from the ATCC collection, were pathogenic on both cultivated and wild rocket.     

Molecular characterization of Fusarium oxysporum f.sp. cichorii pathogenic on chicory (Cichorium intybus)

Fusarium oxysporum is a ubiquitous soilborne ascomycete responsible for vascular wilt in many plant species worldwide. This species comprises more than 120 putative host-specific formae speciales capable of causing marked economic losses. In summer 2009, wilt symptoms, including chlorosis and poor development of the root system, were observed on cultivars of chicory (Cichorium intybus) in northern Italy. The causal agent isolated from symptomatic tissues in this case was identified as F. oxysporum on the basis of both morphological features and molecular analyses. In this work, we attempted to characterize the isolates of F. oxysporum from C. intybus by both biological and molecular approaches. Pathogenicity trials performed on five species of the Asteraceae family with isolates of F. oxysporum from C. intybus indicated that the pathogen has a unique host range, infecting chicory only. Neither lettuce nor endive, lawn daisy or Paris daisy developed the disease. Five cultivars within C. intybus species were tested, and the cv. ??Clio?? was the most susceptible. Phylogenetic analyses relative to the ribosomal intergenic spacer (IGS) and translation elongation factor 1-alpha (EF1-??) assigned isolates pathogenic to chicory to a single cluster, distinct from other pathogenic F. oxysporum. In light of these findings, we propose to designate this organism as Fusarium oxysporum f.sp. cichorii.     

Effect of different organic amendments on lettuce fusarium wilt and on selected soilborne microorganisms

This study evaluated the effect of different organic amendments on lettuce fusarium wilt caused by Fusarium oxysporum f. sp. lactucae in pots under controlled conditions. Their effects on the density of the pathogen, on the total fungi and on fluorescent Pseudomonas spp. were also evaluated after two subsequent lettuce crops. A significant reduction in the severity of the symptoms of F. oxysporum f. sp. lactucae was found after the use of Brassica carinata pellets (52–79% reduction) and compost (49–67% reduction), while Brassica green manure and cattle and chicken manure only provided partial control of fusarium wilt. However, variations in effectiveness were observed for the same treatment in repeated trials. In general, an increase was observed in Pseudomonas and a decrease in fungal populations in the growing medium, which was obtained by mixing a blonde sphagnum peat and a sandy loam soil with B. carinata pellets and compost after two consecutive cropping cycles. Prolonging the Brassica and compost treatments from 30 to 60 days did not significantly affect disease severity, plant growth or the microbial population of the total fungi or Pseudomonas. The largest lettuce biomass was obtained in the non‐inoculated growing medium amended with brassica flour, chicken manure, B. carinata pellets and compost, as a consequence of fertilization. The treatment with B. juncea green manure, B. carinata (pellets and flour) and compost applied 30 days before planting led to promising results and merits further investigation for use under field conditions.     

Management of downy mildew of sweet basil (Ocimum basilicum) caused by Peronospora belbahrii by means of resistance inducers, fungicides, biocontrol agents and natural products

To control downy mildew of sweet basil (Ocimum basilicum L.), incited by Peronospora belbahrii Thines, a number of compounds were tested in 2011 and 2012 under glasshouse conditions. These included copper-based fungicides, biocontrol agents, and compounds previously reported to induce resistance in plants to pathogens. Results were compared with those provided by fungicides registered for downy mildew control in Italy. The tested compounds were used alone or applied in rotation in spray programs. In all trials, the greatest reduction in disease incidence and severity was found with treatments that included metalaxyl-M?+?copper hydroxide, a mineral fertilizer ‘Alexin’, mandipropanid, and azoxystrobin. The glucohumates activator complex and acibenzolar-S-methyl also provided significant disease control (P?<?0.05). The mineral fertilizer Alexin, the glucohumates activator complex and acibenzolar-S significantly reduced disease incidence and severity 20 days after the last treatment compared with the untreated control (P?<?0.05). Among the copper-based products, the greatest reductions in disease incidence and severity were provided by copper hydroxide with terpenic alcohols and copper oxychloride?+?copper hydroxide. The mineral fertilizer Kendal and prohexadione-Ca, as well as mustard oil, partially reduced disease incidence and severity compared with the untreated control (P?<?0.05), whereas the biocontrol agent Bacillus subtilis QST 713 and thyme oil extract were not effective in two out of three trials. When different combinations of various products used in rotation were tested, effective control was found either using a rotation of fungicides with compounds that can induce resistance, as well as by using rotation with different resistance-inducing compounds on their own.     

Effect of antagonistic<Emphasis Type="Italic">Fusarium</Emphasis> spp. and of different commercial biofungicide formulations on Fusarium wilt of lettuce

Five experimental trials were carried out to test different biological control agents against Fusarium wilt of lettuce, cause byFusarium oxysporum f.sp.lactucae. In the presence of a very high disease incidence, the best results in terms of disease control as well as increased growth response were shown byTrichoderma harzianum T 22 (RootShield), which, at 3 gl ⁻¹ of substrate, provided very consistent results.F. oxysporum IF 23 gave good disease control but in two out of five trials reduced the biomass produced. Less consistent, but still significant results were provided byF oxysporium MSA 25, at 3 gl ⁻¹ of substrate, and byTrichoderma viride TV 1. The twoF. oxysporum agents Fo 251/2 and Fo 47 and the mixture ofT. harzianum + T. viride (Remedier) partially reduced disease incidence but were less effective than the above mentioned. Less interesting results were offered byStreptomyces griseoviridis (Mycostop). The results obtained show that biological control can play a role in the management of Fusarium wilt of lettuce.     

Processing of remote sensing information to retrieve leaf area index in barley: a comparison of methods

Precision Agriculture - Leaf area index (LAI) is a key variable in understanding and modeling crop-environment interactions. With the advent of increasingly higher spatial resolution satellites and...     

Population structure of Phytophthora infestans collected on potato and tomato in Italy

Late blight caused by the oomycete Phytophthora infestans is a disease of potato and tomato of worldwide relevance and is widespread throughout Europe and the Mediterranean region. While pathogen populations in northern Europe have been sampled and characterized for many years, the genetic structure of populations from southern Europe, including Italy, has been less studied. Between 2018 and 2019, we collected 91 samples of P. infestans from potato and tomato crops in Italy, Algeria, and Tunisia on FTA cards and genotyped them using 12-plex microsatellites. These samples were compared to genotypes of P. infestans previously collected within the framework of the EuroBlight network and from published sources. Four clonal lineages were identified: 13_A2 (Blue 13), 2_A1, 23_A1, and 36_A2. Two other isolates collected could not be matched to any currently known clonal lineage. The 13_A2 and 36_A2 lineages were found exclusively in southern Italy and Algeria, while 2_A1 was only found in Algeria. This is the first report of the 36_A2 lineage in Italy. Two isolates from Solanum nigrum were 13_A2, suggesting this weed host could be a reservoir of inoculum. The 23_A1 lineage was found widely on infected tomato crops in Italy and is the same as the lineage US-23 that is widespread in North America. Differences in genotypes across the country suggests that there may be different sources of introduction into Italy, possibly via infected seed tubers from other countries in Europe, tubers for consumption from North Africa, or tomatoes.     

Lamb’s lettuce (Valerianella olitoria): new host of Fusarium oxysporum f. sp. conglutinans

Journal of Plant Diseases and Protection - A new wilt of lamb’s lettuce (Valerianella olitoria) was detected in northern Italy in 2003 and the causal agent of the disease was identified as...     

Efficacy of different steam distribution systems against five soilborne pathogens under controlled laboratory conditions

The efficacy of three steam application techniques (steam injection, iron pan and sheet steaming) was evaluated against five soilborne pathogens under controlled laboratory conditions. Injection and pan steam systems proved to be efficient and feasible alternatives to traditional sheet steaming for suppressing Fusarium oxysporum f. sp. basilici at 60% moisture field capacity in sandy-loam soil. Injecting steam was the best technique to suppress F. oxysporum f. sp. basilici, F. oxysporum f. sp. raphani, F. oxysporum f. sp. conglutinans, Rhizoctonia solani and Phytophthora capsici. The mycelia of R. solani and P. capsici were very sensitive to heat and were effectively killed by injection of steam and by the pan steam system at 80% and 40% moisture field capacity.