Incidence,pathogenicity and diversity of Alternaria spp. associated with alternaria leaf spot of canola (Brassica napus) in Australia

Studies were undertaken to determine Alternaria spp. associated with leaf spot symptoms on canola (Brassica napus) in two cropping seasons (2015, 2016) across southern Australia. Major allergen Alt a1 and plasma membrane ATPase genes were used to identify Alternaria spp. In 2015, 112 isolates of seven Alternaria spp. were obtained, with A. metachromatica predominating. In 2016, 251 isolates of 12 Alternaria spp. were obtained, with A. infectoria predominating. Alternaria spp. isolates were morphologically and phylogenetically identified and studies to determine their pathogenicity on both B. napus (cv. Thunder TT) and B. juncea (cv. Dune) confirmed 10 species (A. alternata, A. arborescens, A. brassicae, A. ethzedia, A. hordeicola, A. infectoria, A. japonica, A. malvae, A. metachromatica and A. tenuissima) as pathogenic on both Brassica species. Alternaria ethzedia, A. hordeicola and A. malvae were recorded for the first time in Australia on any host and the record of A. arborescens was the first for New South Wales (NSW) and South Australia (SA). Other first records included A. infectoria on B. napus in NSW; A. japonica on B. napus in NSW and Western Australia (WA); A. metachromatica on any host in NSW, Victoria (VIC), WA and SA; and A. tenuissima on B. napus in NSW, SA and WA. It is evident that alternaria leaf spot on canola across southern Australia is not solely caused by A. brassicae, but that a range of other Alternaria spp. are also involved to varying degrees, depending upon the year and the geographic locality.     

Multiple Alternaria species groups are associated with leaf blotch and fruit spot diseases of apple in Australia

Leaf blotch and fruit spot of apple caused by Alternaria species occur in apple orchards in Australia. However, there is no information on the identity of the pathogens and whether one or more Alternaria species cause both diseases in Australia. Using DNA sequencing and morphological and cultural characteristics of 51 isolates obtained from apple leaves and fruit with symptoms in Australia, Alternaria species groups associated with leaf blotch and fruit spot of apples were identified. Sequences of Alternaria allergen a1 and endopolygalacturonase gene regions revealed that multiple Alternaria species groups are associated with both diseases. Phylogenetic analysis of concatenated sequences of the two genes resulted in four clades representing A. arborescens and A. arborescens‐like isolates in clade 1, A. tenuissima/A. mali isolates in clade 2, A. alternata/A. tenuissima intermediate isolates in clade 3 and A. longipes and A. longipes‐like isolates in clade 4. The clades formed using sequence information were supported by colony characteristics and sporulation patterns. The source of the isolates in each clade included both the leaf blotch variant and the fruit spot variant of the disease. Alternaria arborescens‐like isolates were the most prevalent (47%) and occurred in all six states of Australia, while A. alternata/A. tenuissima intermediate isolates (14%) and A. tenuissima/A. mali isolates (6%) occurred mostly in Queensland and New South Wales, respectively. Implications of multiple Alternaria species groups on apples in Australia are discussed.     

Species prevalence and disease progression studies demonstrate a seasonal shift in the Alternaria population composition on potato

To assess the incidence of early blight/brown spot (EB/BS) in Flanders (Belgium), potato fields in 22 locations were monitored and scored over the duration of the growing seasons 2014 and 2015. The average disease incidence was shown to be higher in 2014 than in 2015. Soil type, rainfall and temperature were also analysed in relation to disease incidence. In 2014, potato plants grown in sandy soils had more EB/BS disease than those grown in clay or loamy soils. However, the low disease incidence in 2015 meant that differences in disease levels between soil types could not be discerned for that growing season. A windowpane analysis demonstrated that rainfall and humidity accounted for the differences in disease incidence between the two growing seasons. During the course of the survey, the species composition in leaves with symptoms was assessed using real‐time PCR. Remarkably, small‐spored Alternaria species, such as A. alternata and A. arborescens, rather than the more virulent A. solani were the predominant species on potato leaves throughout the growing season. As the disease progressed, the proportion of A. solani increased. In view of these results, the virulence of a collected set of Alternaria isolates was assessed by an in vitro assay. Despite A. solani being more virulent than A. alternata or A. arborescens, the most abundant species isolated from potato leaves with symptoms was A. arborescens.     

Effect of air temperature, rain and drought on hot water weed control

The influence of rain and drought before, and air temperature during, weed control with hot water was studied in laboratory experiments on the test weed Sinapis alba (white mustard). The plants were grown in a greenhouse and treated outdoors. There was no difference in weed control effect when S. alba plants at the four‐leaf stage were treated at the air temperatures 7°C and 18^°C. The effective energy dose for a 90% fresh weight reduction was 465 kJ m^?2 for both air temperatures. Weed control of S. alba at the four‐ to six‐leaf stage in rainfall above the rainwater run‐off level increased the required effective energy dose by 20% (i.e. 120 kJ m^?2) compared with dry plants. A short period of drought just before treatment on S. alba at the two‐ to four‐leaf stage increased the plant fresh weight reduction, which was 22% at low energy dose (190 kJ m^?2) and 44% at high energy dose (360 kJ m^?2). Hot water weed control should thus be carried out when the plants are drought stressed and avoided when the plants are wet. The air temperature seems to be of little importance in the range 7–18^°C.     

外源水杨酸对盐胁迫下棉花幼苗激素含量及生长特性的影响

以中棉所4l号和中棉所49号为试验材料,通过盆栽试验,研究外源水杨酸(SA)对盐胁迫下棉花幼苗激素水平和生长特性的影响。结果表明:(1)0.6%Na Cl胁迫条件下,棉花幼苗叶片中ABA含量增加,CTK、GA和IAA含量减少,在0.05 mmol·L~(-1)SA浸种+0.2 mmol·L~(-1)叶面喷施复合处理下,中棉所41号和中棉所49号幼苗中ABA含量分别降低了59.14%和76.71%,CTK、GA、IAA含量分别提高了55.39%、21.05%、22.39%和17.08%、12.5%、18.20%,说明SA处理可有效缓解盐胁迫的伤害;(2)ABA/IAA+GA、CTK/IAA和ABA/CTK值在0.6%Na Cl胁迫处理下分别为增高、降低和增高,0.05 mmol·L~(-1)SA浸种+0.2 mmol·L~(-1)叶面喷施复合处理下,中棉所41号和中棉所49号幼苗中ABA/IAA+GA和ABA/CTK值分别降低了63.40%、74.03%和71.66%、79.99%,CTK/IAA值分别增加了28.41%和21.18%,说明SA可使幼苗体内激素恢复动态平衡,促进幼苗的生长发育;(3)0.6%Na Cl胁迫处理下棉花幼苗的株高、根鲜重、茎鲜重和叶鲜重都表现为降低,在不同浓度外源SA浸种和喷施处理下都有所恢复,幼苗根表现最为明显,用0.05 mmol·L~(-1)SA浸种+0.2 mmol·L~(-1)叶面喷施处理0.6%Na Cl胁迫下,两品种棉花幼苗单株鲜重分别增加了24.20%和22.39%。SA能通过调控棉花幼苗激素含量从而提高棉花幼苗的耐盐性,其中以0.05 mmol·L~(-1)SA浸种+0.2 mmol·L~(-1)叶面喷施对缓解棉花幼苗盐胁迫的伤害效果明显。     

外源水杨酸对野生龙葵幼苗干旱胁迫的缓解效应

利用20%的PEG6000模拟干旱胁迫,同时用不同浓度（0、0.5、1.0、1.5、2.0 mmol·L^-1）的水杨酸(SA)喷施幼苗,研究了不同浓度水杨酸处理对干旱胁迫下野生龙葵幼苗生长的影响。结果表明：干旱胁迫下,龙葵幼苗植株变矮、鲜重降低、根长缩短,叶绿素和可溶性蛋白含量减少,抗氧化酶活性、游离脯氨酸和丙二醛含量增加;经SA处理干旱胁迫下龙葵幼苗株高、根长和鲜重都有明显增加,特别是1.5 mmol·L^-1 SA处理组分别增加20.8%、28.0%和29.7%,1.5 mmol·L^-1 SA处理组龙葵幼苗叶绿素含量提高31.9%、脯氨酸含量提高65.4%,可溶性蛋白含量提高42.8%,超氧化物歧化酶（SOD）、过氧化物酶（POD）与过氧化氢酶（CAT）活性达到最高,与对照相比分别增加了30.2%、87.8%和50.3%;SA处理使丙二醛（MDA）含量降低了37.8%。综合来看,适当浓度的SA可以缓解干旱对龙葵幼苗造成的伤害,并以1.5 mmol·L^-1外源SA缓解效果最好。     

解淀粉芽胞杆菌对小麦黄花叶病的生物防治

为探索新型生防菌剂解淀粉芽胞杆菌对小麦黄花叶病的防治作用,通过盆栽和田间药效试验研究了解淀粉芽胞杆菌对小麦黄花叶病的防治效果和对小麦幼苗的促生长作用。结果表明,解淀粉芽胞杆菌对小麦黄花叶病有较好的预防效果和一定的治疗效果,浓度为500~2 000 mg/L时,预防效果为24.86%~84.55%,治疗效果为13.61%~62.58%,预防效果明显优于治疗效果。其中灌根处理的防治效果显著高于喷雾、拌种处理,且随着施用浓度的增大,防治效果提高;当灌根处理浓度为2 000 mg/L时效果最好,预防和治疗效果分别达到84.55%和62.58%。另外解淀粉芽胞杆菌对小麦有一定的促生作用,并可提高麦苗的地上部鲜重,浓度为1 200 mg/L时,地上部鲜重增重最大,较对照提高52.76%。表明解淀粉芽胞杆菌可作为生防菌剂防治小麦黄花叶病。     

Control of plant diseases by natural products: Allicin from garlic as a case study

This review aims to increase awareness of the potential for developing plant protection strategies based on natural products. Selected examples of commercial successes are given and recent data from our own laboratory using allicin from garlic are presented. The volatile antimicrobial substance allicin (diallylthiosulphinate) is produced in garlic when the tissues are damaged and the substrate alliin (S-allyl-l-cysteine sulphoxide) mixes with the enzyme alliin-lyase (E.C.4.4.1.4). Allicin is readily membrane-permeable and undergoes thiol-disulphide exchange reactions with free thiol groups in proteins. It is thought that these properties are the basis of its antimicrobial action. We tested the effectiveness of garlic juice against a range of plant pathogenic bacteria, fungi and oomycetes in vitro. Allicin effectively controlled seed-borne Alternaria spp. in carrot, Phytophthora leaf blight of tomato and tuber blight of potato as well as Magnaporthe on rice and downy mildew of Arabidopsis. In Arabidopsis the reduction in disease was apparently due to a direct action against the pathogen since no accumulation of salicylic acid (a marker for systemic acquired resistance, SAR) was observed after treatment with garlic extract. We see a potential for developing preparations from garlic for use in organic farming, e.g. for reducing the pathogen inoculum potential in planting material such as seeds and tubers. We have tested various encapsulation formulations in comparison to direct treatment. Note added in proof: The complete chemical synthesis of azadirachtin has now been achieved. Nature (2007) 448: 630–631     

Molecular characterization and pathogenicity of <Emphasis Type="Italic">Alternaria</Emphasis> species on wheat and date palms in Oman

This study was conducted to investigate the Alternaria species associated with leaf spot of date palm and wheat in Oman. Out of 98 date palm leaf samples and 146 wheat leaf samples, Alternaria was isolated from 27 and 23% of the samples developing leaf spot symptoms, respectively. Identification of Alternaria isolates using sequences of the internal transcribed spacer region of the ribosomal RNA (ITS rRNA), glyceraldehyde-3-phosphate dehydrogenase (GPDH), translation elongation factor (TEF) and RNA polymerase II subunit (RPB2) genes, showed that the isolates belong to seven Alternaria species or species complexes. A. burnsii - A. tomato and A. arborescens species complexes (58 and 4%, respectively) and A. alternata (38%) were the species recovered from the symptomatic date palm leaves. A. alternata (67%), A. burnsii - A. tomato species complex (15%), A. jacinthicola (3%), A. ventricosa (3%), A. slovaca (6%) and Alternaria caespitosa (6%) were isolated from wheat. Pathogenicity test showed that tested isolates of A. alternata (DPM19, WDK12), A. burnsii - A. tomato species complex (DPM31), A. jacinthicola (WBR4) and A. slovaca (WDK9, WDK7) were pathogenic on date palm, while A. alternata (DPM19, WDK12), A. burnsii - A. tomato species complex (DPM31, WDK11) and A. slovaca (WDK9, WDK7) were pathogenic on wheat. This is the first report of date palm and wheat as new hosts for A. burnsii - A. tomato species complex and the first reports of A. burnsii - A. tomato species complex, A. caespitosa A. slovaca, and A. ventricosa in Oman. The study shows that several species of Alternaria are associated with leaf spot in date palm and wheat in Oman, with some isolates having the ability to cause infection in both hosts.     

Control of infection of tomato fruits by <Emphasis Type="Italic">Alternaria</Emphasis> and mycotoxin production using plant extracts

Tomato fruits are susceptible to infection by Alternaria species. In addition, Alternaria species may contaminate the fruits with mycotoxins. There is thus interest in control systems to minimise pathogenicity and control toxin production. The objectives of this study were to examine the effect of plant extracts of Eucalyptus globulus and Calendula officinalis on the growth of strains of Alternaria alternata and A. arborescens, on pathogenicity of tomato fruits and mycotoxin production. The growth bioassays showed that the ethanolic and chloroformic fractions of E. globulus were the most effective in reducing growth of A. alternata (66–74 %) and A. arborescens (86–88 %), respectively at 2500 μg/g. The effects of plant extracts on mycotoxin biosynthesis were variable and strain dependent. The most effective fractions in decreasing mycotoxin accumulation were the ethanolic and chloroformic extracts of E. globulus, which reduced tenuazonic acid by 89 %, alternariol by 75–94 % and almost complete inhibition of alternariol monomethyl ether. All the tested fractions reduced percentage of infected tomato fruits when compared to the controls. The ethanolic and chloroformic fractions of E. globulus completely inhibited growth of A. alternata and A. arborescens on unwounded fruits and reduced the aggressiveness on wounded fruits of strains of both species significantly.     

Chemical Control of Alternaria sp. Causing Leaf Blight of Wheat

Abstract

A replicated fungicidal trial was conducted to control leaf blight of wheat caused by Alternaria sp. on Bijaga yellow. Out of the 5 fungicides used zineb and thiram were found to be most effective in controlling the disease.     

Reduced sclerotial viability of Stromatinia cepivora and control of white rot disease of onion and garlic by means of soil bio-solarization

The suppressive effects of soil bio-solarization, which is a new method of soil disinfestation that combines soil bio-fumigation with soil solarization, against the sclerotial viability of Stromatinia cepivora and the subsequent control of white rot disease of onion and garlic were evaluated. Soil was bio-fumigated with fresh amendments of cow manure, chicken manure, horse manure, cruciferous plant residues, or Allium waste, at 30,000 kg/ha. After bio-fumigation, the soil was irrigated and covered with a 200 μm transparent plastic sheet for 60 days. Plots that received fresh amendment and remained uncovered and untreated served as controls. Solarization alone increased the maximum soil temperature to 55.3 °C, 50.3 °C and 46.3 °C at 10, 20, and 30 cm depths, respectively, which led to significant reductions (98.0%, 89.3%, and 62.7%, respectively) in the sclerotial viability of S. cepivora. Soil bio-solarization with cruciferous plant residues or Allium waste resulted in the strongest negative effects on the sclerotial viability of S. cepivora, with reductions of 100.0%, 98.7%, and 87.3% or 100.0%, 99.3%, and 87.7%, at 10, 20, and 30 cm depths, respectively. Compared to the non-treated control, these treatments significantly reduced the incidence of white rot disease in onion and garlic, which led to increases in onion and garlic yield in fields that were heavily infested by S. cepivora.

     

除草剂对小麦田雀麦的生物活性测定

为筛选防除雀麦Bromus japonicus的高效除草剂,采用室内生物测定法研究了13种除草剂对雀麦的除草活性及5种除草剂的田间药效试验。结果表明,在田间推荐剂量的低剂量下,氟唑磺隆、啶磺草胺、氟噻草胺、甲基二磺隆、异丙隆、磺酰磺隆、丙苯磺隆7种除草剂对雀麦具有很高的防除效果,21 d鲜重抑制率分别为88.30%、86.32%、83.97%、78.47%、76.76%、72.83%、71.39%,高剂量下的21 d鲜重抑制率达98.57%、95.36%、91.58%、91.46%、89.47%、82.48%、82.20%;其中氟唑磺隆各剂量下的防效较其它除草剂高。而嘧啶肟草醚、苯唑草酮、炔草酯、吡氟酰草胺、唑啉草酯、精噁唑禾草灵6种除草剂对雀麦防效较差。氟唑磺隆、啶磺草胺、氟噻草胺、甲基二磺隆、异丙隆5种除草剂的田间药效试验表明,氟唑磺隆对雀麦防效最高,高剂量下20 d株防效达85.04%,药后40 d株防效和鲜重防效分别达83.94%和84.17%,未见小麦有明显药害症状,建议田间推荐用量为21.00~42.00 g(a.i.)/hm~2。表明雀麦对不同除草剂的敏感性存在差异,在供试的13种除草剂中氟唑磺隆对雀麦防效最高,较为安全,为防除雀麦的理想除草剂。     

Antifungal effect and reduction of <Emphasis Type="Italic">Ulmus minor</Emphasis> symptoms to <Emphasis Type="Italic">Ophiostoma novo-ulmi</Emphasis> by carvacrol and salicylic acid

There are still no effective means to control Dutch elm disease (DED), caused by the vascular fungi Ophiostoma ulmi and O. novo-ulmi. Plant phenolics may provide a new strategy for DED control, given their known antifungal activity against pathogens and their involvement in plant defence mechanisms. The in vitro antifungal activity of salicylic acid, carvacrol, thymol, phenol, o-cresol, m-cresol, p-cresol, and 2,5-xylenol against the DED pathogens was tested. Also, the protective effect of watering Ulmus minor seedlings with these compounds was tested against O. novo-ulmi. Salicylic acid, carvacrol, and thymol showed the strongest antifungal in vitro activity, while carvacrol and salicylic acid provided the strongest in vivo protection against O. novo-ulmi (63 and 46% reduction of leaf wilting symptoms with respect to controls, respectively). The effect of the treatments on tree phenology was low, and a significant negative relation was observed between the number of days to bud burst and the leaf wilting symptoms after inoculation, probably determined by genetic differences among the elm tree progenies used. The treatments with salicylic acid, carvacrol and thymol induced the highest shift in phenolic metabolite profile with respect to control trees. The protective effect of carvacrol and salicylic acid is discussed in terms of their combined activity as antifungal compounds and as inductors of tree defence responses.     

Molecular identification and pathogenicity of Fusarium and Alternaria species associated with root rot disease of wolfberry in Gansu and Ningxia provinces,China

Wolfberry (Lycium barbarum) ranks in the top 10 best-selling medicinal plants in China and it has been used for centuries as a medicine and a food supplement. It is suggested to have benefits on human health due to the rich content of polysaccharides, carotenoids, flavonoids, and alkaloids contained in its fruits, leaves, and root bark. Recently, severe root rot diseases have been causing plant losses in major growing areas. Here, we report fungi causing root rot disease in Chinese wolfberry plants. The analysis of nucleotide sequences of the internal transcribed spacer (ITS) region revealed a total of 92 isolates isolated from both soil and plant material samples. Fusarium spp. were the most abundant (58%), followed by Penicillium spp. (9%), and Alternaria spp. (5%). Fusarium spp. included F. oxysporum (36%), F. solani (30%), F. chlamydosporum (9%), F. nematophilum (9%), and F. tricinctum (8%). Sequences from the translation elongation factor 1-α gene (TEF-1α) were used to confirm the identity of Fusarium spp. and showed the predominance of F. oxysporum and F. solani. To confirm the pathogenicity of isolates, four isolates belonging to Fusarium spp. and one isolate belonging to Alternaria spp., isolated from wolfberry root tissues with root rot symptoms, were tested in outdoor and laboratory conditions. Results revealed that the five tested isolates were pathogenic with varying degrees of aggressiveness and ability to induce symptoms of root rot in wolfberry seedlings. The five isolates were recovered from inoculated seedlings, completing Koch's postulates. This is the first report on causative agents of root rot in Chinese wolfberry.     

小麦茎基腐病防治药剂及抗病品种的筛选

为获得防治小麦茎基腐病的有效药剂和抗病品种,测定12种杀菌剂对小麦茎基腐主要病原菌假禾谷镰孢菌Fusarium pseudograminearum的室内毒力、对小麦生长的影响及对小麦茎基腐病的室内防治效果,并鉴定144份小麦品种（系）对茎基腐病的抗性。结果表明,12种杀菌剂对假禾谷镰孢菌均有一定的抑制效果,其中15%氰烯菌酯·5%己唑醇的抑制率最高,EC₅₀为0.002 mg/L,其次是6.6%嘧菌酯·1.1%咯菌腈·3.3%精甲霜灵、25 g/L咯菌腈和430 g/L戊唑醇,EC₅₀分别为0.016、0.069和0.099 mg/L。12种杀菌剂拌种处理对小麦出苗、株高、根长和鲜重均有不同程度的影响,尤其对出苗率影响最大,其中15%氰烯菌酯·5%己唑醇处理的出苗率最低,为30.41%。15%氰烯菌酯·5%己唑醇拌种处理的防治效果最好,为70.43%;其次是430 g/L戊唑醇和25 g/L咯菌腈·37.5 g/L精甲霜灵,防治效果分别为56.34%和53.34%。在供试144份小麦品种（系）中,仅3份对小麦茎基腐病表现为中感,其余141份均表现为高感,无免疫和抗病品种。综上,目前防治小麦茎基腐病时建议选用15%氰烯菌酯·5%己唑醇等杀菌剂进行拌种处理,但应严格控制药剂用量,以防影响小麦出苗。     

Growth of seedlings of Agropyron repens (L.) Beauv. and Agrostis gigantea Roth in cereal crops

Experiments were undertaken to define the conditions under which seeds and seedlings of Agropyron repens and Agrostis gigantea may start infestations in cereal crops. When seedlings were planted early or late in spring wheat and spring barley, most growth of shoots and rhizomes was produced by Agropyron planted early in wheat. Late planting halved the amount of shoot growth and severely inhibited rhizome formation. In winter wheat given a moderate or zero amount of nitrogen fertilizer in spring, growth of the weed seedlings was slow. Rhizomes were not produced during the time the crop was growing but only after harvest. Agrostis made more growth than Agropyron in most treatments throughout most of the experiment. Late planting decreased growth more than in the spring cereals. Nitrogen fertilizer, although it had little effect on the amount of growth made by winter wheat, increased the growth of the early-planted seedlings but decreased that of the late-planted ones of both weed species. When planted into plots given nitrogen, more seedlings of both species died after late than after early planting. Clearly, the amount of growth and rhizome produced by seedlings of these two species will depend on the type of cereal, the time of emergence of the seedlings in relation to the cereal, and on other factors affecting the relative vigour of cereal and weed. Evidently, where the weed seedlings emerge early in weakly or moderately competitive cereal crops or when growth is unchecked in the cereal stubble, seedlings could give rise to infestations.     

The allelopathic effect of three Amaranthus spp. (pigweeds) on wheat (Triticum durum)

The allelopathic effect of Amaranthus retroflexus L., Amaranthus blitoides S. Wats, and Amaranthus gracilis Desf. on wheat Triticum durum L. was investigated under laboratory, glasshouse and field conditions. Laboratory experiments showed that fresh shoot or root extract of the three weed species reduced germination, coleoptile length, root length and root dry weight of wheat seedlings. The inhibitory effects were rate dependent, with low concentrations of shoot extract promoting shoot growth of wheat. Fresh plant extracts were more phytotoxic than dried plant extracts and shoot extracts had higher detrimental effects than root extracts. In pot experiments, dried shoot extract of A. gracilis increased shoot and root dry weights of wheat seedlings. For A retroflexus and A. blitoides the extracts of these and dried shoots (8 g kg^?1), which had been added to soil mixtures significantly reduced ger-mination and growth of wheat seedlings. Addition of up to 16 g kg^?1 of A. gracilis residues promoted shoot growth of wheat and had no significant harmful effect on root growth. Roots appeared more sensitive to allelopathic effect than shoots. Under field conditions, incorporation of A. retroflexus or A. blitoides residues in the soil reduced height, grain and straw yield of wheat, whereas A. gracilis residues stimulated plant height and increased yield.     

Differential phytotoxicity of glyphosate in maize seedlings following applications to roots or shoot

The transport and differential phytotoxicity of glyphosate was investigated in maize seedlings following application of the herbicide to either roots or shoots. One-leaf maize seedlings (Zea mays L.) were maintained in graduated cylinders (250 mL) containing nutrient solution. Half of the test plants were placed in cylinders (100 mL) containing different ¹⁴C-glyphosate concentrations; the remainder received foliar appliation of ¹⁴C-glyphosate. After 26 h, the roots and the treated leaves were washed with distilled water, and the plants placed again in cylinders (250 mL) containing fresh nutrient solution for 5 days. Plants were weighed, and split into root, seed, cotyledon, coleoptile, mesocotyl, first leaf and apex. The recovery of ¹⁴C-glyphosate was over 86%. For both application treatments, the shoot apex was the major sink of the mobilized glyphosate (47.9 ± 2.93% for root absorption and 45.8 ± 2.91% for foliar absorption). Expressed on a tissue fresh weight basis, approximately 0.26 μg a.e. g⁻¹ of glyphosate in the apex produced a 50% reduction of plant fresh weight (ED₅₀) when the herbicide was applied to the root. However, the ED₅₀ following foliar absorption was only 0.042 μg a.e. g⁻¹ in the apex, thus maize seedlings were much more sensitive to foliar application of the herbicide.     

Pathogenicity,Morpho-Species and Mating Types of <Emphasis Type="Italic">Alternaria</Emphasis> spp. causing Alternaria blight in <Emphasis Type="Italic">Pistacia</Emphasis> spp. in Turkey

Alternaria genus includes many plant pathogens on numerous hosts, causing leaf spots, rots and blights. Alternaria blight has been observed as one of the important fungal diseases of pistachio (Pistacia vera L.) as well as its wild relatives (P. terebinthus, P. lentiscus, P. khinjuk, P. atlantica, P. mutica) in Turkey. Alternaria species were sampled from Pistacia spp. hosts from different geographic regions in Turkey during field trips in late spring to early fall of 2013. Alternaria blight symptoms were observed mainly on fruits and rarely on leaves. Four hundred and twenty two of the isolates were morphologically defined as A. alternata, A. tenuissima, A. arborescens and also intermediate morpho-species between A. alternata/A. arborescens. Pathogenicity of the isolates was confirmed with host inoculations on detached fruits. Mating types of 270 isolates of Alternaria spp. from the collection were identified using a PCR-based mating type assay that amplifies either a MAT1-1 or a MAT1-2 fragment from the mating locus. Although a strongly clonal population structure was expected due to the putative asexual reproduction of these fungi, both idiomorphs were detected at equal frequencies at several different spatial scales. The distribution of mating types within each geographic region, within host species as well as in overall collection was not significantly different from 1:1. Amplified fragments of partial idiomorph sequences were obtained for representative isolates. Parsimony trees were depicted based on sequence data of mating type genes for these representative isolates as well as some other Alternaria species obtained by Genebank. Several point mutations presented a few clusters which are supported by high bootsrapped values. The Alternaria blight disease agents both from cultivated and wild hosts were pathogenic on pistachio which may cause difficulties to control the disease because of extensity of pathogen sources. Besides, equal mating type distribution of the pathogen at both geographic and host species levels suggests a potential for sexual reproduction of Alternaria spp. in Turkey.