番茄早疫病菌对3种杀菌剂的抗药性监测

[目的]测定番茄早疫病菌对3种化学杀菌剂的敏感性。[方法]从山西省晋中、长治、临汾及五寨地区的番茄早疫病株的果实或叶片上采集番茄早疫病菌,将检测到的抗性菌株分别接种在含嘧菌酯、腐霉利和代森锰锌药物的平板上,测定不同分离菌株对这3种杀菌剂的敏感性。[结果]共采集分离到124株番茄早疫病菌。五寨菌株对3种杀菌剂的敏感性测定表明,其平均EC50值分别为0.033、1.969和9.328μg/ml,最低抑制浓度分别为1.0、8.0和50.0μg/ml。以此作为番茄早疫病菌对这3种杀菌剂的相对敏感基线,所测晋中、长治及临汾菌株与五寨菌株相比,均未对腐霉利及嘧菌酯产生抗药性,而对代森锰锌已普遍产生抗药性,最低达66.7%。[结论]番茄早疫病菌对代森锰锌的抗性处于中抗水平,对嘧菌酯及腐霉利未产生抗性。     

Genetics of rate limiting disease reaction to Alternaria solani in Tomato

A study was conducted to understand the genetics of rate limiting disease reaction to Alternaria solani in tomato. The results from χ² analysis and Castle Wright estimation revealed that resistance is an oligogenic character controlled by two to few genes. In general, the results for predominant gene effects reveal that both additive and non-additive effects are involved in the inheritance of early blight resistance. The results for predominant gene effects obtained for various crosses studied are discussed along with their implications for improvement of this trait.     

秦冠、富士苹果杂交后代抗早期落叶病的遗传分析

采用秦冠、富士杂交F1代,对苹果早期落叶病的抗性遗传倾向进行研究。结果表明,杂交F1代斑点病的遗传倾向在不同年份表现一致,病情指数由小到大依次为秦冠×富士<富士×秦冠,而褐斑病的遗传倾向在不同组合不同年份表现不一致。秦冠、富士杂交F1代的斑点病病情指数均值略高于或低于亲中值,表明秦冠、富士杂交后代抗斑点病的遗传中加性效应较大,在后代中选择抗病单株潜力大。褐斑病病情指数均高于亲中值,表明褐斑病遗传中非加性效应占有较大比重。     

云南省荞麦叶枯病病原菌鉴定及其生物学特性

为明确云南省荞麦叶枯病病原菌种类,采用常规组织分离法获得病原菌菌株LW2015.3,通过形态学特征及分子生物学技术对菌株LW2015.3进行鉴定,并研究其生物学特性。结果表明,荞麦叶枯病病原菌的分生孢子呈倒棍棒状或倒梨状,褐色,具3～8个横隔膜,0～4个纵斜隔膜,大小为16.5～45.0μm×5.0～13.5μm,厚垣孢子呈球形,直径为6.0～12.0μm;该菌株ITS序列系统发育进化分析结果表明,菌株LW2015.3与链格孢Alternaria alternata(登录号:MG195995.1)的同源性为100%,结合形态学特征与分子鉴定结果确定云南省荞麦叶枯病病原菌为链格孢A. alternata(登录号:KT362732.1)。该病原菌菌丝生长适宜温度为20～30℃,25℃为最适温度;当p H为6～9时菌丝生长速率加快,pH 7最适菌丝生长;PDA培养基和PSA培养基最适菌丝生长;该病原菌对以麦芽糖为碳源和以硝酸钠为氮源时的利用率最高;菌丝的致死温度为50℃,10 min;不同光照条件对菌丝生长的影响有显著差异,连续光照最有利于菌丝生长。     

Effects of all‐male,mixed‐sex and all‐female freshwater prawn in polyculture with major carps and molas in the fallow rice fields

This study was conducted to evaluate the effects of all‐male, mixed‐sex and all‐female freshwater prawn (Macrobrachium rosenbergii) in a polyculture with major carps (Catla catla and Labeo rohita) and self‐recruiting small fish molas (Amblypharyngodon mola) in the fallow rice fields of Bangladesh. There were three treatments with three replicates. All ponds were stocked with carps and molas plus either all‐male prawns (treatment MP), mixed‐sex prawns (MFP) or all‐female prawns (FP). Prawn, mola, catla and rohu were stocked 20 000, 20 000, 1750 and 750 ha^?1, respectively, in all treatments. The prawns were fed twice daily, starting at 8% body weight and gradually reduced to 3% body weight. The fish were fed in the morning with mustard oil cake and rice bran (1:2 ratios) at 3% body weight. Significantly higher production of prawns (697 kg ha^?1) was obtained in treatment MP, which yielded 34.7% and 56.2% more production than MFP and FP respectively. Significantly higher total production of 1620 kg ha^?1 and a higher benefit–cost ratio of 2.10:1 were also obtained in treatment MP. It can be concluded that an all‐male prawn culture is economically more viable than all‐female and mixed‐sex prawn cultures, along with other fish like major carps and the nutrient‐dense molas in the polyculture.     

The Role of Phenolics and Peroxidase in Resistance to Alternaria triticina in Bread Wheat (Triticum aestivum L.)

Total phenolic content in eight diverse wheat lines showed that PF-70354 YACO'S' had the highest (802.90 ± 1.35 μg g⁻¹ fresh weight) and Agra Local possessed the lowest amount (684.72 ± 5.28 μg g⁻¹ fresh weight). However, for further experiments two lines namely, ACC-8226 and MP-845, with contrasting disease scores under field trials were assessed. Pre-infectional levels of total phenolics and peroxidase activity were higher in ACC-8226 than in MP-845. Furthermore, the amount of phenolics and peroxidase activity in each case increased after inoculation. The post-infectional levels of phenolics and peroxidase were again higher in ACC-8226 than in MP-845. The peroxidase activity decreased with age in both the varieties, with very little peroxidase activity after 35th day. However, the amount of phenolics started to decrease with the progress of disease and age in MP-845, whereas in ACC-8226 an elevated level of it was maintained. Our findings not only support that ACC-8226 is the resistant and MP-845 is the susceptible variety but also provide important biochemical parameters for plant breeders to authentically identify potential breeding material and plan effective breeding strategies using these tools.     

Evaluation of tangerine hybrid resistance to Alternaria alternata

The Alternaria Brown Spot, caused by Alternaria alternata, is a major fungal disease in some kinds of tangerines, tangor, mandarins and pomelos. In Brazil as well as worldwide, A. alternata can cause necrosis in fruits, branches and leaves, causing substantial profit loss. In the present research, in laboratory conditions and in the field, we evaluated the resistance to the fungus, in leaves and fruits, for 22 varieties and hybrids of tangerines. To this end, we evaluated genotypes belonging to the Germplasm Bank of the Estação Experimental de Citricultura de Bebedouro. The resistant genetic materials (found in leaves and fruits) represented four varieties of clementines (Citrus clementina); six varieties of mandarins (two belonging to C. reticulata, two to C. tangerina, one to C. deliciosa and one to C. nobilis); one tangelo (C. tangerina × C. paradisi); two mandarin hybrids (one resulting from crossing C. nobilis × C. deliciosa and the other from crossing C. clementina × C. reticulata); one tangor hybrid (C. clementina) and two satsuma hybrids (C. unshiu × C. deliciosa). We also determined a relation between the inoculation of leaves and fruits. The resistance and susceptibility following inoculation in leaves and fruits supports a relationship between these organs and the physiological responses observed for the evaluated genotypes.     

Molecular genetic characterisation of the Asc locus of tomato conferring resistance to the fungal pathogen Alternaria alternata f. sp. lycopersici

The Alternaria stem canker disease of tomato is caused by the fungal pathogen Alternaria alternata f. sp. lycopersici and its host-selective AAL-toxins. Resistance to the pathogen and insensitivity to the toxins are conferred by the Asc locus on chromosome 3L. Sensitivity to AAL-toxins is a relative character; the toxins inhibit development of all tested tomato tissues but susceptible cultivars are much more sensitive than resistant cultivars. In addition to tomato, some other plant and animal species are sensitive to the toxins as well. The likely mode of action of AAL-toxins is interference with sphingolipid biosynthesis by specific inhibition of ceramide synthase activity. To molecularly isolate Asc, transposon tagging and positional cloning strategies are applied. As a first step, transposon insertions and restriction fragment length polymorphism (RFLP) markers are identified in proximity of the Asc locus. Subsequently, the transposons are used to inactivate Asc by insertion mutagenesis, and the RFLP markers are used to identify yeast artificial chromosomes (YACs) with tomato DNA inserts. Once an Asc-insertion mutant and/or a YAC encompassing Asc has been obtained, physical isolation and characterisation of Asc will be conceivable. Elucidation of the molecular role of Asc will illuminate the specificity of host recognition by Alternaria alternata f. sp. lycopersici.Abbreviations AAL-toxin Alternaria alternata lycopersici-toxin - A. a. lycopersici Alternaria alternata f. sp. lycopersici - Asc Alternaria stem canker - HST host-selective toxin     

Inheritance of resistance to early blight disease in a diploid potato population

Early blight disease, caused by Alternaria solani Sorauer, is a serious disease of potato foliage and tubers that occurs in most potato‐growing regions world‐wide. Developing new potato cultivars with resistance to early blight may reduce losses in the field and in storage, and lessen the need for fungicide applications. A total of 280 clones, derived from 72 maternal half‐sib families from a diploid random‐mated hybrid population of Solarium phureja×Solarium stenotomum were examined for resistance to early blight. The clones that were evaluated in a replicated field trial for 2 years in Pennsylvania, USA, had similar early blight intensity both years. Significant differences were found among families, within families and for the interaction of years × within families. Broad‐sense heritability for resistance, measured as area under the disease progress curve (AUDPC), was estimated as 0.73, with a 95% confidence interval of 0.65‐0.78, and narrow‐sense heritability was estimated as 0.61 ± 0.29 (P = 0.05). The correlation of AUDPC for early blight between years was 0.57 (P < 0.0001). These results suggest that this diploid population is worthy of use in breeding for early blight resistance.     

分根区交替灌溉对盆栽甜玉米水分及氮素利用的影响

分根区交替灌溉(APRI)是高效节水新技术，该文通过盆栽试验，研究了不同水肥条件下，3种不同灌溉方式对甜玉米干物质积累、水分和氮素利用的影响。结果表明：在施肥和充分供水条件下，与常规灌溉(CI)相比，分根区交替灌溉节水29.1%，总干物质量和冠干物质量仅分别减少6.3%和5.6%，而水分利用效率和氮肥表观利用率分别提高24.3%和16.4%，这表明分根区交替灌溉的节水节肥效应要与合理施肥和适宜的灌水量相结合才能发挥更好的作用。而部分根干燥灌溉(PRD)由于总干物质量下降太多，水分利用效率和氮肥表观利用率都没有得到提高。