Overexpression of auxin/indole-3-acetic acid gene MdIAA24 enhances Glomerella leaf spot resistance in apple(Malus domestica)

Auxin is throughout the entire life process of plants and is involved in the crosstalk with other hormones,yet its role in apple disease resistance remains unclear.In this study,we investigated the function of auxin/indole-3-acetic acid(IAA)gene Md IAA24 overexpression in enhancing apple resistance to Glomerella leaf spot(GLS)caused by Colletotrichum fructicola(Cf).Analysis revealed that,upon Cf infection,35S::Md IAA24 plants exhibited enhanced superoxide dismutase(SOD)and peroxidase(POD)activity,as well as a greater amount of glutathione(reduced form)and ascorbic acid accumulation,resulting in less H_(2)O_(2)and superoxide anion(O_(2)^(-))in apple leaves.Furthermore,35S::Md IAA24 plants produced more protocatechuic acid,proanthocyanidins B1,proanthocyanidins B2 and chlorogenic acid when infected with Cf.Following Cf infection,35S::Md IAA24 plants presented lower levels of IAA and jasmonic acid(JA),but higher levels of salicylic acid(SA),along with the expression of related genes.The overexpression of Md IAA24 was observed to enhance the activity of chitinase andβ-1,3-glucanase in Cfinfected leaves.The results indicated the ability of Md IAA24 to regulate the crosstalk between IAA,JA and SA,and to improve reactive oxygen species(ROS)scavenging and defense-related enzymes activity.This jointly contributed to GLS resistance in apple.

Genomic Selection for Frogeye Leaf Spot Resistance in Soybean

Soybean frogeye leaf spot(FLS) disease is a global disease affecting soybean yield, especially in the soybean growing area of Heilongjiang Province. In order to realize genomic selection breeding for FLS resistance of soybean, least absolute shrinkage and selection operator(LASSO) regression and stepwise regression were combined, and a genomic selection model was established for 40 002 SNP markers covering soybean genome and relative lesion area of soybean FLS. As a result, 68 molecular markers controlling soybean FLS were detected accurately, and the phenotypic contribution rate of these markers reached 82.45%. In this study, a model was established, which could be used directly to evaluate the resistance of soybean FLS and to select excellent offspring. This research method could also provide ideas and methods for other plants to breeding in disease resistance.

ORYZA SATIVA SPOTTED-LEAF 41(OsSPL41) Negatively Regulates Plant Immunity in Rice

Identification of immunity-associated leucine-rich repeat receptor-like protein kinases(LRR-RLK) is critical to elucidate the LRR-RLK mediated mechanism of plant immunity.Here,we reported the map-based cloning of a novel rice SPOTTED-LEAF 41(Os SPL41) encoding a putative LRR-RLK protein(Os LRR-RLK41/Os SPL41) that regulated disease responses to the bacterial blight pathogen Xanthomonas oryzae pv.oryzae(Xoo).An 8-bp insertion at position 865 bp in a mutant spotted-leaf 41(spl41) allele led to the formation of purple-brown lesions on leaves.Functional complementation by the wild type allele(Os SPL41) can rescue the mutant phenotype,and the complementary lines showed similar performance to wild type in a number of agronomic,physiological and molecular indices.Os SPL41 was constitutively expressed in all tissues tested,and Os SPL41 contains a typical transmembrane domain critical for its localization to the cell membrane.The mutant exhibited an enhanced level of resistance to Xoo in companion of markedly up-regulated expression of pathogenesis-related genes such as Os PR10a,Os PAL1 and Os NPR1,while the level of salicylic acid was significantly increased in spl41.In contrast,the over-expression lines exhibited a reduced level of H_(2)O_(2) and were much susceptible to Xoo with down-regulated expression of pathogenesis-related genes.These results suggested that Os SPL41 might negatively regulate plant immunity through the salicylic acid signaling pathway in rice.

Impact of Three Isolates of Cercosporidium personatum (Berk. Et M.A Curt.), a Pathogen of Late Leaf Spot, on Defoliation and Yield in Groundnut (Arachis hypogaea L.) under Controlled Conditions

Late leaf spot caused by Cercosporidium personatum is one of the most widespread groundnut leaf diseases. Along with early leaf spot and rust, it is one of the main fungal diseases hampering groundnut production worldwide. Late leaf spot accounts for significant yield losses throughout the world where groundnuts are grown. This reduction in yield caused by the disease could result in yield losses of between 50% and 70%. In Burkina Faso, the disease is present throughout the country, with incidence varying according to region and season. Could the variability in the incidence of the disease be linked to the nature of the isolates or to the conditions from each agro-ecological zone? In this study, the aim was to assess the capacity of three isolates from three agroclimatic zones of the country to defoliate and reduce groundnut yield. To this end, three isolates of Cercosporidium personatum (Berk. Et M.A Curt.) were collected in these zones and evaluated on three contrasting groundnut varieties. A split-splot design was used for the experiment. Isolates were prepared from samples collected in farmers’ fields. After incubation in the laboratory, leaf spots showing good sporulation were scraped off with a scalpel after immersing the leaves in distilled water. Inoculations were carried out under controlled environment. After inoculation with the isolate, the percentage of defoliation and the reduction in yield of these varieties were then evaluated. Inoculation was carried out from the 30th day after sowing with Cercosporidium personatum spore suspensions at 105 spores/ml. The study showed that the percentage of defoliation (P = 0.0001) and the reduction in yield (P = 0.0001) were significant. The study revealed that, whatever the variety, isolate I3TF from the Upper Basins region in the South Sudanese zone caused the greatest defoliation and the greatest reduction in yield. The variety TS32-1, regardless of the isolate used for the treatment, recorded the best yield. The variety PC79-79, regardless of the isolate used for the treatment, recorded the lowest percentage of defoliation. The highest defoliation recorded under the effect of the isolates was of the order of 72.20%;the highest yield reduction was of the order of 87.20% compared with the water control.

Molecular Characterization,Morphology and Pathogenicity of Curvularia pseudobrachyspora,A New Causal Agent of Leaf Spot on Banana

[Objectives]The paper was to study molecular characterization,morphology and pathogenicity of Curvularia pseudobrachyspora,a new causal agent of leaf spot on banana.[Methods]Banana(Musa acuminate)leaves with streaks or long ellipse-shaped lesions were sampled in an orchard of Danzhou City,Hainan Province,China in 2021.Fungus isolates were isolated from the diseased tissues and further identified as C.pseudobrachyspora based on morphological characteristics of colony,conidiophore and spore,phylogenetic analyses of the ITS region,GAPDH and TEF-1αgenes.[Results]In the pathogenicity test,the fungus re-isolated from inoculated leaves with necrotic lesions was identified morphologically and molecularly,fulfilling Koch's postulates.[Conclusions]C.pseudobrachyspora is a new pathogen causing leaf spot of banana in China and the world.

Morphological and Molecular Identification of Alternaria alternata Causing Leaf Spot Disease on Huangdi Banana in China

[Objectives]The paper was to identify Alternaria alternata causing leaf spot disease on Huangdi banana in China.[Methods]Fungal isolates were isolated and identified by morphological features,molecular identification and pathogenicity test.[Results]There were light to dark brown,tiny oval spots on leaves.The causal agent isolated from affected leaves was identified as A.alternata based on the morphological properties,coupled with sequence analyses of the internal transcribed spacer(ITS)region,large subunit ribosomal DNA(LSU rDNA)and the translation elongation factor 1-alpha(TEF-1α)gene.Koch s postulates were fulfilled by successful re-isolation of pathogen from the artificial inoculated leaves.[Conclusions]To our knowledge,this is the first report of leaf spot caused by A.alternata on Huangdi banana in China.The identification of A.alternata as the causal agent of the observed leaf spot disease on Huangdi banana is critical to the prevention and control of this disease in the future.

Influence of Planting Date on the Incidence and Severity of Leaf Spot Disease in Telfairia occidentalis Hook f.

Telfairia occidentalis Hook f. is attacked by a destructive fungal pathogen Epicoccum sorghinum which causes leaf spot disease in the field. In Came-roon, this critically important seed and leaf vegetable is predominantly culti-vated under natural environmental conditions. An experiment was conducted in 2019 and 2020 during the long and short rainy seasons in Santchou to de-termine the influence of planting dates between seasons on the incidence and severity of leaf spot disease. The design used was a 2 by 4 factorial random-ized complete block design with three replications and four sowing dates. Data for disease incidence and severity documented fortnightly, were submitted to analysis of variance using SPSS version 23, and the means were separated by Duncan’s multiple range test (DMRT) at a 95% confidence interval. Statistical analysis revealed that the long rainy season registered a significantly (p p < 0.05) disease incidences and severities to other planting dates investi-gated. We established that the first three planting dates in the long rainy season could be a management practice to reduce disease prevalence.

Loss Rate Estimation of Yield and Output Value of Tobacco Leaf Infected by Tobacco Blown Spot (Alternaria alternata)

[Objective] The paper was to study the effect of tobacco blown spot on the yield and output value of tobacco leaf.[Method]The upper,middle and lower leaves in tobacco plant were selected during the harvest period of tobacco to carry out loss rate estimation of yield and output value of tobacco leaf caused by different disease levels of brown spot.Regression correlation analysis was also conducted.[Result]The disease levels of brown spot had extremely significant strong negative correlation with single leaf weight of tobacco leaf,and it had extremely significant strong positive correlation with the loss rate of single leaf weight.The increase speed of loss rate of single leaf weight of middle and upper leaves was obviously faster than that of lower leaves.The loss rates of single leaf weight of upper,middle and lower leaves were 3.18%-28.95%,3.43%-28.88% and 10.07%-26.90%,respectively.The higher the disease level of blown spot was,the lower the yield and output value of tobacco leaf was,and the corresponding loss rate was also higher.Correlation analysis showed that the disease level of blown spot had extremely significant strong negative correlation with the yield and output value of tobacco leaf,and it had extremely significant strong positive correlation with the loss rate of yield and output value.The negative impact of blown spot on the output value of tobacco leaf was far greater than that on the yield.The highest loss rate of the yield of tobacco leaf was 28.56%,while the highest loss rate of output value reached 89.67%.[Conclusion] The study provided theoretical basis for accurately holding the critical period for the control of blown spot,thus reducing the damage on tobacco leaf and improving the output value of tobacco leaf.

Study on Biological Characteristics of the Pathogen of Pistacia vera Leaf Brown Spot

[Objective] The paper was to study the occurrence rule of Pistacia vera leaf brown spot and the biological characteristics of its pathogen.[Method] The occurrence rule of P.vera leaf brown spot was investigated in field.A fungus was isolated and purified from the diseased tissue of P.vera,its cultural trait and morphological characteristics were observed in indoor experiment,and the classification status was identified according to its morphology.The effects of different temperatures on mycelial growth of the pathogen,as well as the effects of different temperatures and humidity on spore germination of the pathogen were also studied.[Result] P.vera leaf brown spot was a fungal disease,which mainly infected the leaves and fruits of P.vera,causing leaf spot and blight.The disease had serious incidence in introduction place of P.vera in China.The fungal disease was identified to be Alternaria alternaria,the appropriate temperature for mycelial growth was 20-25 ℃,the appropriate temperature for spore germination was 25-30 ℃,and the appropriate relative humidity was over 95%.[Conclusion] Late spring and early summer,as well as late summer and early autumn are two peak periods for incidence of the disease,continuous rain in summer is the decisive condition for the infection and outbreak of P.vera leaf brown spot.

Occurrence and Damage of Maize Gray Leaf Spot and Its GPS Monitoring

Maize gray leaf spot is a kind of leaf disease seriously threatened the production of maize,which occurs all around the world.The occurrence and damage conditions of maize gray leaf spot at home and abroad and in Yunnan Province are described,the latest research process of maize gray leaf spot are summarized,and the integrated control methods of maize gray leaf spot and its GPS monitoring are further introduced.

Investigation and Prevention of Leaf Spot in Radix Pseudoxtellariae in Southeast State of Guizhou Province

[ Objective] The paper was to isolate the pathogen of leaf spot in Radix pseudoxtellariae, and to select the best fungicide with good antibacterial effectagainst the disease. [ Method] The pathogen was isolated from the diseased leaves, and the antibacterial activities of four fungicides including carbendazim, chlorothalonil, thiophanate-methyl and mancozeb against the pathogen were measured through mycelial growth method. [ Result ] The microscopic examination resultsshowed that the main pathogens of leaf spot in R. pseudoxtellariae were Phyllosticta commonsii and Alternaria sp.. Antibacterial results showed that four fungicidesall had apparent inhibition effect against leaf spot in R. pseztdoxtellariae, of which carbendazim had the best effect with the inhibition rate of 76.6% ; followed bythiophanate-methyl with the inhibition rate of 72.3% ; the third was mancozeb with the inhibition rate of 68.7%, and the inhibition rate of chlorothalonil was the

Study on the Bacterial Carrying Seeds as the Primary Infection Sources of Curvularia Leaf Spot in Maize

[Objective] The aim was to study the bacterial carrying seeds as the primary infection sourcs of Cunularia leaf spot of maize, and to provide the theo-retical basis for the control of the disease in production. [ Method] Through slide germination and seed tissue isolation method, the viabilities of seeds with internaland external bacterial carrying were detected ; the infection of bacterial carrying of seeds on the young seedling was detected indoors by sand culture method ; and the infection of bacterial carrying seeds on maize was detected using field cultivation method. [Result] The conidia of Gunularia and mycelia carried by maize seeds could survive through the winter. Intemal bacterial carrying of seed affected the germination of seeds, but external bacterial carrying did not affect the germination; internal and external bacterial carrying seeds could infect the radicle and gemmule of maize seedling. [Condusion] The conidia of Curvularia and mycelia carried by maize＇seeds could survive through the winter and infect the seedling, which would make the seedlings have weak growth.

Comparative QTL Mapping of Resistance to Gray Leaf Spot in Maize Based on Bioinformatics

The integration QTL map for gray leaf spot resistance in maize was constructed by compiling a total of 57 QTLs available with genetic map IBM2 2005 neighbors as reference. Twenty-six ＂real QTLs＂ and seven consensus QTLs were identified by refining these 57 QTLs using overview and meta-analysis approaches. Seven consensus QTLs were found on chromosomes 1.06, 2.06, 3.04, 4.06, 4.08, 5.03, and 8.06, and the map coordinates were 552.53,425.72, 279.20, 368.97, 583.21, 308.68 and 446.14 cM, respectively. Using a synteny conservation approach based on comparative mapping between the maize genetic map and rice physical map, a total of 69 rice and maize resistance genes collected from websites Gramene and MaizeGDB were projected onto the maize genetic map IBM2 2005 neighbors, and 2 （Rgene32, htl）, 4 （RgeneS, rp3, scmv2, wsm2）, and 4 （ht2, Rgene6, Rgene8 and Rgene7） positional candidate genes were found in three consensus QTLs on chromosomes 2.06, 3.04, and 8.06, respectively. The results suggested that the combination of meta-analysis of gray leaf spot in maize and sequence homologous comparison between maize and rice could be an efficient strategy for identifying major QTLs and corresponding candidate genes for the gray leaf spot.

Dispersal routes of Cercospora zeina causing maize gray leaf spot in China

The gray leaf spot caused by Cercospora zeina has become a serious disease in maize in China.The isolates of C.zeina from Yunnan,Sichuan,Guizhou,Hubei,Chongqing,Gansu,and Shaanxi were collected.From those,127 samples were used for genetic diversity analysis based on inter-simple sequence repeat(ISSR)and 108 samples were used for multi-gene sequence analysis based on five gene fragments.The results indicated that populations of C.zeina were differentiated with a relatively high genetic level and were classified into two major groups and seven subgroups.The intra-population genetic differentiation of C.zeina is the leading cause of population variation in China,and interpopulation genetic similarity is closely related to the colonization time and spread direction.The multi-gene sequence analysis of C.zeina isolates demonstrated that there were nine haplotypes.Genetic diversity and multi-gene sequence revealed that Yunnan population of C.zeina,the earliest colonizing in China,had the highest genetic and haplotype diversity and had experienced an expansion event.With the influence of the southwest monsoon in the Indian Ocean,C.zeina from Yunnan gradually moved to Sichuan,Guizhou,Shaanxi,Gansu,and Chongqing.Meanwhile,C.zeina was transferred directly from the Yunnan into the Hubei Province via seed and then came into Shaanxi,Henan,and Chongqing along with the wind from Hubei.

Differentiation of xanthomonads causing the bacterial leaf spot of poinsettia in China from the pathotype strain of Xanthomonas axonopodis pv. poinsettiicola

In October 2003, a new bacterial disease with symptoms similar to those caused by Xanthomonas axonopodis pv. poinsettiicola was observed on poinsettia leaves at a flower nursery in Zhejiang Province of China. Three Xanthomonas strains were isolated from infected plants and classified as X. axonopodis. They were differentiated from the pathotype strain LMG849 of X. axonopodis pv. poinsettiicola causing bacterial leaf spot of poinsettia by comparison of pathogenicity, substrate utilization and BOX-PCR genomic fingerprints.

Pseudocercospora leaf and fruit spot disease of citrus: Achievements and challenges in the citrus industry: A review

Citruses are the worlds’ second fruit crops by volume next to banana. It is one of the most important commodity in tropical Africa as source of foreign currency, raw material for agro-industries and source of employment. The production and productivity of citrus in tropical Africa including Ethiopia are critically threatened by a number of diseases. Among others, pseudocercospora leaf and fruit spot of citrus caused by a fungus Pseudocercospora angolensis is the most destructive disease of citrus. Literature reviews have been made by searching the available information on leaf and fruit spot of citrus. Journal articles, research papers, workshop proceedings, Thesis research, manuals, and quarantine regulations were among the information sources of the review. The disease is widespread in 22 African countries including Ethiopia with a single report around Yemen in the Arabian Peninsula. Scattered research efforts have been made by different researchers in Africa mainly dealing with its geographic distribution, biology, and management practices. Fungicides, plant extracts/essential oils, and host resistance are among the research efforts made for the control of P. angolensis. Even though the disease is not yet reported to the rest of the world, it becomes a serious concern as an important quarantine pest thereby critically affecting the world trade and germplasm exchange of the citrus industry. Therefore, the purpose of this paper is to compile the scattered information on various aspects of leaf and fruit spot of citrus mainly to avail the information for researchers, development workers and policy people. Moreover, this review will suggest future research and development direction towards better understanding and sustainable management practices of the disease.

Epidemiology of the Groundnut (<i>Arachis hypogaea</i>L.) Leaf Spot Disease: Genetic Analysis and Developmental Cycles

Groundnut leaf spot is one of the important factors limiting groundnut productivity in Africa particularly in the Democratic Republic of Congo (DR Congo). Early and late leaf spot disease of groundnut caused by Cercospora arachidicola Hori and Cercosporidium personatum (Berk & Curt.) Deighton, respectively, can cause considerable yield losses without fungicide management. The main objectives of this research were to analyze plant and disease developmental cycles. Significant differences were observed among the groundnut varieties evaluated for resistance to the leaf spot disease. The results show that plant development cycle can be divided into three developmental stages. A first stage characterized by a low production of leaves, a second stage with a significant leaf development and finally a third stage with a reduction of leaves. Interestingly, the leaf spot disease cycle was also divided in three stages. The disease stage characterized by the highest level of symptom expression was not associated with the plant phase with the highest emerged leaves. Disease symptoms reached the highest pick only after the phase of intense leaf development. The molecular analysis revealed that all the groundnut varieties analyzed were genetically closely related even though they showed different reactions to the leaf spot disease.

Spotted-Leaf Mutants of Rice(Oryza sativa)

Many rice spotted-leaf （spl） mutants are ideal sources for understanding the mechanisms involved in blast resistance, bacterial blight resistance and programmed cell death in plants. The genetic controls of 50 spotted-leaf mutants in rice have been characterized and a few spotted-leaf genes have been isolated as well. This article reviews the odgin, genetic modes, isolation and characterization of spotted-leaf genes responsible for their phenotypes, and their resistance responses to main rice diseases.

Association Analysis and Identification of SNP Markers for Stemphylium Leaf Spot (Stemphylium botryosum f. sp. spinacia) Resistance in Spinach (Spinacia oleracea)

Stemphylium leaf spot, caused by Stemphylium botryosum f. sp. spinacia, is an important fungal disease of spinach (Spinacia oleracea L.). The aim of this study was to conduct association analysis to identify single nucleotide polymorphism (SNP) markers associated with Stemphylium leaf spot resistance in spinach. A total of 273 spinach genotypes, including 265 accessions from the USDA spinach germplasm collection and eight commercial cultivars, were used in this study. Phenotyping for Stemphylium leaf spot resistance was evaluated in greenhouse;genotyping was conducted using genotyping by sequencing (GBS) with 787 SNPs;and single marker regression, general linear model, and mixed linear model were used for association analysis of Stemphylium leaf spot. Spinach genotypes showed a skewed distribution for Stemphylium leaf spot resistance, with a range from 0.2% to 23.5% disease severity, suggesting that Stemphylium leaf spot resistance in spinach is a complex, quantitative trait. Association analysis indicated that eight SNP markers, AYZV02052595_115, AYZV02052595_122, AYZV02057770_10404, AYZV02129827_205, AYZV0-2152692_182, AYZV02180153_337, AYZV02225889_197, and AYZV02258563_213 were strongly associated with Stemphylium leaf spot resistance, with a Log of the Odds (LOD) of 2.5 or above. The SNP markers may provide a tool to select for Stemphylium leaf spot resistance in spinach breeding programs through marker-assisted selection (MAS).

Evaluation of Gray Leaf Spot Tolerant Genotypes from CIMMYT in the Highland Maize Production Eco-systems of Bhutan

Bhutan is a small landlocked country located in the eastern Himalayas. Over 69% of the population is engaged in agriculture. Rice, maize, wheat, barley, buckwheat and millets are the major cereal crops cultivated. Rice is the most preferred food crop of the Bhutanese. Maize is a primary food crop after rice and it ranks first among food crops in production. The cultivation ranges from less than 300 m asl （metres above sea level） nearly up to 2,800 m asl. In 2007, a new, extremely serious problem of GLS （gray leaf spot） in maize that was previously never reported in Bhutan was confirmed. This disease spread rapidly in the highland maize growing areas causing production losses of over 50% to 70%. All the maize varieties cultivated in the country were found to be highly susceptible to the disease. In order to contain this devastating disease, the national maize program drew short and long term strategies with the help of a CIMMYT Expert. As an immediate short term action to contain GLS, systemic fungicide Tilt 25 EC （active ingredient propiconazole） was supplied free of cost to the farmers. A longer term strategy pursued was the introduction, e＇valuation and selection of GLS tolerant genotypes for the highland ecosystem. Over 100 GLS tolerant genotypes vcere introduced from CIMMYT Colombia, Mexico, Zimbabwe and Nepal. These materials were initially evaluated in a disease hotspot sites and then further tested in multi-location trials in GLS affected areas across the country. Farmers were engaged for Participatory Variety Selection by organizing farmer＇s field days at the trial sites. Finally, in 2011 considering the need of GLS tolerant varieties for farmers, two GLS tolerant genotypes ICAV305 and S03TLYQAB05 were provisionally released. In the 2011 season, these two provisionally released genotypes were put under large scale demonstration in the GLS affected areas in nine districts across the country. In 2012, the two genotypes were formally released by the Technology Release Committee of the Ministry of Agriculture and Forest. Rapid seed increase of the new varieties was initiated through farmers from Community Based Seed Production groups and so far 75% seed replacement of GLS affected farmers has been accomplished.