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.

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.

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.

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).

The severity and cause of leaf spot disease of Pongamia pinnata L. and fungicidal control of the pathogen

A survey on the symptom and severity of the leaf spot disease of Pongamia pinnata L. was conducted in the nurseries of the Institute of Forestry and Environmental Sciences, University of Chittagong （IFESCU）, Bangladesh Forest Research Institute （BFRI） and Aronnak Nursery in Chittagong. The highest infection percentage and disease index were found in IFESCU nursery, followed by BFRI and the lowest was recorded in Aronnak nursery. The associated organism of leaf spot disease of P. pinnata was isolated from the diseased plant parts and the pathogenicity was established with the isolated fungus. Colletorichum gloeosprioides Penz was proved to be pathogenic. The inhibition of mycelial growth of C. gloeosporioides was observed and identified as suitable fungicides （Bavistin, Cupravite and Dithane M-45） and doses （0.05, 0.10, 0.50, 1.00, 1.50 and 2.00）. The lowest and highest mycelial growth were respectively found on Bavistin and on Cupravite at the concentration of 0.05 after 8th day of incubation. It indicates that out of the three tested fungicides, Bavistin showed most effective, followed by Diathane M-45, and Cupravite was ineffective for its very little inhibition on mycelial growth.

Field Efficacy of 33.5% Oxine-copper SC against Leaf Spot Disease on Waxberry

Leaf spot disease seriously affects the yield and quality of waxberry, but there is no registration agent for prevention and control of the disease. The field trials showed that the control efficacy of 33.5% oxine-copper SC against leaf spot disease on waxberry reached above 74% when used at the dosage of 167.5-223.3 mg/kg. 33.5% Oxine-copper SC could be used to control leaf spot disease on waxberry.

Morphological and Molecular Identification of Curvularia geniculata Associated with Leaf Spot Disease of Banana in China

[Objectives]The paper was to identify the causal agent of leaf spot of banana in Hainnan,China.[Methods]Fungus isolates were isolated from the diseased tissues,and morphological characteristics of colony and spore were observed.Furthermore,phylogenetic analyses and pathogenicity test were conducted to confirm the pathogen.[Results]The fungus isolates from the diseased tissues was identified as Curvularia geniculata.[Conclusions]C.geniculata is a new pathogen causing leaf spot of banana in Hainan,China.This finding will help to broaden the distribution and host range of C.geniculata,indicating that it poses potential damage to banana in China.

Neofusicoccum parvum Causing Leaf Spot of Camellia drupifera in China

[Objectives]The study was to identify the causal agent of leaf spots of Camellia drupifera in Hainan Province,China.[Methods]Phylogenetic analyses,spore morphology and pathogenicity tests were adopted to identify the pathogen.[Results]The fungus was identified as Neofusicoccum parvum.The colonies were initially pale to white on PDA,with diffuse yellow pigment around the colonies in the agar after 5 d.After 10 d,the aerial mycelium became gray,and the substrate mycelium became black.Thirty days later,a large number of conidia were generated on OMA.Conidia were hyaline,nonseptate,and fusiform.The mean size of 100 conidia was(13.6-25.4)×(6.2-10.3)μm;the mean length/width ratio was(2.5±0.3)μm.[Conclusions]N.parvum was the causal agent of leaf spots of C.drupifera observed in Hainan Province,China.

Comparative Effect of Foliar Application of Cow Dung, Wood Ash and Benlate on the Disease Initiation and Development of Roselle (Hibiscus sabdariffa L.) Leaf Spot Disease Caused by Coniella musaiensis Var. Hibisci. in Makurdi, Central Nigeria

A study on the comparative effect of cow dung, wood ash and benlate for the control of leaf spot disease of Roselle (Hibiscus sabdariffa L.) was carried out following the preparation and foliar application of the materials on selected Roselle plants of the green and red accessions (Acc1 & Acc3) in the field. The cow dung was fermented for 14 days while sour milk was added to wood ash, dissolved and all filtered and labeled. The spraying commenced soon after the plants were thinned to one and was done weekly until after 50% of the plants had flowered. Results showed significant (p = 0.05) difference between benlate, the synthetic fungicide and the bio-fertilizers (cow dung and wood ash) for the two years of the study. Disease severity was significantly lower in the benlate than in the bio-fertilizers. There was no significant difference in yield between the treatments although higher yield was recorded in benlate. Though the bio-fertilizers could not suppress infection, they aided the growth of the plants by boosting luxuriant growth. The result showed that these bio-fertilizers cannot be used as substitute to the synthetic fungicide for the control of this leaf spot disease caused by Coniella musaiensis var. hibisci. However, since they give equally good yield the bio-fertilizers can still be used to minimize the reliance upon use of chemical fungicides.

Evaluation of Tomato Lines against Septoria Leaf Spot under Field Conditions and Its Effect on Fruit Yield

Field studies were conducted at Hazara Agriculture Research Station, Abbottabad to evaluate thirteen AVRDC lines along with one commercial check (Roma) for potential of fruit yield against septoria leaf spot during summer season 2014. The disease established itself by natural infection and disease severity was estimated with the help of 0 - 5 disease rating scale after 15 days interval from the onset of symptoms. The lines showed significant difference in % septoria leaf spot infection. The disease severity % increased up to 100% in line AVTO1314 whereas the lowest % severity was recorded in AVTO1173 which showed the highest yield (468.1 g) with average fruit weight 122.22 g while the significantly lowest mean yield/plant (35.05 g) was calculated in line AVTO1314 with fruit weight 47.92 g. It was concluded that the line AVTO1173 could be useful in genetic programs for incorporating resistant genes in local tomato germplasm against septoria leaf spot disease.

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.

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.

First Report of Phomopsis Leaf Spot on Patchouli [Pogostemon cablin( Blanco) Benth. ]Caused by Diaporthe arecae in China

A severe leaf spot disease on patchouli,was observed in Guangdong,China.Early symptom appeared as circular or irregularly shaped and dark brown spots along the leaf margins and tips.As the disease progressed,the spots enlarged and with masses black,sessile conidiomata were observed in lesions.The results of morphology,molecular biology and pathogenicity test indicate that the causal agent of leaf disease of patchouli is Diaporthe arecae.

Identification and Control of Radish Alternaria Leaf Spot, Black Rot, Soft Rot, Virus Disease and Hollowness

The damage characteristics and occurrence regularity of radish alternaria leaf spot, black rot, soft rot, virus disease and hollowness are introduced in the paper, and the corresponding control method is proposed from two aspects of agricultural control and chemical control.