Incidence Of Leaf Blight Research Articles

Novel characterisation of Curvularia geniculata associated with leaf blight on Costus igneus in India

Costus igneus Nak, commonly referred as insulin plant or spiral flag, is a perennial herb belonging to the family Costaceae. Owing to its ability to regulate the blood sugar level, it is considered as a boon plant for diabetic patients, hence popularly known as the “sugar plant”. Although few foliar diseases have been documented on C. igneus, they generally occur in minor frequency under Indian conditions. However, in May 2022, a moderate to severe incidence of leaf blight was observed on insulin plants at University of Agricultural Sciences, GKVK, Bangalore, and nearby medicinal gardens. The affected leaves exhibited light brown lesions coalesced to form papery blight, gradually leading to complete drying of leaves. The current study aimed to identify, characterize, and document the fungal pathogen responsible for the disease, with a focus on its morphological, molecular, and biological characteristics to ensure accurate identification. Additionally, the study sought to determine optimal conditions for pathogen growth and sporulation to support the development of effective disease management strategies. The associated fungus was isolated, purified and identified as Curvularia geniculata through morphological and multigene phylogenetic analysis, using internal transcribed spacer (ITS) and large sub unit (LSU) regions of rDNA, and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene. Biological characterization revealed that cornmeal agar (CMA) at 30 °C and pH of 7 were ideal for better growth and abundant sporulation. These findings, highlighting the emergence of C. geniculata as a novel fungal pathogen infecting C. igneus in India, are crucial for developing effective disease management strategies to safeguard the medicinal properties of the plant.

A Genome-Wide Association Study of Nigerien and Senegalese Sorghum Germplasm of Exserohilum turcicum, the Causal Agent of Leaf Blight

In Senegal, sorghum ranks third after millet and maize among dryland cereal production and plays a critical role in the daily lives of millions of inhabitants. Yet, the crop’s productivity and profitability are hampered by biotic stresses, including Exserohilum turcicum, causing leaf blight. A total of 101 sorghum accessions collected from Niger and Senegal, SC748-5 and BTx623, were evaluated in three different environments (Kaymor, Kolda, and Ndiaganiao) in Senegal for their reactions against the leaf blight pathogen. The results showed that 11 out of the 101 accessions evaluated exhibited 100% incidence, and the overall mean incidence was 88.4%. Accession N15 had the lowest incidence of 50%. The overall mean severity was 31.6%, while accessions N15, N43, N38, N46, N30, N28, and N23 from Niger recorded the lowest severity levels, ranging from 15.5% to 25.5%. Accession N15 exhibited both low leaf blight incidence and severity, indicating that it may possess genes for resistance to E. turcicum. Also, the accessions evaluated in this study were sequenced. A GWAS identified six novel single-nucleotide polymorphisms (SNPs) associated with an average leaf blight incidence rate. The candidate genes were found in chromosomes 2, 3, 5, 8, and 9. Except for SNP locus S05_48064154, all five SNPs associated with the leaf blight incidence rate were associated with the plant defense and stress responses. In conclusion, the candidate genes identified could offer additional options for enhancing plant resistance against E. turcicum through plant breeding or gene editing.

Incidence, Severity, and Prevalence of Sorghum Diseases in the Major Production Regions in Niger

Sorghum ranks second to pearl millet as the most important cereal in Niger and is used primarily for food, feed, and other uses. During the 2022 growing season, 96 fields from the five major sorghum production regions of Dosso, Maradi, Tahoua, Tillabéri, and Zinder were surveyed for foliar and panicle diseases. In each field, 40 plants were assessed using a W-shaped pattern to cover the whole field. A total of 19 diseases, including leaf blight, anthracnose, long smut, zonate leaf spot, bacterial leaf stripe, oval leaf spot, and rough leaf spot were documented. Leaf blight (100%) was detected in all the fields surveyed. In the regions of Dosso and Zinder, anthracnose was found in all the surveyed fields while oval leaf spot was detected in all surveyed fields in Maradi and Zinder. The highest mean incidence of leaf blight (95%) was recorded in the regions of Tahoua and Zinder while oval leaf spot (80%), anthracnose (56%), and gray leaf spot (25%) were highest in Maradi region. The highest mean severities of leaf blight (30%), long smut (29%), grain mold (18%), and anthracnose (13%) were recorded in Maradi region. The severity of head smut was 100% in all the regions where the disease was observed. Fields with incidence of 90% and above identified during the survey are considered as ‘hot spots’ for disease resistance screening. This work is significant because the information generated by the study can be utilized by sorghum workers, students, funding agencies and government officials to prioritize research projects.

Endogenous Salicylic acid Estimation in Wheat leaves treated with Salicylic acid and infected with Alternaria triticina

This study was aime to measure the accumulation of endogenous salicylic acid, as indicator for systemic acquired re-sistance of wheat plants of “Utique” variety. The plant was sprayed with salicylic acid (SA) or water as control, at the five-leaf stage, later infected with leaf blight caused by Alternaria triticina. Leaf samples were removed after 10, 20, and 30 days of inoculation to test their endogenous content of salicylic acid as it is the primary internal signal indicating the emergence of systemic acquired resistance in plants, by the spectrophotometer measuring. Endogenous SA values were ascending dramatically from 10 days to 20 days and maximum with 30th day significantly, while control plants exhibit lower values in all day periods, insignificantly. SA treatments proved reduction in disease incidence after 10 days with 54% and after 20 days with 64%, while after 30 days the reduction recorded high percentage of 80%. In comparison between the time intervals, disease severity was clearly reduction and reached to 83% after 10 days of inoculation then decreased to 72% for both 20th and maintained its stability on the 30th day of inoculation by 72%. This study was proved the reduction of wheat leaf blight incidence and disease severity as a result of treatment by using 1Millimolar (mM) of SA was leading to accumulation of significant levels of endogenous SA as indicator for internal induced resistance in plant.

First Report of Leaf Blight on Dumasia villosa Caused by Boeremia exigua in China.

Dumasia (Fabaceae, tribe Phaseoleae, subtribe Glycininae), a genus of trifoliate vines, is widely distributed in tropical and subtropical regions of Asia and Africa (Pan & Zhu 2010). In October 2021, lesions were observed on Dumasia villosa leaves on Longwen mountain of Guizhou Normal University, Guiyang City, Guizhou Province, China. The incidence of leaf blight on observed D. villosa leaves was 10%. All necrotic spots were close to insect-feeding sites. Necrotic spots were grey or black, and circular (2 to 10 mm in diameter) or irregular (2 to 20 mm long) in shape. Stems and pods showed no disease symptoms. Pathogen isolation was conducted following surface sterilization with ethanol. After growth for 5 days on potato dextrose agar in a moist climate chamber at 26°C under a 16 h/8 h light/dark cycle, colonies were 5.2 to 5.6 cm in diameter, olivaceous grey in colour, and sparse, white, aerial mycelia with irregular margins were evident. Conidia were hyaline, ellipsoidal to oblong, mostly 1-septate, and occasionally aseptate with dimensions ranging from 3.5 to 7.0 × 1.5 to 3.5 μm (n = 30). To confirm the species of the isolate, ribosomal DNA internal transcribed spacer (ITS) and β-tubulin (tub2) genes were amplified and sequenced using primers ITS1/ITS4 and Btub2Fd/Btub4Rd (White et al. 1990), respectively. The obtained 529 bp ITS sequence (GenBank accession no. OL872186) shares 99.61% identity with the sequences of Boeremia exigua (MF662797 and GU395499). The obtained 299 bp tub2 sequence (OM830712) shares 100% identity with the sequence of B. exigua (KR653201). Based on morphology and DNA sequence analysis, the isolate was identified as B. exigua. To fulfil Koch's postulates, healthy leaves of 8-week-old D. villosa plants (n = 6) were wounded with a sterilized hypodermic needle and inoculated with 2 μL of a conidial suspension (106 conidia/mL). Six plants were inoculated with 2 μL of sterile distilled water as controls. After 3 days in a moist climate chamber at 26°C under a 16 h/8 h light/dark cycle, dark spots were only present on conidia-inoculated leaves, while controls remained healthy. Boeremia exigua was reisolated from disease spots and confirmed using the same morphological and molecular methods described above. To our knowledge, this is the first report of leaf blight on D. villosa caused by B. exigua, although this fungus has been reported to infect leguminous plants, including field pea (Li et al. 2012), white clover (Wang et al. 2020), and soybean (Schaffrath et al. 2020). In China, B. exigua has also been reported to infect other plants, such as walnut (Cai et al. 2021; Wang et al. 2021) and Japanese ginseng (You et al. 2015). This identification suggests that D. villosa could be a potential reservoir for the pathogen affecting other leguminous crops that might be economically important.

Integrated Management of Maize Leaf Blight Caused by Helminthosporium maydis

Leaf blight (Helminthosporium maydis Nisikado) is one of the most devastating diseases in maize. The innovative idea to manage crop diseases is the integrated method (chemical and bio-control agents), as it involves the least amount of fungicidal load in the environment. Thus, in the present study, the objectives were formulated to screen the different systemic and non-systemic fungicides against the mycelial growth of leaf blight pathogen under in vitro conditions and to investigate the effect of different fungicides and bio-agents against leaf blight disease under field conditions. Among fungicides, systemic fungicides viz., propiconazole, tebuconazole and hexaconazole were best (100%) and significantly superior in inhibiting the mycelial growth of the fungus at 0.1 per cent concentration. Mancozeb (0.2%) was recorded 92.78 per cent inhibition over control followed by propineb at 0.2 per cent (93.33%). In the field experiments, seed treatment (ST) with TNAU-Pf1 @ 10 g/kg seed + foliar spray of propiconazole (0.1%) and ST with TNAU-Pf1 @ 10 g/kg seed + foliar spray of tebuconazole (0.1%) at 40 DAS recorded the lowest incidence of leaf blight and maximum grain yield in maize.

First Report of Leaf Blight Caused by Alternaria tenuissima on Senna nomame in China.

Senna nomame (Makino) T. C. Chen is an annual plant in the Fabaceae. This plant can be used in a tonic, as a diuretic, and for the prevention of obesity due to the presence of anthraquinones, flavonoids, and lipase inhibitors isolated from the aerial parts and seeds (Hatano et al. 1997). In June to September 2019, a severe foliar blight was observed on the leaves of 1-year-old S. nomame landrace plants in Qinglong (40.41°N, 118.95°E) in Qinhuangdao City, Hebei Province, China. The incidence of leaf blight was as high as 67% in the fields (n≥3). Symptoms began with small, brown spots at the margins and tips of leaves, with gray or yellowish-brown spots in the center of leaves. The spots gradually expanded to irregular large yellowish-brown lesions, and the leaves gradually withered. The pathogen was isolated from 20 leaves with typical symptoms from 10 individual plants. Leaf pieces (2 to 4 mm2) were excised from the junction of diseased and healthy tissues, disinfected in 75% ethanol for 15 s, rinsed in sterile distilled water, and placed on potato dextrose agar (PDA) plates. Colonies of 69% of the isolated fungi had round margins, and the olive-green fluffy aerial mycelia began to sporulate after 3 days at 28°C. On potato carrot agar (PCA), pure cultures formed yellowish brown mycelium with a light-colored, taupe-white center. Conidiophores were brown, simple or branched, and produced numerous conidia in short chains of three to six conidia. The conidia (n=50) were inverted pear-shaped or orbicular-ovate, light brown to brown, with a cylindrical short beak at the tip, and 19.9 to 30.4 μm (mean 25.4±3.6 μm) × 10.4 to 17.1 μm (mean 13.4±1.9 μm), with two to four transverse septa and zero to three longitudinal septa. The fungal isolates U-2, U-2-1, and U-2-2 were further characterized by sequencing of the rDNA ITS (MN712241, MZ781312, MZ781313), actin (ACT) (MN752246, MZ593671, MZ593672), calmodulin (CAL) (ON811636 to ON811638), ATPase (ON872785 to ON872787), and Alt a 1 (ON792172 to ON792174) genes using ITS1/ITS4, ACT-512F/ACT-738R, CALDF1/CALDR1, ATPDF1/ATPDR1, and Alt-for/Alt-rev primers for PCR amplification, respectively (Yang et al. 2009; Elfar et al. 2018). The sequences of the amplicons showed 99% to 100% identity with Alternaria tenuissima isolates: ITS (569/570 bp; MK560480 ), ACT (243/243 bp; MK593135), Alt a 1 (509/512 bp; MK593137), CAL (717/721 bp; MG925128), ATPase (1196/1197 bp; MG740623). Therefore, based on morphological characteristics and DNA sequence data, the isolates were identified as A. tenuissima. For pathogenicity tests, leaves on 10 healthy 1-year-old potted S. nomame plants were inoculated by wounding with a sterile needle and sprayed with a conidial suspension (2×105 spores/mL). Sterile water was used as the control. Inoculated plants were incubated in a greenhouse at 28°C with a 12 h photoperiod (75% to 80% relative humidity). The pathogenicity test was repeated three times. Lesions were observed on inoculated plants seven to nine days after inoculation, but no lesions were observed on control plants. A. tenuissima was successfully re-isolated from the symptomatic leaves and identified by morphology and sequencing of PCR amplicons. A. tenuissima has caused brown leaf spot on kiwifruit (Li et al. 2019) in China and pigeonpea (Sharma et al. 2012) in India. To our knowledge, this is the first report of A. tenuissima causing leaf blight on S. nomame in China. This new finding is essential in the diagnosis and management in field production.

Estimates of genetic gains in the carrot using different selection indices

The carrot is one of the most important and preferred vegetables in Brazil due to its versatility and nutritional significance, especially as a source of vitamins. The selection of carrot genotypes should consider several agronomically important characteristics to allow more suitable and balanced gains. The aim of the present study was to estimate genetic gains in the carrot using different selection indices. Thirty-six carrot genotypes were evaluated in two experiments, the first conducted between 16 November 2017 and 1 March 2018, and the second between 5 March and 18 June 2018 in, Brasilia. In both trials. the experimental design was of randomised blocks with three replications. The plots were sown directly onto the seedbed, which had a total working area of 1.8 m2. The incidence of leaf blight was evaluated 78 to 98 days after sowing, at intervals of seven days, giving a total of four evaluations. The harvest was carried out at 105 days when the characteristics of the yield components were measured. An analysis of variance was applied, together with five selection indices: direct selection, classic, desired gain, weight- and parameter-free, and genotype-ideotype. There were differences between genotypes for most of the characteristics under evaluation. The genotype-ideotype index afforded the greatest gains for the characteristics being evaluated, with an economic weight equal to the coefficients of genetic variation; however other indices were also efficient and offered balanced gains, with the exception of the desired-gain index.

Management of Alternaria Leaf Blight in Pigeonpea through Host Plant Resistance and Micronutrient Application

Background: Pigeonpea [Cajanus cajan (L.) Millsp] is one of the primary grain legume crops grown in India for its high quality vegetable protein, animal feed and fodder. It is affected by various fungal and viral diseases. Among these, leaf blight caused by Alternaria alternata is one of the most destructive diseases and recently the disease of minor importance becomes major one in Tamil Nadu. Use of resistant cultivar is the most effective, economically viable and eco-friendly tool for combating the plant diseases. The micronutrients play a key role in many physiological and biochemical functions of the plants which influences plant pathogenic interaction. The micronutrients viz., Zn.Mn,Cu and Fe found to have greater impact on reducing the plant disease severity. Developing integrated disease management strategy involving disease resistant variety, micronutrient and fungicide application would be the best sustainable method for controlling the pigeonpea leaf blightMethods: Twenty four pigeonpea genotypes along with two local varieties viz., CO5 and CO6 were evaluated in the field for their resistance against Alternaria alternata leaf blight disease, consecutively for three years from 2015-16 to 2017-18 using the disease resistance scale ranging from 0 to 9. Field experiments were also conducted for three consecutive Kharif season from 2015 to 2018 to evaluate the efficacy of the foliar application of different micronutrients and combination fungicide viz., carbendazim 12% + mancozeb 63% on the incidence of leaf blight disease. Result: A total of 24 pigeonpea genotypes were screened for their resistance against leaf blight under field condition. Among these, four genotypes viz., BDN2, IPA 8F, IPA 15F and MA6 were found resistance and nine genotypes were moderately resistant and remaining 11 genotypes showed susceptible reaction to leaf blight. The results of the field experiment on micronutrient and fungicide application revealed that foliar spraying of MnSO 4 @0.2% on 30 days after sowing and carbendazim 12%+ mancozeb 63%@ 1g / lit on 45 days after sowing recorded the lowest leaf blight incidence of 8.1 PDI (Per cent Disease Index) with the highest disease reduction of 76.9% as against 35 PDI in the untreated control plot. The above treatments also recorded the highest grain yield of 905 kg/ ha as against 703 kg/ in the untreated control.

Comparative evaluation of different media and pH for the culturing of Bipolaris setariae causing leaf blight in browntop millet in India

Browntop millet was newly included in the millet cropping system in India as one of the small millet. Incidence of leaf blight was observed to be severe in all millet growing regions of India and the causal organism was confirmed as B. setariae using molecular tools viz., ITS and GPDH genes. As the crop was newly included in the millet system, investigation was needed to carry out about disease causing agents their biology and culture conditions. In this study, an attempt was made to identify the ideal culturing and physiological requirements for culturing B. setariae. Results revealed that solid media such as Czapek Dox agar (CDA) and host leaf decoction agar with 2 per cent sucrose are ideal for better growth and abundant sporulation while, pH 6.0 to pH 7.0 were found to be ideal for radial mycelial growth and sporulation. These cultural and physiological conditions can be used for the future studies while working on the pathogen causing browntop millet leaf blight.

Strategies for the Management of Leaf Blight Disease Caused by Alternaria alternata in Gloriosa superba (L.)

Leaf blight caused by Alternaria alternata (Fr.) Keissler is a severe disease of Gloriosa, causing severe yield loss in every part of Gloriosa growing areas of Tamil Nadu. The foliar pathogen was isolated from disease-infected leaves and proved its pathogenicity. Further, the molecular analysis of the pathogen using 18S rDNA confirmed the pathogen as Alternaria alternata. Attempts were made to explore the biocontrol agents and fungicides for the management of leaf blight incidence under field conditions. Four field trials conducted from 2014 to 2018 revealed that foliar application of talc-based formulation of Bacillus subtilis significantly reduced the leaf blight incidence and increased the seed yield under field conditions. Besides, prophylactic application of these biocontrol agents has also increased the plant growth parameters like plant height, number of flowers/plant, no. of pods/plant and number of seeds/pod. Similarly, foliar application of chlorothalonil (0.1%) and mancozeb (0.2%) was also credited to managing the leaf blight disease under field conditions.

Assessment of Disease Incidence of Leaf Blight (Alternaria alternata) Disease of Carrot in Jodhpur District of Rajasthan

Assessment of Disease Incidence of Leaf Blight (Alternaria alternata) Disease of Carrot in Jodhpur District of Rajasthan

Assessment of Bacterial Leaf Blight Incidence and Severity in Rice Growing Areas of Pakistan

Assessment of Bacterial Leaf Blight Incidence and Severity in Rice Growing Areas of Pakistan

Incidence of leaf blight disease of Egusi melon in South-west Nigeria

Egusi melon (Citrullus lanatus (Thumb) Mansf.) is an important vegetable crop grown for edible seeds and oil in West Africa. Leaf Blight Disease (LBD) is one of the major constraints to its production, with potential to cause economic damage. The objective of this study was to investigate the incidence and distribution of leaf blight on Egusi melon in Southwestern Nigeria. A survey of LBD of Egusi melon was conducted in 2015 and 2016, in five southwestern States of Nigeria (Ogun, Oyo, Osun, Ekiti and Ondo States). Twenty plants each, were randomly sampled from 150 farms comprising 30 farms each, from each State. The distribution of different Egusi melon varieties planted was recorded. “Bara” cv. was the most cultivated variety (51.6%); followed by “Bojuri” (30.4%) and “Serewe” (18%). Leaf blight was observed in most farms in the five States, from 73% in Osun and Oyo states to 83% in Ondo State. Disease incidence and severity varied with locations and cultivars, and ranged from 0.0-87.5±18% and 1.0±0-4.5±0.8 in Osun State to 20.0±19 - 95.0±4.5% and 2.3±1.5 - 5.0±0 in Ondo State. Out of the twelve fungal pathogens from ten genera isolated from infected plants, only Colletotrichum truncatum, C. gloeosporioides and Lasiodiplodia theobromae caused Leaf blight on Egusi melon.
 Key words: Colletotrichum gloeosporioides, Colletotrichum truncatum, Lasiodiplodia theobromae

Gene effects from Bipolaris maydis incidence and severity on popcorn

Popcorn suffers severe economic losses resulting from harmful effects caused by several diseases such as southern corn leaf blight (SCLB), which is one of the main leaf diseases able to cause considerable damages to corn crops. The realization conducting genetic studies in order to identify genotypes presenting genetic resistance to this disease it is essential. Accordingly, the aim of the current study is to estimate gene effects and combining abilities in popcorn, with emphasis on the resistance to Bipolaris maydis. Full diallel crosses were performed, including reciprocal crosses between eight lines (L76, L88, L70, L77, L55, L61, P1 and P8), in order to produce 56 hybrids (F1’s and reciprocal hybrids). The experiment followed a randomized block design, with four replicates; in two different cultivation periods (first and second periods), in Campos dos Goytacazes, RJ. Southern corn leaf blight incidence and severity, caused by B. maydis, were assessed in each cultivation period. No reciprocal effect was observed for the evaluated characteristics, since the diallel analysis did not find significant effect from this variation source. With respect to SCLB incidence and severity in the two cultivation periods, the mean square of the effects showed that the dominance components were superior to the additivity ones. Hybrids that stood out in the two cultivation periods to the assessed features were: L88 x L61, L88 x L70, L88 x L76, L61 x L77, L61 x P1, L70 x P1, P1 x L76, L77 x L76, and P8 x L77.

Temporal Analysis of Bacterial Leaf Blight in Clonal Eucalyptus Plantations in Brazil

Bacterial leaf blight is an important disease in Eucalyptus spp. plantations since it can cause defoliation, affecting plant development. A better understanding of the disease epidemiology is important for its control. Thus, the aim of this study was to analyze bacterial leaf blight temporal progress in the initial establishment in the field of different eucalyptus clones. It also targeted to correlate the incidence and area under the disease-progress curve (AUDPC), with variables related to growth and meteorological data. Bacterial leaf blight progress curves were analyzed based on incidence and carried out AUDPC calculation. Pearson’s coefficient was used to verify the correlations between bacterial leaf blight incidence and AUDPC with clone initial growth and meteorological factors. Gompertz or Logistic models were the best adjustment to data, according to the assessed clones. A difference in AUDPC was observed between clones regarding bacterial leaf blight incidence during the assessment period. Clones were divided into three groups with different tolerance levels. A negative correlation was observed between bacterial leaf blight incidence, AUDPC, and growth variables of clones. During the assessment period, average air temperature, rainfall, and air relative humidity favored disease incidence. The clones A469, VM01, and 373 were the most tolerant to the disease.

Direct selection for phenotypic traits in carrot genotypes

ABSTRACT Selection of more productive carrot genotypes is fundamental for crop breeding programs aiming to increase productivity and reduce cost production. Thus, the aim of this work was to evaluate gains from direct selection and to measure its effects on other agronomic traits of interest in carrots. Thirty six carrot genotypes were evaluated in two experiments: the first, sown in the second half of November 2016 and the second one in the first week of March 2017. The experimental plots covered a useful area of 1.5 m2, in transversal rows and 0.10-m double spacing between single rows x 0.20-m between double rows in a randomized block design with 3 replicates. At 90 days, the incidence of leaf blight was evaluated using a note scale and 100 days after sowing, roots were harvested measuring the number and mass of total, commercial and non-commercial roots of each plot. The direct selection of commercial root mass allowed to estimate indirect and expressive gains for most evaluated traits, allowing to select seven genotypes (populations 758, 751, 737, 736, 735, 744 and 742) which can be released as cultivar or for the formation of a broader genetic-based population.

First Report of Leaf Spot Caused byPseudocercospora vitisonBidens pilosain Brazil

Bidens pilosa L. (Asteraceae) is an aggressive weed in annual and perennial crops with high potential to reduce crop yields in several countries (Dias et al. 2017). It also may host pathogens such as Alternaria dauci (J.G. Kuhn) J.W. Groves & Skolko (Lin et al. 2015) and Podosphaera xanthii (Castagne) U. Braun & N. Shishkoff (Cho et al. 2013). In Brazil, this weed is distributed across all grape-producing areas. Leaf blight on grape, caused by Pseudocercospora vitis (Lev.) Speg., is an important disease that causes premature defoliation. In March 2018, plants of B. pilosa showing leaf spots were found in a 1-ha organic orchard of fox grape cultivar Bordo in the metropolitan region of Curitiba in Parana state, Brazil. The orchard had high leaf blight incidence (above 80%). The disease normally started in early summer; in December, and around March, complete defoliation occurred caused by leaf blight. B. pilosa was distributed throughout the orchard, and around 50% of leaves were infected. Leaf spots initially appeared slightly chlorotic, becoming pale brown to dark brown. Lesions were circular or irregular, 2 to 8 mm in diameter, and often coalesced. Microscopic examination revealed that conidia were hyaline to light brown, cylindrical, straight or slightly curved, with a rounded apex. They had 4 to 10 transverse septa, 24 to 82 μm in length and 5 to 8 μm in width, with conidiophores grouped in synnema. Isolates were recovered from lesions on tissue surfaces that were disinfested by immersion in 70% alcohol for 30 s and then in 0.5% NaClO for 30 s. Pieces were washed three times with sterile distilled water and cultured on potato dextrose agar (PDA) at room temperature for 9 days under continuous fluorescent light. Hyphal tips of the obtained colony were transferred to V8 agar medium and cultured at room temperature for 4 weeks under continuous fluorescent light. Individual spores were collected and deposited in V8 agar medium to obtain one monosporic isolate (PCLEMID02). The colony presented slow growth, with 15-mm diameter after 1 week of PDA cultivation at 25°C under a 12-h photoperiod, and was dark gray on top, black on reverse. The morphological and cultural characteristics of the isolate were consistent with those described for Pseudocercospora sp. (Ellis 1971). To confirm the species, the nuclear gene regions ITS, ACT, and EF-1α of isolate PCLEMID02 were amplified and sequenced for multigene phylogenetic analysis. The DNA sequences generated were deposited in GenBank (MH330685, MH891492, and MH891491). Phylogenetic analysis was performed with the concatenated sequence alignment of three genes using MEGA 6.0 software. The neighbor-joining phylogenetic tree showed that isolate PCLEMID02 from B. pilosa clustered in one separate clade with 100% bootstrap support with sequences of P. vitis (GenBank GU269829.1, GU320533.1, and GU384541.1). To perform the pathogenicity test, a suspension containing 1 × 10⁴ conidia/ml was prepared from one isolate (PCLEMID02) with 3-week-old cultures grown on V8 agar. The conidial suspension was sprayed on the leaf surface of B. pilosa and grapes. It used 20 leaves ranging in age from 30 to 45 days. Another 20 leaves received water instead of inoculum and served as controls. All leaves were left in a moist chamber for 24 h and subsequently stored in a greenhouse at 28 ± 2°C with a 12-h photoperiod. Only the inoculated leaves showed symptoms. Leaf blight on grape and leaf spots on B. pilosa were observed 12 and 25 days after inoculation, respectively. Both the inoculated leaves and the controls were submitted to the reisolation process. The pathogen was effectively reisolated only on symptomatic leaves and presented the same cultural, morphological, and molecular characteristics as the colony used for inoculation. Thus, B. pilosa is a host of P. vitis and may allow the survival of the pathogen in the dormancy period of the grapevine and, consequently, contribute primary inoculum for the development of leaf blight on grape.

Comparison of analyses types in carrot experiment: square lattice versus randomized blocks design

ABSTRACT The square lattice 4x4 design was compared to a randomized block design, for carrot F1 hybrids. Sixteen experimental carrot hybrids were evaluated in Brasília, in 2014/15 and 2015/16 agricultural years. A square lattice 4x4 design with three replications was used. The experimental plot consisted of 1.5 m2 useful area. The experimental area was installed on the second half of November 2014 and 2015. Cultural practices were the usually given to the carrot crop in Brazilian savannah region. The incidence of leaf blight was evaluated 90 days after sowing date and, after 100 days, roots were harvested and yield components evaluated. We evaluated the three possible analyses in lattice: 1) as randomized block design; 2) intrablock analysis with adjusted treatments and blocks within unadjusted repetitions; 3) analysis with recovery of interblock information with adjusted treatments. The analysis in lattice permitted to reduce the mean squares of error and coefficients of variation; moreover, these were more efficient than the randomized block design experiments for most evaluated characters. Thus, use of the analysis in lattice is preferred in experiments with carrot when evaluating large number of treatments.

Incidence and severity of leaf, panicle and fruit blights of litchi caused by Alternaria alternata

Leaf, panicle and fruit blights of litchi (Litchi chinensis Sonn.) caused by Alternaria alternata (Fr.) Keissler is a recent and economically important disease of litchi. The incidence and severity of this disease was assessed during 2012–2017 in continuous monitoring of the disease at National Research Centre on Litchi, Muzaffarpur and farmers’ orchards in Bihar. The results revealed an average incidence of leaf blight from 7.1 to 82.6% on nursery plants while percent disease severity index (PDI) was 43.3–71.2 during 2012–2017. Disease incidence of panicle blight (on tree basis) in different orchards during 2014–2016 was from 6.3 to 77.1% in cv. ‘Shahi’ and 17.0–58.9% in cv. ‘China’. However, the maximum number of trees recorded less than 20% blighted panicles. Incidence of fruit blight in cv. ‘China’ ranged from 6.6 to 17.3%. The analysis of prevailing weather conditions revealed that a temperature of about 28–30 °C and humidity 60–85% were congenial for development of blight disease on panicles and fruits. A. alternata is an opportunistic pathogen on numerous hosts. Due to its large spore and dark pigment, this is resistant to UV radiation and spores can float in the air enabling long distance dispersal. Litchi being cultivated over a large area in Bihar and adjoining states of India, the pathogen has the potential to spread causing heavy yield losses.