scholarly journals First report of Fusarium pallidoroseum (Cooke) Sacc. on Bael (Aegle marmelos Correa) causing leaf spot and die back disease in nursery

2021 ◽  
Vol 8 (2) ◽  
pp. 108-111
Author(s):  
SANTOSH KUMAR ◽  
HEMANT KUMAR SINGH ◽  
SANJEEV KUMAR
Keyword(s):  
Leaf Area ◽  
Leaf Spot ◽  
Rainy Season ◽  
Severe Infection ◽  
Deciduous Tree ◽  
Pathogenicity Test ◽  
Aegle Marmelos ◽  
Causal Organism ◽  
Indigenous Fruit ◽  
Fusarium Pallidoroseum

Bael is a very popular indigenous fruit of India. Cultivation of bael is a lucrative venture because of its high pharmaceutical importance. The deciduous tree with trifoliate aromatic leaves offering of bael leaves is a compulsory ritual of the worship of lord shiva. In bael nursery, disease appeared during post rainy season (September) as irregular pustules, which was brown in colour, increases very fast and covers the most of the leaf area. After severe infection, affected leaves become dry and fall off. The disease progresses downward causing dieback symptoms but roots are remain healthy and they produces new shoots after destroying the vegetative parts. This type of symptoms incited by Fusarium pallidoroseum (Cooke) Sacc. was identified as a causal organism. The pathogenicity test of the fungus was established. Fusarium pallidoroseum produce smooth and creamyhite colony, grew rapidly on PDA medium at 250C to 260C and produced rose pink colored woolly to cottony, flat spreading colonies when mature. The mass of the mycelium was very compact in nature. The fungus produced both macro and micro conidia, which are hyaline, septate and ends are also hook shaped. Mycelia are thin and septate. Macro conidia were produced from phialides on unbranched or branched conidiophpres. Macro conidia born in sporodochia were curved; possess a foot cell, 3-5 septate.  Micro conidia are single celled, smooth, hyaline, ovoid to cylindrical.

scholarly journals First Report of Pilidium concavum Causing Tan-Brown Leaf Spot on Strawberry in China

Plant Disease ◽  
2012 ◽  
Vol 96 (9) ◽  
pp. 1377-1377 ◽  
Author(s):  
W. L. Geng ◽  
P. Hu ◽  
Z. Ma ◽  
X. Y. Zhao ◽  
Y. M. Wei
Keyword(s):  
Leaf Spot ◽  
Morphological Characteristics ◽  
Leaf Tissue ◽  
Brown Rot ◽  
Pathogenicity Test ◽  
Causal Organism ◽  
First Report ◽  
Molecular Features ◽  
Brown Leaf Spot ◽  
Brown Leaf

In April 2011, a survey of diseases was conducted on strawberry plants grown in greenhouses in the town of Xingshou, Changping District, Beijing, China. A tan-brown leaf spot with the presence of pink spore masses was observed on older leaves of strawberry plants. In general, the leaf spots began as small, round, water-soaked lesions in the middle or on the margin of leaves, which enlarged gradually up to 1 to 3 cm in diameter and were circular or irregular and brown to dark brown. Occasionally, the center of some spots cracked in the middle lesion under dry conditions. Eventually, black sporodochia were produced on the upper surface of spots and exuded pink conidial masses under humid conditions. Fungal structures were taken directly from the diseased leaves and examined microscopically for morphological characteristics. Sporodochia, 172 to 451 × 138 to 343 μm, were dark and suborbicular. Conidiophores, 8.4 to 48.3 × 0.8 to 2.1 μm, were hyaline, unicellular, and cylindrical. Conidia, 3.1 to 10.2 × 1.5 to 3.0 μm, were hyaline, aseptate, and canoe-shaped to allantoid, forming singly. For further study, the fungus was isolated in pure culture on potato dextrose agar (PDA) medium from symptomatic leaf tissue. In culture, the mycelium was white at first and then changed to brownish. The sporodochia were light colored at first and turned brownish or almost black in older cultures. To identify the fungus, the ITS1-5.8S-ITS2 rDNA region of the isolate was amplified by PCR with primers ITS1 (5′-TCCGTAGGTGAACCTGCGG-3′) and ITS4 (5′-TCCTCCGCTTATTGATATGC-3′) and sequenced. The 462-nt sequence (GenBank Accession No. JQ995228) was identical to that of Pilidium concavum (1). To validate Koch's postulates, pathogenicity was tested by inoculating 20 leaves on 10 healthy strawberry plants with a mycelial plug from a 15-day-old colony (0.5 cm in diameter). Controls were treated with plugs of PDA medium. The inoculated and control plants were then maintained in growth chambers at 25°C (12 h of light per day, 80% humidity). After 12 days, 100% of the inoculated leaves showed symptoms identical to those observed on leaves in the field while the control leaves remained healthy. The original fungus was reisolated from inoculated leaves showing the symptoms. Thus, it was concluded that the fungus was the causal organism of the leaf spot. On the basis of morphological characteristics, molecular features, and pathogenicity tests, the pathogen of tan-brown leaf spot on strawberry was identified as P. concavum. To our knowledge, this is the first report of P. concavum causing tan-brown leaf spot on strawberry in China. This fungus was reported to cause leaf spot on Paeonia suffruticosa in China (2). It also caused tan-brown rot on strawberry fruit in our pathogenicity test. References: (1) L. Cardin et al. Plant Dis. 93:548, 2009. (2) Y. B. Duan et al. Plant Dis. 94:271, 2010.

scholarly journals Photosynthesis of Blueberry Leaves as Affected by Septoria Leaf Spot and Abiotic Leaf Damage

Plant Disease ◽  
2004 ◽  
Vol 88 (4) ◽  
pp. 397-401 ◽  
Author(s):  
I. Roloff ◽  
H. Scherm ◽  
M. W. van Iersel
Keyword(s):  
Leaf Area ◽  
Disease Severity ◽  
Leaf Spot ◽  
Abiotic Factors ◽  
Lesion Size ◽  
Leaf Conductance ◽  
Yield Potential ◽  
Leaf Spots ◽  
Virtual Lesion ◽  
Septoria Leaf Spot

Leaf spots caused by fungal pathogens or abiotic factors can be prevalent on southern blueberries after harvest during the summer and fall, yet little is known about how they affect physiological processes that determine yield potential for the following year. In this study, we measured CO2 assimilation and leaf conductance on field-grown blueberry plants affected by Septoria leaf spot (caused by Septoria albopunctata) or by edema-like abiotic leaf blotching. Net assimilation rate (NAR) on healthy leaves varied between 6.9 and 12.4 μmol m-2 s-1 across cultivars and measurement dates. Infection by S. albopunctata had a significant negative effect on photosynthesis, with NAR decreasing exponentially as disease severity increased (R2 ≥0.726, P < 0.0001). NAR was reduced by approximately one-half at 20% disease severity, and values approached zero for leaves with >50% necrotic leaf area. There was a positive, linear correlation between NAR and leaf conductance (R2 ≥ 0.622, P < 0.0001), suggesting that the disease may have reduced photosynthesis via decreased CO2 diffusion into affected leaves. Estimates of virtual lesion size associated with infection by S. albopunctata ranged from 2.8 to 3.1, indicating that the leaf area in which photosynthesis was impaired was about three times as large as the area covered by necrosis. For leaves afflicted by edema-like damage, there also was a significant negative relationship between NAR and affected leaf area, but the scatter about the regression was more pronounced than in the NAR-disease severity relationships for S. albopunctata (R2 = 0.548, P < 0.0001). No significant correlation was observed between leaf conductance and affected area on these leaves (P = 0.145), and the virtual lesion size associated with abiotic damage was significantly smaller than that caused by S. albopunctata. Adequate carbohydrate supply during the fall is critical for optimal flower bud set in blueberry; therefore, these results document the potential for marked yield losses due to biotic and abiotic leaf spots.

Characterization and pathogenicity of Bipolaris peregianensis: the causal organism for leaf spot of hybrid bermudagrass in China

2016 ◽  
Vol 148 (3) ◽  
pp. 551-555
Author(s):  
Wu Zhang ◽  
Jinxiang Liu ◽  
Pinghui Huo ◽  
Tao Zhang ◽  
Zhibiao Nan
Keyword(s):  
Leaf Spot ◽  
Causal Organism

scholarly journals Heritability of peach tree resistance to bacterial leaf spot

2017 ◽  
Vol 52 (5) ◽  
pp. 366-369 ◽  
Author(s):  
André Luiz Varago ◽  
Idemir Citadin ◽  
Marcos Robson Sachet ◽  
Gener Augusto Penso ◽  
Maria do Carmo Bassols Raseira
Keyword(s):  
Leaf Area ◽  
Disease Severity ◽  
Leaf Spot ◽  
Field Conditions ◽  
Broad Sense Heritability ◽  
Peach Tree ◽  
Bacterial Leaf Spot ◽  
Tree Resistance ◽  
Leaf Area Duration ◽  
Xanthomonas Arboricola

Abstract: The objective of this work was to evaluate the broad-sense heritability reaction to bacterial leaf spot (Xanthomonas arboricola pv. pruni), in peach tree populations obtained from directed crosses. Disease severity and defoliation of the genotypes were evaluated in field conditions, with posterior measurement of the healthy leaf area duration (HAD). The observed average heritability (0.51) indicates that the use of the evaluated genitors can be effective for the development of cultivars with higher resistance to the disease.

scholarly journals First Report of a Leaf Spot on Conyza sumatrensis Caused by Phoma macrostoma in China

Plant Disease ◽  
2012 ◽  
Vol 96 (1) ◽  
pp. 148-148 ◽  
Author(s):  
J. Liu ◽  
H. D. Luo ◽  
W. Z. Tan ◽  
L. Hu
Keyword(s):  
Leaf Spot ◽  
Fungal Pathogens ◽  
Biological Diversity ◽  
Biocontrol Agent ◽  
Continuous Light ◽  
The United States ◽  
Leaf Spot Disease ◽  
Pathogenicity Test ◽  
Dry Land ◽  
First Report

Conyza sumatrensis (Asteraceae), an annual or biennial plant, is native to North and South America. It is an invasive, noxious weed that is widespread in southern and southeastern China. It invades farm land and causes great losses to dry land crops, including wheat, corn, and beans. It also reduces biological diversity by crowding out native plants in the infested areas (3,4). During a search for fungal pathogens that could serve as potential biological control agents of C. sumatrensis, a leaf spot disease was observed in 2010 in Chongqing, China. An isolate (SMBC22) of a highly virulent fungus was obtained from diseased leaves. Pathogenicity tests were performed by placing 6-mm-diameter mycelial disks of 7-day-old potato dextrose agar (PDA) cultures of SMBC22 on leaves of 15 healthy greenhouse-grown plants of C. sumatrensis; the same number of control plants was treated with sterile PDA disks. Treated plants were covered with plastic bags for 24 h and maintained in a growth chamber with daily average temperatures of 24 to 26°C, continuous light (3,100 lux), and high relative humidity (>90%). Lesions similar to those observed in the field were first obvious on the SMBC22-inoculated leaves 3 days after inoculation. Symptoms became severe 7 to 9 days after inoculation. Control plants remained healthy. The fungus was reisolated from inoculated and diseased leaves and it was morphologically the same as SMBC22. The pathogenicity test was conducted three times. A survey of 10 southern and southeastern Chinese provinces revealed that the disease was widespread and it attacked leaves and stems of seedlings and mature plants of C. sumatrensis. Lesions on leaves were initially small, circular, and water soaked. The typical lesion was ovoid or fusiform, dark brown, and surrounded by a yellow halo. The spots coalesced to form large lesions and plants were often completely blighted. Fungal colonies of SMBC22 on PDA plates were initially white and turned dark gray. Colonies were circular with smooth edges with obvious rings of pycnidia on the surface. Aerial hyphae were short and dense. Pycnidia, black and immersed or semi-immersed in the medium, were visible after 12 days of incubation. Pycnidia were 72 to 140 μm in diameter. Conidia were produced in the pycnidia and were hyaline, unicellular, ellipsoidal, and 4.4 to 6.1 × 1.6 to 2.2 μm. To confirm identification of the fungus, genomic DNA was extracted from mycelia of a 7-day-old culture on PDA at 25°C (2). The internal transcribed spacer (ITS) gene of rDNA was amplified using primers ITS4/ITS5. The gene sequence was 524 bp long and registered in NCBI GenBank (No. HQ645974). BLAST analysis showed that the current sequence had 99% homology to an isolate of Phoma macrostoma (DQ 404792) from Cirsium arvense (Canada thistle) in Canada and reported to cause chlorotic symptoms on that host plant (1). To our knowledge, this is the first report of P. macrostoma causing disease on C. sumatrensis in China. P. macrostoma, thought of as a biocontrol agent of broadleaf weeds in Canada, has been patented in the United States. The current isolate of P. macrostoma is considered as a potential biocontrol agent of C. sumatrensis. References: (1) P. R. Graupner et al. J. Nat. Prod. 66:1558, 2004. (2) S. Takamatsu et al. Mycoscience 42:135, 2001. (3) W. Z. Tan et al. Page 177 in: Manual of Emergency Control Technology Invasive Pests in China. G. L. Zhang, ed. Science Press, Beijing, 2010. (4) C. Wang et al. J. Wuhan Bot. Res. 28:90, 2010.

scholarly journals First Report of a Leaf Spot on Snow Lotus Caused by Alternaria carthami in China

Plant Disease ◽  
2008 ◽  
Vol 92 (2) ◽  
pp. 318-318
Author(s):  
S. Zhao ◽  
G. Xie ◽  
H. Zhao ◽  
H. Li ◽  
C. Li
Keyword(s):  
Leaf Spot ◽  
Disease Incidence ◽  
Leaf Spot Disease ◽  
Tianshan Mountain ◽  
Causal Organism ◽  
Saussurea Involucrata ◽  
First Report ◽  
Spot Disease ◽  
Initial Symptoms ◽  
Snow Lotus

Snow lotus (Saussurea involucrata Karel. & Kir. ex Sch. Bip.) is an economically important medicinal herb increasingly grown in China in recent years. In June of 2005, a leaf spot disease on commercially grown plants was found in the QiTai Region, south of the Tianshan Mountain area of Xinjiang, China at 2,100 m above sea level. Disease incidence was approximately 60 to 70% of the plants during the 2006 and 2007 growing seasons. Initial symptoms appeared on older leaves as irregularly shaped, minute, dark brown-to-black spots, with yellow borders on the edge of the leaflet blade by July. As the disease progressed, the lesions expanded, causing the leaflets to turn brown, shrivel, and die. A fungus was consistently isolated from the margins of these lesions on potato dextrose agar. Fifty-eight isolates were obtained that produced abundant conidia in the dark. Conidia were usually solitary, rarely in chains of two, ellipsoid to obclavate, with 6 to 11 transverse and one longitudinal or oblique septum. Conidia measured 60 to 80 × 20 to 30 μm, including a filamentous beak (13 to 47 × 3.5 to 6 μm). According to the morphology, and when compared with the standard reference strains, the causal organism of leaf spot of snow lotus was identified as Alternaria carthami (1,4). Pathogenicity of the strains was tested on snow lotus seedlings at the six-leaf stage. The lower leaves of 20 plants were sprayed until runoff with conidial suspensions of 1 × 104 spores mL–1, and five plants sprayed with sterile distilled water served as controls. All plants were covered with a polyethylene bag, incubated at 25°C for 2 days, and subsequently transferred to a growth chamber at 25°C with a 16-h photoperiod. Light brown lesions developed within 10 days on leaflet margins in all inoculated plants. The pathogen was reisolated from inoculated leaves, and isolates were deposited at the Key Oasis Eco-agriculture Laboratory of Xinjiang Production and Construction Group, Xinjiang and the Institute of Biotechnology, Zhejiang University. No reports of a spot disease caused by A. carthami on snow lotus leaves have been found, although this pathogen has been reported on safflower in western Canada (3), Australia (2), India (1), and China (4). To our knowledge, this is the first report of a leaf spot caused by A. carthami on snow lotus in China. References: (1) S. Chowdhury. J. Indian Bot. Soc. 23:59, 1944. (2) J. A. G. Irwin. Aust. J. Exp. Agric. Anim. Husb. 16:921, 1976. (3) G. A. Petrie. Can. Plant Dis. Surv. 54:155, 1974. (4) T. Y. Zhang. J. Yunnan Agric. Univ.17:320, 2002.

scholarly journals Stagonosporopsis pogostemonis: A Novel Ascomycete Fungus Causing Leaf Spot and Stem Blight on Pogostemon cablin (Lamiaceae) in South China

Pathogens ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 1093
Author(s):  
Zhang-Yong Dong ◽  
Ying-Hua Huang ◽  
Ishara S. Manawasinghe ◽  
Dhanushka N. Wanasinghe ◽  
Jia-Wei Liu ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
South China ◽  
Leaf Spot ◽  
Large Subunit ◽  
Fungal Species ◽  
Leaf Spot Disease ◽  
Causal Organism ◽  
Stem Blight ◽  
Southern Chinese ◽  
Pogostemon Cablin

Pogostemon cablin is one of the well-known Southern Chinese medicinal plants with detoxification, anti-bacterial, anti-inflammatory, and other pharmacological functions. Identification and characterization of phytopathogens on P. cablin are of great significance for the prevention and control of diseases. From spring to summer of 2019 and 2020, a leaf spot disease on Pogostemon cablin was observed in Guangdong Province, South China. The pathogen was isolated and identified based on both morphological and DNA molecular approaches. The molecular identification was conducted using multi-gene sequence analysis of large subunit (LSU), the nuclear ribosomal internal transcribed spacer (ITS), beta-tubulin (β-tubulin), and RNA polymerase II (rpb2) genes. The causal organism was identified as Stagonosporopsis pogostemonis, a novel fungal species. Pathogenicity of Stagonosporopsis pogostemonis on P. cablin was fulfilled via confining the Koch's postulates, causing leaf spots and stem blight disease. This is the first report of leaf spot diseases on P. cablin caused by Stagonosporopsis species worldwide.

scholarly journals Alternaria leaf spot of broccoli caused by Alternaria alternata in Bangladesh

2021 ◽  
Author(s):  
Sayma T. Nira ◽  
Md. Farhad Hossain ◽  
Nur Uddin Mahmud ◽  
Oliul Hassan ◽  
Md. Tofazzal Islam ◽  
...  
Keyword(s):  
Alternaria Alternata ◽  
Leaf Spot ◽  
Maximum Growth ◽  
Pathogenicity Test ◽  
Culture Studies ◽  
Alternaria Leaf Spot ◽  
Cultural Methods ◽  
Molecular Phylogenetic ◽  
Alternaria Sp

  This study aimed to isolate and characterise the pathogen associated with Alternaria leaf spot on broccoli and to evaluate the inhibitory effects of fungicides against it. We isolated and identified the fungal pathogen as Alternaria sp. using morphological and cultural methods. Based on the aligned sequences of the internal transcribed spacer (ITS) and molecular phylogenetic analysis by the neighbour-joining method, the isolates (Ab1 and Ab2) were confirmed as Alternaria alternata. The conidia of the isolates were dark brown, cylindrical, obclavate to muriform. The conidiophores were olivaceous brown, septate, and branched. The conidial morphology of the isolates ranged from 52.4–92.4 × 10–20 μm with 2–6 transverse and 0–3 longitudinal septa. Both isolates yielded positive results in the pathogenicity test on broccoli leaves by developing brown and circular spots with concentric rings on the leaves surrounded by yellow halos. The culture studies revealed that the maximum growth of the pathogen was obtained at 30 °C and pH 6.0. Tilt 250 WC showed the highest potential in suppressing the mycelial growth of the A. alternata in vitro at a concentration as low as 50 µg/mL. The results from this study contributed to the positive identification of the pathogen and characterised A. alternata as a destructive pathogen of broccoli which may be successfully controlled by the fungicide Tilt.  

scholarly journals First Report of Ramularia coleosporii causing Leaf Spot on Perilla frutescens in Korea

Plant Disease ◽  
2021 ◽  
Author(s):  
Md Aktaruzzaman ◽  
Tania Afroz ◽  
Hyo-Won Choi ◽  
Byung Sup Kim
Keyword(s):  
Leaf Spot ◽  
Ipomoea Batatas ◽  
Rust Fungus ◽  
Morphological Characteristics ◽  
Perilla Frutescens ◽  
Herbaceous Plant ◽  
Pathogenicity Test ◽  
Conidial Suspension ◽  
Single Spore ◽  
First Report

Perilla (Perilla frutescens var. japonica), a member of the family Labiatae, is an annual herbaceous plant native to Asia. Its fresh leaves are directly consumed and its seeds are used for cooking oil. In July 2018, leaf spots symptoms were observed in an experimental field at Gangneung-Wonju National University, Gangneung, Gangwon province, Korea. Approximately 30% of the perilla plants growing in an area of about 0.1 ha were affected. Small, circular to oval, necrotic spots with yellow borders were scattered across upper leaves. Masses of white spores were observed on the leaf underside. Ten small pieces of tissue were removed from the lesion margins of the lesions, surface disinfected with NaOCl (1% v/v) for 30 s, and then rinsed three times with distilled water for 60 s. The tissue pieces were then placed on potato dextrose agar (PDA) and incubated at 25°C for 7 days. Five single spore isolates were obtained and cultured on PDA. The fungus was slow-growing and produced 30-50 mm diameter, whitish colonies on PDA when incubated at 25ºC for 15 days. Conidia (n= 50) ranged from 5.5 to 21.3 × 3.5 to 5.8 μm, were catenate, in simple or branched chains, ellipsoid-ovoid, fusiform, and old conidia sometimes had 1 to 3 conspicuous hila. Conidiophores (n= 10) were 21.3 to 125.8 × 1.3 to 3.6 μm in size, unbranched, straight or flexuous, and hyaline. The morphological characteristics of five isolates were similar. Morphological characteristics were consistent with those described for Ramularia coleosporii (Braun, 1998). Two representative isolates (PLS 001 & PLS003) were deposited in the Korean Agricultural Culture Collection (KACC48670 & KACC 48671). For molecular identification, a multi-locus sequence analysis was conducted. The internal transcribed spacer (ITS) regions of the rDNA, partial actin (ACT) gene and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene were amplified using primer sets ITS1/4, ACT-512F/ACT-783R and gpd1/gpd2, respectively (Videira et al. 2016). Sequences obtained from each of the three loci for isolate PLS001 and PLS003 were deposited in GenBank with accession numbers MH974744, MW470869 (ITS); MW470867, MW470870 (ACT); and MW470868, MW470871 (GAPDH), respectively. Sequences for all three genes exhibited 100% identity with R. coleosporii, GenBank accession nos. GU214692 (ITS), KX287643 (ACT), and 288200 (GAPDH) for both isolates. A multi-locus phylogenetic tree, constructed by the neighbor-joining method with closely related reference sequences downloaded from the GenBank database and these two isolates demonstrated alignment with R. coleosporii. To confirm pathogenicity, 150 mL of a conidial suspension (2 × 105 spores per mL) was sprayed on five, 45 days old perilla plants. An additional five plants, to serve as controls, were sprayed with sterile water. All plants were placed in a humidity chamber (>90% relative humidity) at 25°C for 48 h after inoculation and then placed in a greenhouse at 22/28°C (night/day). After 15 days leaf spot symptoms, similar to the original symptoms, developed on the leaves of the inoculated plants, whereas the control plants remained symptomless. The pathogenicity test was repeated twice with similar results. A fungus was re-isolated from the leaf lesions on the inoculated plants which exhibited the same morphological characteristics as the original isolates, fulfilling Koch’s postulates. R. coleosporii has been reported as a hyperparasite on the rust fungus Coleosporium plumeriae in India & Thailand and also as a pathogen infecting leaves of Campanula rapunculoides in Armenia, Clematis gouriana in Taiwan, Ipomoea batatas in Puerto Rico, and Perilla frutescens var. acuta in China (Baiswar et al. 2015; Farr and Rossman 2021). To the best of our knowledge, this is the first report of R. coleosporii causing leaf spot on P. frutescens var. japonica in Korea. This disease poses a threat to production and management strategies to minimize leaf spot should be developed.

scholarly journals Field Characterization of Partial Resistance to Gray Leaf Spot in Elite Maize Germplasm

2020 ◽  
Vol 110 (10) ◽  
pp. 1668-1679
Author(s):  
James O. Nyanapah ◽  
Patrick O. Ayiecho ◽  
Julius O. Nyabundi ◽  
Washington Otieno ◽  
Peter S. Ojiambo
Keyword(s):  
Disease Resistance ◽  
Leaf Area ◽  
Plant Development ◽  
Leaf Spot ◽  
Partial Resistance ◽  
Inflection Point ◽  
Inbred Lines ◽  
Gray Leaf Spot ◽  
Diseased Leaf ◽  
Diseased Leaf Area

Forty-eight inbred lines of maize with varying levels of resistance to gray leaf spot (GLS) were artificially inoculated with Cercospora zeina and evaluated to characterize partial disease resistance in maize under field conditions from 2012 to 2014 across 12 environments in western Kenya. Eight measures of disease epidemic—that is, final percent diseased leaf area (FPDLA), standardized area under the disease progress curve (SAUDPC), weighted mean absolute rate of disease increase (ρ), disease severity scale (CDSG), percent diseased leaf area at the inflection point (PDLAIP), SAUDPC at the inflection point (SAUDPCIP), time from inoculation to transition of disease progress from the increasing to the decreasing phase of epidemic increase (TIP), and latent period (LP)—were examined. Inbred lines significantly (P < 0.05) affected all measures of disease epidemic except ρ. However, the proportion of the variation attributed to the analysis of variance model was most strongly associated with SAUDPC (R2 = 89.4%). Inbred lines were also most consistently ranked for disease resistance based on SAUDPC. Although SAUDPC was deemed the most useful variable for quantifying partial resistance in the test genotypes, the proportion of the variation in SAUDPC in each plot was most strongly (R2 = 93.9%) explained by disease ratings taken between the VT and R4 stages of plant development. Individual disease ratings at the R4 stage of plant development were nearly as effective as SAUDPC in discerning the differential reaction of test genotypes. Thus, GLS rankings of inbred lines based on disease ratings at these plant developmental stages should be useful in prebreeding nurseries and preliminary evaluation trials involving large germplasm populations.

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