scholarly journals The Influence of Silicon on Components of Resistance to Blast in Susceptible, Partially Resistant, and Resistant Cultivars of Rice

2001 ◽  
Vol 91 (1) ◽  
pp. 63-69 ◽  
Author(s):  
K. W. Seebold ◽  
T. A. Kucharek ◽  
L. E. Datnoff ◽  
F. J. Correa-Victoria ◽  
M. A. Marchetti
Keyword(s):  
Leaf Area ◽  
Incubation Period ◽  
Calcium Silicate ◽  
Magnaporthe Grisea ◽  
Upland Rice ◽  
Lesion Size ◽  
Diseased Leaf ◽  
Infection Efficiency ◽  
Components Of Resistance ◽  
Diseased Leaf Area

The application of silicon (Si) fertilizers reduces the severity of blast, caused by Magnaporthe grisea, in irrigated and upland rice; however, little research has been conducted to examine the epidemiological and etiological components of this reduction. Four cultivars of rice with differential susceptibilities to race IB-49 of M. grisea were fertilized with three rates of a calcium silicate fertilizer and inoculated with the pathogen to test the effects of Si on the following components of resistance to blast: incubation period, latent period, infection efficiency, lesion size, rate of lesion expansion, sporulation per lesion, and diseased leaf area. For each cultivar, the incubation period was lengthened by increased rates of Si, and the numbers of sporulating lesions, lesion size, rate of lesion expansion, diseased leaf area, and number of spores per lesion were reduced. Lesion size and sporulation per lesion were lowered by 30 to 45%, and the number of sporulating lesions per leaf and diseased leaf area were significantly reduced at the highest rate of Si. The net effect of Si on these components of resistance is an overall reduction in the production of conidia on plants infected with M. grisea, thereby slowing the epidemic rate of blast.

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.

Components of Resistance to Late Leafspot in Peanut. I. Levels and Variability - Implications for Selection1

1988 ◽  
Vol 15 (1) ◽  
pp. 25-30 ◽  
Author(s):  
Z. A. Chiteka ◽  
D. W. Gorbet ◽  
F. M. Shokes ◽  
T. A. Kucharek ◽  
D. A. Knauft
Keyword(s):  
Latent Period ◽  
Incubation Period ◽  
Lesion Size ◽  
Necrotic Area ◽  
Cercosporidium Personatum ◽  
Components Of Resistance ◽  
Lesion Diameter ◽  
Lesion Number ◽  
Resistant Genotypes

Abstract Components of resistance to late leafspot (Cercosporidium personatum (Berk. & Curt.) Deighton) in peanut were evaluated for 116 genotypes in three tests during 1986. The tests were conducted in greenhouses at Gainesville and Quincy, Florida and in the field near Marianna, Florida. The components of resistance evaluated were spore incubation period, latent period, lesion number per leaf, percent leaf necrotic area, lesion size, and amount of sporulation. Significant differences were observed in at least one test for each component. The greatest variability among genotypes was observed for lesion diameter and latent period. Resistant genotypes had smaller lesions, longer latent periods, and reducded sporulation. Among the most resistant genotypes were UF81206-1, UF81206-2. 72×32B-3-2-2-2-2-l-b3-B, and US 29-b3-B (85701).

scholarly journals The Pi40 Gene for Durable Resistance to Rice Blast and Molecular Analysis of Pi40-Advanced Backcross Breeding Lines

2009 ◽  
Vol 99 (3) ◽  
pp. 243-250 ◽  
Author(s):  
J. P. Suh ◽  
J. H. Roh ◽  
Y. C. Cho ◽  
S. S. Han ◽  
Y. G. Kim ◽  
...  
Keyword(s):  
Leaf Area ◽  
Resistance Genes ◽  
Rice Blast ◽  
Blast Resistance ◽  
Recurrent Parent ◽  
Diseased Leaf ◽  
Breeding Lines ◽  
Advanced Backcross ◽  
Diseased Leaf Area ◽  
Backcross Breeding

Rice blast severely reduces production in both irrigated and water-stressed upland ecosystems of tropical and temperate countries. Nearly 50 blast resistance genes have been identified and some of those are incorporated into several rice cultivars. However, most of the resistance genes break down in a few years because of their race specificity and the rapid change in pathogenicity of the blast fungus (Magnaporthe grisea). The objective of this study was to analyze advanced backcross breeding lines (ABL) possessing the gene Pi40 for durable rice blast resistance. In all, 4 resistant genotypes, 4 japonica cultivars, and 10 monogenic differential rice genotypes with some known resistance genes were bioassayed in the greenhouse using seven sequential plantings and 29 virulent M. grisea isolates of Korea. The genotypes with the Pi40 gene had <3% diseased leaf area, which was significantly below the disease threshold level of 40% considered for durable blast resistance. Moreover, the genotypes with the Pi40 gene expressed compatibility with only two to three virulent M. grisea isolates supporting durability of resistance, in contrast to susceptible cultivars with >50% diseased leaf area and 10 compatible isolates. Of the 10 known resistance genes tested, Piz-t, Piz-5, and Pi9 showed differential reactions to the pathogen isolates in seven plantings. Genotyping of the ABL with 260 simple sequence repeat (SSR) markers revealed rapid conversion toward recurrent parent genotypes with fewer donor chromosomal segments (5.3 to 14.5%). Our study based on a sequential testing and background selection of breeding lines with the resistance gene Pi40 provided valuable information for durable blast resistance breeding in rice.

scholarly journals Evaluation efficiency of severity of angular leaf spot in common bean based on diseased and healthy leaf area

2013 ◽  
Vol 13 (3) ◽  
pp. 178-185
Author(s):  
Rafael Augusto da Costa Parrella ◽  
João Bosco dos Santos ◽  
Nádia Nardely Lacerda Durães Parrella ◽  
Diego Velásquez Faleiro e Silva
Keyword(s):  
Common Bean ◽  
Leaf Area ◽  
Leaf Spot ◽  
Chemical Control ◽  
Angular Leaf Spot ◽  
Diseased Leaf ◽  
Healthy Leaf ◽  
Progress Curve ◽  
Diseased Leaf Area ◽  
Dry And Rainy Seasons

This study compared severity of angular leaf spot in common bean lines, based on the healthy and diseased leaf area, and the graded scale. We used 12 common bean lines in the dry and rainy seasons. Two contiguous experiments were conducted in each season, with and without chemical control of the pathogen. We evaluated the percentage of the healthy and diseased leaf area; severity based on a graded scale and the area under the disease progress curve; and yield. The diseased or healthy leaf area is efficient to evaluate the severity of angular leaf spot with a sample of 20 to 30 leaflets per plot. For all traits, the results of central and border areas did not differ, indicating that the evaluation of border rows is unnecessary and, finally, the severity assessment of the upper plant half can discriminate the lines more efficiently.

scholarly journals Silicon and manganese on rice resistance to blast

Bragantia ◽  
2012 ◽  
Vol 71 (2) ◽  
pp. 239-244 ◽  
Author(s):  
Isaías Severino Cacique ◽  
Gisele Pereira Domiciano ◽  
Fabrício Ávila Rodrigues ◽  
Francisco Xavier Ribeiro do Vale
Keyword(s):  
Leaf Area ◽  
Incubation Period ◽  
Nutrient Solution ◽  
Lesion Size ◽  
Conidial Suspension ◽  
Progress Curve ◽  
Significant Difference ◽  
Leaf Tissues ◽  
Foliar Concentration ◽  
Mn Concentration

Blast, caused by the fungus Pyricularia oryzae, is the most important fungal disease of rice. The effect of silicon (Si) and manganese (Mn), and their interaction, on rice resistance to blast was investigated. Rice plants (cultivar "Metica 1") were grown in hydroponic solution with 0 or 2 mmol L-1 of Si and with 0.5, 2.5, and 10 mmol L-1 of Mn. Sixty-day-old plants were inoculated with a conidial suspension of P. oryzae and the incubation period (IP), the number of lesions (NL) per cm² of leaf area, the lesion size (LS), and blast severity were evaluated. Blast severity was scored at 48, 72, 96, and 144 hours after inoculation and data were used to obtain the area under blast progress curve (AUBPC). Silicon concentration was significantly higher in leaf tissues of plants supplied with this element than on its absence, regardless of Mn rates. There was no significant difference in Si concentration among the Mn rates for both - Si and +Si treatments. The Mn concentration was significantly higher in the tissues of plants from the - Si treatment as compared to plants of the +Si treatment, but only at the rate of 10 mmol L-1 of Mn. There was a significant increase in Mn concentration as the rates of this micronutrient increased from 0.5 to 10 mmol L-1 regardless of the Si treatments. The IP significantly increased in the +Si treatment. The Mn rates had no effect on the IP regardless of the Si treatments. The NL was significantly lower in the presence of Si regardless of the Mn rates. The Mn rates had no effect on NL regardless of the Si treatments. The addition of Si to the nutrient solution significantly reduced both LS and AUBPC regardless of Mn rates. However, in the absence of Si, the values for LS and AUBPC were significantly lower at the Mn rate of 10 µmol L-1 as compared to the rate of 0.5 µmol L-1. Overall, the results from this study showed the potential of Si to decrease blast development on rice regardless of the foliar concentration of Mn.

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.

scholarly journals Competition between drought-tolerant upland rice cultivars and weeds under water stress condition

2013 ◽  
Vol 31 (2) ◽  
pp. 291-302 ◽  
Author(s):  
F.B. Cerqueira ◽  
E.A.L. Erasmo ◽  
J.I.C. Silva ◽  
T.V. Nunes ◽  
G.P. Carvalho ◽  
...  
Keyword(s):  
Water Stress ◽  
Leaf Area ◽  
Stress Condition ◽  
Upland Rice ◽  
Total Concentration ◽  
Dry Weight ◽  
Rice Cultivars ◽  
Drought Tolerant ◽  
Water Stress Condition ◽  
Water Conditions

The objective of this study was to evaluate the competitiveness of two cultivars of upland rice drought-tolerant, cultured in coexistence with weed S. verticillata, under conditions of absence and presence of water stress. The experiment was conducted in a greenhouse at the Experimental Station of the Universidade Federal de Tocantins, Gurupi-TO Campus. The experimental design was completely randomized in a factorial 2 x 2 x 4 with four replications. The treatments consisted of two rice cultivars under two water conditions and four densities. At 57 days after emergence, were evaluated in rice cultivars and weed S. verticillata leaf area, dry weight of roots and shoots and total concentration and depth of roots. Was also evaluated in rice cultivars, plant height and number of tillers. Water stress caused a reduction in leaf area, the concentration of roots and vegetative components of dry matter (APDM, and MSR MST) of rice cultivars and Jatoba Catetão and weed S. verticillata. The competition established by the presence of the weed provided reduction of all vegetative components (MSPA, and MSR MST) of cultivars and Jatoba Catetão. It also decreased the number of tillers, the concentration of roots and leaf area. At the highest level of weed competition with rice cultivars, a greater decrease in vegetative components and leaf area of culture, regardless of water conditions.

scholarly journals Variability in Puccinia melanocephala Pathogenicity and Resistance in Sugarcane Cultivars

Plant Disease ◽  
2014 ◽  
Vol 98 (12) ◽  
pp. 1728-1732 ◽  
Author(s):  
J. W. Hoy ◽  
M. C. Avellaneda ◽  
J. Bombecini
Keyword(s):  
Leaf Area ◽  
Quantitative Resistance ◽  
Durable Resistance ◽  
Lesion Size ◽  
Brown Rust ◽  
Host Genotype ◽  
Disease Response ◽  
Puccinia Melanocephala ◽  
Pathogen Variability ◽  
Pathogenic Variability

Brown rust, caused by Puccinia melanocephala, is an important disease of sugarcane worldwide, controlled primarily with host plant resistance. Disease response shifts from resistant to susceptible have been repeatedly observed for cultivars. However, information is limited concerning pathogen variability related to host reactions. To evaluate variability in the pathogen population and characterize resistance responses in different host genotypes, seven cultivars were inoculated with four urediniospore collections from three cultivars. Greenhouse-grown plants were inoculated under controlled conditions favorable for infection and disease development. Severity assessed as leaf area occupied by lesions, lesion density, and lesion size was determined and compared. Three cultivars that shifted from resistance to high susceptibility while under cultivation exhibited differential disease severity when inoculated with spore collections from two of the respective cultivars. Two cultivars exhibited consistent moderate to high levels of quantitative resistance against all spore collections and two cultivars, including one with the Bru1 resistance gene, were highly resistant to all collections. Differential reactions were best revealed by assessing percent leaf area. Pathogenic variability related to host genotype was confirmed, and quantitative resistance was detected that could be useful to improve breeding and selection for effective, durable resistance to brown rust.

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