SWEET CORN INBREDS WITH PARTIAL RESISTANCE TO NORTHERN LEAF BLIGHT AND STEWART'S WILT

Approximately 200 sweet corn inbred lines were screened for two years for resistance to northern leaf blight, caused by Exserohilum turcicum, and Stewart's wilt, caused by Erwinia stewartii. Inbreds with the best levels of partial resistance to races 1 and 2 of E. turcicum included IL11d, IL676a, IL677a, IL685d, IL766a, IL767a and IL797a. Inbreds with the best partial resistance to E. stewartii included IL126b, IL676a, IL767a, IL772a, IL774g, IL797a, IL798a and M6011. Several of these resistant and moderately resistant inbreds had common ancestors; however, inspection of pedigrees suggested that resistance was derived from Puerto Rican, Bolivian, and other tropical sources and/or dent corn. Thus, many of the sweet corn inbreds may carry different genes for resistance and can be used for the development of populations with improved resistance.

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Partial Resistance to Northern Leaf Blight and Stewart's Wilt in Sweet Corn Germ Plasm

Plant Disease ◽

10.1094/pd-75-1094 ◽

1991 ◽

Vol 75 (11) ◽

pp. 1094 ◽

Cited By ~ 9

Author(s):

A. C. Meyer

Keyword(s):

Partial Resistance ◽

Germ Plasm ◽

Sweet Corn ◽

Corn Germ ◽

Leaf Blight ◽

Northern Leaf Blight ◽

Stewart's Wilt

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Disease Severity and Yield of Sweet Corn Hybrids with Resistance to Northern Leaf Blight

Plant Disease ◽

10.1094/pdis.1998.82.1.57 ◽

1998 ◽

Vol 82 (1) ◽

pp. 57-63 ◽

Cited By ~ 14

Author(s):

J. K. Pataky ◽

R. N. Raid ◽

L. J. du Toit ◽

T. J. Schueneman

Keyword(s):

Disease Severity ◽

Partial Resistance ◽

Yield Loss ◽

Sweet Corn ◽

Correlation Coefficients ◽

Inbred Lines ◽

Leaf Blight ◽

Northern Leaf Blight ◽

Corn Hybrids ◽

Highly Correlated

Reactions of supersweet (sh2) sweet corn to northern leaf blight (NLB) and associated yields were evaluated in Belle Glade, Florida and Urbana, Illinois in yield-loss trials, hybrid evaluations, and evaluations of breeding materials. Hybrids differed significantly for NLB in all trials. Severity of NLB ranged from 0 to 66% on 35 sh2 hybrids in yield-loss trials, and from 0 to 60% on 80 sh2 hybrids in hybrid evaluations. NLB ratings ranged from 1 to 9 (approximately 0 to 80% severity) on 375 hybrids and 186 inbred lines in evaluations of breeding materials. Various methods of rating NLB and ratings from multiple dates were highly correlated, with correlation coefficients ranging from 0.76 to 0.98. Yield, measured as weight of ears and number of marketable ears from inoculated plots as a percentage of that from control plots, decreased as disease severity increased. Linear or quadratic regression models explained 31 to 70% of the variation in percent yield as a function of disease severity at harvest. The effects of NLB on yield were limited by NLB-resistance in several hybrids, including CCO 3268, Chieftain, Crisp N Sweet 710A, Day Star, Envy, Forever, GSS 1526, Jupiter, Midship, Prime Plus, Sch 5005, and SummerSweet 7630. Although high levels of partial resistance to NLB were prevalent among 375 new experimental sh2 hybrids and 186 sh2 inbred lines evaluated in 1995, use of the gene HtN may increase in the near future as breeders are incorporating this resistance into new inbreds and hybrids. Breeders and plant pathologists would be wise to continue improving partial resistance to NLB without using the gene HtN in genotypes with adequate levels of partial resistance, because the widespread use of the gene HtN will select for virulent races of Exserohilum turcicum which occur in Florida, or for races with new combinations of virulence.

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Quantitative Trait Loci in Sweet Corn Associated with Partial Resistance to Stewart's Wilt, Northern Corn Leaf Blight, and Common Rust

Phytopathology ◽

10.1094/phyto.2001.91.3.293 ◽

2001 ◽

Vol 91 (3) ◽

pp. 293-300 ◽

Cited By ~ 34

Author(s):

A. F. Brown ◽

J. A. Juvik ◽

J. K. Pataky

Keyword(s):

Quantitative Trait Loci ◽

Quantitative Trait ◽

Partial Resistance ◽

Sweet Corn ◽

Phenotypic Variability ◽

Leaf Blight ◽

Northern Corn Leaf Blight ◽

Trait Loci ◽

Stewart's Wilt ◽

Corn Leaf Blight

Partial resistance to Stewart's wilt (Erwina stewartii, syn. Pantoea stewartii), northern corn leaf blight (NCLB) (Exserohilum turcicum), and common rust (Puccinia sorghi) was observed in an F2:3 population developed from a cross between the inbred sweet corn lines IL731a and W6786. The objective of this study was to identify quantitative trait loci (QTL) associated with partial resistance using restriction fragment length polymorphic markers. Phenotypic data were collected for 2 years for Stewart's wilt, NCLB, and common rust but, due to significant family-environment interaction, analysis was conducted individually on data from each year. In 2 years of evaluation for the three diseases, a total of 33 regions in the maize genome were associated with partial resistance describing from 5.9 to 18% of the total phenotypic variability. Of six regions common in both years, three were associated with partial resistance to Stewart's wilt (chromosomes 4:07, 5:03, and 6:04), one was associated with NCLB (chromosome 9:05), and two were associated with common rust (chromosomes 2:04 and 3:04). The rust QTL on 3S mapped to within 20 cM of the rp3 locus and explained 17.7% of the phenotypic variability. Some of the QTL associated with partial resistance to the three diseases have been reported previously, and some are described here for the first time. Results suggest it may be possible to consolidate QTL from various elite backgrounds in a manner analogous to the pyramiding of major resistance genes. We also report here on two QTL associated with anthocyanin production on chromosomes 10:6 and 5:03 in the general location of the a2 gene.

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Classification of Sweet Corn Hybrid Reactions to Common Rust, Northern Leaf Blight, Stewart's Wilt, and Goss' Wilt and Associated Yield Reductions

Phytopathology ◽

10.1094/phyto-78-172 ◽

1988 ◽

Vol 78 (2) ◽

pp. 172 ◽

Cited By ~ 23

Author(s):

J. K. Pataky

Keyword(s):

Sweet Corn ◽

Leaf Blight ◽

Northern Leaf Blight ◽

Stewart's Wilt ◽

Corn Hybrid

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Interaction of Ht and Partial Resistance to Exserohilum turcicum in Maize

Plant Disease ◽

10.1094/pdis.1997.81.3.277 ◽

1997 ◽

Vol 81 (3) ◽

pp. 277-282 ◽

Cited By ~ 19

Author(s):

P. E. Lipps ◽

R. C. Pratt ◽

J. J. Hakiza

Keyword(s):

Partial Resistance ◽

Specific Resistance ◽

Field Studies ◽

Leaf Blight ◽

Disease Development ◽

Exserohilum Turcicum ◽

Northern Leaf Blight ◽

Progress Curve ◽

Lesion Number ◽

Lower Severity

Components of northern leaf blight resistance in maize due to race-specific resistance controlled by the Ht gene, partial resistance derived from inbred H99, and a combination of the two kinds of resistance, were studied subsequent to inoculation with Exserohilum turcicum race O. Lesion types, number of lesions (lesion number), percent leaf area affected (severity), and area under the disease progress curve (AUDPC) based on lesion number and severity were assessed in field studies conducted at two locations in Uganda and one location in Ohio in 1993. Lesion types observed were consistent for genotypes across locations. In general, significant differences among genotypes for data based on lesion number and severity were consistent for AUDPC based on lesion number and severity, respectively, at all locations. In Ohio, both Ht and partial resistance were effective in limiting disease development. In Uganda, susceptible inbreds (A619, A635, and B73) generally had higher severity than genotypes with partial resistance (H99, Mo17, and Babungo 3). However, there was a difference in response among genotypes depending on disease intensity at each location. Ht resistance and moderate partial resistance did not greatly affect lesion number at the higher disease intensity location, compared with the susceptible inbreds, but at the lower disease intensity location genotypes with partial resistance had fewer lesions than susceptible inbreds or the Ht conversions of the susceptible inbreds. At both plot locations, genotypes with partial resistance had lower severity than the susceptible inbreds or Ht conversions of the susceptible inbreds. Hybrids derived from crossing H99 with genotypes with moderate levels of partial resistance (Mo17 and Babungo 3) did not have significantly lower lesion numbers than hybrids of susceptible inbreds crossed with H99, but severity was significantly lower on these hybrids at the high disease intensity location. Results indicate that the level of partial resistance in H99 would be as effective in controlling northern leaf blight as using Ht resistance, or a combination of Ht resistance and moderate levels of partial resistance as found in Mo17.

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Reactions of Open-Pollinated Sweet Corn Cultivars to Stewart's Wilt, Common Rust, Northern Leaf Blight, and Southern Leaf Blight

Plant Disease ◽

10.1094/pdis.1998.82.8.939 ◽

1998 ◽

Vol 82 (8) ◽

pp. 939-944 ◽

Cited By ~ 8

Author(s):

J. K. Pataky ◽

L. J. du Toit ◽

P. Revilla ◽

W. F. Tracy

Keyword(s):

Cluster Analysis ◽

Sweet Corn ◽

Morphological Characteristics ◽

Hierarchical Cluster ◽

Leaf Blight ◽

Northern Leaf Blight ◽

Sources Of Resistance ◽

Significant Difference ◽

Southern Leaf Blight ◽

Stewart's Wilt

Over 800 open-pollinated (OP) varieties of sweet corn were grown and named in the century prior to the development of hybrids, but only a few of the historically important OP cultivars exist today. Alleles that could improve disease resistance of modern sweet corn may be present in the OP cultivars still in existence. The objectives of this research were to compare 36 OP sweet corn cultivars to modern commercial hybrids for reactions to Stewart's wilt, common rust, northern leaf blight (NLB), and southern leaf blight (SLB), and to classify the OP cultivars based on phenotypic reactions to these four diseases. Plants were inoculated in 1994, 1995, and 1996 with Erwinia stewartii, Puccinia sorghi, Exserohilum turcicum, or Bipolaris maydis. Symptoms were rated on a whole-plot basis, and ratings were analyzed by analysis of variance (ANOVA). Means were separated by Bayesian least significant difference values. Some of the OP cultivars had phenotypes that were intermediate to moderately resistant to Stewart's wilt, common rust, NLB, or SLB, but none of the cultivars were more resistant than the best commercial hybrids. Distributions of ratings for rust, NLB, and SLB were less disperse for the OP cultivars than for commercial hybrids. Hence, the resistance of modern sweet corn germ plasm to Stewart's wilt, rust, and NLB appears to be greater than that of the OP cultivars. OP cultivars and four standard hybrids were placed into groups based on a hierarchical cluster analysis of disease reactions. The seven groups formed from the cluster analysis of disease ratings were considerably different than those formed from isozyme variation and morphological characteristics. The partial resistance of some cultivars, e.g., Golden Sunshine, Country Gentleman, Stowell's Evergreen, and Red, may be relatively diverse since these cultivars were placed in different groups based on isozyme and morphological variation. OP cultivars with moderate levels of resistance may be sources of resistance alleles not present in commercial hybrids.

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Effects of Races 0 and 1 ofExserohilum turcicumon Sweet Corn Hybrids Differing forHt-and Partial Resistance to Northern Leaf Blight

Plant Disease ◽

10.1094/pd-78-1189 ◽

1994 ◽

Vol 78 (12) ◽

pp. 1189 ◽

Cited By ~ 7

Author(s):

J. K. PATAKY

Keyword(s):

Partial Resistance ◽

Sweet Corn ◽

Leaf Blight ◽

Northern Leaf Blight ◽

Corn Hybrids

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Transmission of Erwinia stewartii from Plants to Kernels and Reactions of Corn Hybrids to Stewart's Wilt

Plant Disease ◽

10.1094/pdis.2002.86.2.167 ◽

2002 ◽

Vol 86 (2) ◽

pp. 167-172 ◽

Cited By ~ 15

Author(s):

P. M. Michener ◽

J. K. Pataky ◽

D. G. White

Keyword(s):

Sweet Corn ◽

F1 Hybrids ◽

Enzyme Linked Immunosorbent Assay ◽

Corn Hybrids ◽

Food Grade ◽

Kernel Infection ◽

Dent Corn ◽

The Mean ◽

Erwinia Stewartii ◽

Stewart's Wilt

Stewart's wilt reactions of 98 food-grade, white corn hybrids, 3 yellow dent corn hybrids, and 23 sweet corn hybrids and infection of kernels by E. stewartii were evaluated in 1998, 1999, and 2000. Stewart's wilt symptoms were rated from 1 (no appreciable spread of symptoms) to 9 (dead plants) following inoculation. The mean Stewart's wilt ratings for the food-grade, white corn and yellow dent corn hybrids were 1.9, 2.4, and 2.9 in 1998, 1999, and 2000, respectively. The mean Stewart's wilt ratings for the sweet corn hybrids were 3.8, 4.2, and 4.6 in 1998, 1999, and 2000, respectively. Hybrids with ratings less than 3 were classified as resistant. Hybrids with ratings between 3 and 4.5 were classified as moderate. Hybrids with ratings greater than 4.5 were classified as susceptible. Ears harvested from each row in 1998 and 1999 were assayed for E. stewartii using an enzyme-linked immunosorbent assay (ELISA)-based seed health test. Kernels from 16 hybrids were positive for E. stewartii in 1998. Kernels from 11 hybrids were positive for E. stewartii in 1999. Kernel infection by E. stewartii was affected considerably by the level of host resistance (i.e., reactions of seed parent plants). For hybrids classified as resistant, estimates of kernel infection were 0.024 and 0.0007% in 1998 and 1999, respectively. For hybrids with moderate reactions to Stewart's wilt, estimates of kernel infection were 0.19 and 0.07% in 1998 and 1999, respectively. For hybrids with susceptible reactions to Stewart's wilt, estimates of kernel infection were 11.6 and 7.8% in 1998 and 1999, respectively. Based on high levels of Stewart's wilt resistance in food-grade, white corn hybrids, and low rates of kernel infection by E. stewartii in resistant and moderate hybrids, there is an exceedingly low probability of introducing E. stewartii to areas where it does not occur by transmitting the bacterium in grain of the food-grade, white corn hybrids evaluated in this study. Although all of the kernels harvested in these experiments were produced as grain on open-pollinated F1 hybrids, the rates of kernel infection observed for hybrids with resistant, moderate and susceptible reactions to Stewart's wilt are applicable to seed produced on inbred lines with equivalent Stewart's wilt reactions.

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