Identification and Inheritance of Delayed First Pustule Appearance to Common leaf Rust in Sweet Corn

Partial resistance effectively reduces common leafrust (Puccinia sorghi Schw.) epidemics in sweet corn (Zea mays L.). One measurable field component of partial resistance is delayed first pustule appearance (FPA), influenced by latent period and infection efficiency. This is the first report of delayed FPA against common rust in sweet corn. Our objectives were to determine 1) if differences in delayed FPA could be assessed in a field environment, 2) the relationship between delayed FPA and disease severity, and 3) the inheritance of delayed FPA. FPA was screened in a field environment during 1992 and 1993 using two susceptible U.S. station inbreds and 32 breeding lines selected for partial resistance to common rust. The range in mean delay in FPA on a genotype basis was 2.4 to 5.0 days in 1992 and 1.5 to 7.4 days in 1993. Although the rank correlation of genotypes between years was small (r = 0.27), several breeding lines had longer delayed FPA in both years while others produced shorter FPA delay in both years. Seven commercial sweet corn hybrids with a wide range of partial resistance did not differ (P ≤ 0.05) for delayed FPA. There was no correlation between disease severity and delayed FPA (r2 = 0.00 to 0.21) for breeding lines or commercial hybrids, indicating that selection for delayed FPA may be conducted independently of disease severity. In a generation mean analysis conducted in 1993 and 1994 for three high x low delayed FPA crosses, the genetic control of delayed FPA was primarily additive. Dominant genetic effects were found in two crosses and epistasis was not significant in any cross.

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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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Susceptibility of spring wheat cultivars and breeding lines to Septoria nodorum Berk.

Agricultural and Food Science ◽

10.23986/afsci.72132 ◽

1983 ◽

Vol 55 (4) ◽

pp. 315-332

Author(s):

Reijo Karjalainen ◽

Aino Laitinen ◽

Tapio Juuti

Keyword(s):

Disease Severity ◽

Spring Wheat ◽

Effective Means ◽

Rank Correlation ◽

Grain Weight ◽

Symptom Expression ◽

Septoria Nodorum ◽

Wheat Cultivars ◽

Breeding Lines ◽

1000 Grain Weight

Screening techniques for detecting the susceptibility of spring wheat cultivars and breeding lines to Septoria nodorum Berk. were studied in trials carried out in southern Finland. Small screening plots were artificially inoculated with the pathogen and subsequent observations showed that the early cultivars Apu, Ulla, Hja 21600 and the late cultivar Tähti were the most susceptible. The rank correlation between field assessments from naturally infected plots and assessment from artificially inoculated small screening plots was moderately high. The correlations between 1000 grain weight and disease severity were negatively significant in some susceptible cultivars, but also in some resistant cultivars A weak positive correlation between 1000 grain weight and disease severity was observed in some resistant and also in some susceptible varieties. Although our results do not show consistent trends we conclude that the use of small screening plots is an effective means of detecting differences in symptom expression among breeding lines and cultivars.

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Widespread Occurrence of Common Rust, Caused by Puccinia sorghi, on Rp-Resistant Sweet Corn in the Midwestern United States

Plant Disease ◽

10.1094/pdis.1999.83.12.1177d ◽

1999 ◽

Vol 83 (12) ◽

pp. 1177-1177 ◽

Cited By ~ 9

Author(s):

J. K. Pataky ◽

W. F. Tracy

Keyword(s):

United States ◽

North America ◽

Sweet Corn ◽

The United States ◽

Rock Falls ◽

Corn Hybrids ◽

Widespread Occurrence ◽

Puccinia Sorghi ◽

No Formation ◽

Leaf Surfaces

Single, dominant resistance genes have been used successfully for the past 15 years to control common rust, caused by Puccinia sorghi, on sweet corn in the United States. Most sweet corn hybrids grown in the Midwest for mid- to late-season processing have Rp resistance, which is expressed as hypersensitive reactions resulting in chlorotic or necrotic flecks with little or no formation of urediniospores. Many, but not all, Rp-resistant sweet corn hybrids carry the gene Rp1D. Biotypes of P. sorghi in North America have been avirulent on plants with the Rp1D gene, except for an isolate collected in Kansas in 1990 (1). In a sweet corn nursery in Urbana, IL, in 1997, small uredinia of P. sorghi occurred on 27 of 79 Rp-resistant sweet corn hybrids that also were infected severely with southern rust caused by P. polysora (2). During August and September 1999, small uredinia or fully susceptible reactions to common rust were observed on several Rp-resistant sweet corn hybrids grown in an area bounded by Mendota, IL, Ripon, WI, and Le Sueur, MN. Southern rust also was prevalent and frequently severe in the area. Isolates of P. sorghi from Rp-resistant corn were collected during September 1999 from Mendota, Rock Falls, and Dekalb, IL; Sun Prairie, Madison, and Ripon, WI; and Rochester, Stanton, and Le Sueur, MN. Ten two-leaved seedlings of one susceptible sweet corn hybrid and five Rp-resistant hybrids, including hybrids known to carry the gene Rp1D, were inoculated in greenhouse trials. Each location (collection) was a separate trial. Inocula were prepared from several uredinia of P. sorghi per location. One set of seedlings also was inoculated with P. polysora. Susceptible reactions (uredinia with urediniospores) were observed on all inoculated seedlings. Uredinia and urediniospores of P. sorghi and P. polysora from seedlings inoculated in the greenhouse were compared directly. All isolates of P. sorghi were confirmed based on 6- to 7-day latent periods, formation of uredinia on both leaf surfaces, and urediniospores that were mostly spherical, cinnamon colored, and moderately echinulate. This is the first widespread occurrence in North America of a biotype of P. sorghi that is virulent on Rp-resistant sweet corn. References: (1) S. H. Hulbert et al. Plant Dis. 75:1130, 1991. (2) J. K. Pataky et al. Purdue Univ. AES Bull. No. 758:99, 1997.

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Susceptibility of US sweet corn hybrids to Puccinia sorghi Schw. in Hawaii

Crop Protection ◽

10.1016/0261-2194(88)90045-2 ◽

1988 ◽

Vol 7 (4) ◽

pp. 249-251 ◽

Cited By ~ 6

Author(s):

Soon Kwon Kim ◽

J.L. Brewbaker ◽

M. Logrono ◽

G. Srinivasan

Keyword(s):

Sweet Corn ◽

Corn Hybrids ◽

Puccinia Sorghi

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Sweet Corn (Zea mays) Hybrids Respond Differently to Simulated Imazethapyr Carryover

Weed Technology ◽

10.1017/s0890037x00041403 ◽

1997 ◽

Vol 11 (1) ◽

pp. 92-97 ◽

Cited By ~ 7

Author(s):

Thomas L. Rabaey ◽

R. Gordon Harvey

Keyword(s):

Zea Mays ◽

Sweet Corn ◽

Rapid Test ◽

Field Studies ◽

Corn Hybrids ◽

Greenhouse Study ◽

Wide Range

Eleven sweet corn hybrids representing a wide range of injury with imazethapyr in a greenhouse study were evaluated in simulated imazethapyr carryover field studies conducted at Arlington, WI. Imazethapyr at 0, 11, 22, and 44 g ai/ha was applied and incorporated 15 d prior to planting sweet corn. The greatest injury occurred 28 d after planting, with reductions in height ranging from 0 to 25%. Reductions in corn ear yields were similar all years for 10 of the 11 hybrids. Reductions in corn ear yield for ‘Crisp N’ Sweet 710,’ ‘Cornucopia,’ ‘Super Sweet Jubilee,’ ‘Excellency,’ and ‘DMC 20–35′ were less than for ‘Natural Sweet 9000,’ ‘Jubilee,’ ‘Zenith,’ ‘Green Giant 40,’ and ‘Green Giant 97.’ In 1992, plots were prepared for an actual imazethapyr carryover study by applying imazethapyr PPI at 70 and 140 g/ha and planting soybean. In 1993, four sweet corn hybrids were planted. Corn ear yield of Green Giant 97 was reduced following previous-year applications of 140 g/ha imazethapyr. Corn ear yields of Excellency, Super Sweet Jubilee, and Jubilee were not reduced at either actual carryover rate. These studies indicate variability among sweet corn hybrids in susceptibility to imazethapyr. Greenhouse results were indicative of field responses and may be useful as a rapid test to determine hybrid susceptibility.

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Reactions of Rp-Resistant, Processing Sweet Corn Hybrids to Populations of Puccinia sorghi Virulent on Corn with the Rp1-D Gene

HortScience ◽

10.21273/hortsci.36.2.324 ◽

2001 ◽

Vol 36 (2) ◽

pp. 324-327 ◽

Cited By ~ 7

Author(s):

Jerald K. Pataky ◽

Mirian Gonzalez ◽

James L. Brewbaker ◽

Frederik J. Kloppers

Keyword(s):

United States ◽

South Africa ◽

Zea Mays ◽

Sweet Corn ◽

Corn Hybrids ◽

Midwestern United States ◽

Puccinia Sorghi ◽

The Past ◽

Preliminary Research ◽

Moderately Resistant

Resistance to Puccinia sorghi Schwein. based on the Rp1-D gene has been used successfully in North America for the past 15 years to control common rust on sweet corn (Zea mays L.). The objective of this preliminary research was to examine rust reactions of Rp-hybrids grown for processing in the midwestern United States against biotypes of P. sorghi virulent against Rp1-D. In Sept. 1999, isolates of P. sorghi virulent on corn with the Rp1-D gene were collected throughout the midwestern United States. Rust reactions of 41 Rp-resistant, processing sweet corn hybrids and nine non-Rp hybrids were evaluated during the 1999-2000 season in Argentina, Hawaii, Mexico, and South Africa, where populations of P. sorghi are virulent against Rp1-D. Sporulating uredinia were observed on all hybrids in all locations. Although rust reactions varied among locations, mean standardized scores of nine non-Rp hybrids that were included in the trial as controls ranked nearly the same as in previous trials. Thirteen hybrids with standardized scores above 0.25 were more susceptible than the hybrid with the lowest mean rust rating, `Green Giant Code 27'. Thirty-two hybrids were intermediate in reaction to P. sorghi virulent against Rp1-D. Reactions were moderately resistant for nine hybrids with mean standardized scores below -0.50, including two moderately resistant, non-Rp hybrids (`GG Code 27' and `GG Code 6') that were included as controls. Additional trials are necessary to confirm reactions of these hybrids. If the Rp-hybrids that were moderately susceptible or susceptible in this trial are infected by P. sorghi virulent against Rp1-D, secondary inoculum will be abundant and infection will be severe if the weather is wet.

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First Report of Puccinia sorghi Virulent on Sweet Corn with the Rp1-D Gene in Florida and Texas

Plant Disease ◽

10.1094/pdis.2000.84.10.1154a ◽

2000 ◽

Vol 84 (10) ◽

pp. 1154-1154 ◽

Cited By ~ 6

Author(s):

M. C. Pate ◽

J. K. Pataky ◽

W. C. Houghton ◽

R. H. Teyker

Keyword(s):

New York ◽

North America ◽

Sweet Corn ◽

Leaf Tissue ◽

Tween 20 ◽

Experimental Unit ◽

Corn Hybrids ◽

Widespread Occurrence ◽

Puccinia Sorghi ◽

Corn Hybrid

For the past 15 years, the Rp1-D gene has controlled common rust on sweet corn in North America. In August and September 1999, isolates of Puccinia sorghi were collected from Rp1-D sweet corn hybrids in Illinois, Wisconsin, Minnesota, Michigan, and New York. This was the first widespread occurrence in the continental United States of P. sorghi virulent on the Rp1-D gene (1). Isolates of P. sorghi collected from Los Mochis, Mexico, in March 2000 had a pattern of virulence similar to the pattern for the isolates collected in the Midwest in 1999 (2). In April and May 2000, small uredinia were observed on Rp1-D sweet corn in Florida and Texas. In Florida, isolates were collected from six different locations within a 13-km radius near Belle Glade. Three isolates were collected each from Rp1-D and non-Rp sweet corn hybrids. Isolates also were collected from two Rp1-D sweet corn hybrids and a non-Rp sweet corn hybrid near Hondo, TX. Inocula of isolates were increased through one uredinial generation in the greenhouse. Several 1-cm2 pieces of leaf tissue with sporulating uredinia were placed in 15 ml of a solution of water and Tween 20. This inoculum was placed in whorls of five two-leaved seedlings of a susceptible hybrid, ‘Primetime.’ Urediniospores from newly formed uredinia were collected 10 days later and used as inocula to assay each isolate. Two isolates from Florida (one each from an Rp1-D and a non-Rp hybrid) were assayed on a non-Rp susceptible check, 20 different single Rp genes, and nine compound Rp genes. Other isolates were assayed on two replicates of a non-Rp susceptible check, a source of Rp1-D, and five single Rp genes that were effective against the isolates collected from the Midwest in 1999 and from Mexico in 2000. Each experimental unit consisted of five plants grown in 10-cm-diameter pots. Plants at the two-leaf stage were inoculated three times within 5 days by filling whorls with a urediniospore suspension. Rust reactions were rated 10 days after the final inoculation. Isolates collected in Florida from non-Rp hybrids were avirulent on Rp1-D but those collected in Texas from non-Rp hybrids were virulent on Rp1-D. Isolates collected in Florida and Texas from Rp1-D hybrids had a similar pattern of virulence as isolates collected from the Midwest in 1999 and from Mexico in March 2000; that is, effective single Rp genes included Rp1-E, Rp-G, Rp1-I, and Rp1-K. A source that we previously believed was Rp1-L now appears to be Rp-G. These are the first reports from Florida and Texas of P. sorghi virulent on Rp1-D, and they are the first occurrences of virulence against Rp1-D in the continental U.S. in 2000. Apparently, P. sorghi with virulence against Rp1-D has become established in an area where common rust inocula for North America overwinters. References: (1) J. K. Pataky and W. F. Tracy. Plant Dis. 83:1177, 1999. (2) J. K. Pataky et al. Plant Dis. 84:810, 2000.

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SWEET CORN EAR RESISTANCE TO THE EUROPEAN CORN BORER (Ostrinia nubilalis, Hubner) AND ITS RESPONSE IN SINGLE CROSSES.

HortScience ◽

10.21273/hortsci.27.6.645f ◽

1992 ◽

Vol 27 (6) ◽

pp. 645f-645

Author(s):

Mary S. Joyce ◽

Dave W. Davis

Keyword(s):

Ostrinia Nubilalis ◽

European Corn Borer ◽

Sweet Corn ◽

Corn Hybrids ◽

Corn Borer ◽

Breeding Lines ◽

Corn Breeding ◽

Resistant Lines ◽

Additive Gene ◽

Neonate Larvae

Development of sweet corn hybrids having resistance to ear feeding by the European corn borer (ECB) (Ostrinia nubilalis, Hübner) would save growers millions of dollars annually. Sweet corn breeding lines have been developed which show resistance to ear feeding. To determine whether resistance in these lines was heritable, testcrosses were made between 6 resistant lines and 2 susceptible inbreds. The testcrosses, resistant lines, susceptible inbreds, and Jubilee, a standard susceptible hybrid, were planted in randomized complete blocks replicated 8 times at each of 2 locations. Primary ears were infested, on the ear tip, at mid-silk (R3) with approximately 50 neonate larvae and were evaluated for damage 25 - 30 days later using a 9 point scale. The resistant parents and their testcrosses had 15% to 64% more resistant ears (less than 1% kernel damage at the tip only) than Jubilee. The inbreds and their commercial hybrid did not differ in resistance from Jubilee. Resistance to ECB appears to be polygenic and it has been suggested that some level of non-additive gene action is important. While the specific traits responsible for ear resistance are not known, the resistance of the breeding lines was transmitted to the testcrosses.

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