Progress 10/01/99 to 09/30/05
Outputs
Over the five year period of this project, we screened materials for head smut resistance and for tolerance to root rots. Head smut resistance trials were conducted on both commercial hybrids as a service to sweet corn breeding companies, and on a portion of a genetic mapping population developed at the University of Hawaii. The nursery provides a reliable screening tool for sweet corn breeders to identify resistant hybrids in their program, which they can target to appropriate environments where head smut is a problem. With the mapping population, we were able to differentiate between resistant and susceptible inbred lines, although resistance was more qualitative than quantitative. The largest issue with this material was its day length sensitivity, which delayed silking and tasseling in the Oregon environment. In some cases, lines did not flower before frost terminated growth. Because it is essential to see reproductive structures when scoring head rot, we felt that
there was some uncertainty in our genotype scores. Corn root rot trials were conducted during the project period. Trials were initially conducted in farmers fields, but later trials were performed at the research station where disease nurseries were developed. Over 75 hybrids contributed by six companies were evaluated during the 5 year period. We evaluated both sugary/sugary enhanced and supersweet hybrids. While it was difficult to achieve uniform results from year to year, we did see consistent trends. For example, Jubilee and Reward were generally quite susceptible. We identified several hybrids with resistance, including Coho, which is one of the main hybrids used by the processing industry at present. During this time period, the processing industry went from growing primarily one main hybrid (Jubilee, which had dominated the acreage for the past 30 years), to a situation where currently in the Willamette Valley, about 15 hybrids are being used by processors for production.
Generally, processors and growers are finding that there are new hybrids that give them profitable yields in the presence of root rot. We expect to see the numbers of hybrids decline as processors concentrate on a limited group that are high yielding and fit their processing needs.
Impacts
Because profit margins are so thin, growers cannot afford sweet corn yields to drop below about 9 T/A. Both head smut and root rot will reduce yields into the non economic range. For head smut resistance, the screening of commercial hybrids has allowed seed companies to determine which of their materials are resistant to head smut. Sweet corn is a 'keystone' crop for vegetable production in western Oregon because of its acreage and use in rotations. If its production were to decline, we would likely see a decline in all vegetable production in the Willamette Valley. It was grown on 29,000 acres in 2004 with a value of about $21 million. Five years ago, it appeared that we would loose production of this crop in the valley because of low yields and lack of profitability Root rot trials were instrumental in identifying high yielding, root rot tolerant hybrids, allowing production to return to profitability.
Publications
- Kean, D., J. Myers, J. Stang, and P. Mes. 2005. Vegetable Variety Trials 2004. OSUES EM8777. (http://eesc.orst.edu/agcomwebfile/edmat/EM8777-04e.pdf).
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Progress 01/01/04 to 12/31/04
Outputs
Head smut trial. We evaluated the 28 recombinant inbred lines (RILs) from in the A, G,I and J sets for head smut resistance. Overall disease incidence was somewhat more severe than 2003, with 68% of the plants infected of the susceptible check Kandy King. The I-series RILs continue to show the best segregation for susceptibility/ resistance, and should allow us to map one or more genes for resistance to head smut. Markers can then be identified that are associated with resistance to aid breeding programs in the development of resistant inbreds. We also tested 18 commercial sweet corn hybrids for head smut resistance in the same trial. None were completely resistant, but 10 entries had incidence of 8% or less. Corn Root Rot Trials. We conducted two trials for root rot tolerance in 2004 of sugary/sugary enhanced materials this year. There were not enough supersweet hybrids received to warrant a root rot trial, but these were evaluated in a regular yield trial. One root
rot trial was grown on a farm 10 miles south of Corvallis. Overall disease levels were low in this trial, and data were not collected beyond disease incidence at the 6 leaf stage. A second root rot trial, grown on the Vegetable Research Farm had moderate levels of root rot. Corn has been grown continuously on this plot for the past 4 years, and this strategy appears to be successful in developing a plot with consistent disease. Seventeen entries were grown, including two check hybrids and two supersweet synthetics from the University of Hawaii program. Entries were evaluated for root lesions at the six leaf stage, and again at harvest maturity. All entries except the supersweet synthetics were evaluated for yield and quality. Root rot severity ranged from 9 to 45% on radicle roots at the six leaf stage. The severity increased to 20 to 52% on nodal roots at harvest maturity. Coho, which appears to have some resistance, was among the top three ranked hybrids, along with CSU YP1-1 and GH
6198. Reward, a normally susceptible check, was not significantly different from these top hybrids. Jubilee had one of the highest severity ratings. Overall, yield did not show a significant correlation with percent root rot on nodal roots, but rather, was more closely related to days to maturity. Highest yielding in the trial was GH 2669. Currently in the Willamette Valley, about 15 hybrids are being used by processors for production. This is in contrast to just one major hybrid and two or three minor ones being used just five years ago. Generally, processors and growers are finding that there are new hybrids that give them profitable yields in the presence of root rot. We expect to see the numbers of hybrids decline as processors concentrate on a limited group that are high yielding and fit their processing needs.
Impacts
For head smut resistance, the I series RILs should allow us to map one or more genes for resistance to head smut. Markers can then be identified that are associated with resistance to aid breeding programs in the development of resistant inbreds. Sweet corn is a 'keystone' crop for vegetable production in western Oregon because of its acreage and use in rotations. If its production were to decline, we would likely see a decline in all vegetable production in the Willamette Valley. Low yields caused by sweet corn decline have made sweet corn production unprofitable for growers and reduced the quality of ears coming into the processing plant. Root rot trials assist in identifying high yielding, root rot tolerant hybrids.
Publications
- Kean, D., J. Myers, J. Stang, and P. Mes. 2004. Vegetable Variety Trials 2003. OSUES EM8777. (http://eesc.orst.edu/agcomwebfile/edmat/EM8777-03.pdf).
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Progress 01/01/03 to 12/31/03
Outputs
Head smut trial. We evaluated the parents Hi 34a and Tzi 17, and 44 recombinant inbred lines (RILs) from the 'I' set for head smut resistance. Overall disease incidence was somewhat more severe than 2002, with an overall percent infection of 38% for the susceptible check 'Kandy King'. We had moved the site to a new location on the Vegetable Farm and were expecting less severe infections until inoculum had a chance to build up in the soil. Variation for resistance of RILs was normally distributed. We also grew the head smut seed treatment trial coordinated by University of Idaho. The trial included 12 treatments. The control had an overall infection rate of 31.2%. Six treatments showed significantly lower percent infection than the control. None of the six treatments were significantly different from the standard Captan 400/Thiram 42S/Allegiance treatment. Corn Root Rot Trials. We conducted three trials for root rot tolerance in 2003. A sugary/sugary enhanced trial was
grown near Stayton, Oregon, a supersweet trial in North Albany, and a combined trial at the OSU Botany Farm. Twenty-three entries split nearly equally between the two endosperm types were grown. Root rot infection was mild at the Botany farm and moderate at the other sites. All hybrids exhibited root rot infected roots. Yields were generally good at all sites with some varieties achieving over 12 T/A. For sugary types, GH 2041 showed consistently high yields at the two locations. Obsession was a supersweet hybrid with low root rot ratings and relatively high yields.
Impacts
For head smut resistance, the I series RILs should allow us to map one or more genes for resistance to head smut. Markers can then be identified that are associated with resistance to aid breeding programs in the development of resistant inbreds. Sweet corn is a 'keystone' crop for vegetable production in western Oregon because of its acreage and use in rotations. If its production were to decline, we would likely see a decline in all vegetable production in the Willamette Valley. Low yields caused by sweet corn decline have made sweet corn production unprofitable for growers and reduced the quality of ears coming into the processing plant. Root rot trials assist in identifying high yielding, root rot tolerant hybrids.
Publications
- Kean, D., Myers, J., Stang, J, and Mes, P. 2003. Vegetable variety trials 2002. OSUES EM8777.(http://eesc.orst.edu/agcomwebfile/edmat/EM8777.pdf)
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Progress 01/01/02 to 12/31/02
Outputs
Head smut trial. We evaluated recombinant inbred lines (RILs) from four populations developed by the University of Hawaii sweet corn breeding program. Overall disease incidence was lower than 2001. 'Kandy King' (susceptible check) had 26% plants infected compared to 51% in 2001. Twenty of 28 lines had similar reactions in 2002 as in 2001. Of the 20, six were susceptible in both years. Four lines had susceptible plants in 2001 but none in 2002, and four showed the reverse pattern. Two sets segregated for resistance while the 'I' set was completely susceptible. High levels of infection and increased replication will be necessary to obtain accurate ratings for RILs when attempting to map genes for resistance to head smut. Corn root rot trials. We conducted two trials for root rot tolerance and a separate trial to evaluate processing quality of sweet corn hybrids. In addition to the 24 experimental entries, 'Jubilee', 'Reward' (susceptible), and 'Bonus' (tolerant) were
planted as checks. Hybrids were planted into untreated soil, and soil fumigated with either 320 GPA methyl bromide/chlorpicrin, or 75 GPA metham sodium (Vapam). Root rot was evaluated at the six leaf stage and at harvest maturity. Leaf firing was rated three times during silking and ear fill. Yield data were collected at harvest maturity. Overall levels of root rot were moderate. All hybrids had root rot at the six-leaf stage. Root rot was generally less in the methyl bromide treatments, while the Vapam treatment was intermediate. Firing varied among hybrids, but did not correspond to levels observed in check hybrids in past years. Firing was increased in methyl bromide and Vapam plots compared to the control. Diabrotica (twelve-spot cucumber beetle) feeding on roots was significantly higher in fumigated plots. Yield differences among hybrids did not correlate with root rot severity or firing symptoms. Only in the methyl bromide plots at the Botany Farm was a significant yield
increase observed. Fumigation delayed maturity, confounding collection of yield data. Based on performance in fumigated vs. nonfumigated treatments, GH 5702, GH 2385, Esquire, GH 1861, GH 2757, and Bonus have tolerance to root rot. GH 2385 and GH 1861 had high yield over trials and GH 1861 had similar processing quality to Jubilee. In general, fumigation is not useful for measuring root rot tolerance because of confounding factors. Root rot symptoms and firing are not good predictors of yield under moderate disease conditions. Our primary interest should be in yield per se in identifying sweet corn hybrids for western Oregon processors. All sweet corn hybrids evaluated to date are susceptible to root rot although they may vary in degree of susceptibility. Some hybrids show tolerance, but none exhibit resistance. Because of its sensitivity to root rot and relatively low yield potential, use of Jubilee is declining and newer hybrids, such as GH 1861, are taking its place.
Impacts
For head smut resistance, the G and J series RILs should allow us to map one or more genes for resistance to head smut. Markers can then be identified that are associated with resistance to aid breeding programs in the development of resistant inbreds. Sweet corn is a 'keystone' crop for vegetable production in western Oregon because of its acreage and use in rotations. If its production were to decline, we would likely see a decline in all vegetable production in the Willamette Valley. Low yields caused by sweet corn decline have made sweet corn production unprofitable for growers and have reduced the quality of ears coming into the processing plants. Root rot trials are identifying new hybrids with tolerance that will replace Jubilee in western Oregon. We could potentially see an increase in sweet corn yields of one to two tons per acre, resulting in an additional farm gate value of $2.5-5 million.
Publications
- Kean, D., J. Myers, and P. Mes. 2002. Vegetable Variety Trials 2001. OSUES EM8777. (http://eesc.orst.edu/agcomwebfile/edmat/EM8777-01.pdf).
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Progress 01/01/01 to 12/31/01
Outputs
Three su1 alleles, su1-P, su1-am and su1-66, have a full kernel phenotype which is indistinguishable from kernels with genotypes containing the wild type allele Su1. However, the three alleles produce kernels with unique phenotypes in double mutant combinations with the genes dull1 and sugary2. Kernels with the double mutant genotypes are more collapsed than the kernel phenotypes of either su2 or du1. Kernels of the double mutants also are glassy. In du double mutants, su1-P produces the most collapsed kernel phenotype followed by su1-66 and su1-am kernels. In su2 double mutants, su1-66 kernels have the most extreme phenotypes followed by su1-P and su1-am kernels. In order to study the phenotypic relationships between these three su1 alleles, we have created heteroallelic combinations of the three alleles in combination with both du1 and su2. In addition, F2 and F3 generations from the heteroallelic combinations have been classified. In all cases, the experiments were
conducted in a W64A background. In combination with both du1 and su2, su1-P and su1-66 were dominant to su1-am. Kernels on F2 ears segregated 3:1: while F3 ears selected for the su1-am genotype were uniform. F3 ears selected for su1-P or su1-66 fell into two classes; approximately 1/3 of the ears were uniform and 2/3 continued to segregate. The interaction between su1-P and su1-66 was more complex. In combination with su1, the heteroallelic combination produced F2 ears with no segregation. In combination with du1, su1-66 was the dominant to su1-P.
Impacts
These studies demonstrate the independent action of the three su1 alleles.
Publications
- Shannon, J.C., D.L. Garwood, and C.D. Boyer. 2002. Genetics and physiology of starch development. In: R. Whistler and J. BeMiller, Eds. Starch, 2nd Edition. Academic Press, Orlando, FL (in press).
- Boyer, C.D. and J.C. Shannon. 2002. Carbohydrates of the kernel. In: L.A. Johnson and P.J. White, Eds. Corn Chemistry and Technology. Amer. Assoc. Cereal Chemists, St. Paul, MN (in press).
- Bertoft, E., C. Boyer, R. Manelius, and A-K. Avall. 2000. Observations on the alpha-amylolysis pattern of some waxy starches from inbred line Ia452. Cereal Chem. 77:657-664.
- Boyer, C.D. and L.C. Hannah. 2000. Kernel mutants of corn. In: A.R. Hallauer, Ed. Specialty Corn, 2nd Edition. CRC Press, Boca Raton, FL, pp. 1-31.
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