Progress 10/01/05 to 06/30/07
Outputs
For the last three years, research on identifying resistance to PSD and PSS has been conducted at the University of Arkansas by Drs. Pat Fenn and Pengyin Chen. This research has identified two highly effective sources of resistance to PSD and one source of resistance to PSS. A single, dominate resistance gene to PSD was found in PI 80837. This gene is different and appears to be more effective than a gene in a Missouri germplasm line MO/PSD 259. In addition, PI 80837 also contained a single, dominate resistance gene for PSS that was independent of the PSD resistance gene. Molecular markers have been developed for PSD and work is underway to refine these markers and to find markers for PSS for use in marker assisted selection breeding. Both the PSD and the PSS resistance genes appear to be easily inherited and have been incorporated in to UofA's Soybean Breeding program. This winter four advanced lines were increased in a winter nursery and are well on their way to
being developed into commercial cultivars. Additional germplasm lines have been screened for resistance. In addition, there was an indication that weathering damage may be reduced by the PSD resistance genes. Lines with these genes showed significantly less seed damage than lines without the genes when harvest was delayed six to seven weeks. Results from the 2006 tests show that there are at least two different genes for resistance to PSD and maybe as many as four genes. There appeared to be at least two sources (and possibly three) for resistance to PSS. Resistance to PSD and PSS has been incorporated into four advanced breeding lines which will eventually be developed into commercially available cultivars. In cooperation with the USDA at Stoneville, MS, the core soybean germplasm collection is being screened for resistance to PSD, PSS and soybean rust. A number of crosses between PSS susceptible and resistant cultivars has been made. These will be evaluated for resistance and also
used in studies to find molecular markers for these genes that can be used in breeding. The ultimate goal of this research is to incorporate PSD and PSS resistance into the University of Arkansas soybean breeding program.
Impacts
The resistance to seed pathogens identified from this research will provide breeders genetic resources to be incorporated into adapted soybean cultivars. Soybean varieties with resistance will prevent yield loss and quality reduction under unfavorable production conditions. The high crop yield and good seed quality from new and improved varieties should translate into higher profits to Arkansas soybean producers.
Publications
- Jackson, E.W., C. Feng, P. Fenn, and P. Chen. 2006. Inheritance of resistance to Phomopsis seed decay in soybean in PI 80837 and MO PSD-0259 (PI 56264). Crop Sci. 45:2400-2404.
- Jackson, E.W., C. Feng, P. Fenn, and P. Chen. 2006. Inheritance of resistance to purple seed stain by Cercospora kikuchii in PI 80837 soybean. Crop Sci. 46:1462-1466.
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Progress 01/01/06 to 12/31/06
Outputs
PI 360841 was found to have strong resistance to Phomopsis infection under Arkansas conditions. Crosses were made between this line and Phomopsis susceptible genotypes to determine the mode of inheritance of its resistance. Lines resulting from crosses with Phomopsis-resistant PI 360841 have been harvested and are being prepared for seed assays to determine the mode of inheritance of resistance from this source. Approximately 800 plants have been harvested from these lines. Plants from some lines showed more robust growth and seed production than the parents. These selections will be retained for further testing in 2007. Progeny of PI 360841 x PI 80837 (a source of strong resistance to both Phomopsis seed decay and purple seed stain) have been harvested from inoculated plots, The seed has excellent appearance and will be assayed for latent (symptomless) seed infection before selecting the best lines to screen and increase in 2007. Seed infection for 2006 at Kibler was
1.4% for PI 80837 and 1.7% for PI 306841, while the susceptible PI 91113 had 17% infection. Crosses between PI 360841 and PI 80837 or MO/PSD-0259 indicate that these genes are different from those found in PI 80837 and MO/PSD-0259. Research on the inheritance of resistance to Phomopsis seed infection in PI 80837 and breeding line MO/PSD-0259 was completed. Both have dominant genes for resistance to Phomopsis, and PI 80837 has resistance to purple seed stain. Lines (F4) were planted in the field and F5 plants have been selected for increase and final selection in the field in 2006. These lines have genes for resistance to both major seed pathogens. Seed from Phomopsis and purple seed stain resistant F5 lines from the cross PI 80837 x MO/PSD-0259 was harvested in October. Samples will be sent for increase in a winter nursery. Field trials for agronomic performance, yield, and seed quality will be conducted in 2007 at three locations in eastern Arkansas. Crosses were made in 2004 between
the high-yielding adapted cultivar Asgrow 4715, line 496-307162 (a high-yielding maturity group II) and Phomopsis resistant PI 80837 and MO/PSD-0259. Seed has been harvested from select plants from F4 generations of AS 4715 and line 498-307162 (both are high-yielding adapted genotypes) crossed with PI 80837. Seed quality appears to be very good. Seed will be assayed for latent Phomopsis and purple seed stain infection. The best selections will be undergoing a final selection in 2007 for resistance and agronomic characteristics before increase. Crosses are being made between PI 360841 x PI 417479 (both are sources of strong resistance to Phomopsis seed decay) to determine if they carry different genes for resistance to seed infection. Molecular markers are being examined to determine if these plant introductions are similar lines as suggested by previous research. Thirty experimental lines and cultivars were screened for Phomopsis resistance in inoculated field plots. The seed will be
assayed for seed infection by Phomopsis and for purple seed stain. Several showed good resistance to Phomopsis in last year's trials.
Impacts
The resistance to seed pathogens identified from this research will provide breeders genetic resources to be incorporated into adapted soybean cultivars. Soybean varieties with resistance will prevent yield loss and quality reduction under unfavorable production conditions. The high crop yield and good seed quality from new and improved varieties should translate into higher profits to Arkansas soybean producers.
Publications
- Jackson, E.W., C. Feng, P. Fenn, and P. Chen. 2006. Inheritance of resistance to purple seed stain caused by Cercospora kikuchii in PI 80837 soybean. Crop Sci. 46:1462-1466.
- Jackson, E.W., P. Fenn, and P. Chen. 2005. Inheritance of resistance to Phomopsis seed decay in soybean PI 80837 and MO/PSD-0259 (PI 56264). Crop Sci. 45:2400-2404.
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Progress 01/01/05 to 12/31/05
Outputs
Plant Introduction (PI) 360841, which has shown excellent resistance to Phomopsis seed decay in our tests over three years, was found to have two complementary dominant genes for resistance. Further crosses with PI 360841 showed that resistance in PI 360841 is genetically different from that in resistant line MO/PSD-0259 and in resistant PI 80837. Thus, PI 360841 appears to have two new, uncharacterized genes for resistance to this destructive seed disease. Crosses of PI 360841 with PI 80837 produced plants with three genes for resistance to Phomopsis seed decay and one gene for resistance to purple seed stain. These progeny were twice the height of either parent and had excellent seed quality. Lines from this cross will be selected in the field next season.Individual plant selections (F5 plants) for resistance to Phomopsis seed decay and purple seed stain were made from F4 lines of the cross PI 80837 x MO/PSD-0259. These plants have two genes for resistance to
Phomopsis seed decay and one for resistance to purple seed stain. Final line selections will be made next season and seed increased for testing at several locations. Seed from these lines has excellent quality at harvest and showed little damage from stink bugs. Seed from plants harvested on Nov. 12, 2005, 6 to 7 weeks after maturity showed no external damage or discoloration from fungal infection or stink bugs. The high-yielding, adapted cultivar Asgrow 4715 and line 498-307162 (high-yielding MG II) were crossed with Phomopsis seed decay resistant PI 80837 and with MO/PSD-0259. F3 lines were planted in 2005 and individual plant selections made based on characteristics of the high-yielding parents. Seed from these selections, with less than 3% seed infection will be planted next season and selections for agronomic type and seed quality will be made from F4 lines.Twenty MG I, II, III and IV lines were screened for a final time in inoculated field plots. The objective is to find other
sources of resistance to Phomopsis seed decay and to purple seed stain. Five or six of these lines had very low (0 to 3 %) seed infection compared to susceptible lines and cultivars with 18 to 40 % seed infection. Vegetative compatibility of 100 Arkansas isolates of Phomopsis longicolla indicate that broad diversity occurrs among isolates of this seed pathogen. Compatibility groups were not related to genetic source, site, or year of collection of the isolates.This diversity suuggests that a mechanism for maintaining this diversity exists, and has important implications for adatpability and the use of resistance to manage Phomopsis seed decay.
Impacts
Genetic resistance to Phomopsis seed infection and to purple seed stain will be the most economical and enviromentally safe approach to controlling these major seed pathogens. The discovery of two new genes for resistance to Phomopsis in PI 360841,together with our previous research on three other genes, is a major step toward this goal. This research also indictes that other sources of genetic resistance are avaiable but need to be characterized. Resistance to Phomopsis seed infection could also be associated with improved field weathering
Publications
- Jackson, E.W., Fenn, P. and Chen, P. 2005. Inheritance of resistance to Phomopsis seed decay in soybean PI 80837 and MO/PSD-0259 (Pi 562694. Crop Science. 45:2400-2404.
- Smith, S.E., Fenn, P. and Correll, J.C. 2005. Vegetative compatibility reveals genetic diversity in the soybean seed pathogen Phomopsis longicolla in Arkansas. Phytopathology 95: S135.
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Progress 01/01/04 to 12/30/04
Outputs
41. Research has continued to characterize inheritance and molecular mapping of two genes that confer resistance to Phomopsis seed infection and decay, and one gene that confers resistance to Cercospora seed infection and purple seed stain. About 160 simple sequence repeat markers (SSR) from the soybean molecular map were used to screen parents and segregating F2 populations for polymorphisms. Bulk segregant analysis was used. Inheritance data for disease reaction and for segregation of SSR markers linked to the resistant phenotypes confirmed our previous conclusion that three, single dominant genes control these resistances. The susceptible parent in all crosses was `Agripro 350'. The gene that controls Phomopsis resistance from line MO/PSD-0259 was mapped to soybean molecular linkage group (MLG) B2. From PI 80837, the gene that confers resistance to Phomopsis infection was mapped to MLG F, whereas the gene conferring resistance to Cercospora infection and purple
seed stain mapped to MLG G. All three genes map to chromosomal locations that have been shown to contain clusters of resistance genes for other major diseases of soybean. Linked SSR markers may be useful for marker-assisted selection to help incorporate these genes in breeding programs. The strong resistance to Phomopsis seed decay in PI 360841 is being investigated in crosses to susceptible parents. Initial data suggest that resistance in PI 360841 is controlled by a single dominant gene. New crosses and F3 lines will be screened in 2005 to confirm inheritance and determine if resistance from this PI is different from that in MO/PSD-0259 and PI 80837. F2 plants from crosses of resistant parents and two high-yielding adapted cultivars were selected for the high-yielding phenotype, and lines will be screened in 2005 for Phomopsis and Cercospora resistances.
Impacts
42. Identifying and utilizing genetic resistance to seed-infecting fungi will be a reliable and cost-effective approach to manage seed infection and seed decay in soybean. Single gene inheritance of resistance is relatively easy to handle in breeding programs and molecular markers will enhance breeding efforts. These genes can be easily incorporated into elite high-yielding genotypes.
Publications
- Jackson, E.W., P. Fenn, P. Chen and P.K. Miller. 2004. Inheritance of resistance to Phomopsis seed decay in soybean PI 80837. Proc. Southern Soybean Disease Workers. 31st Ann. Mtg. St Louis, MO p.8.
- Jackson, E.W., P. Fenn, P. Chen and P.K. Miller. 2004. Inheritance of resistance to purple seed stain in soybean PI 80837. Proc. Southern Soybean Disease Workers.31st Ann. Mtg. St. Louis, MO p.9.
- Jackson, E.W., P. Fenn, P. Chen and C. Feng. 2004. Inheritance of resistance to Phomopsis seed decay and to purple seed stain in soybean PI 80837. p. 99. Abstracts of the VII World Soybean Research Conference. Foz do Iguassu, Brazil.
- Jackson, E.W. and P. Fenn. 2004. Development of screening assays to identify resistance to Phomopsis seed decay in soybean. p. 153. Abstracts of the VII World Soybean Research Conference. Foz do Iguassu, Brazil.
- Jackson, E.W., P. Fenn, S. Smith, P. Chen, C. Feng and P. K. Miller. 2004. Inheritance of resistance to Phomopsis seed decay in PI 80837 and MO/PSD-0259. Phytopathology 94: S45.
- Jackson, E.W., P. Fenn, P. Chen and C. Feng. 2004. Inheritance of resistance to Phomopsis and Cercospora seed infection in PI 80837 and MO/psd-0259 soybean and SSR mapping of resistance genes. p. 74. Program/Abstracts,10th Biennial Conference of the Cellular and Molecular Biology of the Soybean. Columbia, MO.
- Moreno, L., T. Ishibachi, P. Chen and P. Fenn. 2004. Soybean seed yield and quality under ultra-short season production systems. Discovery 5: 48-52.
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Progress 01/01/03 to 12/31/03
Outputs
A number of F1, F2 and F2:3 lines were screened for resistances to Phomopsis seed infection and to Cercospora infection (purple seed stain) in the field in 2003. Field plots were inoculated three times with conidial suspensions of Phomopsis longicolla during growth stages R5 to R7 and over-head irrigated. Seed were collected, surface disinfested and plated on acidified PDA to assay infection. Resistance to Phomopsis infection from PI 80837 and that in breeding line MOPSD-0259 was found to fit the 3:1 (R:S) model for control by single dominant genes. There was no evidence for maternal inheritance. F2:3 line data confirmed single dominant gene resistance for both sources of resistance. F2 data from a cross between the two sources of resistance fit a 15:1 (R:S) model indicating that each resistant parent carries a different gene for resistance. This was confirmed by F2:3 line data. Resistance to Cercospora seed infection in PI 80837 was also found to fit a 3:1 (R:S)
model indicating control by a single dominant gene. A linkage test showed that resistance in PI 80837 to Phomopsis seed infection and Cercospora infection are not linked. Work has begun to map these sources of resistance using SSR markers to develop marker-assisted selection. Both sources of resistance were crossed to two elite southern cultivars and two high-yielding breeding lines, and F2 populations will be screened in the field in 2004. Eighteen lines in maturity groups I to IV were field screened. Several of these have reported earlier to possibly have resistance to Phomopsis seed infection. A collection of P. longicolla isolates from resistant and susceptible germplasm showed diverse colony morphologies, cultural interactions indicating incompatibility, and possible differences in virulence to resistant and susceptible soybean genotypes.
Impacts
Identifying and utilizing genetic resistance to seed-infecting fungi will be a reliable and cost-effective means to control seed infection and seed decay in soybean. Simpleinheritance indicates that genetics markers should be easy to find, which will speed up any breeding program. Single dominant genes can be easily incorporated into elite, high-yielding genotypes.
Publications
- E.W. Jackson, P. Fenn and P. K. Miller. 2003. Identification and characterization of soybean germplasm with resistance to seed infection by Phomopsis longicolla and Cercospora kikuchii. Proc. 30th Ann. Mtg. Southern Soybean Disease Workers. Little Rock, AR. p. 12.
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Progress 01/01/02 to 12/31/02
Outputs
Field plots were established at two locations (Kibler and Clarkdale) to screen selected cultivars, plant introductions (PIs) and lines for resistance to Phomopsis seed infection and purple seed stain. In general those PIs and lines that showed good resistance in 2001 also showed good levels of resistance in the 2002 tests. Levels of seed infection in 2002 were greater than in 2001 because of the cooler temperatures and more evenly distributed rainfall in 2002. Crosses were made between several Phomopsis-resistant PIs and one line (PIs 417479, 80837, 360841, 82264 and MOPSD-0259) to susceptible parents (AP 350, PI 91113) to study inheritance of resistance. A resistant PI and the MOPSD-0259 line were crossed. Four F2 populations were planted under overhead irrigation, inoculated twice at the R5 to R6 growth stages, and the seed assayed by plating for Phomopsis spp. and Cercospora kikuchii. For the cross AP 350 x PI 80837, seed infection in the F2 plants suggests that
resistance to Phomopsis infection is controlled by one or a few genes. An F2 population from the cross of PI 80837 x MOPSD-0259, both resistant to Phomopsis seed decay, segregated in ratio of 15:1 (resistant:susceptible) plants which suggests that the parents carry different genes for resistance. Seed have been collected and F3 lines will be screened in 2003 to confirm these results. Backcrosses will also be made to confirm these results. Eighteen PIs and varieties in maturity groups I, II, and III which have been reported to have resistance to Phomopsis seed infection were screened in the field. Significant differences were found, but replicated tests will need to be made in 2003. Crosses between four resistant PIs and four elite cultivars and lines (two MG II and two MG IV) that yield will under Arkansas conditions, are being made. F2 populations from these crosses will be raised in 2003 and field screened. A survey of morning glory plants in soybean fields indicated that 100% of
the plants were infected by Phomopsis longicolla. This important weed host might contribute to survival of this pathogen and complicate attempts to control soybean seed infection.
Impacts
Identifying and utilizing genetic resistance to seed-infecting fungi will be a reliable and cost-effective means to control seed infection and seed decay in soybean. Control by one or a few genes indicates that incorporation of resistance into adapted, high-yielding lines and varieties should be straightforward and accomplished fairly rapidly. Sources of resistance in early maturity groups I, II and III will be important in development of early and ultra-early soybean planting systems for Arkansas.
Publications
- Jackson, E.W., Cordell, M. and Fenn, P. 2002. Weed hosts of Phomopsis longicolla in Arkansas soybean fields. Proc. Southern Soybean Disease Workers Annual Mtg. Orlando, FL. Feb 3rd. (Abstr.) p.12.
- Jackson, E.W., Cordell, M. and Fenn, P. 2002. Weed hosts of Phomopsis longicolla in Arkansas soybean fields. Phytopathology 92: S150.
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Progress 01/01/01 to 12/31/01
Outputs
Research continued to refine methods to screen for resistance to Phomopsis seed infection using seedlings and adult plants. Leaf samples from V2-3 seedlings were better than stem pieces as indicators of resistance to Phomopsis seed infection in cultivars and lines reported to have resistance to seed infection. Decreasing the physical size of leaf samples gave better separation of susceptible from resistant material as expected if resistance to latent infection is expressed in juvenile leaves. In adult plant screening, inoculum levels of 50,000 to 500,000 spores/ml gave no differences in percent seed infection. A resistant breeding line (MOPSD-0259) consistently had 3- to 4-fold less seed infection than did the moderately resistant cv. Williams 82 over this range of inoculum levels. Replicated field plots with either overhead or furrow irrigation determined which plant introductions (PIs), lines and cultivars showed resistance to Phomopsis seed infection under local
conditions in 2001. Plots were inoculated three times with Phomopsis spores (100,000 to 200,000 spores/ml) between R5 and R7 to supplement natural inoculum. Excellent seed infection occurred; with 50% to 75% seed infection in susceptible entries. Four PIs that were resistant in the seedling and adult plant tests in the greenhouse had 0% to 4% Phomopsis infection at both field locations. Two of these four had no purple seed stain which suggests that they have genes for resistance to both major seed pathogens. Several lines from Missouri also had good resistance to Phomopsis infection in the field plots. Several commercial cultivars also showed low levels of Phomopsis seed infection in field plots. Crosses were made between susceptible parents and several MG IV PIs that showed Phomopsis resistance to determine the mode of inheritance. Crosses among resistant PIs were done to determine if resistance from two sources can be combined. New crosses were planned and set up with cooperation of
our soybean breeder to examine the heritability of resistance from additional PIs and some putatively resistant cultivars we identified in variety tests during 1999 and 2000.
Impacts
Good agreement has been found between the seedling screening results, the data from adult plant screens for resistance and seed infection data from the field. Refinement of the seedling screening system will enable pathologists and breeders to quickly identify resistant germplasm and thus accelerate efforts to incorporate Phomopsis resistance into adapted cultivars. Phomopsis resistance will give a reliable and cost-effective means for control of seed infection and decay.
Publications
- Jackson, E.W. and Fenn, P. 2001. Development of screening assays for resistance to Phomopsis seed infection in soybeans. Proc. Southern Soybean Disease Workers Ann. Mtg. St. Louis, MO. (Abstract).
- Fenn, P. and Miller, P.K. 2001. Cultivar differences in seed and pod infection by Phomopsis spp. Proc. Southern Disease Workers Ann. Mgt. St. Louis, MO. (Abstract).
- Jackson, E.W., Fenn, P. and Cordell, M. 2001. Weed hosts of Phomopsis longicolla in Arkansas: A potential source of inoculum for Phomopsis seed infection in soybeans. Proc. Arkansas Crop Protection Assoc. 2001 Research Conference, Fayetteville, Ar. (Abstract).
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Progress 01/01/00 to 12/31/00
Outputs
Research was initiated to determine whether assessing the levels of latent Phomopsis infection in soybean seedlings could be used as a screening technique to determine resistance to Phomopsis seed infection. Using V2-V3 seedlings of two susceptible cultivars (Williams 82 and Pioneer 9482) and a resistant line (MO/PSD-0259), experiments were done to optimize inoculum concentration, dew period, and time of incubation before sampling. Leaf disks and stem pieces were taken from surface-disinfested leaves and stems and plated on acidified potato dextrose agar. Latent infection was measured by the incidence of leaf disks or stem pieces that yielded Phomopsis colonies. Plants also were grown to the R6 stage, inoculated with 100,000 conidia/ml, given a 72-hr dew period, returned to the greenhouse, and at R8 seed were harvested and bioassayed for incidence of seed infection. At 15,000 conidia/ml, 39 hr of dew and a 24 hr incubation period, Phomopsis was recovered significantly
more from leaf disks of seedling trifoliates of the two susceptible cultivars than from the resistant line. There were no differences in the incidence of latent infection of stem pieces or leaf disks from primary leaves between the susceptible cultivars and the resistant line. Seed infection in the greenhouse was significantly greater for the susceptible cultivars than for the resistant line. Twenty-seven cultivars, plant introductions and lines with known or suspected differences in susceptibility to Phomopsis seed infection were screened for latent infection of seedling trifoliates and for seed and pod infection. Several plant introductions and lines reported to be resistance showed low incidences of latent leaf infection and seed infection (PI 82264, PI 80837, PI 417479, PI 360841) Some showed low levels of pod infection. All 27 entries were screened in the field during 2000, but because of heat and drought no conclusive data were obtained.
Impacts
Progress to date indicates that the incidence of latent Phomopsis infection of first trifoliate leaves correlates with resistance to seed infection. With more refinement, a reliable screening technique might be developed to help identify new sources of resistance to Phomopsis seed infection and assist breeding programs.
Publications
- Jackson, E., Fenn, P., Miller, P., and K. Brown. 1999. Resistance to Phomopsis seed infection and decay in soybeans. Arkansas Crop Protection Association Research Conference. Abstract p.17.
- Jackson, E.W., Fenn, P., and Miller, P.K. 2000. Resistance to Phomopsis seed infection in soybeans. Phytopathology 90(6):S38.
- Jackson, E.W. 2000. Resistance to Phomopsis Seed Infection in Soybeans. M.S. Thesis, University of Arkansas Fayetteville, 69 pp.
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