More than 50 weed species infest drill-seeded rice in the U.S. and one of the most prevalent aquatic weeks is ducksalad (Heteranthera limosa). During the summer of 1988, a field experiment was conducted to identify rice accessions from the USDA/ARS rice germplasm collection for allelopathic effects to ducksalad. In this field experiment, 5,000 accessions were evaluated for allelopathic activity. Five to seven seeds of each rice accession were planted in hills about 75cm apart in two replications. Allelopathic activity was recorded as 1) radius of the area affected by allelochemical from the base of the rice plant and 2) percentage of weed control within the affected area. Ducksalad was rated at the panicle initiation stage of rice development. Of the 5,000 accessions that were evaluated, approximately 191 were identified as having evident allelopathic activity. The accessions that demonstrated allelopathic activity originated in 26 countries (Afghanistan, Argentina, Australia, Brazil, Columbia, Dominican Republic, France, India, Iran, Iraq, Israel, Italy, Japan, Malaysia, Mexico, Pakistan, Peru, Philippines, Portugal, Republic of Korea, People Republic of China, Soviet Union, Taiwan, Thailand, Turkey, and United States)

Dilday, R. H.

Nastasi, Paolo

Smith, Roy J., Jr.

English

UARK (University of Arkansas )

Journal of the Arkansas Academy of Science Volume 43 Article 7 1989 Allelopathic Observations in Rice (Oryza sativa L.) to Ducksalad (Heteranthera limosa) R. H. Dilday USDA/ARS Paolo Nastasi University of Arkansas, Fayetteville Roy J. Smith Jr. USDA/ARS Follow this and additional works at: https://scholarworks.uark.edu/jaas  Part of the Agronomy and Crop Sciences Commons, and the Botany Commons Recommended Citation Dilday, R. H.; Nastasi, Paolo; and Smith, Roy J. Jr. (1989) "Allelopathic Observations in Rice (Oryza sativa L.) to Ducksalad (Heteranthera limosa)," Journal of the Arkansas Academy of Science: Vol. 43 , Article 7. Available at: https://scholarworks.uark.edu/jaas/vol43/iss1/7 This article is available for use under the Creative Commons license: Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0). Users are able to read, download, copy, print, distribute, search, link to the full texts of these articles, or use them for any other lawful purpose, without asking prior permission from the publisher or the author. This Article is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Journal of the Arkansas Academy of Science by an authorized editor of ScholarWorks@UARK. For more information, please contact scholar@uark.edu. Proceedings Arkansas Academy of Science, Vol. 43, 1989 21ALLELOPATHIC OBSERVATIONS INRICE (ORYZA SATIVA L.) TODUCKSALAD(HETERANTHERA LIMOSA)R.H. DILDAY P. NASTASI R.J. SMITH, JR.USDA/ARS University of ArkansasStuttgart, AR 72160USDA/ARSStuttgart, AR 72160 Stuttgart, AR 72160ABSTRACTMore than 50 weed species infest drill-seeded rice in the U.S. and one of the most prevalent aquaticweeks is ducksalad (Heteranthera limosa). During the summer of 1988, a field experiment was con-ducted to identify rice accessions from the USDA/ARS rice germplasm collection for allelopathic effectsto ducksalad. In this field experiment, 5,000 accessions were evaluated for allelopathic activity. Five toseven seeds ofeach rice accession were planted inhills about 75cm apart in two replications. Allelopathicactivity was recorded as 1) radius of the area affected by allelochemical from the base of the rice plantand 2) percentage of weed control within the affected area. Ducksalad was rated at the panicle initiationstage of rice development. Of the 5,000 accessions that were evaluated, approximately 191 were iden-tified as having evident allelopathic activity. The accessions that demonstrated allelopathic activity originatedin 26 countries (Afghanistan, Argentina, Australia, Brazil, Columbia, Dominican Republic, France, India,Iran, Iraq, Israel, Italy, Japan, Malaysia, Mexico, Pakistan, Peru, Philippines, Portugal, Republic of Korea,People Republic of China, Soviet Union, Taiwan, Thailand, Turkey, and United States).INTRODUCTIONRice is one of the leading food crops of the world. In1985, the valueof rice production in the U.S. was over one billion dollars (Anonymous,1986). However, annual losses due to weeds in rice have been estimatedat about 17% of the potential production or one million metric tonsvalued at 205 million dollars (Chandler, 1981). More than 50 weedspecies infest direct-seeded rice in the U.S. (Barrett and Seaman, 1980;Smith et al., 1977). Ducksalad (Heteranthera limosa [Sw.]Willd.], isone of the most frequently reported aquatic weeds in rice (Chandler,1981; Smith et al., 1977). Effective weed control programs for riceinclude preventive, cultural, mechanical, chemical, and biological prac-tices (Smith et al., 1977; Smith and Moody, 1979). The most recentand perhaps least exploited control practice is the biological method.Inrecent years, one biological strategy of weed control, allelopathy,has received increased attention. In 1977 it was estimated that thedevelopment ofnew technology from allelopathics "would benefit U.S.agriculture by two percent of its totalproduction, or about twobilliondollars annually" (Anonymous, 1977).Allelopathy, the direct or indirect harmful effect of one plant onanother through the production of chemical compounds that escapeinto the environment occurs widely innatural plant communities (Rice,1974; Whittaker and Feeny, 1971). Allelopathy is postulated to be oneofthe major mechanisms by which weeds affect crop growth (Bell andKoeppe, 1972; Gressel and Holm, 1964; Rice, 1974). Inaddition to theexistence of allelopathy in weeds, several workers have reported thatcrops such as rye (Selecale cereals L.),barley (Hordeum vulgare L.),wheat (Triticum aestivum L.), tobacco (Nicotiana tabacum L.),sunflower (Helianthus annuus L.), and oats (Avena sativa L.) releasetoxic substances into the environment either through root exudationor from decaying plant material (McCalla and Haskins, 1964; Patrickand Koch, 1958; Patrick et al., 1963).Putnam and Duke (1974) postulated that "wildancestors" of existingcrops may have possessed high allelopathic activity and this characterwas reduced or lost as they were hybridized and selected for usefulcharacteristics. Fay and Duke (1977) evaluated 3,000 accessions ofAvenaspp. germplasm for production of scopoletin (6-methoxy-7-hydroxycoumarin), a chemical identified as the allelopathic agent in a wide rangeof wildplants, and found that four accessions exuded up to three timesas much as 'Garry', a standard oat cultivar.The objective ofthis study was toevaluate germplasm accessions fromthe rice portion of the USDA/ARS Small Grains Collection forallelopathic activity on ducksalad.MATERIALS ANDMETHODSA field experiment was conducted in 1988 to identify rice accessionswith allelopathic properties to ducksalad as part of the USDA/ARSrice germplasm evaluation project. Approximately 5,000 accessions wereseeded in hills ina 75 X 75 cm grid. Between five and seven seeds ofeach accession were planted inhills, with two replications from April28 toApril30, 1988. The seedlings emerged between April10 and April12, 1988. The test was irrigated on May 13 and June 1, 1988 to insureuniform seedling emergence. Apermanent flood was applied on June15, 1988. The test was conducted at the Rice Research and ExtensionCenter, Stuttgart, Arkansas, on a Crowley silt loam (fine montmoril-lonitic, thermic Typic Albaqualf) naturally infested with ducksalad.Allelopathic activity toducksalad was recorded from July 11 throughJuly 20, 1988, or at the panicle initiation stage, for most of the acces-sions. Two methods were used to record allelopathic activity: 1) theradial area (cm) from the base of the rice plant that had reduced orno weed growth due to allelochemicals, and 2) the percentage of weedcontrol within the affected area.Plant height (cm), days to maturity, plant type, panicle type, hullcover or pubescence, hull color, lemma color, awning, lodging, andgrain type were recorded for each accession. Plant height was measuredincm from ground level to the center of the mature panicle. Maturitywas determined by calculating the number of days from the date ofseedling emergence to the date that 507b of the panicles had emerged.Plant type, panicle type and lodging were recorded in the field. Graintype, hull cover, hull color, lemma color, and awning were recordedin the laboratory after threshing. The accessions were characterized ashaving extra long (>7.50 mm), long (6.61-7.50 mm), medium (5.51-6.60mm) or short grain (<5.5O mm).A total of82 kg N/ha as urea was applied to plots based on a three-way splitapplication. Thirty-one kg N/ha as urea were applied inJune14, 1988 when the seedlings were at the fourth true leaf stage of develop-ment. The remaining 41 kg N/ha were applied inequal increments onJuly 7, 1988 and 12 days later on July 26, 1988. The test was irrigatedon May 13 and June 1, 1988 to insure uniform seedling emergence. Apermanent flood was applied on June 15, 1988.RESULTS AND DISCUSSIONField observations from the replicated test identified 191 accessions,or about fourpercent of the 5,000 accessions withapparent allelopathic21Journal of the Arkansas Academy of Science, Vol. 43 [1989], Art. 7Published by Arkansas Academy of Science, 1989Proceedings Arkansas Academy of Science, Vol. 43, 198922Allelopathic Observations in Rice (Oryza sativa L.) to Ducksalad (Heteranthera limosa)activity to ducksalad. The accessions that demonstrated allelopathic ac-tivity originated in 26 countries (Afghanistan, Argentina, Australia,Brazil,Columbia, Dominican Republic, France, India, Iron, Iraq, Israel,Italy, Japan, Malaysia, Mexico, Pakistan, Peoples Republic of China,Peru, Philippines, Portugal, Republic ofKorea, Soviet Union, Taiwan,Thailand, Turkey and United States). The range inplant height amongthe 191 accessions that demonstrated apparent allelopathic activity toducksalad was from60 to 190 cm and the days to maturity, from seedlingemergence to 50% heading, ranged from 70 to 141 days. The acces-sions included long, medium and short grain types.Table 1. Origin, weed response, and plant characteristics of 10 germ-plasm accessions that demonstrated allelopathic activity to ducksalad(Heteranthera limosa).Radial Percent Plant Seed 3Germplasm Country of Moan Wood Height Grain1 Days to2 CoatIdentification Origin Activity Control (cm) Typo Maturity Color(iiun)India AC 1423 India 17.5 a* 85. 0 a 128 c M 115 b RedNSSI, 10/7.8 STP 8 U.S. 16.5 n 85.0 a 136 be I. 90 cd Lt.DrTono Ursa AJ'J Uoin. Hop. !<>.:. a ll.'i.O u 160 a 1. iV/ a l.i.. !U-Phil HCVR Philippines 15.0 a 90.0 a 160 a M 141 a Lt.ttrRed Khosha Cerma Afghanistan 15.0 a 85.0 a 143 h L 89 cd Lt.BrDondunl Kunluz Afghanistan 15.0 a 85.0 a 135 be L 104 bed Lt.BrTsai Yuan Chon Taiwan 15.0 a 90.0 a 137 be S 109 be Lt.BrMon Z Wuan China 15.0 a 82.5 a 127 c M 87 d Lt.BrIR 644 1 63 11 Philippines 15.0 a 85.0 a 71 e M 91 cd Lt.BrNATO/9209 Sol// U.S. 15.0 a 85.0 a 96 d M 90 cd Lt.BrAR0S/3/NR0SControl U.S. Cultivars 0.0 b 0.0 b1/ Grain type: S-short, M-medium and L ¦ long.2/ Days to maturity: From seedling emergence to 50Z of the panicles emerged3/ Seed coat color: Lt. Br.-Light Brown*Means within columns with the same letter are not significantly different atthe 0.05 level.There were 10 accessions (Table 1) that demonstrated a radius ofac-tivitygreater than 15 cm and weed control within the area of activitythat was greater than 80%. Other plant characteristics such as days tomaturity, plant height, grain type, and seed coat color for the 10 ac-cessions are also listed in Table 1.The IBPGR-IRRI Rice Advisory Committees report on "Descrip-tors for Rice Oryza sativa L." (Anonymous, 1980) defines differentplant characteristics in rice. The followingplant descriptions for the10 accessions are defined in the IBPGR-IRRI report. Tono Brea 439and NATO/9209 Sel//AROS/3/NROS had an intermediate plant type;whereas the other eight accessions possess an open plant type. Allofthe accessions had an intermediate panicle type. NATO/9209Sel//AROS/3/NROS has a glabrous (smooth) hull cover; whereas theother nine accessions had short hairs throughout the hull. DonduniKunluzhad a purple hull; India AC 1423 had a black hull;Phil MGVRhad a mottled, speckled, or piebald hull; and the other seven acces-sions had a straw (yellow) hull. Allof the 10 accessions had a strawcolored lemma. Tono Brea 439, Phil MGVR,Tsai Yuan Chon, andNATO/9209 Sel//AROS/3/NROS did not have awns; NSSL 10/78 STP8, Donduni Kunluz, Mon Z Wuan, and IR644 1 63 11 had short awnsand the seed were partly awned; whereas, India AC 1423 and RedKhosha Cerma had long awns and the seed were fully awned. IR644163 11and NATO/9209 Sel//AROS/3/NROS had moderately strongculm strength; Mon Z Wuan had a culm strength between moderateand intermediate; Tono Brea 439 had a culm strength between weakand very weak; and the remaining six accessions had a very weak culm.CONCLUSIONSApproximately four percent of the 5,000 rice accessions that wereevaluated for allelopathy to ducksalad demonstrated some allelopathicactivity. A four percent frequency rate suggests that about 600 acces-sions inthe rice collection may suppress ducksalad. The 191 accessionsthat demonstrated allelopathic activity also exhibited genetic diversityfor plant characteristics such as plant height, maturity, grain type, planttype, hull cover, hull color, and culm strength. Tests to isolate andidentify the allelochemicals that are responsible for the allelopathicactivity are presently being conducted.LITERATURE CITEDANONYMOUS. U.S. Dep. Agric. 1977. Report of the research plan-ning conference on the role of secondary compounds in plantinteractions (allelopathy). A Conf. sponsored by ARS-USDA,Mississippi State Univ., March 15-16, 1977. 124 pp.ANONYMOUS. 1980. Descriptors for Rice Oryza sativa L. IBPGR-IRRI Rice Advisory Committee, International Rice ResearchInstitute, p. 1-21.ANONYMOUS. U.S. Department of Agriculture. 1986. AgriculturalStatistics. Page 23. U.S. Gov. Printing Office, Washington, D.C.BELL, D.T. and D.E. KOEPPE. 1972. Noncompetitive effects ofgiantfoxtailon the growth of corn. Agron. J. 64:321-325.BARRETT, S.C.H. and D.E. SEAMAN. 1980. The weed flora ofCalifornia rice fields. Aquatic Bot. 9:351-376.CHANDLER, J.M. 1981. Estimated losses of crops to weeds. Pages95-109 in D. Pimentel (ed.), Handbook of Pest Management inAgriculture Vol. 1, CRC Press, Inc., Boca Raton, FL.FAY, P.K. and W.B. DUKE. 1977. An assessment of allelopathicpotential inAvena germplasm. Weed Sci. 25:224-228.GRESSEL, J.B. and L.D. HOLM.1964. Chemical inhibition ofcropgermination by weed seed and the nature of the inhibition byAbutilon theophrasti. Weed Res. 4:44-53.McCALLA,T.M.and F.A. HASKINS. 1964. Phytotoxic substancesfrom soil microorganisms and crop residues. Bacteriol. Rev.28:181-207.PATRICK, Z.A. and L.W. KOCH. 1958. Inhibition of respirationgermination and growth by substances arising during the decom-position of certain plant residues in the soil. Can. J. Bot.36:621-647.PATRICK, A.Q., T.A. TOUSSOUN, and A. SNYDER. 1963. Phy-totoxic substances inarable soils associated with decompositionof plant residues. Phytopathology 53:152-161.PUTNAM, A.R. and W.B. DUKE. 1974. Biological suppression ofweeds: Evidence for allelopathy in accessions ofcucumber. Science185:370-372.RICE, E.L. 1974. Allelopathy. Academic Press Inc., New York. 353 pp.SMITH, R.J. JR., W.T. FLINCHUM, and D.E. SEAMAN. 1977.Weed control inU.S. rice production. U.S. Dep. Agric. Handb.457. U.S. Gov. Printing Office, Washington, DC. 78 pp.SMITH, R.J. JR. and K. MOODY. 1979. Weed control practices inrice. pp. 458-462 in Vol. 2 Integrated Plant Protection forAgricultural Crops and Forest Trees, T. Kommedahl (ed.), Proc.of Symposia IX International Congress of Plant Protection,Washington, DC, USA. August 5-11, 1979.WHITTAKER,R.H. and P.P. FEENY. 1971. Allelochemics: chemicalinteractions between species. Science 171:757-770.22Journal of the Arkansas Academy of Science, Vol. 43 [1989], Art. 7https://scholarworks.uark.edu/jaas/vol43/iss1/7

Allelopathic Observations in Rice (Oryza sativa L.) to Ducksalad (Heteranthera limosa)

ScholarWorks@UARK

Journal of the Arkansas Academy of ScienceVolume 43 Article 71989Allelopathic Observations in Rice (Oryza sativa L.)to Ducksalad (Heteranthera limosa)R. H. DildayUSDA/ARSPaolo NastasiUniversity of Arkansas, FayettevilleRoy J. Smith Jr.USDA/ARSFollow this and additional works at: http://scholarworks.uark.edu/jaasPart of the Agronomy and Crop Sciences Commons, and the Botany CommonsThis article is available for use under the Creative Commons license: Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0). Users are able toread, download, copy, print, distribute, search, link to the full texts of these articles, or use them for any other lawful purpose, without asking priorpermission from the publisher or the author.This Article is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Journal of the Arkansas Academyof Science by an authorized editor of ScholarWorks@UARK. For more information, please contact scholar@uark.edu, ccmiddle@uark.edu.Recommended CitationDilday, R. H.; Nastasi, Paolo; and Smith, Roy J. Jr. (1989) "Allelopathic Observations in Rice (Oryza sativa L.) to Ducksalad(Heteranthera limosa)," Journal of the Arkansas Academy of Science: Vol. 43 , Article 7.Available at: http://scholarworks.uark.edu/jaas/vol43/iss1/7Proceedings Arkansas Academy of Science, Vol. 43, 1989 21ALLELOPATHIC OBSERVATIONS INRICE (ORYZA SATIVA L.) TODUCKSALAD(HETERANTHERA LIMOSA)R.H. DILDAY P. NASTASI R.J. SMITH, JR.USDA/ARS University of ArkansasStuttgart, AR 72160USDA/ARSStuttgart, AR 72160 Stuttgart, AR 72160ABSTRACTMore than 50 weed species infest drill-seeded rice in the U.S. and one of the most prevalent aquaticweeks is ducksalad (Heteranthera limosa). During the summer of 1988, a field experiment was con-ducted to identify rice accessions from the USDA/ARS rice germplasm collection for allelopathic effectsto ducksalad. In this field experiment, 5,000 accessions were evaluated for allelopathic activity. Five toseven seeds ofeach rice accession were planted inhills about 75cm apart in two replications. Allelopathicactivity was recorded as 1) radius of the area affected by allelochemical from the base of the rice plantand 2) percentage of weed control within the affected area. Ducksalad was rated at the panicle initiationstage of rice development. Of the 5,000 accessions that were evaluated, approximately 191 were iden-tified as having evident allelopathic activity. The accessions that demonstrated allelopathic activity originatedin 26 countries (Afghanistan, Argentina, Australia, Brazil, Columbia, Dominican Republic, France, India,Iran, Iraq, Israel, Italy, Japan, Malaysia, Mexico, Pakistan, Peru, Philippines, Portugal, Republic of Korea,People Republic of China, Soviet Union, Taiwan, Thailand, Turkey, and United States).INTRODUCTIONRice is one of the leading food crops of the world. In1985, the valueof rice production in the U.S. was over one billion dollars (Anonymous,1986). However, annual losses due to weeds in rice have been estimatedat about 17% of the potential production or one million metric tonsvalued at 205 million dollars (Chandler, 1981). More than 50 weedspecies infest direct-seeded rice in the U.S. (Barrett and Seaman, 1980;Smith et al., 1977). Ducksalad (Heteranthera limosa [Sw.]Willd.], isone of the most frequently reported aquatic weeds in rice (Chandler,1981; Smith et al., 1977). Effective weed control programs for riceinclude preventive, cultural, mechanical, chemical, and biological prac-tices (Smith et al., 1977; Smith and Moody, 1979). The most recentand perhaps least exploited control practice is the biological method.Inrecent years, one biological strategy of weed control, allelopathy,has received increased attention. In 1977 it was estimated that thedevelopment ofnew technology from allelopathics "would benefit U.S.agriculture by two percent of its totalproduction, or about twobilliondollars annually" (Anonymous, 1977).Allelopathy, the direct or indirect harmful effect of one plant onanother through the production of chemical compounds that escapeinto the environment occurs widely innatural plant communities (Rice,1974; Whittaker and Feeny, 1971). Allelopathy is postulated to be oneofthe major mechanisms by which weeds affect crop growth (Bell andKoeppe, 1972; Gressel and Holm, 1964; Rice, 1974). Inaddition to theexistence of allelopathy in weeds, several workers have reported thatcrops such as rye (Selecale cereals L.),barley (Hordeum vulgare L.),wheat (Triticum aestivum L.), tobacco (Nicotiana tabacum L.),sunflower (Helianthus annuus L.), and oats (Avena sativa L.) releasetoxic substances into the environment either through root exudationor from decaying plant material (McCalla and Haskins, 1964; Patrickand Koch, 1958; Patrick et al., 1963).Putnam and Duke (1974) postulated that "wildancestors" of existingcrops may have possessed high allelopathic activity and this characterwas reduced or lost as they were hybridized and selected for usefulcharacteristics. Fay and Duke (1977) evaluated 3,000 accessions ofAvenaspp. germplasm for production of scopoletin (6-methoxy-7-hydroxycoumarin), a chemical identified as the allelopathic agent in a wide rangeof wildplants, and found that four accessions exuded up to three timesas much as 'Garry', a standard oat cultivar.The objective ofthis study was toevaluate germplasm accessions fromthe rice portion of the USDA/ARS Small Grains Collection forallelopathic activity on ducksalad.MATERIALS ANDMETHODSA field experiment was conducted in 1988 to identify rice accessionswith allelopathic properties to ducksalad as part of the USDA/ARSrice germplasm evaluation project. Approximately 5,000 accessions wereseeded in hills ina 75 X 75 cm grid. Between five and seven seeds ofeach accession were planted inhills, with two replications from April28 toApril30, 1988. The seedlings emerged between April10 and April12, 1988. The test was irrigated on May 13 and June 1, 1988 to insureuniform seedling emergence. Apermanent flood was applied on June15, 1988. The test was conducted at the Rice Research and ExtensionCenter, Stuttgart, Arkansas, on a Crowley silt loam (fine montmoril-lonitic, thermic Typic Albaqualf) naturally infested with ducksalad.Allelopathic activity toducksalad was recorded from July 11 throughJuly 20, 1988, or at the panicle initiation stage, for most of the acces-sions. Two methods were used to record allelopathic activity: 1) theradial area (cm) from the base of the rice plant that had reduced orno weed growth due to allelochemicals, and 2) the percentage of weedcontrol within the affected area.Plant height (cm), days to maturity, plant type, panicle type, hullcover or pubescence, hull color, lemma color, awning, lodging, andgrain type were recorded for each accession. Plant height was measuredincm from ground level to the center of the mature panicle. Maturitywas determined by calculating the number of days from the date ofseedling emergence to the date that 507b of the panicles had emerged.Plant type, panicle type and lodging were recorded in the field. Graintype, hull cover, hull color, lemma color, and awning were recordedin the laboratory after threshing. The accessions were characterized ashaving extra long (>7.50 mm), long (6.61-7.50 mm), medium (5.51-6.60mm) or short grain (<5.5O mm).A total of82 kg N/ha as urea was applied to plots based on a three-way splitapplication. Thirty-one kg N/ha as urea were applied inJune14, 1988 when the seedlings were at the fourth true leaf stage of develop-ment. The remaining 41 kg N/ha were applied inequal increments onJuly 7, 1988 and 12 days later on July 26, 1988. The test was irrigatedon May 13 and June 1, 1988 to insure uniform seedling emergence. Apermanent flood was applied on June 15, 1988.RESULTS AND DISCUSSIONField observations from the replicated test identified 191 accessions,or about fourpercent of the 5,000 accessions withapparent allelopathic21Journal of the Arkansas Academy of Science, Vol. 43 [1989], Art. 7Published by Arkansas Academy of Science, 1989Proceedings Arkansas Academy of Science, Vol. 43, 198922Allelopathic Observations in Rice (Oryza sativa L.) to Ducksalad (Heteranthera limosa)activity to ducksalad. The accessions that demonstrated allelopathic ac-tivity originated in 26 countries (Afghanistan, Argentina, Australia,Brazil,Columbia, Dominican Republic, France, India, Iron, Iraq, Israel,Italy, Japan, Malaysia, Mexico, Pakistan, Peoples Republic of China,Peru, Philippines, Portugal, Republic ofKorea, Soviet Union, Taiwan,Thailand, Turkey and United States). The range inplant height amongthe 191 accessions that demonstrated apparent allelopathic activity toducksalad was from60 to 190 cm and the days to maturity, from seedlingemergence to 50% heading, ranged from 70 to 141 days. The acces-sions included long, medium and short grain types.Table 1. Origin, weed response, and plant characteristics of 10 germ-plasm accessions that demonstrated allelopathic activity to ducksalad(Heteranthera limosa).Radial Percent Plant Seed 3Germplasm Country of Moan Wood Height Grain1 Days to2 CoatIdentification Origin Activity Control (cm) Typo Maturity Color(iiun)India AC 1423 India 17.5 a* 85. 0 a 128 c M 115 b RedNSSI, 10/7.8 STP 8 U.S. 16.5 n 85.0 a 136 be I. 90 cd Lt.DrTono Ursa AJ'J Uoin. Hop. !<>.:. a ll.'i.O u 160 a 1. iV/ a l.i.. !U-Phil HCVR Philippines 15.0 a 90.0 a 160 a M 141 a Lt.ttrRed Khosha Cerma Afghanistan 15.0 a 85.0 a 143 h L 89 cd Lt.BrDondunl Kunluz Afghanistan 15.0 a 85.0 a 135 be L 104 bed Lt.BrTsai Yuan Chon Taiwan 15.0 a 90.0 a 137 be S 109 be Lt.BrMon Z Wuan China 15.0 a 82.5 a 127 c M 87 d Lt.BrIR 644 1 63 11 Philippines 15.0 a 85.0 a 71 e M 91 cd Lt.BrNATO/9209 Sol// U.S. 15.0 a 85.0 a 96 d M 90 cd Lt.BrAR0S/3/NR0SControl U.S. Cultivars 0.0 b 0.0 b1/ Grain type: S-short, M-medium and L ¦ long.2/ Days to maturity: From seedling emergence to 50Z of the panicles emerged3/ Seed coat color: Lt. Br.-Light Brown*Means within columns with the same letter are not significantly different atthe 0.05 level.There were 10 accessions (Table 1) that demonstrated a radius ofac-tivitygreater than 15 cm and weed control within the area of activitythat was greater than 80%. Other plant characteristics such as days tomaturity, plant height, grain type, and seed coat color for the 10 ac-cessions are also listed in Table 1.The IBPGR-IRRI Rice Advisory Committees report on "Descrip-tors for Rice Oryza sativa L." (Anonymous, 1980) defines differentplant characteristics in rice. The followingplant descriptions for the10 accessions are defined in the IBPGR-IRRI report. Tono Brea 439and NATO/9209 Sel//AROS/3/NROS had an intermediate plant type;whereas the other eight accessions possess an open plant type. Allofthe accessions had an intermediate panicle type. NATO/9209Sel//AROS/3/NROS has a glabrous (smooth) hull cover; whereas theother nine accessions had short hairs throughout the hull. DonduniKunluzhad a purple hull; India AC 1423 had a black hull;Phil MGVRhad a mottled, speckled, or piebald hull; and the other seven acces-sions had a straw (yellow) hull. Allof the 10 accessions had a strawcolored lemma. Tono Brea 439, Phil MGVR,Tsai Yuan Chon, andNATO/9209 Sel//AROS/3/NROS did not have awns; NSSL 10/78 STP8, Donduni Kunluz, Mon Z Wuan, and IR644 1 63 11 had short awnsand the seed were partly awned; whereas, India AC 1423 and RedKhosha Cerma had long awns and the seed were fully awned. IR644163 11and NATO/9209 Sel//AROS/3/NROS had moderately strongculm strength; Mon Z Wuan had a culm strength between moderateand intermediate; Tono Brea 439 had a culm strength between weakand very weak; and the remaining six accessions had a very weak culm.CONCLUSIONSApproximately four percent of the 5,000 rice accessions that wereevaluated for allelopathy to ducksalad demonstrated some allelopathicactivity. A four percent frequency rate suggests that about 600 acces-sions inthe rice collection may suppress ducksalad. The 191 accessionsthat demonstrated allelopathic activity also exhibited genetic diversityfor plant characteristics such as plant height, maturity, grain type, planttype, hull cover, hull color, and culm strength. Tests to isolate andidentify the allelochemicals that are responsible for the allelopathicactivity are presently being conducted.LITERATURE CITEDANONYMOUS. U.S. Dep. Agric. 1977. Report of the research plan-ning conference on the role of secondary compounds in plantinteractions (allelopathy). A Conf. sponsored by ARS-USDA,Mississippi State Univ., March 15-16, 1977. 124 pp.ANONYMOUS. 1980. Descriptors for Rice Oryza sativa L. IBPGR-IRRI Rice Advisory Committee, International Rice ResearchInstitute, p. 1-21.ANONYMOUS. U.S. Department of Agriculture. 1986. AgriculturalStatistics. Page 23. U.S. Gov. Printing Office, Washington, D.C.BELL, D.T. and D.E. KOEPPE. 1972. Noncompetitive effects ofgiantfoxtailon the growth of corn. Agron. J. 64:321-325.BARRETT, S.C.H. and D.E. SEAMAN. 1980. The weed flora ofCalifornia rice fields. Aquatic Bot. 9:351-376.CHANDLER, J.M. 1981. Estimated losses of crops to weeds. Pages95-109 in D. Pimentel (ed.), Handbook of Pest Management inAgriculture Vol. 1, CRC Press, Inc., Boca Raton, FL.FAY, P.K. and W.B. DUKE. 1977. An assessment of allelopathicpotential inAvena germplasm. Weed Sci. 25:224-228.GRESSEL, J.B. and L.D. HOLM.1964. Chemical inhibition ofcropgermination by weed seed and the nature of the inhibition byAbutilon theophrasti. Weed Res. 4:44-53.McCALLA,T.M.and F.A. HASKINS. 1964. Phytotoxic substancesfrom soil microorganisms and crop residues. Bacteriol. Rev.28:181-207.PATRICK, Z.A. and L.W. KOCH. 1958. Inhibition of respirationgermination and growth by substances arising during the decom-position of certain plant residues in the soil. Can. J. Bot.36:621-647.PATRICK, A.Q., T.A. TOUSSOUN, and A. SNYDER. 1963. Phy-totoxic substances inarable soils associated with decompositionof plant residues. Phytopathology 53:152-161.PUTNAM, A.R. and W.B. DUKE. 1974. Biological suppression ofweeds: Evidence for allelopathy in accessions ofcucumber. Science185:370-372.RICE, E.L. 1974. Allelopathy. Academic Press Inc., New York. 353 pp.SMITH, R.J. JR., W.T. FLINCHUM, and D.E. SEAMAN. 1977.Weed control inU.S. rice production. U.S. Dep. Agric. Handb.457. U.S. Gov. Printing Office, Washington, DC. 78 pp.SMITH, R.J. JR. and K. MOODY. 1979. Weed control practices inrice. pp. 458-462 in Vol. 2 Integrated Plant Protection forAgricultural Crops and Forest Trees, T. Kommedahl (ed.), Proc.of Symposia IX International Congress of Plant Protection,Washington, DC, USA. August 5-11, 1979.WHITTAKER,R.H. and P.P. FEENY. 1971. Allelochemics: chemicalinteractions between species. Science 171:757-770.22Journal of the Arkansas Academy of Science, Vol. 43 [1989], Art. 7http://scholarworks.uark.edu/jaas/vol43/iss1/7

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Allelopathic Observations in Rice (Oryza sativa L.) to Ducksalad (Heteranthera limosa)

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