Which soils are comfortable for oilseed rape seeds (Brassica napus) to survive?

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1 Plnt Soil Environ. Which soils re comfortle for oilseed rpe seeds (Brssic npus) to survive? S. Gruer, E.A. Weer, W. Clupein Institute of Crop Science, Agronomy (340), University of Hohenheim, Stuttgrt, Germny ABSTRACT The study should revel the effects of soil texture nd of seed chrcteristics of oilseed rpe (Brssic npus L.) on seed survivl in the soil y uril experiment. Seeds of 58 conventionl nd new trit ccessions (geneticlly modified nd/or with ltered seed ingredients) were uried for six months in sndy lom (SL), cly (C) or silty cly lom (SICL) in the sesons 2008/2009 nd 2009/2010 in Germny. Between 84 93% (2008/2009) nd 64 87% (2009/2010) of the conventionl seeds survived in the soil, nd so did 41 67% nd 8 44% of the new trit seeds. Significntly more seeds were found in C nd SICL compred to SL. Seed survivl lso significntly depended on the genotype, with high nd low seed survivl in oth conventionl nd new trit ccessions. Seed survivl rtes re proly linked with moisture nd oxygen provided y different soils. As soils with good wter storge conditions seem to hve higher proility for oilseed rpe seeds from hrvest losses to survive, other mesures such s growing low dormncy vrieties nd proper soil tillge re especilly relevnt to void volunteers on these soils. Keywords: dormncy; GMO; snd; persistence; soil texture Oilseed rpe (cnol; Brssic npus L.; OSR) is mjor oil crop in temperte regions of Europe. Huge seed losses during mechnicl hrvest of on verge 4000 seeds/m 2, corresponding to 100-fold of the regulr sowing density, respectively, dropping onto the soil (Weer et l. 2009), cn result in lrge nd long-lsting soil seed nks. The seed survivl of OSR in the soil is minly cused y secondry dormncy tht seeds cquire when they get uried y soil tillge under specific mient conditions, such s wter stress nd drkness (Pekrun et l. 1997, Weer et l. 2010). The soil seednk stnds for long-time source for volunteers with weedy effects in ll crops. Furthermore, prticulr volunteers cn spoil the qulity of the hrvest of ny following OSR in the sme re y seed dmixtures. This issue cn pply to geneticlly modified OSR, which, however, is not n option t the moment in Europe. Currently, the issue of volunteers is rther relted to seed ingredients, for instnce the pttern of ftty cids, which cn e spoiled if seeds from nother (volunteer) vriety re mixed with the grown crop. Another new dete out OSR volunteers ws rised in the Europen pulic long with commercil cultivtion of hericide tolernt vrieties from conventionl reeding (Clerfield system), which re tolernt to cetolctte synthse inhiitors. Thus, OSR volunteers remin still n issue of reserch, nd mesures for their control should e further developed. It is well known tht the size of the soil seed nk depends on the mode nd time of post-hrvest tillge (Pekrun et l. 1998, Gruer et l. 2010), nd on the genotype (Momoh et l. 2002, Gruer et l. 2009). Both fctors cn theoreticlly e controlled y pproprite mngement prctice. Externl fctors, however, such s temperture or soil moisture, which re crucil fctors for dormncy induction, cnnot e influenced nd result from interction of current wether conditions with soil texture. A regression nlysis from survey of frmers fields in Germny reveled cropping frequency nd region (soil/climte) s most relevnt fctors determining the numers of OSR volunteers (Gruer et l. 2012). A more specific definition of the soils tht offer higher risk for volunteers would help frmers to etter pln their gronomic mesures eforehnd. There ws no field tril for OSR until now where different 280

2 Plnt Soil Environ. Vol. 60, 2014, No. 6: soils were tested for seed survivl under the sme environmentl conditions which exclusively llows determining the effect of soil. The study should give evidence (i) whether the size of the soil seed nk of OSR vries depending on soil texture; (ii) whether seed survivl depends on seed chrcteristics; (iii) which soil chrcteristics could e responsile for differences in seed survivl. The seed survivl ws tested in uril experiment. MATERIAL AND METHODS The experiment took plce t two fields (field 1, field 2) t the reserch sttion Ihinger Hof of the University of Hohenheim/Germny (48 44'N, 8 56'E, 478 m.s.l., Ø 8.1 C, Ø 693 mm) during the sesons 2008/2009 nd 2009/2010. Three different soils were filled in excvted holes ( m/hole) in the ground t oth fields in depth of 0 20 cm. The soils hd contct to the in situ soil (silty cly lom) under the filled soil mteril, nd were isolted from the nturl mient soil nd mong ech other y wooden plnks to void lterl flow of soil mteril. The soils for seed uril (sndy lom, SL; cly, C; silty cly lom, SICL) were otined from three frms in Southern Germny, one of them the originl soil from the experimentl site (field 1) Ihinger Hof, nd differed in soil prmeters such s texture, wter content nd nitrogen content (Tle 1). The experimentl design for field 1 ws splitplot design with three replictes (locks), where the three soils were used s min plots, nd the OSR ccessions s su-plots. In field 2, the min plots (soils) were rrnged in Ltin squre design, nd su-plots (seed smples from different OSR ccessions) were completely rndomised in ech min plot. Soils were rought to the experimentl re fter dry storge, crushed in situ y hnd rke nd slightly re-compcted. The soils remined in situ during the sesons 2008/2009 nd 2009/2010. Weeds were removed y hnd. Seed smples from conventionl OSR were derived from officil Germn field trils (hrvested 2008 nd 2009) nd were uried in field 1. Seed smples from ccessions with ltered seed ingredients ( new trit ccessions ) were otined from reeders nd were derived from hrvest 2008; they were uried in field 2, together with the stndrd vrieties Smrt nd Express (Tle 2). Seeds were plced in polyester gs (10 10 cm) with mesh width of < 0.5 mm in numer of 500 seeds per tretment replicte. All gs were uried in depth of 10 cm nd protected y mesh wire from predtion y irds nd mmmls. Only seeds which fell dormnt could survive under these conditions ecuse germinted seeds were not le to emerge nd perished in the gs. To generte dry conditions which induce dormncy, the uril res were protected from precipittion four weeks efore nd three weeks fter uril, nmely from 6 th August th Septemer 2008, nd 16 th July 3 rd Septemer 2009, respectively. In field 1, the experimentl re of 6 m 2 per replicte ws kept dry under moile rin shelters mde of wooden slts nd plstic foil. The rin shelters were used for the conventionl ccessions. The new trit ccessions were uried in field 2 in n open-ir greenhouse to comply with the regultions for GMOs. The outer structure of the greenhouse ws solid frme comined with wire mesh, which could e covered or uncovered y plstic foil. After six months uril, seeds of oth trils were exhumed t the eginning of the growing seson in Mrch 2009, or 2010, respectively. Seeds were counted nd germinted t 20 C under light nd following tretment with lternting light nd temperture conditions ccording to Weer et l. (2010). The seeds which germinted during this two-phse germintion test were clssified s survivors with full viility. The sttisticl evlution ws performed y the procedure Glimmix with help of the sttisticl progrmme SAS 9.3 (SAS Institute Inc. Cry, Tle 1. Properties of three soils used for uril experiment of oilseed rpe seeds t Ihinger Hof/Germny Soil texture Minerl prticles (%) C Soil moisture (weight %) 1) t Minerl N 2) snd silt cly (% DM) (kg/h) Bulk density 2) (g/cm 3 ) SICL /8 11/ C /17 16/ SL /3 5/ SICL silty cly lom; C cly; SL sndy lom (USDA 2013). 1) efore uril in ech yer; moisture: field 1/field 2; 2) efore urying C t totl cron; DM dry mtter ph 2) 281

3 Plnt Soil Environ. Tle 2. Winter oilseed rpe (Brssic npus L.) ccessions used for seed uril experiments 2008/2009 nd 2009/2010 t the experimentl sttion Ihinger Hof/Germny 2008/ /2010 Field 1: conventionl Alkido, Argon, Bldur, Billy, Cnti, Cindi, Cooper, Elektr, Expert, Express, Fngio, Fvorit, Hycolor, Ldog, Lilin, Lioness, Lorenz, Nemx, PR4631, Smrt, Turus, Tenno, Trnt, Zeppelin Adrin, Bldur, Cindi, Cooper, Elektr, Express, Fngio, Fvorit, Hmmer, Komndo, Ldog, Lorenz, Nemx, PR46W15, PR46W31, Petrol, Smrt, Turus, Vision, Zeppelin Field 2: new trits Stndrds nd isogenic lines: Drkkr 1), Lisor 2), Smrt, Express GM with ltered ingredients: RedSin (Reduced Sinpin), Resver (with Resvertrol) Conventionl with ltered ingredients: Thick 3), Thin, Holli 1 4), Holli 2, Yellow 1 3), Yellow 2, Yellow 3 5), Blck 3,5) 1) isogenic to RedSin; 2) isogenic to Resver; 3) Blck, Thick high seed fire; Yellow low seed fire (Gruer et l. 2012); 4) High Oleic, Low Linoleic; 5) only in 2009/2010 USA). For the evlution of seed uril, dt were processed using the logit trnsformtion. The model for the Glimmix procedure ws: survived seeds/totl seeds = suplot replicte (soil) + + soil + ccession + soil ccession (field 1) survived seeds/totl seeds = column replicte (soil) + + soil + ccession + soil ccession (field 2) Where: residuls (oth fields), nd suplot replicte (field 1) or column replicte (field 2), respectively, were considered s rndom. RESULTS AND DISCUSSION All remining, unerthed seeds ppered intct nd hd germinility of > 99% (dt not shown). Soil seed survivl rnged from 84 93% (2008/2009) nd 64 87% (2009/2010) for the conventionl ccessions, nd 41 67% nd 8 44% for the new trit ccessions (Figure 1). The survivl rte ws lower in the second yer, which is proly result of seed geing for the new trit ccessions (seeds derived from hrvest 2008). Soil texture nd ccession most significntly ffected seed survivl (Tle 3). Interctions of soil ccession were only found for conventionl ccessions in the first yer: SL resulted in higher discrimintion of the survivl rtes (dt not shown). Significntly lower survivl with pproximtely 10 80% less seeds surviving occurred in SL in oth groups of ccessions (Figure 1). For the conventionl ccessions, there ws genotypic vrition in seed survivl similr to the study of Gruer et l. (2004). Accessions with low fire content seemed to hve survived to lesser extent thn ccessions with high fire content, though moleculr-genetic studies did not show link etween fire content nd seed dormncy s pre-condition for seed survivl (Schtzki et l. 2013). The vrition mong the new trit ccessions (Figure 2) cn e lso well explined y the known genotypic vrition nd disposition to dormncy tht rnged etween 1% (Yellow 1) nd 59% (Thick; dt not shown) nd tht significntly correlted with seed survivl (Weer et l. 2011). Moisture, temperture, nutrients nd noxi cn e considered relevnt soil chrcteristics involved in induction of nd relese from dormncy. Generlly, under soil wter potentil nd temperture djusted to the sme level seed survivl seems similr in different soil types (Long et l. 2009). The results from Lutmn et l. (2003) correspond to ours, with higher seed survivl of OSR in silty cly thn in sndy lom; other results, however, Seed survivl SICL 2008/ / / /2010 Conventionl conventionl New new trits Figure 1. Survivl (%) of oilseed rpe seeds from conventionl nd new trit ccessions fter six months uril in silty cly lom (SICL), cly (C) nd sndy lom (SL) t Ihinger Hof, Germny, in two sesons. Vlues with the sme letters re not significntly different t P < 0.05; comprisons only within yer genotype C SL c 282

4 Plnt Soil Environ. Vol. 60, 2014, No. 6: Tle 3. Vrinces for survivl of oilseed rpe seeds from conventionl nd new trit-ccessions, fter six months uril in different soils in two sesons t Ihinger Hof/Germny 2008/2009 conventionl soil Effect ccession soil ccession df F-vlue P > F-vlue < < /2010 conventionl df F-vlue P > F-vlue < < /2009 new trits df F-vlue P > F-vlue < /2010 new trits df F-vlue P > F-vlue < < seem different (Pekrun et l. 1998). These differences cn hve een cused y the descried vrition in rinfll mong the experimentl sites of Pekrun et l. (1998). High soil wter tension is reson for low germintion of OSR (Willims nd Shykewich 1971) nd one of the pre-conditions for induction of seed dormncy (Pekrun et l. 1997, Weer et l. 2010). High soil wter tension is determined y (i) wter storge cpcity of the soil (depending on the soil texture), nd (ii) y precipittion. The wter contents of the three soils in our experiment ws ctully different t the Reltive seed survivl (%) Drkkr RedSin Lisor Resver Holli 1 Holli 2 Thick Thin Blck Yellow 1 Yellow 2 Yellow 3 time of seed uril (Tle 1), ut ll soils provided similr dry conditions eyond the permnent wilting point (AG Boden 2005). All following rinfll ws the sme for oth res nd soils, thus the results could only refer to the differences in soil. Annul ryegrss (Lolium rigidum) seeds from pot experiment hd greter numer of vile nd primrily dormnt seeds surviving in sndy lom compred to cly soil (Nrwl et l. 2008), ut this grss species hd generlly short survivl time, nd there ws no further induction of dormncy. In contrst, OSR seeds survive 10 yers nd more (Lutmn et l. 2003, D Hertefeldt et l. 2008), nd primry dormncy is usully zero or low in mture seeds (Gruer et l. 2004). Thus ll surviving OSR seeds in the current study must hve fllen dormnt during seed uril. Consequently, if cly soils tend to provide conditions for non-dormnt seeds to perish (Nrwl et l. 2008), seeds with long-term dormncy or dormncy induction such s OSR could well survive. Hypoxi is nother fctor which cn induce dormncy (Benvenuti nd Mcchi 1995, Pekrun et l. 1997, Momoh et l. 2002). Sndy soils with greter pore volume nd gs exchnge fcilitted emergence of Dtur strmonium, wheres emergence ws inhiited y cly soils (Benvenuti 2003). Also soil compction which might e stronger in cly soils cn impede germintion of weed seeds, t lest prtly due to hypoxi (Prej nd Stniforth 1985) nd to soil moisture (Terpstr 1995). For OSR, we hypothesize the following scenrio: phse 1 is dormncy induction within the first weeks fter seed uril while the seeds re under dry conditions (Pekrun et l. 1998, Lutmn et l. 2003, Gruer et l. 2010). More seeds fll dormnt under dry conditions, in interction with their genotypic disposition. In phse 2, t exposure of the res to Express Smrt Figure 2. Reltive seed survivl rtes (= devition from vriety men cross two sesons nd three soils) of new trit oilseed rpe ccessions nd stndrds, uried for six months t Ihinger Hof/ Germny; mens of two sesons nd three soils 283

5 Plnt Soil Environ. nturl precipittion, higher relese from dormncy nd (ftl) germintion of rpeseeds uried in sndy soils occurred due to higher gs exchnge rtes, nd mye lso ecuse of higher temperture fluctution due to the low het cpcity of ir. Fluctutions in temperture re n effective wy to rek dormncy in OSR (Weer et l. 2010). A uril experiment with seeds unerthed t weekly intervls could give further evidence out the temporl progress of dormncy development nd dormncy reking in contrsting soils. Agronomic mesures such s the choice of low-dormncy vriety nd suitle tillge opertions seem to e prticulrly importnt in fields with hevier soils. Acknowledgements We thnk Kirstin Frick nd the collegues from Ihinger Hof for their contriution to the study. REFERENCES AG Boden (2005): Soil Guide. Bundesnstlt für Geowissenschften und Rohstoffe und Niedersächsisches Lndesmt für Bodenforschung, Hnnover. Benvenuti S. (2003): Soil texture involvement in germintion nd emergence of uried weed seeds. Agronomy Journl, 95: Benvenuti S., Mcchi M. (1995): Effect of hypoxi on uried weed seed germintion. Weed Reserch, 35: D Hertefeldt T., Jørgensen R.B., Pettersson L.B. (2008): Longterm persistence of GM oilseed rpe in the seednk. Biology Letters, 4: Gruer S., Pekrun C., Clupein W. (2004): Seed persistence of oilseed rpe (Brssic npus): Vrition in trnsgenic nd conventionlly red cultivrs. Journl of Agriculturl Science, 142: Gruer S., Emrich K., Clupein W. (2009): Clssifiction of cnol (Brssic npus) winter cultivrs y secondry dormncy. Cndin Journl of Plnt Science, 89: Gruer S., Bühler A., Möhring J., Clupein W. (2010): Sleepers in the soil Verticl distriution y tillge nd long-term survivl of oilseed rpe seeds compred with plstic pellets. Europen Journl of Agronomy, 33: Gruer S., Hüsken A., Dietz-Pfeilstetter A., Möllers C., Weer E.A., Stockmnn F., Thöle H., Schtzki J., Dowideit K., Renrd M., Becker H.C., Schiemnn J., Clupein W. (2012): Biologicl confinement strtegies for seed- nd pollen-medited gene flow of GM cnol (Brssic npus L.). AgBioForum, 15: Long R.L., Stedmn K.J., Pnett F.D., Adkins S.W. (2009): Soil type does not ffect seed geing when soil wter potentil nd temperture re controlled. Plnt nd Soil, 320: Lutmn P.J.W., Freemn S.E., Pekrun C. (2003): The long-term persistence of seeds of oilseed rpe (Brssic npus) in rle fields. Journl of Agriculturl Science, 141: Momoh E.J.J., Zhou W.J., Kristinsson B. (2002): Vrition in the development of secondry dormncy in oilseed rpe genotypes under conditions of stress. Weed Reserch, 42: Nrwl S., Sindel B.M., Jessop R.S. (2008): Dormncy nd longevity of nnul ryegrss (Lolium rigidum) s ffected y soil type, depth, rinfll, nd durtion of uril. Plnt nd Soil, 310: Prej M.R., Stniforth D.W. (1985): Seed-soil microsite chrcteristics in reltion to weed seed germintion. Weed Science, 33: Pekrun C., Lutmn P.J.W., Beumer K. (1997): Induction of secondry dormncy in rpe seeds (Brssic npus L.) y prolonged imiition under conditions of wter stress or oxygen deficiency in drkness. Europen Journl of Agronomy, 6: Pekrun C., Hewitt J.D.J., Lutmn P.J.W. (1998): Culturl control of volunteer oilseed rpe (Brssic npus). Journl of Agriculturl Science, 130: Schtzki J., Allm M., Klöppel C., Ngel M., Börner A., Möllers C. (2013): Genetic vrition for secondry seed dormncy nd seed longevity in set of lck-seeded Europen winter oilseed rpe cultivrs. Plnt Breeding, 132: Terpstr R. (1995): Dormncy of seeds of shepherd s purse in lternting wet nd dry, compressed ggregted soil: A lortory experiment. Journl of Applied Biology, 32: USDA (2013): Ntionl Soil Survey Hndook. Aville t soils.usd.gov/technicl/hndook/ pge visited 12/2013 Weer E.A., Frick K., Gruer S., Clupein W. (2009): An ssessment tool for volunteer oilseed rpe in griculturl prctice. Mitteilungen der Gesellschft für Pflnzenuwissenschften, 21: (In Germn) Weer E.A., Frick K., Gruer S., Clupein W. (2010): Reserch nd development towrds lortory method for testing the genotypic predisposition of oilseed rpe (Brssic npus L.) to secondry dormncy. Seed Science nd Technology, 38: Weer E.A., Frick K., Stockmnn F., Gruer S., Clupein W. (2011): Seed persistence of novel trit oilseed rpe (Brssic npus L.) genotypes in different soils. In: Proceedings of the 13 th IRC, Prgue, Willims J., Shykewich C.F. (1971): Influence of soil wter mtric potentil nd hydrulic conductivity on the germintion of rpe (Brssic npus L.). Journl of Experimentl Botny, 22: Received on Ferury 20, 2014 Accepted on April 25, 2014 Corresponding uthor: Apl. Prof. Dr. Sine Gruer, University of Hohenheim, Agronomy (340), Institute of Crop Science, Stuttgrt, Germny e-mil: Sine.Gruer@uni-hohenheim.de 284