The influence of chemical seed treatment on germination, seedling survival and yield of canola

[摘要] ENGLISH ABSTRACT:The influence of chemical seed treatments on the germination, seedlingsurvival and yield of canola (cv. Varola 44) was investigated in a series ofincubation studies, glasshouse experiments, as well as field trials in thecanola producing areas in the Western Cape Province.Incubation experiments were conducted to compare germination and seedlinggrowth of untreated (control) seed with that of seed treated at differentapplication rates (0.5, 1.0 and 2.0 times the recommended) of Cruiser® andSA-combination (which consists of Thiulin® at 0.5g a.i.; Apron® at 0.0815 ga.i.; Gaucho® at 0.6125 g a.i. and Rovral® at 0.9975 g a.i.). The resultsindicated that seed treatment (all rates of SA-combination and highest rate ofCruiser) delayed germination and seedling growth, especially if the seed wassubjected to the Accelerated Ageing Test.Glasshouse studies with pasteurised soil at different water contents, seedsources (storage periods) and planting depths confirmed the phytotoxiceffects of the chemical seed treatments in the absence of soil bornepathogens. From the results it became clear that extreme water conditions(very wet or dry) increased the suppressing effect on germination andseedling growth, but that no phytotoxic reactions occurred in moist (favourablesoil water conditions) soil, regardless of application rate of the chemicalsused, planting depth and seed source. In a second glasshouse experimentconducted in moist soil (kept at 50% of field water capacity to prevent anytoxic effects) from seven different localities that were naturally infested withpathogens, both chemicals proved to be effective where soil borne pathogens(Rhizocfonia so/ani and Pythium spp.) occurred. No clear trend could howeverbe found due to either chemical or application rates used.Finally, field trials were conducted to study the effect of chemical seedtreatments on the plant populations and yield of canola planted in differentrow widths (17 and 34 cm) and seeding rates (3, 5 and 7 kq.ha'). Resultsshowed that treated seeds produced more plants.rn and yielded more thanuntreated seeds at Roodebloem Experimental Farm, while the highestseeding rate produced significantly more plants.rn (Roodebloem andLanggewens Experimental Farms), but not significantly higher yields than thelowest seeding rate at the same locality. Although row width did not have aneffect on plant population, yield (Roodebloem 2003) was significantly less atthe wider (34 cm) rows. As in earlier experiments, no consistent differencesbetween the two chemicals used were found.These results clearly illustrated both the negative (in the absence ofpathogens) and positive (where soil borne pathogens do occur) effects thatchemical seed treatments may have on the germination, seedling growth andeven yield of canola under local environmental and soil conditions. Becauseno significant differences were found between the chemicals used, bothchemicals should be regarded as efficient. More research, especially underfield conditions and with more cultivars, is needed before the registration of achemical for seed treatment could be considered.

[发布机构] Stellenbosch University