CULTIVAR EVALUATION: EVOLUTION OF SYSTEMS TRIALS TO COMPARETRANSGENIC AND NON-TRANSGENIC CULTIVARS

摘要

Systems trials allow cultivar performance and economic returns to be compared when cultivars are produced according to thepest management program appropriate for the cultivar type, while Official Cultivar Trials (OCTs) impose commonmanagement on all cultivars. Thus, the OCT protocol for testing cultivars may be inadequate as the sole source ofperformance data for transgenic cultivars containing pest management traits. The objective of this trial is to compare neteconomic returns from producing non-transgenic and transgenic pest managing cultivars in their intended production system.Sixteen cultivars, four each representing non-transgenic, Roundup Ready~R, Bollgard~R, and stacked (RoundupReady+Bollgard) cultivars, were planted on 10 May in a randomized complete block design with four replications. Plot sizewas 6-rows, 36-inch row spacing, 50 feet long. Cultivars in the trial included Deltapine DeltaPearl, FiberMax~R 989, PhytogenGA161, Stoneville 580, Deltapine 5415R, FiberMax 989R, Stoneville 4793R, SureGrow 521R, Deltapine 448B, DeltapineNucotn 33B, FiberMax 966B, Stoneville 4691B, Deltapine 555BR, Deltapine 458BR, FiberMax 989BR, and Stoneville4892BR. Cultivars chosen for inclusion in the trial presently have large seed market share in Georgia, proven performance inthe University of Georgia Official Cultivar Trials (www.griffin.peachnet.edu/cotton/), or have promise as new cultivars forGeorgia growers (and are projected to be commercially available within 1-2 years). The cultivars Stoneville 4691B,Stoneville 4892BR, FiberMax 966B, Deltapine 555BR, FiberMax 989, Deltapine Nucotn 33B, and Deltapine 458BR werethe highest yielders in the trial (statistically speaking), while Deltapine 555BR had the highest gin turnout. Insect densitieswere unusually low in 2001 at the Tifton, GA trial site. Densities of lepidopteran pest insects never triggered an insecticideapplication for their control on either Bollgard or non-Bollgard cultivars, thus we could not effectively compare insect controlcosts under more normal pest insect pressure between Bollgard and non-Bollgard insect management systems. Weedmanagement was excellent with either the Roundup Ready or non-Roundup Ready herbicide regimes. Yellow nutsedge(Cyperus esculentus L.) and smallflower morningglory (Jacquemontia tamnifolia L.) were observed sporadically in the trialprior to applications of herbicides. Thereafter, densities of weed species remained low. Net returns averaged $536.43/acre forRoundup Ready cultivars, while stacked (Bollgard + Roundup Ready) cultivars returned an average of $584.76/acre. Lowdensities of insect and weed pests prohibited us from separating cultivars and types (e.g., transgenic or not) on the basis ofefficacy of pest management. Net returns from this trial appear to be more influenced by yield potential of the backgroundgenotype than by presence or absence of genes conferring pest management traits. As of this writing, HVI fiber data was notyet available, thus discounts or premiums imposed by the marketing system could not be factored into net returns for eachcultivar. Based on HVI fiber data collected in the University of Georgia Official Cultivar Trials, we expect cultivar variationin fiber properties and perhaps color/trash grades to slightly alter net returns for cultivars we studied. In summary, stacked(Bollgard plus Roundup Ready) cultivars produced the highest returns. In the absence of more normal insect and weed pestpopulations, net returns in this trial were more related to yield potential of the background genotype than to presence oftransgenically mediated, pest management, traits. Results of ‘systems’ trials combined with data from state OCTs shouldassist producers in choosing cultivars and production systems to better optimize profits.