تعیین اثر نهایی عوامل اقلیمی و فنوتیپی بر ریسک و میانگین عملکرد لاین‌های گندم آبی در تحقیقات به نژادی

اهداف این پژوهش، تعیین آثار نهایی مستقیم و غیرمستقیم عوامل اقلیمی و فنوتیپی، سال معرفی رقم به عنوان تلاش به‌نژادگران و عوامل مکانی و روند زمانی بر میانگین و واریانس عملکرد دانه لاین‌های گندم آبی کشور یود. در این مطالعه، داده‌های پنل از 24 ایستگاه تحقیقات کشاورزی طی دوره 1393 1374 جمع آوری شد. روش تحقیق استفاده از رویکرد تعادل جزیی بوده بطوریکه برای تعیین آثار نهایی از تابع تولید تصادفی جاست پاپ و تحلیل فضایی دوربین استفاده گردید. طبق نتایج، متغیرهای مورد مطالعه در این پژوهش به روش ایم، پسران و شین مانا بودند. اثر نهایی مستقیم کلیه متغیرهای فنوتیپی( تعداد روزهای تا ظهور سنبله، تعداد روزهای تا رسیدن فیزیولوژیکی، طول دوره پر شدن دانه و وزرن هزار دانه ) و متغیرهای اقلیمی ( میانگین درجه حرارت سالانه و مجموع بارندگی در فصول زراعی ) بر میانگین و واریانس عملکرد دانه لاین‌های گندم نان آبی از لحاظ آماری معنی‌داری بود. اثر نهایی مستقیم متغیرهای روند زمانی و سال معرفی رقم، بر میانگین و واریانس عملکرد دانه لاین‌های گندم آبی در طول دوره مثبت ولی از لحاظ آماری معنی دار نبود. تلاش به‌نژاد‌گران توانست در طول دوره، سالانه میانگین عملکرد دانه لاین‌های گندم نان آبی را 69/5 کیلوگرم در هکتار بهبود بخشد. ضریب تبیین تعدیل شده مدل78/4 درصد محاسبه شد.

determination of marginal effects of climatic and phenotypic factors on risk and average yield of irrigated wheat lines in breeding research

introductionone of the important and effective economic activities in the field of agricultural economic is release varieties or crop improvement technology. this is done to increase the yield and production of various products and to increase food security, self reliance and reduce dependency (aghaei asadi, 2010 ). historically, breeders have focused more on increasing of yield varieties, however, reducing variability and instability in yield of varieties at different locationa and times is considered on important breeding goal (byerlee moya, 1993). a lot of factors especially phenotype factors effect on the mean and risk of lines yield in wheat breeding. the one of important models for determine mutual effect on both mean and risk of lines yield is just and pope production function. one of the basic requirement of the just and pope model is that there be no a priori restrictions on the marginal risk effects so that an factor could be either risk increasing or risk decreasing.(just and pope, 1979). the objectives of this research were to determine the direct and indirect marginal effects of environmental and phenotypic factors, variety release year as breeders’ efforts in genetic improvement, location and time trend factors on the mean ans variance of grain yield of irrigated bread wheat lines. materials and methodsin this study, the required panel data were collected from 23 agricultural locations during 1995 2014 in iran. the methodolgy of this study was partial equilibrium method and the marginal effects of the variables on the mean and variance of wheat grain yield were assessed using stochastic production function of just and pope and spatial durbin models(sdms). just and pope production function was estimated with linear functions in three steps as follows: yht =β 0+ β 1 trend + β 2 dhe + β 3 dma+ β 4 tgw+ β 5 gfd+ β 6 mtem+ ɓ7s9rain + ɓ8 ph + λ rlyear + ɓ1dloc1 …+ ɓ23dloc23 + ϵhtstep 1ln (ei) 2 = φ0+ φ1 trend + φ2 dhe+ φ3 dma+ φ4 tgw+ φ5 gfd + φ6mtem + φ7 s9rain + φ8 ph + ə rlyear + + ϵhstep 2 yht =α0+ α 1 trend + α 2 dhe + α 3 dma+ α 4 tgw+ α 5 gfd+ α 6 mtem+ α 7s9rain + α 8 ph + λ rlyear + weight + ϵhtstep 3where; yht: mean yield of bread wheat lines (kg/ha) in year t, trend: time trend, ln (ei) 2 : yield risk for bread wheat lines in year t,, dhe: days to heading in year t, dma: days to physiological maturity, gfd: mean of grain filling duration in year t, tgw: thousand grain weight (tgw) (g), mtem: mean of annual temperature ( mtem ) (0c), s9rain: sum of rainfall during cropping season ( s9rain ) (mm), ph , dloch: dummy variables of locations,rlyear(h=1, 2, …..23): variety release year, φ.β: δ, ɑ: models parameters and ϵht:, residuals results and discussionaccording to the regression results, the study of spatial spillover effects using spatial durbin models (sdm) shwoed that the direct marginal effects of all the phenotypic factors( mean of days to heading, mean of days to physiological maturity, mean of grain filling duration and mean of thousand grain weight) and climatic factors (mean of annual temperature and sum of rainfall during cropping season) on the mean and variance of grain yield of irrigated bread wheat lines were statistically significant. the direct marginal effect of time trend and variety release year on the mean and variance of grain yield of irrigated bread wheat lines was positive but not statistically significant . the annual direct marginal effect of variety release year on the mean of grain yield of irrigated bread wheat lines was estimated to be 69.5 kg/ha in the period of 1995 2014. adjusted r2 of the model was estimated at 78.4 %. conclusionin general, the direct marginal effects of all the phenotypic factors on the mean of grain yield of irrigated bread wheat lines was satistically significant. the direct marginal effect of time trend and variety release year on on the mean of grain yield of irrigated bread wheat lines was positive.