Effect of source and sink limitation on yield and some agronomic characteristics in modern bread wheat cultivars under post anthesis water deficiency | Omejitveni vpliv vira in ponora na pridelek in nekatere agronomske lastnosti novejših sort krušne pšenice v razmerah pomanjkanja vode po antezi

English. In order to examine the effect of source and sink limitation and post anthesis water deficiency stress in determining of grain yield potential in nine modern bread wheat cultivars in the west of Iran with arid and semi-arid weather that is one of the main centers of crop diversity in the world, a split plot-factorial experiment based on randomized complete block design with three replications was used in crop year 2010-2011. Three treatments includes: control, flag leaf removal and removal of half of each spike was applied in the field research campus of agriculture and natural resources of Razi University. Water deficiency stress was started at anthesis and continued till physiological maturity (withholding of irrigation). Water deficiency caused significant reduction in the grain yield and the 1000 grain weight and caused significant increase in the number of fertile spikelets per spike. Flag leaf removal (source limitation) treatments showed that flag leaf contribution in grain yield production during grain filling in control and post-anthesis water deficiency stress condition were 10.1% and 13.4% respectively. In both conditions removal of spikelets spike-1 (sink limitation) treatment had higher significant effect on fertility of spikelets, grains spike-1, grain yield spike-1 and 1000 grain weight than flag leaf removal. Flag leaf removal treatment in some cultivars not only had no reduction effect on grain yield and 1000 grain weight but also increased them. These results may be due to an increase in photosynthesis rate of remaining leaves and/or increase in amount of carbohydrates remobilization that is stored in the stems. This phenomenon is called the compensatory effect. In both water regimes, there was a correlation between lower grain weight, no grains spike-1 and fertile spikelet spike-1 and lower yield potential of ‘Chamran’ cultivar. But, ‘Zarin’ and ‘Pishgam’ cultivars due to higher grain yield potential in post-anthesis under water deficiency stress and control, performed more studies, to advise farmers to cultivate them. There are probably better than any other cultivars that are common in these regions and sowing of them by farmers will be associated with less risk.

Slovenian. Za preučevanje omejitvenega učinka vira in ponora v razmerah pomankanja vode po antezi na potencial pridelka zrnja pri devetih novejših sortah krušne pšenice je bil v zahodnem Iranu, s sušnim in polsušnim podnebjem, na območju enega izmed glavnih centrov diverzitete kulurnih rastlin, izveden “split-plot” faktorski poskus, temelječ na naključno izbranih blokih v treh ponovitvah v pridelovalni sezoni 2010-2011. Tri obravnavanja so obsegala: kontrolo, odstranitev najvišjega lista (“zastavarja”) in odstranitev polovice vsakega klasa na raziskovalnem polju Kampusa za agronomijo in naravne vire Razi univerze. Stres pomanjkanja vode je nastopil ob antezi s prekinitvijo namakanja in je trajal do fiziološke zrelosti. Pomanjkanje vode je povzročilo značilno zmanjšanje pridelka zrnja, zmanjšanje teže 1000 zrn in značilno povečanje števila fertilnih klaskov na klas. Odstranitev lista zastavarja (omejitev vira) je pokazala, da ta prispeva pridelku zrnja v obdobju polnjenja zrn v kontroli in v poanteznem stresu pomankanja vode 10.1 %, oziroma 13.4 %. V obeh razmerah je imela odstranitev klaskov v klasu (omejitev ponora) večji značilni vpliv na fertilnost klaskov, število zrn na klas, pridelek zrnja na klas in na težo 1000 zrn kot odstranitev lista zastavarja. Odstranitev lista zastavarja pri nekaterih sortah ne samo, da ni zmanjšala pridelka zrnja in teže 1000 zrn ampak ju je celo povečala. To bi lahko bilo posledica povečanja fotosinteze preostalih listov in /ali povečanja količine sproščenih ogljikovih hidratov iz zalog v steblu. Ta pojav se imenuje nadomestni učinek. V obeh vodnih režimih je bila korelacija med parametri kot so manjša teža zrnja, nič zrn na klas in fertilnimi klaski na klas z manjšim potencialom pridelka pri sorti ‘Chamran’. Toda s sortama ‘Zarin’ in ‘Pishgam’, bi bilo zaradi njunega večjega potenciala v pridelku zrnja v razmerah  sušnega stresa po cvetenju kot v kontroli, potrebno opraviti še več poskusov predenj bi svetovali kmetom njuno pridelovanje. Ti dve sta verjetno boljši kot katerakoli druga sorta, ki so pogoste v tem območju, in njuno sejanje bi kmetom povzročilo manjše tveganje glede na okoljske strese.