Irrigated Wheat (Triticum aestivum L.) Traits Effects on Potential Yield under Current and Future Climates in Iran

Wheat (Triticum aestivum L.) known as a main crop in Iran. It is the main source of calories and protein which directly provides 37 percent of the food calories and 40 percent of daily protein for people in Iran. Breeding to produce new cultivars is always an important way to increase crops yield. New cultivars breeding is a very complex process because there is an interaction between climate and genotype and the time is limited to produce new cultivars adapted to new climates. The target trait identification can accelerate new cultivar breeding process. The objectives of this study were to explore the potential benefit of irrigated wheat traits over the country to increase the yield.

This study was performed at potential yield simulation using SSM-Wheat crop model to evaluate different traits impact on irrigated wheat potential yield in Iran. For this purpose, the protocol presented by Global Yield Gape Analysis (GYGA) was used to identify the same climate zones and the main weather stations for irrigated wheat in Iran. The potential yield of irrigated wheat was simulated by SSM-iCrop model for the area covered by each main weather stations. The average potential yield was calculated at the country level by scaling up the simulated results within the area covered by weather stations using the GYGA protocol. All the simulations and calculations were done for existing cultivars and for the cultivars with desired plant traits, identified in this study, under current and future climates. The effect of desired plant on potential yield was quantified by comparison of simulation results between existing cultivars and the cultivars with desired plan traits. Future climate (2055) scenario were created for the sites using the baseline 1986-2005 and the projections for delta mean air temperature (and precipitation) which is the difference between the future air temperature (and precipitation) and baseline air temperature (and precipitation). Deltas of air temperature and precipitation were obtained from the international panel on climate change report which it used 42 GCM model outputs under RCP4.5 climate change scenario to calculate them.

In this study, the effect of increasing and decreasing of biological days from tillering to stem elongation, biological days from anthesis to philological maturity, the rate of canopy development and radiation use efficiency on irrigated wheat potential yield were evaluated. Increasing biological days from anthesis to philological maturity increased the potential yield in all the regions under current (15.3 %) and future climates (16.8%). The potential yield gain from increasing radiation use efficiency was 14.7% under current climate and 13.7% under future climate. The effect of decreasing biological days from tillering to stem elongation, biological days from anthesis to philological maturity, the rate of canopy development and radiation use efficiency on the potential yield were negative. Monpara (2011) reported that increasing duration of grain filling period was an effective trait to increase wheat yield in India. Yang et al. (2008) demonstrated that the yield of rice increased with increasing cumulative radiation receiving during grain filling period. There was positive correlation between cumulative radiation receiving during grain filling and grain filling duration. With longer stay green duration, the potential yield of wheat increased thereby raising photosynthesis during wheat grain filling period (Spano et al., 2003).

Increasing radiation use efficiency positive effect on potential yield in the regions with warmer climate was higher than the region with lower average temperature over the year. Increasing radiation use efficiency had negative effect on potential yield in some cooler regions. Increasing biological days from tillering to stem elongation just had positive effect on potential yield in the region with warmer climate and its effect was negative in the regions with cool climate. The faster canopy development had no significant effect on potential yield.