Abstract: In most wheat growing moderate regions and
especially in the north of Iran climate, is affected grain filling by
several physical and abiotic stresses. In this region, grain filling often
occurs when temperatures are increasing and moisture supply is
decreasing. The experiment was designed in RCBD with split plot
arrangements with four replications. Four irrigation treatments
included (I0) no irrigation (check); (I1) one irrigation (50 mm) at
heading stage; (I2) two irrigation (100 mm) at heading and anthesis
stage; and (I3) three irrigation (150 mm) at heading, anthesis and
early grain filling growth stage, two wheat cultivars (Milan and
Shanghai) were cultured in the experiment. Totally raining was 453
mm during the growth season. The result indicated that biological
yield, grain yield and harvest index were significantly affected by
irrigation levels. I3 treatment produced more tillers number in m2,
fertile tillers number in m2, harvest index and biological yield. Milan
produced more tillers number in m2, fertile tillers in m2, while
Shanghai produced heavier tillers and grain 1000 weight. Plant height
was significant in wheat varieties while were not statistically
significant in irrigation levels. Milan produced more grain yield,
harvest index and biological yield. Grain yield shown that I1, I2, and
I3 produced increasing of 5228 (21%), 5460 (27%) and 5670 (29%)
kg ha-1, respectively. There was an interaction of irrigation and
cultivar on grain yields. In the absence of the irrigation reduced grain
1000 weight from 45 to 40 g. No irrigation reduced soil moisture
extraction during the grain filling stage. Current assimilation as a
source of carbon for grain filling depends on the light intercepting
viable green surfaces of the plant after anthesis that due to natural
senescence and the effect of various stresses. At the same time the
demand by the growing grain is increasing. It is concluded from
research work that wheat crop irrigated Milan cultivar could increase
the grain yield in comparison with Shanghai cultivar. Although, the
grain yield of Shanghai under irrigation was slightly lower than
Milan. This grain yield also was related to weather condition, sowing
date, plant density and location conditions and management of
fertilizers, because there was not significant difference in biological
and straw yield. The best result was produced by I1 treatment. I2 and
I3 treatments were not significantly difference with I1 treatment.
Grain yield of I1 indicated that wheat is under soil moisture
deficiency. Therefore, I1 irrigation was better than I0.