Search

The purpose of the experiment was to investigate the relationship between the accumulation of polyamines during the filling period of wheat grain with yield and grain protein under dryland and supplemental irrigation (SI) conditions and also the effect of foliar spraying of urea on the amount of polyamines in grain a factorial experiment was conducted based on randomized complete block design with three replications during two cropping seasons. The examined treatments included water availability (dryland and SI), wheat cultivars (Homa, Sardari, Rijaw, Ouhadi, and Azar2), and foliar application of urea (control and 4% urea foliar application). The results demonstrated that SI (10%) reduced and urea foliar (12%) application increased the percent of grain protein. SI reduced the contents of three PAs by 24%: spermine, spermidine, and putrescine. But urea foliar application increased the three PAs in the first and second years by 31% and 27% in dryland conditions and 12% and 4% in SI conditions, respectively. These results indicated that there is less need for PAs in SI conditions, and they thus exhibit poorer accumulation in the grain; in dryland conditions, however, their content increases with greater access to foliar nitrogen. Older cultivars Sardari and Azar 2 had more polyamines. According to the observed positive correlation between 1000-grain weight and the three PAs under stress conditions, PAs are probably involved in the improvement of grain filling, and urea foliar application can affect drought tolerance by increasing PA accumulation. Moreover, cadaverine exhibited a different function from the other PAs. [ABSTRACT FROM AUTHOR]

In the Mediterranean, unbalanced precipitation distribution causes drought stress in rainfed wheat cultivation. Under such conditions, supplemental irrigation (SI) is a highly efficient practice to reduce the adverse effects of drought stress and improve yield. The present study aimed to assess the effects of SI on traits related to N accumulation and remobilization, chlorophyll concentration, yield and yield components, and water use efficiency (WUE) in different cultivars. Two field experiments with four irrigation levels (I0= rainfed, I1= SI at booting stage, I2= SI at booting and anthesis stages, I3= SI at booting, anthesis, and grain filling stages) and five cultivars (Rejaw, Sardari, Homa, Azar2, and Sirwan) was conducted during the 2015–2016 and 2016–2017 wheat growing seasons. Overall, results showed that SI notably had a positive effect on chlorophyll concentration, N content of plant parts, N remobilization (NR), grain number per spike, 1000-grain weight, biological yield, and grain yield in cultivars. Although the grain yield in the three SI treatments was 237.1 kg ha−1 and 630.4 kg ha−1 more than the other two (I2) and one (I1) SI, respectively, but the WUE was slightly lower in this treatment. The cultivars exhibited apparent differences in their responses to SI. The Sirwan cultivar showed a higher reaction to SI amongst cultivars. The highest N remobilization efficiency (NRE) was observed in I1 (73.69%) and I0 (73.34%) irrigation treatments. Sardari (74.03%) and Azar2 (73.60%) cultivars had higher NRE than other cultivars. The minimum contribution of NR to grain appeared in the I3 treatment (74.54%). [ABSTRACT FROM AUTHOR]

Supplemental irrigation (SI) is the primary strategy to reduce the adverse effects of drought stress on rainfed wheat growth and grain yield in the Mediterranean region. The study aimed to evaluate the effects of SI at critical growth stages on traits related to dry matter (DM) accumulation and remobilization, N utilization efficiency in various cultivars. Two field experiments with four irrigation levels (I0 = rainfed, I1 = SI at booting stage, I2 = SI at booting and anthesis stages, I3 = SI at booting, anthesis, and grain filling stages) and five cultivars (Rejaw, Sardari, Homa, Azar2, and Sirwan) was conducted during the 2015–2016 and 2016–2017 wheat growing seasons. The average higher precipitation in the first growing seasons increased the DM accumulation in vegetative organs, grain yield, and N use efficiency (NUE). The effect of SI on the DM accumulation in crop components at anthesis and post anthesis, crop components DM remobilization (DMR), crop components DMR contribution to grain and DMRE, grain yield, N utilization efficiency (NutilE), N harvest index (NHI), NUE, and grain protein concentration (GPC) in wheat cultivars was assessed. Results showed that overall SI increased DM accumulation at anthesis and post anthesis, DMR, grain yield, NutilE, and NUE in cultivars. SI at anthesis and grain filling stages decreased DMRE, NHI, and GPC. The difference between cultivars was evident in studied traits, and in general, the Sirwan cultivar had more DM accumulation at anthesis and post anthesis and eventually higher grain yield than other cultivars. SI reduced the dependence of the plant on DMR for grain filling so that the DMR contribution to grain yield decreased from 76.79% in rainfed conditions to 62.44% in three times SI (I3) conditions. • A 2-years field experiment was conducted to study the effect of supplemental irrigation on five rainfed wheat cultivars. • supplemental irrigation affected dry matter remobilization, grain yield, and N utilization-related traits. • The cultivars exhibited apparent differences in their responses to supplemental irrigation. [ABSTRACT FROM AUTHOR]