Standardization o waterlogging damage at dierent growth stage o wheat.

Almost 12 percent o cultivated land in the world and 1.1 million ha o agricultural land in Iran encounter waterlogging. Study in Gorgan, Ahvaz, Kermanshah and other countries were used or preparing instructions or insurance agents in order to evaluate waterlogging eect on wheat. Shaikh et al (2008) evaluated 6 wheat genotypes under waterlogged conditions at the initiation o anthesis up to grain illing during 20 days. Results showed that waterlogging eect on biological yield, grain yield, harvest index, plant height, pedancle length, spike number per square meter, spike weight, grain number per spike, 1000 kernel weight was signiicant at 1% probability. Then waterlogging eect at anthesis and grain illing interval lead to 29.9% biological yield loss, 53.7% grain yield loss (average o 2.68 % per day), 35.3% harvest index loss, 10.4% plant height loss, 11% loss o peduncle length, average o 18.4% loss in spike per square meter, 29.6% spike weight loss, 36.5% loss in grain weight per spike, 30.8% loss in 1000 kernel weight. Moghan 3 cultivar had higher grain yield, harvest index, plant height, spike weight, spikelet number per spike and grain number per spike in comparison to other genotypes. Also study in other countries like Australia showed that waterlogging eect on wheat rom mid up to tillering stage (28 days) caused 1.11 % grain yield loss per day. In CIMMYT in Mexico waterlogging ater plant emergence (42 days) caused 1.61 % grain yield loss per day. In China, waterlogging eect at booting stage (15 days) which is the most sensitive stage caused 3.38% per day grain yield loss. In USA, warerlogging eect at 3-4 lea stage (35 days) caused 1.17% loss per day. Based on the result o experiment conducted in Iran and other countries waterlogging eect at dierent growth and developmental stages was concluded as below: 1- Dierent response was observed among genotypes, growth stages and dierent level o waterlogging (duration). Plant can not compensate waterlogging damage in dierent growth stages even or a ew days. 2- Initial growth stage o wheat is more sensitive than other growth stages. In general wheat sensitivity at germination stage is more than heading stage and tillering stage is more sensitive than stem elongation. In other words, waterlogging eect is more when wheat is in initial growth stage. 3- Depending on genotype when waterlogging duration was longer, wheat yield damage was more, but the decline o slope was lower. 4- Average grain yield stage at emergence stage is 3.76% per day, 1.61% at tillering stage, 1.55 at stem elongation, 2.56 at heading stage and 1.5% at illing period in comparison to control (non waterlogged). 5- Studies which are conducted in Iran and other countries showed that response o wheat genotypes to waterlogging are dierent. So that one cultivar at dierent growth stage and dierent waterlogging duration had dierent response. or example Shiraz cultivar during 15 days waterlogging at tillering, had 60.5 % loss o grain yield and 18% loss at stem elongation, but at the same condition Sardari cultivar damage at tillering stage was 12.5% loss and at stem elongation was 36.65% loss, This shows the dierent genotypes response to waterlogging because o dierent morphological and genetical characteristics. Wheat cultivars in Golestan had dierent response to waterlogging, so Moghan 3 cultivar and URWYT-82-17 during 20 days o waterlogging rom anthesis up to grain illing had 44.8 and 67.92%, lowest and highest loss, respectively. Average wheat grain yield damage was 2.39% per day at emergence stage, 2.68 % at tillering stage, 2.14% at stem elongation, 2.68% at heading stage and 1.5% at illing stage. Key words: wheat, waterlogging, stress, yield