In this research, 5 percent of normal Precipitation Index (PNPI), Deciles of Precipitation(DPI),Rainfall Anomaly Index (RAI), Bahlme & Mooley DROUGHT Index (BMDI) and standardized Precipitation Index (SPI) were used in order to investigate DROUGHT in Yazd synoptic station and 31 non synoptic stations all around this province. For this purpose, the present statistical errors were reconstructed via correlation between the stations, after raining data collection from the considered stations. Then, calculation of PNPI, DPI, RAI, BMDI and SPI indexes were calculated on monthly and annual scales. Situation of DROUGHT was determined based on the obtained values from calculation of each index according to tables related to the considered indexes in different classes of DROUGHT during the statistical period. Then indexes were compared to each other, considering DROUGHT given situation for each station. The difference and similarity of each index with other 4 indexes were calculated and investigated. Also after determination of DROUGHT situation in each station, given percentage of DROUGHT different situations via each Index was determined on annual scales, in 33 study stations. After passing the above mentioned stages, it was found that there was the highest percentage value of similarity between the two indexes RAI & DPI, as both indexes indicated similar situation of hard DROUGHT in the stations. These two indexes are considered most efficient to investigate aerology DROUGHT. But considering that static indexes are faced with problem on monthly scales and in stations located in DROUGHT regions, it is recommended to use SPI & BMDI dynamic indexes whose similarity percentages are acceptable.

Inheritance of several yield-based DROUGHT resistance INDICES was studied by a halfdiallel method using seven winter wheat varieties. The parental lines were such chosen as to represent a broad range of DROUGHT stress resistance. The experiment was conducted in a split-plot design at the research farm, Faculty of Agriculture, Zanjan University, Iran, in 1998. Irrigated vs. rainfed regimes were considered as the main plots. The F1 hybrids and parental varieties constituted the subplots. From the grain yield data, some DROUGHT resistance INDICES such as geometric mean productivity (GMP), mean productivity (MP), standard superiority measure (SP), stress susceptibility index (SSI), stress tolerance index (STI), superiority measure (P), and tolerance (TOL) were calculated. Genetic components of variance and heritabilities were estimated using Gardner and Eberhart’s Method 3, Model II. Significant differences among parents and F1s were observed for all INDICES except for SSI and TOL. Significant general combining abilities (GCA) were obtained for GMP, MP, P, SP, STI, and TOL but not for SSI. Therefore, except for SSI, other INDICES could be regarded as heritable. The specific combining ability (SCA) effects were also highly significant for GMP, MP, P, SP, and STI. However, additive variances were more important than dominance ones. Narrow-sense heritability estimates were very low for SSI, low for TOL, but moderate for GMP, MP, P. SP, and STI. Thus selection based on the latter INDICES could be more promising than on SSI and TOL. It seems that SP and STI might be better yield-based DROUGHT resistance INDICES to be employed in plant breeding programs, because of their moderate narrow-sense heritabilities and the inherent ability of selecting high yielding genotypes in either stressed or non-stressed conditions.

Iran, due to its geographical location, has low rainfall and is considered a dry land. As a result, different regions of the country grapple with DROUGHT. The presence of water management systems, such as aqueducts and reservoirs, in most parts of the country, along with a variety of methods for conserving water for irrigation, may contribute to this claim. Considering that DROUGHT is an inherent phenomenon in Iran's climate, people have invented and used numerous methods to combat it and store water. The aim of this study is to monitor and evaluate DROUGHT in Iran. In order to realize this goal, precipitation data from synoptic, rain gauge, and climatology stations were extracted over a 51-year period, from 1970 to 2020. The results obtained from examining DROUGHT occurrences in five ten-year periods reveal that, with the exception of the third decade (1991 to 2000), DROUGHT has prevailed in the majority of Iran's regions compared to other decades. On the other hand, in the recent decades leading to 2020, the intensity of DROUGHT occurrences, especially in the Middle Zagros, has intensified, which has consistently been among the regions with the highest rainfall in Iran after the Caspian region. This situation can cause concern in Iran, a country where its agricultural production hub is established along the Zagros mountain range. Moreover, the fluctuating behavior of Iran's DROUGHTs, with return periods of 2 to 5 years, has complicated the management strategies for these types of hazards. These conditions appear to have created numerous issues in many areas of Iran, particularly in the agricultural sector of the western provinces, due to the lack of conformity with these types of occurrences.

DROUGHT is one of the major natural disasters which affect human society more than all other calamities. In order to monitor the DROUGHT conditions in Nahavand City, the province of Hamedan, the monthly and annual rainfall data of the Varayeneh and Vasaj Stations were collected for 41 years (1969-2009). The DROUGHT condition were analyzed using Rainfall Anomaly Index (RAI), Standard Index of Annual Precipitation (SLAP), Percentage of Normal Index (PNI), Deciles Index (DI), Standardized Precipitation Index (SPI), Chinese Z Index (CZI), Modified CZI (MCZI) and Z Score Index (ZSI). The results indicate that the most severe DROUGHT recorded at both the Varayeneh and Vasaj stations based on the PNI, SPI, CZI, DI and ZSI INDICES in the water year of 1998-1999. According to the MCZI index, a severe DROUGHT, was observed at both the Vasaj and Varayeneh stations in the water year of 1970-1971. Based on SLAP index, five severe DROUGHT cases were observed at the Varayeneh station, and seven severe DROUGHT cases were observed at the Vasaj station. Based on the RAI index, five severe DROUGHTs were observed at the Varayeneh station and seven severe DROUGHTs were observed at the Vasaj station. Moreover, based on the majority of these INDICES, the most severe DROUGHT of this 40-year period in Nahavand City occurred in the water year of 1998-1999.

DROUGHT is the most harmful climatic event whose impacts are more important in regional scale. Thus, the aim of this study is to introduce a method for DROUGHT regional analysis. In this study, rainfall trend analysis by Mann-Kendal test and homogeneity test by run test were investigated and showed rainfall homogeneity and no significant rainfall trend. Then, using two important deciles and standardized precipitation INDICES of 8 stations in the region, DROUGHT condition for selected stations and period were compared and its results were investigated for the region. The results showed that DROUGHT cover 60 percent of the area averagely. The study also showed that rainfall deciles have relationship with longitude only. In other words, DROUGHT occurs more frequently and with higher intensities eastward.

In order to identify DROUGHT tolerance barley genotypes, screen quantitative INDICES DROUGHT tolerance and appointment best INDICES, one experiment carried out with 20 barley genotype. This experiment excuted in RCBD with three replications under full irrigation and DROUGHT stress conditions during 2009-2010, cropping season in broujerd agricultural research station. In order to evaluation of barley genotype for DROUGHT stress, stress susceptibility index (SSI), stress tolerance index (STI), geometric mean productively (GMP), tolerance index (TOL), mean productivity and harmonic mean (HM), data were collected. The result indicated significant different among all genotypes with respect to all quantitative INDICES and yield performance in both environments. This show the possibility of selection for DROUGHT tolerance among genotypes, and involvement of superior ones inbreeding programs. The result of experiment showed that No.7 (MB-79-4) genotype in the irrigation condition and NO.14 (MB-82-4) in dry condition has the highest grain yield. Highest HM, GMP, MP and STI were obtained in the No. 11 and 14 (CB-83-15 and MB-82-4) genotypes. Evaluation of genotypes for stress TOL and SSI index showed that No. 6 (CB-83-17) genotype has high index. Correlation analysis between yield and all INDICES revealed that MP, GMP, HM and STI are all INDICES for screening of DROUGHT tolerance genotypes. Accordingly, genotypes No. 7, 11, 14 and 19 (MB-79-4, CB-83-15, MB-82-4 and MB-79-15) were selected as DROUGHT tolerance genotypes. Biplot multivariate technique located the genotype No. 7, 11, 14 and 19 (MB-79-4, CB-83-15, MB-82-4 and CB-84-10) near the vectors related to DROUGHT resistance INDICES.

In order to investigate the effects of terminal DROUGHT stress on yield, yield components and assimilate remobilization in 8 wheat cultivars and lines for introducing of DROUGHT tolerance and susceptible ones, two experimental separated designs were occur using randomized complete blocks with three replications. A field study was conducted in 2009 in Agriculture and Natural Resources Experiment Station of Markazi province. The first experiment was water stress in post flowering stage and second experiment was irrigation with normal regime. The yield and yield components, plant height, day to flowering, harvest index and peduncle length were measured in this study. Response of cultivars and lines under optimum irrigation and water stress conditions were different. Water stress reduced most traits a well as yield and yield components. Results showed that some cultivars at water stress condition, showed tolerance and had relatively high yield For example, lines C-84-4 and C-82-12 showed high more tolerance under optimum and water stress, condition lines C-78-14 and Shariar cultivar showed high yield at optimum irrigation and lines C-81-14 and C-83-7 showed high yield at water stress condition. In order to evaluate stress INDICES among cultivars and lines we used 6 INDICES such as harmonic mean (Harm), stress tolerance index (STI), tolerance index (TOL), Mean productivity (MP), stress susceptibility index (SSI) and Geometric mean productivity (GMP). Results showed that all of these INDICES were the best, because there were the greatest correlations between yield and harvest index under water stress and optimum irrigation.

In order to study the reaction of fifteen maize hybrids to different levels of DROUGHT stress, and evaluate DROUGHT tolerance INDICES, an experiment was conducted in split plot arrangement using randomized complete block design with four replications in Gharakhil (Ghaemshahr) Agricultural Station, in 2006. The main plots consisted of DROUGHT stress levels and sub-plots included maize hybrids. Six DROUGHT tolerance INDICES were calculated for grain yield. Under normal, mild and severe stress conditions, hybrid OSGT14 produced 9.445, 9.270 and 8.352 tha-1, respectively, while under most severe stress, hybred SPGT12 produced the highest grain yield (7.455 tha-1). Based on the highest correlation observed between grain yield and different (INDICES, MP, GMP, Harm and STI, were suitable INDICES. Biplot analysis determined hybrids OSGT14, KSC710GT and KSC-mog 84-062, in group A, as tolerant hybrids and suitable for normal and stress conditions, and hybrids BGT10, KSC 708 GT, BGT15 and KSC712GT as susceptible hybrids. Cluster analysis based on different INDICES, divided hybrids under mild and severe stress conditions, into five, and under most severe stress into six groups. INDICES MP, GMP, Harm and STI, identified hybrids OSGT14 and KSC710GT as tolerant, and BGT15 and KSC708GT as susceptible hybrids to DROUGHT stress, while, INDICES TOL and SSI showed KSC 720 and KSC700 as tolerant and KSC712GT and BGTI0 as susceptible hybrids to DROUGHT stress.

DROUGHT is one of the most important factors limiting the growth and production of crops in most parts of the world and Iran and affects as a multidimensional stress on plants at different levels. In order to study DROUGHT tolerance of durum wheat genotypes, an experiment was conducted in a randomized complete block design with three replications in stress field in Kouhdasht city. Results of analysis of variance showed that the response of the studied genotypes was different for grain yield and the possibility of selection of genotypes based on each of the traits. Comparison of numerical values and rank of each genotype according to DROUGHT tolerance INDICES showed that based on DROUGHT tolerance INDICES according to seed yield of genotypes (Omrab ), (Hana) and (Aria (stork) as DROUGHT tolerant and genotypes, Other genotypes were identified as susceptible genotypes. The results of correlation coefficients between INDICES showed that MP, GMP, HAM, STI INDICES had positive and significant correlation at probability level with grain yield in stress and non-stress conditions. There were some, so it can be said that these INDICES are the best INDICES for identifying superior genotypes. Principal component analysis results showed that the first two components accounted for about of the data variation. According to Gabriel's biplot chart, the studied genotypes were classified into two high yield potential and low yield potential areas, with genotypes (Omrab ), (Hana) and (Aria (stork) being adjacent to vectors. DROUGHT tolerance was identified as superior genotypes. Cluster analysis based on superior INDICES separated the studied genotypes into three general groups, which were in good agreement with the results of Gabriel biplot plotting.

Among different environmental stresses, DROUGHT is of great importance that induces a highly negative effect on crop production. In order to evaluate DROUGHT tolerance in dryland wheat genotypes, 36 genotypes were studied in a randomized complete block design with three replications under rainfed (DROUGHT stress) and supplemental irrigation conditions during 2016– 2017 growing season in Research Farm of Moghan College of Agriculture and Natural Resources. Results showed that there are significant differences among genotypes for grain yield in both rainfed and supplemental irrigation conditions. Combined analysis of variance over two experiments showed that DROUGHT stress significantly increased grain yield. Under supplemental irrigation conditions, the genotypes 22, 34 and 21 had the highest grain yield by an average of 3. 143, 3. 089 and 2. 921 t/ha and under rainfed condition, genotypes 20, 22 and 27 produced the highest grain yield with an average of 2. 647, 2. 610 and 2. 558 t/ha, respectively. In order to identify DROUGHT tolerance genotypes, DROUGHT resistant INDICES such as tolerance index (TOL), stress susceptibility index (SSI), mean productivity (MP), geometric mean productivity (GMP), stress tolerance index (STI) and yield stability index (YSI) were used. GMP, MP and STI INDICES were highly correlated with grain yield under both stress and non-stress conditions. Therefore, they were introduced as suitable INDICES to identify superior genotypes for both environmental conditions. Based on principal component analysis and three dimensional graph, genotypes 22, 34, 33 and 15 were identified as DROUGHT tolerant genotypes and 7, 17, 14 and 1 were identified as DROUGHT sensitive genotypes. Cluster analysis with Ward's method based on grain yield under supplemental irrigation (Yp) and rainfed (Ys) conditions and DROUGHT tolerance INDICES divided the 36 genotypes into four major groups. Therefore, this result was consistent by results from principal component analysis.