Selection based on proper selection indices can be one of the most effective methods for indirect selection of yield and yield components, simultaneously. In order to determination of selection index for improvement of maize yield, 60 single cross maize hybrids were planted in two separate experiments (drought stress and normal conditions) based on randomized complete block design (RCBD) with three replications in Torogh agricultural station of Khorasan Razavi agricultural and natural resources research and education center, Mashad, Iran in 2013-2014. Morphological and phenological traits, yield and yield components were recorded. Selection indices were calculated based on results of stepwise regression considering to phenotypc, genotypic and economic values. Based on stepwise regression results in normal condition, physiological maturity, plant height, kernel depth, kernel no./row and tassel length totally could explain 60.68 percent of gain yield variation, then these traits were used to calculate selection index. In drought stress condition, kernel no./row, plant height, ear height, 1000 kernel weight, ear length and leaves no. above ear could explain 63.77 percent of grain yield variation that these traits were used to calculate of selection index. We used 5 optimum selection indices (smith-hazel) and one basic selection index as Pesk-Baker to screen the maize genotypes. The results showed that the relative efficiency of selection index based on yield and expected genetic gain for all of measured traits in selection index 2 was higher than others in both normal and drought stress conditions. Based on grain yield and selection indices, 20 percent of the best genotypes were selected by each selection indices. Based on derived results in normal condition, genotype no. 60 (ksc704 commercial hybrid) were selected by all of  selection indices as the best genotype, but in drought stress condition, different genotypes were selected by different selection indices like genotypes 16 (ME77006/1×K1263/1), 22 (ME77006/1×K1263/1) and  34 (ME78005/2× A679), that these genotypes at least were selected by 2 or 3 selection indices.

Plant Breeding has utilized a wide range of techniques and methods to improve the quality and quantity of plants. The molecular markers are the tools that have provided a new perspective for plant breeding advancements. This article has reviewed the various advantages and uses of molecular markers and the utilization of the high potential of natural polymorphisms within communities, combined with the abilities of conventional plant breeding methods. The marker attributes are not subject to environmental influence and their high frequency of these markers in their number, high structural diversity are as part of their benefits in identifying identities, determining the genetic diversity of species and studying relationship between populations. They may aid in discovering more information about protecting and maintaining genetic stock collections, identifying varieties, determining genes with chromosomal location and the number of genes controlling traits. Genome sequencing, the preparation of physical and genetic maps, genomic fingerprinting of plants are some of the other applications of this tool in plant breeding. The high efficiency of selection with the help of markers in selection of genotypes has been emphasized as the parent of crosses and selection with the help of a marker in breeding programs and genomic selection. New technologies offers new opportunities to shape genetic variation in the improvement of specific plant breeding programs. Nowadays development of next-generation sequencing technology, genome sequencing and high throughput approaches for markers have facilitated EST-derived simple sequence repeat (EST-SSR) marker development as well as single nucleotide polymorphism (SNP) marker. These markers can be successfully employed in accelerating research and plant breeding programs.

Additive main effect and multiplicative interaction (AMMI) and best linear unbiased prediction (BLUP) are two methods for analyzing multi-environment trials (MET). In this study, seven selected rice lines were evaluated along with two check varieties based on randomized complete block design in Tonekabon, Amol and Sari (Iran) in three growing seasons of 2011-14. To quantify the genotypic stability, the best linear unbiased predictions of the genotype by environment interactions (GEI) were estimated, and singular value decomposition (SVD), which is the basis of AMMI analysis, was performed on the resulting matrix. The likelihood ratio test (LRT) showed that the effect of GEI was significant on grain yield, number of tillers, thousand grains weight and panicle length. Therefore, due to the significant interaction of genotype by environment, BLUP analysis can be performed on this data. The biplot of first principal component (PC1) of the environment versus nominal yield showed that genotypes 7 ([IR 67015-22-6-2-(A37632) × (Amol3 × Ramzanalitarom)]39), 6 (IR67015-22-6-2-(A37632) × (Amol3 × Ramzanalitarom)]126) and 2 ([IR64669-153-2-3 - (A8948) × (4Surinam Deylamani)]2), due to the lowest scores of the PC1, had a small share in the GEI and had more grain yield stability. The biplot of grain yield versus WAASB, placed genotypes in four regions, so that genotypes in the fourth region, including genotypes 6, 7, 8 (Line 843, check variety), and 9 (Shirodi, check variety), were due to large value of response variable (high grain yield) and high stability (low values of WAASB) were very productive and had extensive stability. Identification of genotypes with weighted average of WAASB and response variable (WAASBY) criteria showed that genotypes 6 and 7 were high yields and stable. Based on the multi-trait stability index (MTSI), G6 was also selected as the best genotype in terms of grain yield, evaluated traits and stability of each trait. Totally, genotype 6 was stable and superior based on the results of all methods.

Protection of food security is one of the basic priorities of any country, which is achieved through the development and introduction of new, high-yielding and stress-resistant crop varieties. Considering the wide range of usage; human nutrition, livestock and poultry nutrition as well as use in industrial products production, maize is of special importance in agricultural development programs. To improve a trait with complex behavior and low heritability, indirect selection by other traits or a suitable index developed based on several traits can be used. In this research, 86 maize genotypes were cultivated in the form of randomized complete block design with three replications in the field in the Faculty of Agriculture, Urmia University under two normal and salt stress conditions. The measurement of the traits was done from the tassel appearance to kernel physiological maturity. In order to speed up genotype selection and increase the acuracy of selecting high yielding genotypes, four selection indices including Smith- Hazel, Pasek- Baker, Brim and Robinson were used and calculated. The results of present study revealed that selection based on the Smith- Hazel index with the highest selection efficiency (∆H) will increase the grain yield in normal and grain yield and plant height in salt stress conditions. This index, with its high correlation with the breeding value is introduced as a superior index. Based on this index, R59 and 6*/88 genotypes were introduced as the superior genotypes under normal and salt stress conditions, respectively. Nonetheless, these genotypes were recognized as the best genotypes considering the results of all other investigated indices. Identifying and introducing genotypes tolerant to salinity stress is of particular importance due to the expansion of saline lands and the limitation of access to water suitable for irrigation. Based on the above results, 6*/88 genotype is recommended for the development of promising hybrids for cultivation in areas with water or saline soil.