Evaluating the salt tolerance in fifth generation (M5) of bread wheat lines using the biplot and factor analysis methods

Introduction Soil salinity is one of the major abiotic stresses affecting crop growth and productivity. Effective screening techniques for salinity tolerance would be beneficial in developing yielding wheat varieties. Knowledge of the interrelationships between traits will improve the efficiency of breeding programs especially under saline conditions through appropriate selection criteria. Improving the seed yield of wheat is always the final and major target in plant breeding.. On other hands, Yield is a complex quantitative trait, with low heritability. Some morphophysiological traits and related characters with seed yield due to easy measurement and high heritability can be used as criteria for distinguish salinity tolerant plants and for improvement of seed yield in wheat genotypes. Therefore, there is necessary to examine the relationships between various traits, especially between seed yield and other traits. Biplot is a graphical tool for breeders and is a plot that simultaneously displays the effects of traits and genotypes. The GGE biplot is the most commonly used and most useful type of biplot. The first objective of this study was to describe a genotype by trait (GT) biplot, which is an application of the GGE biplot technique to study of the genotype by trait data and to examine its usefulness in visualizing wheat trait relationships, and its application in M5 lines evaluation, comparison, and selection. The second objective of this study was to evaluating salt tolerance of M5 bread wheat lines clarify the association among some morphophysiological traits of M5 bread wheat using correlation and factor analysis, which provide valuable information for breeding new high yielding wheat lines. Mehtods and Material In this study, 15 bread wheat line selective of 4 generation (M4) lines with 2 parents genotype of them (Arg and Bam) and 2 genotype yazd (Sivand and Narin) were evaluated under two non-stress )2 dSm-1) and stress conditions )10 dSm-1) in a Randomized Complete Block Design (RCBD) with three replications research field of the National Salinity Research Center (NSRC) in Yazd provinc. Each plot consisted two rows 20 cm apart and 1 m in length. for the purpose of determining the salinity of soil during growth season, sampling have been done from the depth to 90. The average of salinity rate in non-stress and salinty condition was 2.3 and 9.7 dS.m-1 respectively.The traits were Yield (Y), Chlorophyll content (CH), Number of Grain per Spike (NG), Number of fertile tillers (NT), Hundred Kernel Weight (KW), Biological Yield (BY), Peduncle Length (PL), Spike Length (SL), Plant Height (PH), Flag Leaf Length (FL), Number of Spikelet per Spike (NS), Awn Length (AL), Peduncle Weight (PL), Harvest Index (HI), Spike Weight (SW), Days to Heading (DH), Days to Physiological Maturity (DM), Grain Weight/Spike (GW), Fluorescence Maximum (FM), Variable Fluorescence (FV), Variable Fluorescence/ Variable Fluorescence (FV/FM), NA+, K+ and K+/NA+. Tolerance indices of stress tolerance index (STI) were calculated in this investigation for salinity. The Fluorescence chlorophyll and chlorophyll content was measured in the reproductive stage using a Chlorophyll Fluorimeter-PEA Plus and SPAD- CL-01 chlorophyll meter, Respectively. All biplots presented in this paper were generated by using the “GGEbiplot” and SAS9.01 software. Also, Person Correlation and Factor analysis carried out using by SAS9.01 and SPSS18 softwares. Results and discussion This study demonstrated that GT biplot was an excellent tool for visual evaluation of superior lines, traits and grouping of them with other statistical techniques. The obtained data were analyzed using factor analysis and genotype trait (GT) biplot method based on site regression model .The biplot vector view indicate that there was a strong positive association between BY (Biological Yield) with seed yield in non-saline and CH (Chlorophyll content ) with seed yield saline conditions. Factor analysis confirmed this results. It seems that CH and BY traits can be used as selection criterion for improving of seed yield in wheat breeding programs, especially under stress conditions in the field. Also, the three-dimensional diagrams derived from STI index and grain yield in non-stress and salt stress conditions confirmed that the number 1, 2 and 8 lines had the highest grain yield in non-stress and salinity conditions and were the most tolerant lines to salinity stress. Conclusions the lack of identification of appropriate morphophysiological traits has been one major factor preventing improvement of yield in salinity environments, as well as the reason why plant breeders have not adopted more analytical approaches to selection. Moreover, any desirable morphophysiological trait should be simple, rapid and more economical than yield to assess. Generally, we conclude that tolerance to salt conditions in bread wheat lines seems to be related to its ability to production of Chlorophyll content. These findings will be useful in selection material for M6 breeding programs. Also, its was confirmed that the number 1, 2 and 8 lines had the highest grain yield in non-stress and salinity conditions and were the most tolerant lines to salinity stress