| چکیده انگلیسی مقاله |
Introduction and Objectives: Seed aging is considered a serious challenge in reducing seed quality, especially in developing countries where wheat plays a crucial role in providing food and where long-term seed storage is essential. Temperature and humidity are two very important factors during the seed storage process, significantly affecting seed vigor and quality (germination capacity). These two factors play a key role in determining the rate of seed aging by directly influencing the preservation or reduction of germination ability. The Accelerated Aging (AA) test is one of the most common tests used by the International Seed Testing Association (ISTA) to determine seed vigor under high temperature and humidity conditions, simulating natural seed aging during long-term storage. Considering the importance of genetic diversity and selecting superior genotypes in wheat breeding programs, this study aimed to identify and select genotypes with desirable germination and seedling traits under accelerated aging conditions. Selecting such genotypes not only enhances seed vigor and health during storage but also serves as an effective tool for breeders to develop new varieties with greater resistance to challenging environmental conditions. Consequently, this improvement in seed quality will lead to higher productivity, more economical production, and greater sustainability in wheat production.
Materials and Methods: In this study, 228 bread wheat genotypes were evaluated for seed aging tolerance during germination and seedling growth stages in the years 2022-2023.The experiment was conducted in a factorial arrangement within a completely randomized design with three replications. To induce seed aging, the Accelerated Aging method was applied at four levels: 0, 48, 72, and 96 hours. Subsequently, to assess germination and seedling growth, a standard germination test was performed according to the criteria of the International Seed Testing Association (ISTA). This test was conducted with three replications of 25 aged seeds for each genotype in Petri dishes using the "between paper" method at the optimal wheat growth temperature for 8 days. The studied parameters included germination percentage (GP), germination index (GI), viability index (VI), simplified viability index (SVI), mean germination time (MGT), mean daily germination (MDG), seedling length (SL), shoot length (SHL), root length (RL), shoot wet weight (SHWW), shoot dry weight (SHDW), root wet weight (RWW), root dry weight (RDW), and allometric coefficient (AL). Data analysis included variance analysis, correlation analysis, cluster analysis dendrogram (heatmap), and biplot representation of principal component analysis using R software version 4.3.2 with the packages agricolae, corrplot, gplots, and factoextra. Additionally, to select superior genotypes, the MGIDI index was calculated using the metan package for multi-environment trials analysis in R software. A selection intensity of 10% (SI) was considered for the selection of genotypes.
Results: Based on the results of the analysis of variance, the effects of different levels of accelerated aging were significant for all traits at the 1% statistical level. Additionally, there was a significant difference between the genotypes studied for all traits at the 1% probability level. The interaction effect of aging × genotype was also significant at the 1% probability level. A strong positive correlation was observed between germination percentage, germination index, viability index, simplified viability index, and mean daily germination under different levels of accelerated aging. In contrast, the correlation of mean germination time with most studied traits was weak. Additionally, with increasing aging levels, a decreasing trend was observed in the mean of most traits. For example, the germination percentage decreased from 91.96% in the normal condition to 60.44%, 29.76%, and 6.11% at aging levels of 48, 72, and 96 hours, respectively. Meanwhile, the mean germination time increased from 1.59 days to 2.62 and 3.01 days at aging levels of 48 and 72 hours, respectively. Cluster analysis results under different levels of accelerated aging classified the studied genotypes into three main groups based on similarities and differences in germination and seedling growth traits. The genotypes in the first group were identified as the best performers in terms of all germination and seedling growth traits. The MGIDI index was used to identify superior genotypes (Aging-tolerant) based on all traits, and its results were in complete agreement with the findings of principal component analysis and cluster analysis.
Conclusion: To further analyze the relationships between the studied bread wheat genotypes under different levels of accelerated aging, principal component analysis (PCA) and cluster analysis were used. Additionally, the MGIDI index was employed more efficiently to identify superior genotypes based on all traits. According to the results, genotypes 624846, 627853, 623090, 627414, 624864, Fong, Alvand, and Koohdasht, had the highest values for all traits related to germination and seedling growth under different levels of accelerated aging, and were identified as aging-tolerant genotypes. In contrast, genotypes 621421, 627236, 624315, Omid, Takab, and VEE/NAC, with the lowest values for these traits were classified as aging-sensitive. The superior identified genotypes could serve as genetic resources for breeding programs aimed at producing genotypes with high seed quality and rapid seedling emergence in the field. |