Journal of Crop Production and Processing

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Alipour Kondari H, Mohammady S, Houshmand S. Evaluation of Genetic Diversity and Comparison of Phenotypic Traits in Irrigated and Rainfed Wheat under Irrigated Cultivation Conditions. Journal of Crop Production and Processing 2025; 15 (2) :95-109
URL: http://jcpp.iut.ac.ir/article-1-3362-en.html

Extended Abstract
Introduction: Wheat (Triticum aestivum) is one of the world's leading staple crops, and the demand for higher production is growing in response to the increasing global population. However, in many regions wheat production has declined as a result of climate change. Therefore, the introduction of new varieties that require less water is necessary. Genetic diversity in plants is crucial for their improvement. Plant breeders use genetic resources, such as crop varieties, for breeding purposes, including tolerance to biotic and abiotic stresses. One approach for evaluating genetic diversity involves the use of morphological markers, which assesses diversity by considering both genetic and environmental influences. The objective of this experiment is to analyze genetic diversity and compare irrigated and rainfed wheat varieties based on their phonological and morphological traits. This comparison aims to identify specific traits in rainfed wheat varieties that contribute to their enhanced drought tolerance.

Materials and Methods
This experiment was conducted at Amiran Farm, in Felard County, Chaharmahal, and Bakhtiari Province, Iran, during the 2023-2024 growing season. The genetic materials used for this study included five irrigated genotypes and five rainfed genotypes. The experimental design was a randomized complete block design with four replications. Each experimental plot consisted of four planting rows, each 1.5 meters long. The row spacing was 20 cm, and the spacing between plants was 30 cm. Additionally, to reduce border effects a row of the Sirvan cultivar was planted around the experimental plot. Sixteen traits were measured, including days to heading, maturity, and grain filling, plant height, peduncle length, flag leaf length, flag leaf width, flag leaf area, seed weight/spike, biological yield, seeds/spike, thousand kernel weight, harvest index, tillers/plant, spike length, and grain yield. Data analysis, including analysis of variance, group comparisons, mean comparisons, and phenotypic correlation assessment were performed using SAS 9.2 software. In addition, genotypic groups were identified using cluster analysis based on Ward's method and the Euclidean squared distance criterion in STATGRAPHICS software.

Results and Discussion
The results of the analysis of variance showed that there were significant differences among the genotypes for almost all the traits, including days to heading, maturity, and grain filling, plant height, peduncle length, flag leaf width and area, seed weight/spike, biological yield, seeds/spike, thousand kernel weight, harvest index, tillers/plant, and grain yield. Additionally, the results of the group comparisons indicated significant differences between the rainfed and irrigated varieties for all the measured traits except flag leaf length, biological yield, and spike length. In other words, rainfed genotypes had fewer days to heading and a shorter grain-filling period compared to the irrigated genotypes, with the Rejave genotype being the earliest among the studied genotypes. Also, this genotype had the highest yield among the rainfed genotypes. The increasing global temperatures and the coincidence of wheat's sensitive growth stages with high temperatures, selecting early maturity and shorter grain filling duration are effective breeding strategies to overcome these conditions. The results of this study demonstrated that rainfed genotypes had superior performance in these key traits compared to irrigated ones, showing a greater ability to escape terminal drought and heat stresses. Irrigated wheat genotypes had shorter peduncle lengths compared to rainfed genotypes. A reduction in peduncle length can lead to the greater grains/spike, thereby increasing overall wheat yield. It was also observed that the irrigated genotypes had shorter peduncles and a higher grains/spike than the rainfed genotypes. The rainfed genotypes also had smaller flag leaf areas compared to the irrigated varieties, indicating that they may have lower transpiration rates. Correlation analysis indicated that plant height and peduncle length had a significant negative correlation with the most economic traits, suggesting that reducing these traits could increase wheat grain yield. Finally, cluster analysis divided the genotypes into rainfed and irrigated wheats.

Conclusions
There was high genetic diversity among the available varieties for most of the traits studied. Moreover, the results of group comparisons showed that, for all studied traits except flag leaf length, biological yield, and spike length, there were significant differences between irrigated and rainfed genotypes. Rainfed varieties were also earlier and had a shorter grain filling period and smaller leaf areas compared to the irrigated varieties. Crossing rainfed and irrigated wheat varieties creates a population with very high diversity and will be used in further experiments in future. This population will be used to develop new varieties with desirable traits.