|
|
:
|
In recent years, drought and water shortage stress have played a significant role in reducing rice cultivation area and yield and are considered a major threat to rice production. Roots are the main plant organ for water and nutrient uptake. Therefore, our understanding of the interactions between roots and drought stress in rice could have a significant impact on global food security. In order to identify the genetic potential of root traits of 36 selected rice genotypes under two conditions of non-stress and drought stress at the maximum tillering and panicle initiation stage (BBCH code: 30), an experiment was conducted in a randomized complete block design with three replications in controlled PVC pipes at the Rice Research Institute of Iran Rasht in 2023. According to the results of comparing the average traits, the highest root length and yield of paddy in condition drought stress related to the Mohammadi-Chaparsar cultivar with an average of 80.51 cm and 6.60 g per plant, respectively. The lowest yield reduction was observed in the Mohammadi-Chaparsar (49.57%), Dullar (51.44%), Gharib Siah-Reihani (55.03%), Hashemi (57.80%), Kian (60.42%) and Anam (62.51%) cultivars. Also, the highest percentage increase in root length (25.52%), root volume (44.68%), root dry weight (63.45%), and root-to-stem ratio (166.79%) in the stress environment was related to the Hassani cultivar, which had the lowest paddy yield and the highest percentage of yield reduction with an average of 1.67 g per plant and 86.96%, respectively. Based on the molecular results of microsatellite markers, a total of 78 alleles with 98.72% polymorphism were identified. The highest and lowest number of alleles were generated by RM247 with 6 alleles (100% polymorphism) and RM431 with 2 alleles (50% polymorphism). Also, the highest average PIC (0.789), Effective number of alleles (5.40), Shannon’s information index (1.74), Marker Index (4.730) and genetic diversity (0.81) were related to RM247 marker. The results of molecular cluster analysis using Jacard similarity coefficient and UPGMA algorithm divided the rice genotypes into four different groups. Mohammadi-Chaparsar and control Dullar cultivars were identified as drought-tolerant rice varieties in the first group due to their suitable root traits and grain yield stability. The lowest average root length in the stress environment (47.18 cm) related to the Anam cultivar, which was also separately placed in the fourth group from a molecular perspective. According to Fernandez's classification and the results of cluster analysis of stress tolerance and sensitivity indices based on paddy yield, 6 rice genotypes were placed in group A and selected. The Mohammadi-Chaparsar, Gharib Siah-Reihani, Hashemi, Dullar, Kian, and Anam cultivars were among the drought stress tolerant genotypes due to their average yield in two environments without stress and drought stress (13.25 and 5.80 g per plant, respectively). The results of cluster analysis of stress tolerance and sensitivity indices based on root biomass also divided the 36 studied genotypes into five groups. In the first group, the Daniyal, Gohar, and Nemat cultivars with the highest root biomass in non-stressed and drought-stressed environments identified as genotypes with relative drought tolerance due to the greater reduction in grain yield. The results obtained from the selected genotypes mentioned, can be used in advancing breeding programs to develop varieties with improved root systems for better uptake of water from deeper and larger volume of soil and appropriate performance in drought-stressed environments.
|