Wheat Growth Indices at Key Developmental Stages and Their Relationship with Grain Yield

Crop growth indices, derived from leaf area expansion and dry biomass accumulation, provide valuable insights into plant growth performances under variable conditions. In this study, the growth behaviour of 10 bread wheat genotypes (Triticum aestivum) was evaluated at tillering, heading, flowering, and grain filling growth stages. The measured traits include relative growth rate (RGR), net assimilate rate (NAR), leaf area ratio (LAR), leaf weight ratio (LWR), and specific leaf area (SLA) with a focus on understanding their role in yield formation. Results revealed a significant difference between years in all growth indices and significant variability between genotypes mainly in traits related to leaf area index (LAR, LWR, and SLA). Yield recorded a positive correlation with RGR only at tillering (r=0.27, p=0.018); and 15/49 was the best performing genotype at this stage. Conversely, LAR index revealed positive correlations with yield at all growth stages, tillering (r = 0.31, p=0.007), heading (r = 0.44, p<0.001), flowering (r = 0.42, p<0.001) and grain filling (r = 0.32, p=0.02), with the best performance in terms of LAR was noted for 15/42 at tillering, Achtar at heading and flowering, and Amal at grain filling. As well, LWR showed a positive correlation with yield at heading (r=0.28, p=0.015), flowering (r=0.24, p=0.052), and grain filling (r=0.28, p=0.058), with 90/55/17 presented the best performance at tillering, Kharouba and Amal at heading and flowering, and 34/29 and Amal at grain filling. Similarly, SLA showed a positive and significant correlation with yield at tillering (r=0.25, p=0.034), heading (r=0.26, p=0.028), and flowering (r=0.4, p=0.001), with 15/42 and 15/49 displaying the best performance at tillering, 15/42 at heading, Achtar and 34/28 at flowering, and 90/55/17 at grain filling. In conclusion, selecting genotypes with a focus on growth indices that mostly contribute to yield at each growth stage offers a promising strategy for enhancing plant growth and ultimately improving yield.