Source and sink traits and their relationship under deficit soil moisture stress conditions in an indeterminate crop: sesame (Sesamum indicum L.)

Sesame is an indeterminate oilseed crop where yield is determined by source and its capacity for synthesis and mobilization of photosynthates. Knowledge of the existing relation between source and sink and its validation under deficit soil moisture conditions is limited in sesame. Therefore, experiments were conducted using 25 sesame genotypes with differing plant architecture in terms of branching pattern (mono to multiple) and leaf area (minimum to maximum) under both irrigated (IR) and deficit soil moisture stress (DS) conditions for two consecutive years 2021 and 2022. The variations existing among the source and sink traits were measured, and the ANOVA of the measured traits revealed a significant differences among the genotypes for source traits, viz. leaf area, stem and leaf dry weight, net photosynthesis, total dry matter and their relationship with sink, i.e. seed yield under IR and DS conditions, and it was further confirmed using regression analysis. The results showed, certain source traits viz., stem dry weight and total dry matter at seed filling stage were positively associated with seed yield at both IR and DS conditions. Additionally, cluster analysis showed that the genotypes IC 54039-B-1 and SI 1802 had a proportional leaf area with good seed yield and displayed a better source and sink relationship, highlighting the fact that photosynthates were efficiently translocated to the sink. The genotypes IC 54039-B-1 and SI 1802 outperformed IR under DS with minimal yield differences and optimal leaf weight, total dry matter, and plant stem weight. These genotypes with better source and sink relationships can be used in sesame crop improvement programmes.