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.

芝麻是一种无限生长型油料作物，其产量由源（source）以及光合产物的合成与转运能力共同决定。目前针对芝麻源库间固有关系，以及该关系在土壤水分亏缺条件下的验证研究仍较为匮乏。为此，本研究于2021年和2022年连续两年，在灌溉（IR）与土壤水分亏缺胁迫（DS）两种处理条件下，针对25份具有不同株型特征的芝麻种质资源开展试验，供试种质的分枝模式涵盖单分枝至多分枝，叶面积范围覆盖最小至最大。研究人员测定了各供试种质的源库相关性状变异，对测定性状开展的方差分析（ANOVA）结果显示，在灌溉与水分亏缺胁迫条件下，不同种质的源性状（包括叶面积、茎干与叶片干重、净光合速率、总干物质积累量）及其与库（即两种处理下的种子产量）的关联均存在显著差异，该结论经回归分析得到进一步验证。研究结果表明，部分源性状——即籽粒灌浆期的茎干干重与总干物质积累量，在两种处理条件下均与种子产量呈显著正相关。此外，聚类分析结果表明，种质IC 54039-B-1与SI 1802叶面积适配性佳、种子产量优异，且源库关系更为优良，这意味着其光合产物可高效转运至库器官。相较于灌溉处理，这两份种质在土壤水分亏缺胁迫下表现更优，产量差异极小，且叶片干重、总干物质积累量及茎干干重均处于最优水平。这类源库关系优良的芝麻种质，可应用于芝麻作物遗传改良项目。