Agronomic and qualitative characteristics of sorghum stay-green QTL introgression lines and their recurrent senescent parents: Evaluation of GxExM interactions

Sorghum crop production in semi-arid tropical (SAT) regions frequently suffers the losses due to abiotic environmental factors (e.g. drought) and stay-green sorghum technology was found to be vital option to alleviate some of these detrimental effects on crop production quantities. Recently, few studies documented the positive effect of sorghum stay-green technology on quality of the stover production while, since far, none exists to document the effects on grain qualities. Therefore, in the present study we dissected the effects of stay-green sorghum technology on production quantities and qualities under different environmental circumstances. Precisely, we studied the effects of genetic (G; i.e. stay-green), environment (E) and management (M) and their interactions (G x E x M) on crop agronomic performance and the main qualitative parameters of stover and grain in order to understand the functional linkages between the studied traits. The studied material included two senescent lines and the set of their stay-green derivatives along with elite post-rainy (rabi) sorghum cultivar (maldandi) as check. Crop was grown in the field conditions in two seasons (rabi 2013-2014 and 2014-2015) under the factorial treatments of irrigation schedules, plant population and fertilizer application. Studied traits included (i) agronomic traits: grain weight (gplant-1; kgha-1), grain size [g per 100 seeds], grain number per panicle, stover weight (gplant-1; kgha-1), (ii) canopy-related traits: Leaf area (LA (cm2)) at booting stage, Leaf area index (LAI [m2 m-2]), visual senescence score (0-100%), biomass partitioning index (Bpi; [(leaf+stem)/leaf dry weight]) and (iii) stover and grain qualitative characteristics: leaf, stem and panicle in-vitro organic matter digestibility (IVOMD [w/w%]), grain protein (w/w%), fat (w/w%) and amylose (w/w%). In accordance with other studies, we found that stay-green material resulted in production advantage (stover, grain or both) compared to their senescent parents especially under severe water limited environments. We also confirmed that majority of investigated stay green lines had constitutively higher stover quality indicators (IVOMD) compared to their senescent parents under most of the treatments. The novel finding in this study is that the stay-green technology also influenced the grain qualities and that grain and stover qualities are likely functionally related (therefore predictable) to plant allometry and capacity to maintain green leaf area (in the crop aging processes and under abiotic stress). In this work we also preliminarily assessed the economic value of the stay-green material and found the stay-green crop has higher likelihood to enhance the market price (stover and grain) when grown across range of environmental conditions. We envisage that understanding and quantification of functional relations among the studied traits and their economic value would accelerate the use of the stay-green technology and related traits in crop improvement programs.