Out of the four grass species selected for this study, rice and sorghum were chosen as starting points for comparisons because their sequence and annotation data sets were considerably better than those of maize and Brachypodium.
The comparison of phenotypic data of plants at the vegetative stage and at plant maturity showed that all four rice varieties selected for this study responded similarly to the drought treatment by reducing shoot and root biomass and tiller numbers (Fig. 1; Additional file 2: Figure S1).
The rice characters selected for this study and their units of measurements are listed with abbreviations [see Supporting Information —Table S1].
Twenty rice varieties, four local (MR219, MAHSURI, UKMRC2, and UKMRC9), and sixteen (IR8, IR20, TETEP, Teqing, IR24, IR36, IR64, Jasmine 85, C4-113, ADT 36, ADT 38, ADT 39, IR39-14, IR50, and TOX 2104-2-1) international varieties were selected for this study.
In addition to these divergent root architectures that have been selected for among rice agro-ecosystems, the increasingly fluctuating levels of stress that is projected to occur across rice growing systems may necessitate more diverse root architectures and better adaptability to uneven distribution of soil resources.
The salt stress levels selected for the both rice and barley were based on a yield loss of 60% for both, the sensitive rice (IR29) and sensitive barley (Maythorpe) [ 21, 18].
The salt stress levels selected for the both rice (7.4 dSm-1/~60 mM NaCl) and barley (17 dSm-1/~150 mM NaCl) were based on past experiments which indicated a yield loss by 60% for both, the sensitive rice (IR29) and sensitive barley (Maythorpe) [ 21, 18].
For example, QTL associated with GS3 [ 3] and GW5/ SW5 [ 4, 5] have been selected for grain size in rice.
To better understand their expansion history and expression divergence, two other genomes were also selected for comparative analyses including rice (model plant for monocot) and Arabidopsis (model plant for dicot) genomes.
This suggested that SD1-EQ might have been selected for during the domestication of rice.
