1a.Objectives (from AD-416):
1. To characterize selected germplasm lines for pre- and post-flowering drought tolerance;
2. To accelerate the development of improved germplasm resources for enhanced drought tolerance breeding programs in different types of sorghums; and
3. To understand the genetic and physiological basis of drought and heat tolerance in sorghums.
1b.Approach (from AD-416):
Our newly developed high throughput screening tools will provide, for the first time, a quantitative measure of the levels of pre- and post-flowering drought tolerance in germplasm collections, mutant populations, and hybrid combinations. This information will expedite the movement of tolerant germplasm into advanced breeding programs. Modification of plant architecture will be evaluated to determine morphologies that enhance yield with less water consumption. Genotypes with improved vegetative and reproductive heat tolerance will be identified, and the genetics underlying the tolerance will be determined. We will develop an irrigation management that optimizes the seasonal distribution of limited water to maximize grain yields of pre-flowering drought tolerant sorghum lines.
In an effort to identify new sources of drought tolerance, we evaluated 650 lines of the Ethiopian collection for characterization of the stay-green and senescent traits. Lines in the sorghum conversion program (approximately 800 lines) have been analyzed for the stay-green metabolite. Six of eight Ethiopian lines identified as potentially stay-green in the Lubbock study were grown out in Puerto Rico during the winter of 2011. Five of the six lines exhibited excellent maintenance of lower leaves. These lines have been crossed to BTx406, and F1 seeds have been planted in a growth chamber with a 10-hour photoperiod to induce flowering. These plants have been crossed to B, R, and A lines. Three Sudanese lines shown to exhibit stay-green phenotypes via both the Burke et al. bioassay and in post-flowering drought stress studies in the field during 2010 have also been crossed to appropriate B, R, and A lines. Segregating lines are in the field and will be analyzed for flowering time, height, and dhurrin content.