Evaluation of Sweet Sorghum Accessions with Seedling Cold Tolerance.

Cultivars with excellent seedling emergence and stand establishment at early spring cold conditions may be planted early in the same region or in more northern latitudes with an extended period of plant growth and can potentially increase either grain yield or stem sugar yield or biomass production of sorghum. Planting cultivar with early spring cold tolerance may also expand sorghum planting geographic regions or allow multiple harvests within a year. Research on early spring cold tolerance in grain sorghum is expanding, but very limited information is available on sweet sorghum. Evaluation of 212 sweet sorghum accessions (selected from the USDA germplasm collection) plus four checks for the early spring cold tolerance was conducted at both lab and field conditions. In this study, a high correlation coefficient between lab germination rate and field germination rate (R2 = 0.503, p <0.0001) was determined. In general, lab germination rate can predict the field germination performance but some discrepancies between field and lab tests were also observed for some accessions. The correlation coefficient of seedling dry weight with the field germination rate was much higher (R2 = 0.257, p <0.0001) than with the lab germination rate (R2 = 0.109, p <0.05). Several sweet sorghum accessions with seedling cold tolerance were identified from both lab and field tests. These accessions will be useful materials for development of sweet sorghum cultivars with early spring cold tolerance. In addition, 652 more sweet sorghum accessions were only screened in the lab for seedling cold tolerance. These accessions identified with good seedling cold tolerance in the lab need to be further confirmed by the field experiment. Seed dormancy can directly affect seed germination rate. The relationship between seed dormancy and germination rate from this study will also be discussed.