1a. Objectives (from AD-416):
1. To characterize selected germplasm lines of sorghum for response to cold stress at early season and at other specified stages of development and accelerate the development of improved germplasm resources for different types of sorghums. 2. To investigate the genetic and physiological basis of cold tolerance in sorghums through genetic studies of tannin genes in sorghum.
1b. Approach (from AD-416):
1. Establish replicated field trial of sorghum lines in various locations to estimate genotype by environment interaction. 2. Perform fine mapping of two QTLs in the population of 109 F6:7 RILS developed from Tx430/SQR, and in two additional mapping population Tx430/SC1103 and Tx430/SC1345, each with 250 F6:7 RILS and characterize, phenotypically and genotypically the 300-line sorghum diversity panel for testa layer.
3. Progress Report:
An understanding of the genetic basis of grain tannin content through QTL mapping and cloning of tannin genes in sorghum was achieved. Results showed that in some genotypes, possible physical linkage between tannin and cold tolerance genes could result in reported association for the traits. However, identification of new non-tannin resources for cold tolerance that harbor different cold tolerance genes have been demonstrated in this project. The effect of cool temperature at two growth stages of sorghum was analyzed and identification of additional genetic sources of cold tolerance for use in breeding programs was performed. Three genotypes, Shan Qui Red (tolerant), SRN39 (susceptible), and Pioneer 84G62 (unknown), were subjected to two temperature regimes, 15/13 C day/night (cold) and 25/23 C day/night (normal), at seedling and flowering stages using growth chambers. Stress at flowering stage could delay maturity and reduce various yield components.