Agronomic characterization of inbred lines & hybrids of sorghum introgressed with QTL for cold tolerance
Cold temperature occurring in the early growing season is a major limitation for sorghum (Sorghum bicolor (L.) Moench) cultivation in the northern and central United States and other temperate regions. Chinese kaoliang sorghum landraces, known to have excellent seedling cold tolerance, were used as a source of genes to improve early-season cold tolerance in sorghum at Purdue University. In the last few years, work focused on introgressing two QTL were identified in a Chinese sorghum line Shan Qui Red (SQR) into five commercial grade inbred lines via marker assisted selection generating five pairs of isogenic lines with and without these markers. Selection for the cold tolerant alleles from the donor kaoliang parent was based on SSR (Simple Sequence Repeat) markers in the two QTL regions. The objective of this study was to compare performance differences between the original inbred and the new cold converted (CC) sorghum sister lines. The iso-lines were grouped into male and female parents and used to generate contrasting hybrids. Four cold converted inbred lines and four cold converted hybrids were evaluated in the growth chamber and field for early-season traits (seedling emergence, seedling vigor, and seedling biomass) under cold stress conditions. Flowering time, mature plant height and final grain yield were evaluated in the field trials. A germination test was conducted in the growth chamber to compare the converted and unconverted lines. Results showed that the effect of the QTL varied with inbred lines. K1597-CC4 and Tx2737-CC showed improved cold tolerance over their unconverted counterparts in seedling emergence and germination under cold stress conditions in the field trial, growth chamber experiment and germination tests. Inbred line Wheatland, both converted and unconverted iso-lines showed good seedling cold tolerance with no significant difference between pairs. Hybrids generally showed superior performance to the lines in both seedling emergence and seedling vigor, due to the effect of heterosis. Though the R-line Tx2737 showed relatively poor seedling emergence, remarkably, Tx2737 hybrids showed the best seedling emergence and germination under cold stress conditions in this study.
Ejeta, Purdue University.
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