| dc.description.abstract | In an effort to speed up the breeding process it would be beneficial to predict the performance of biomass sorghum photoperiod sensitive hybrids without having to make test crosses with the photoperiod insensitive inbred parents first. However, due to the differences in harvest index between biomass hybrids and grain type inbreds, and the confounding effects of maturity genes with heterosis, the ability to identify a relationship between biomass hybrid performance and photoperiod insensitive inbred parents is challenging. Thus, the objectives of this research were to analyze phenotypic traits related to biomass in an effort to identify a potential relationship between hybrid yield, heritability, heterosis and correlation of inbred performance on the performance of the related biomass hybrids, and lastly to conduct a QTL analysis on the inbreds and hybrids to attempt to identify QTL or makers for traits related to biomass yield.
Examination of both photoperiod sensitive inbred parents and their resulting biomass hybrids revealed few trends between the two populations. Statistical difference of phenotypic traits existed in all populations. Despite this, correlations of phenotypic traits between the PI inbreds and their PS hybrids were inconsistent across years with the exception of 3rd internode diameter and hybrid stalk weight per plant.
The range of HPH for the hybrid populations varied greatly depending on the trait. Biomass yield HPH had a range of 1000% and is mostly attributed to the presence of maturity genes. When examining inbreds and hybrids grown in the same year, we report that inbred heritabilties were generally higher for phenotypic traits than their corresponding hybrids. It is speculated that the effects of the maturity genes and heterosis are not only confounded with each other, but that their biomass increasing effects reduced the heritability and increase the heterosis for most of the phenotypic traits in the hybrids.
A genetic map was developed for both populations and both inbred and hybrid phenotypic and NIR trait data was analyzed using these genetic maps. Mapping of QTL was conducted, and several QTL were identified in both the inbreds and hybrids of both populations. Overall, most of the QTL identified were related to stalk characteristics and found on chromosome 7, the chromosome where Dw3, a major height gene, is located. These results suggest chromosome 7 plays a large part in both stalk traits and height. The small population size utilized herein made identification of QLT difficult and greatly over-estimated the explained phenotypic variation. No QTL were identified for biomass yield, which was expected due to the quantitative nature of biomass yield – it is unlikely that such a quantitative trait is controlled by a single gene(s). | en |
