Thesis - Open Access
Master of Science (MS)
Biology and Microbiology
Genome-Wide Association Study (GWAS), Maize, Modifiers, Pollen contamination, Quantitative Trait Loci (QTL), Teosinte crossing barrier 1 (Tcb1)
Pollen cross-contamination has been a major problem for maize breeders. Various mechanical methods applied to avoid the contaminations are ineffective. The genetic factors related to maize fertilization can be used to develop an effective method to prevent pollen contamination. Pollen rejection ability controlled by Teosinte crossing barrier 1 (Tcb1) is such a genetic system. Silks possessing dominant Tcb1-s reject pollen possessing the recessive allele (tcb1). Successful fertilization occurs when Tcb1-s pollen falls upon tcb1 silks. The efficacy of dominant Tcb1-s was, however, reduced when repeatedly backcross with maize inbred lines, which suggests that there are modifiers to Tcb1-s. To find those modifiers, we conducted a QTL mapping experiment using Intermated B73 x Mo17 (IBM) recombinant inbred lines (RILs) for two consecutive years. Two significant QTLs were revealed at chromosome 4L and 5S, for both years. They explained 16 % to 17.6% of total phenotypic variation (R2) and had a negative additive effect with no interaction. Further study of the QTL regions resulted in the identification of twelve candidate genes (nine in 4L and three in 5S) possibly modifying the tcb1 gene action. In order to have further insight of the blocking effect across diverse maize germplasm, we also conducted GWAS using the Goodman Association panel. From this analysis, we identified six candidate loci (at 1L,3L, 4L, 5S, 7L, and 10S, respectively) that were associated with pollen blocking action by Tcb1-s. A total of nine candidate genes were revealed in these loci. The introgression of the Tcb1-s genetic system, along with its appropriate modifying factors, could be a novel and reliable solution for pollen contamination in maize breeding.
Number of Pages
South Dakota State University
Copyright © 2021 the Author
Maharjan, Namrata, "Identification of loci Influencing Teosinte Crossing Barrier 1 (Tcb1) Efficacy in Maize by Quantitative Trait Loci (QTL) Mapping and Genome-Wide Association Study (GWAS)" (2021). Electronic Theses and Dissertations. 5214.