Degree

Doctor of Philosophy (PhD)

Department

School of Plant, Environmental and Soil Sciences

Document Type

Dissertation

Abstract

Salinity is emerging as a major threat to rice production worldwide due to climate change and anthropogenic sources. We performed three different population development approaches using exotic salt tolerant donors in US rice backgrounds to identify the salt tolerant QTLs/genes and tolerant breeding lines. First approach involved development of a biparental introgression lines (ILs) population by utilizing a salinity tolerant donor ‘TCCP’ in an elite rice cultivar ‘Cheniere’ background and mapping of QTLs at germination, seedling, and reproductive stages A total of seven QTLs for five germination traits, 16 QTLs for seven seedling stage traits, and 30 QTLs for ten reproductive stage traits were identified using a genotyping by sequencing (GBS) based SNP linkage map. In the second approach, two multi-parental advanced generation introgression lines (MAGIL) populations were developed using multiple salt tolerant donors such as Pokkali, FL478, and Hasawi in Mermentau and Cheniere background followed by salt tolerance screening. The principal component and cluster-based analysis using morphophysiological traits revealed grouping of the selected lines with tolerant donors whereas clustering based on genotypic data grouped the ILs with the recurrent parents. The third approach involved development of three different populations using earlier developed salinity tolerant ILs CLPK683, CLPK757, JN100, and JN520 to pyramid beneficial alleles/QTLs. The QTLs for shoot Na+ and K+ content, qNa2.2, qK2.1, and qK2.2, from JN100 and qK4.1 and qK8.1 from JN520 were targeted using the molecular markers. Both phenotypic and marker-based selection methods were employed to advance the populations. The F5 populations of each cross were finally evaluated for seedling stage salt tolerance. The visual salt injury score (SIS) and shoot Na+ and K+ concentrations in selected lines indicated salt tolerance greater than IL parents. The targeted QTLs were detected in most salt tolerant pyramided lines. Finally, the salt tolerant breeding lines obtained from these approaches will be used as genetic resource for improved understanding of the salt-tolerance mechanisms, discovery of superior alleles, and development of high-yielding rice varieties with improved salt tolerance

Date

7-16-2022

Committee Chair

Subudhi, Prasanta K.

Available for download on Sunday, July 16, 2023

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