Junaid, Jamshaid Ali (2022-07). Development and Characterization of Advanced Generations A2D1 Chromosome Segment Substitution Lines in Cotton. Doctoral Dissertation.
Thesis
The cotton genus, Gossypium, includes 52 species of which 45 are diploid and 7 are tetraploid. While G. hirsutum L. (2n=4x=52) is by far the most important agriculturally, all of the species are potential sources for genetic introgression and improvement of upland cotton (G. hirsutum). Chromosomal segment substitution lines (CSSLs) can facilitate [1] introgression of germplasm from donor accessions or species into crop species, [2] detection of newly introduced genetic variation, [3] genomic localization of said variation and [4] marker-assisted breeding for genetic improvement. The goal of this research is to increase the genetic capacity of cotton for improvement, specifically by developing and characterizing CSSLs containing novel germplasm from a synthetic A2D1 tetraploid parent. CSSLs were advanced to the BC5F1 generation through backcross breeding and then selfed for three generations to recover the homozygous introgressed segments. Simplex and low-plex KASP/PACE assays were developed and used to select plants putatively containing A2 and/or D1 germplasm; 19 prospective A2D1 chromosome segment substitution lines were selected and then characterized by genome-wide high-density genotyping using the CottonSNP63K array. To evaluate the introgressed genes effects on fiber quality parameters, fiber samples were collected from BC5S1 plants within BC3-derived families. Fiber samples were also collected from 19 identified BC5S2 CSSLs grown at two locations using a randomized complete block design with three replicates and three plants per replication. The fiber samples were characterized using High Volume Instrument (HVI) and Advanced Fiber Information System (AFIS). ANOVA of HVI data showed that differences were significant among BC3-derived families (?=0.05) for all fiber quality parameters except micronaire. ANOVA for identified CSSLs showed the differences (?=0.05) for micronaire, upper half mean length, elongation, strength and short fiber index were significant, but differences for uniformity index were nonsignificant for the greenhouse location. ANOVA for yield-related parameters showed the differences (?=0.05) for seed weight and lint weight were significant, but differences for lint/seed ratio and yield per plant were nonsignificant for the field location. Micronaire readings of the CSSLs ranged from, 3.21 to 5.79 while the TM-1, USDA TM-1, FM-958 and CA-4008 had micronaire readings of 4.54, 4.31, 4.99 and 4.26 respectively for the greenhouse location and 4.54, 4.13, 4.11 and 3.59 respectively for the field location. Fiber strength ranged from 25.4 to 37.6 g/tex for greenhouse plants and 23.8 to 36.1 g/tex for field plants, while the strength for TM-1, USDA TM-1, FM-958 and CA-4008 was 26.53, 35.93, 34.06 and 32.60 g/tex respectively for greenhouse plants and 26, 31.13, 28.93 and 31.66 g/tex respectively for field plants. In both locations, the AFIS values of all of the prospective A2D1 CSSLs had higher value for length-by-number distribution and lower short fiber contents as compared to TM-1. Analysis of flower buds at metaphase I showed that bivalents were the most prevalent configuration in all of the chromosome segment substitution lines (CSSLs). For a few CSSLs, an isolated cell or two formed what seemed to be a quadrivalent, but no CSSLs formed trivalent, pentavalent and hexavalent configurations, so these CSSLs also were deemed to be cytogenetically normal.
