Simple Sequence Repeat–Based Assessment of Genetic Diversity in Cotton Race Stock Accessions

Abstract

gressed into 97 primitive G. hirsutum race stock accessions by a large backcross breeding program (McCarty Effective use of converted day-neutral Gossypium hirsutum L. et al., 1979;McCarty and Jenkins, 1993). The converted race stocks in cotton genetic improvement programs depends on the extent of genetic variation for desirable alleles and the accurate char-primitive accessions are reservoirs of various genes for acterization of the variability within and among germplasm accessions resistance to pests such as boll weevil (Anthonomus in the collection. This study was conducted to survey the molecular grandis grandis Boheman) (McCarty et al., 1986), fuvariation in the converted race stock collection by using simple sesarium wilt [Fusarium oxysporum Schlechtend.:Fr. f. sp. quence repeat (SSR) DNA markers and to determine the genetic vasinfectum (Atk.) W.C. Snyder & H.N. Hans.], and distance of each race stock from a typical G. hirsutum cultigen. The tarnished plant bug (Lygus lineolaris Palisot de Beaumolecular marker data will also provide a measure of the degree to vois) (Jenkins et al., 1979). Introgression can be which the recurrent photoperiodic parent has been recovered during achieved without serious losses in agronomic perforbackcross conversion to day-neutral stocks. Fifty-six flourescently lamance (McCarty et al., 1996). beled SSR primer pairs arranged in multiplex bins were used to geno-Photoperiodic collections of other tetraploid Gossyptype 97 day-neutral BC 4 F 4 race stock accessions. The majority of the accessions had genetic distances Ͻ0.25 from the G. hirsutum standard ium species exist. DeJoodie and Wendel (1992) charac-TM1. There was strong evidence that the accessions were heterozy-terized the diversity of G. tomentosum Nutt. ex Seem, gous or heterogeneous, so 10 plants were genotyped within the most G. mustelinum Miers ex Watt, and G. darwinii Watt diverse nine accessions, those with genetic distance from TM1 Ͼ0.25.relative to G. barbadense L. and G. hirsutum. Unfortu-In some families, the primitive photoperiodic parent was recovered, nately, day-neutral versions of these tetraploid species and in others there was extensive linkage drag from the day-neutral

Pros and cons of using genomic SSRs and EST-SSRs for resolving phylogeny of the genus Gossypium

“…G. hirsutum ''latifolium''-genetically more close to G. hirsutum (Lacape et al 2007), would have least obstacles (Lubbers and Chee 2009) in attempting crosses. Within tetraploids, high genetic similarity estimates between G. barbadense and G. darwinii and G. tomentosum and G. hirsutum are in consistent with the earlier reports (Liu et al 2000;Wendel and Cronn 2003;Lacape et al 2007). Also, the variation in restriction sites in cpDNA and rDNA and in allozyme (14 enzyme systems) demonstrated more distinctiveness of G. tomentosum from G. hirsutum (0.82) than from …”

“…In the present study, higher PIC value for gSSRs versus EST-SSRs suggesting that transcribed portions of the genome are conserved in the genomes (La Rota et al 2005;Eujayl et al 2002). In multiple reports, inconsistency in PIC values data have been reported (Kebede et al 2007;Liu et al 2000;Kalivas et al 2011) which is attributed to the kind of germplasm explored, bottleneck in domestication (Thuillet et al 2004;Vigouroux et al 2005) and the kind of DNA markers (Liu et al 2000;Gutierrez et al 2002). Also, PIC values of the SSRs surveyed on diploid species were higher than the tetraploids.…”

“…It is much likely that during evolution there was enough accumulation of mutations in annealing sites and or the loss of these loci in the diploid species which together may influence the annealing of these primers (Liu et al 2000). In the present study, *97 % of the SSRs were polymorphic.…”

“…Like other cultivated crop species, all the cultivated tetraploids and diploids have a narrow genetic base within their respective gene pool (Liu et al 2005;Rahman et al 2008Rahman et al , 2011Shaheen et al 2010) because of developing cultivars from few genotypes (Rahman et al 2002b(Rahman et al , 2005a. This phenomenon has been demonstrated in multiple investigations (Liu et al 2000;Gutierrez et al 2002;Lacape et al 2007;Rahman et al 2002b). Second, limited use of wild cotton species for breeding new cultivars is another major reason for the narrow genetic base, a major cause of stagnation in cotton productivity worldwide (Rahman et al 2002a;Zhang et al 2005).…”

Development of Simple-Sequence Repeats Markers from Durian (Durio zibethinus Murr. cultv. Matahari) Genomic Library

“…One molecular marker that is widely used for this purpose is simple sequence repeats (SSR) or often called as microsatellites DNA (Hancock, 1999;Liu, Cantrell, McCarty, & Stewart, 2000). The advantage of this markers are co-dominant character, high level of polymorphic, easily to be repeated and stable (Ritschel et al, 2004) and the analysis could be conducted automatically (Schuelke, 2000).…”