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. 2019 Sep 29;8(10):388.
doi: 10.3390/plants8100388.

Identification of Anther Length QTL and Construction of Chromosome Segment Substitution Lines of Oryza longistaminata

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Free PMC article

Identification of Anther Length QTL and Construction of Chromosome Segment Substitution Lines of Oryza longistaminata

Takayuki Ogami et al. Plants (Basel). .
Free PMC article

Abstract

Life histories and breeding systems strongly affect the genetic diversity of seed plants, but the genetic architectures that promote outcrossing in Oryza longistaminata, a perennial wild species in Africa, are not understood. We conducted a genetic analysis of the anther length of O. longistaminata accession W1508 using advanced backcross quantitative trait locus (QTL) analysis and chromosomal segment substitution lines (CSSLs) in the genetic background of O. sativa Taichung 65 (T65), with simple sequence repeat markers. QTL analysis of the BC3F1 population (n = 100) revealed that four main QTL regions on chromosomes 3, 5, and 6 were associated to anther length. We selected a minimum set of BC3F2 plants for the development of CSSLs to cover as much of the W1508 genome as possible. The additional minor QTLs were suggested in the regional QTL analysis, using 21 to 24 plants in each of the selected BC3F2 population. The main QTLs found on chromosomes 3, 5, and 6 were validated and designated qATL3, qATL5, qATL6.1, and qATL6.2, as novel QTLs identified in O. longistaminata in the mapping populations of 94, 88, 70, and 95 BC3F4 plants. qATL3, qATL5, and qATL6.1 likely contributed to anther length by cell elongation, whereas qATL6.2 likely contributed by cell multiplication. The QTLs were confirmed again in an evaluation of the W1508ILs. In several chromosome segment substitution lines without the four validated QTLs, the anthers were also longer than those of T65, suggesting that other QTLs also increase anther length in W1508. The cloning and diversity analyses of genes conferring anther length QTLs promotes utilization of the genetic resources of wild species, and the understanding of haplotype evolution on the differentiation of annuality and perenniality in the genus Oryza.

Keywords: anther length; cell elongation; genetic architecture; outcrossing; perennial species; rice.

Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Distribution of anther length (mm) in cultivars of O. sativa and accessions of O. barthii, O. glumaepatula, and O. longistaminata. Mean ± SE, n = 3.
Figure 2
Figure 2
Breeding scheme of genetic materials used in this study. MAS represents marker-assisted selection.
Figure 3
Figure 3
Box plots of anther length among the 26 BC3F2 populations. A thin horizontal line shows the average anther length in the Taichung 65 (T65) genetic background. Thick horizontal bars represent average values. Ranges between upper and lower quantiles are indicated by grey boxes. Maximum and minimum values excluding outlier are indicated by upper and lower whiskers, respectively. * and ** represent significant differences at P = 0.05 and P = 0.01, respectively.
Figure 4
Figure 4
Validation of the anther length quantitative trait locus (QTLs) located on chromosomes 3, 5, and 6 in BC3F4 populations segregating at only one QTL region. (a)–(e) Graphical genotypes of the parents of BC3F3 and BC3F4 populations, and frequency distributions of anther length in BC3F4 populations for (a) qATL3.3, (b) qATL3.1, (c) qATL5, (d) qATL6.1, and (e) qATL6.2. Graphical genotypes: Yellow, heterozygous; red, homozygous for the W1508 allele. Frequency distributions shown in colors by genotypes at RM5959 (a), RM3525 (b), RM1054 (c), RM7023 (d), and RM7309 (e): Orange, homozygous for T65; yellow, homozygous for W1508; gray, heterozygous; (f) logarithm of odds (LOD) curves in simple interval mapping of anther length for detection of qATL6 (green) in BC3F3 5, qATL6.1 (orange) in BC3F4 17, and qATL6.2 (blue) in BC3F4 14.
Figure 5
Figure 5
Characterization of QTLs using nearly isogenic lines (NIL) carrying W1508 chromosomal segments around QTL regions detected in this study. (a) Anther length (mm) in the NILs. Mean ± SE, n = 3; (b) cell length (µm) in the long axis of anthers in the NILs. * and ** represent significant differences in Dunnett’s multiple comparisons to T65 control at 5% and 1% levels, respectively. The numbers of observed cells were 1460, 997, 953, 879, and 1033 in qATL3.1 NIL, qATL5 NIL, qATL6.1 NIL, qATL6.2 NIL, and T65 respectively.
Figure 6
Figure 6
Construction of chromosome segment substitution lines of O. longistaminata accession W1508 (W1508ILs) in the genetic background of O. sativa L. cv. Taichung 65. Red and white boxes represent homozygous genotypes for W1508 and Taichung 65 alleles, respectively. Yellow boxes represent heterozygous genotypes. Missing genotypes at markers showing heterozygous genotypes at BC3F1 generation are indicated by grey.

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