Nuclear genome size and karyotype analysis of Agave angustifolia Haw. “Cimarron” and “Lineño” (Asparagales, Asparagaceae)

Figures & data

Table 1. Provenance and karyotype analysis in diploid Agave angustifolia cultivars (2n = 2x = 60).

Cultivar	Site of collection	Collector and voucher information	Karyotype formula	Range of chromosome length (μm)	Secondary constriction	Total diploid genome length (μm) ± SE	Index of asymmetry (TF%) ± SE
“Cimarron”	Toliman, Jalisco State México. 19º32′06″N; 103º53′44″W (DSM)	Rodríguez J.M.C. Aa043	42 m+4sm+6st+8t	0.78–4.29	2t	102.69 ± 4.06	33.54 ± 0.47
“Lineño”	Toliman, Jalisco State México. 19º32′06″N; 103º53′44″W (DSM)	Rodríguez J.M.C. Aa041	48 m+2sm+2st+8t	1.18–4.79	2t	121.12 ± 4.03	34.37 ± 0.46

Table 2. Arm ratio (r) of homologous chromosome pairs of Agave angustifolia cultivars.

Chromosome pairs	“Cimarron” 2n = 2x = 60		“Lineño” 2n = 2x = 60
	r = q/p	CC	r = q/p	CC
1	16.19	t	7.12	t
2	10.37	t^a	7.25	t
3	5.79	st	9.00	t
4	5.91	st	6.08	st
5	10.25	t	7.89	t^a
6	1.02	sm	2.66	sm
7	3.42	st	1.24	m
8	1.77	sm	1.27	m
9	1.53	m	1.09	m
10	1.10	t	1.08	m
11	1.00	m	1.05	m
12	1.00	m	1.11	m
13	1.01	m	1.11	m
14	1.01	m	1.06	m
15	1.01	m	1.06	m
16	1.01	m	1.03	m
17	1.00	m	1.01	m
18	1.00	m	1.00	m
19	1.01	m	1.00	m
20	1.00	m	1.00	m
21	1.00	m	1.00	m
22	1.01	m	1.00	m
23	1.01	m	1.02	m
24	1.01	m	1.02	m
25	1.00	m	1.02	m
26	1.01	m	1.02	m
27	1.01	m	1.00	m
28	1.01	m	1.00	m
29	1.11	m	1.00	m
30	1.10	m	1.02	m

^a Large chromosome with nearly terminal centromere provided with secondary constriction. CC: chromosome classification.

Figure 1. Chromosome of diploid Agave angustifolia “Cimarron” (2n = 2x = 60) from Toliman, Jalisco, Mexico: (a) mitotic metaphase; (b) idiogram. Numbers indicate homologous large chromosome pair with secondary constriction. t: telocentric chromosome, st: subtelocentric chromosome, sm: submetacentric chromosome and m: metacentric chromosome. Bar: 10 μm.

Figure 2. Chromosome of diploid Agave angustifolia “Lineño” (2n = 2x = 60) from Toliman, Jalisco, Mexico: (a) mitotic metaphase; (b) idiogram. Numbers indicate homologous large chromosome pairs with secondary constriction. t: telocentric chromosomes, st: subtelocentric chromosome, sm: submetacentric chromosome and m: metacentric chromosome. Bar: 10 μm.

Table 3. Chromosome analysis of Agave angustifolia cultivars.

Cultivar	Ploidy level	Chromosome number and morphology
		Lt^*	Lt	Lst	St	Sst	Ssm	Sm
“Cimarron”	2n = 2x = 60	2	4	4	2	2	4	42
“Lineño”	2n = 2x = 60	2	6	2			2	48
Size (μm)		4.18–8.79	3.6–7.25	3.87–4.39	1.8	1.99–4.39	1.19–2.22	0.84–2.13

Lt^*: large telocentric chromosome with secondary constriction; Lt: large telocentric chromosome; Lst: large subtelocentric chromosome; St: small telocentric chromosome; Sst: small subtelocentric chromosome; Ssm: small submetacentric chromosome; Sm: small metacentric chromosome.

Table 4. Results of Tukey–Kramer test on mean length of homologous monoploid chromosome set (x = 30) of Agave angustifolia cultivars.

Cultivar	Chromosome pairs
	1	2	3	4	5	6	7	8	9	10
“Cimarron”	4.29 a	3.93 a	3.77 a	3.47 a	3.20 a	2.10 a	1.89 a	1.81 a	1.74 a	1.71 a
“Lineño”	4.79 a	4.62 b	4.51 b	4.40 b	4.17 b	2.16 a	2.13 a	2.03 a	1.92 a	1.78 a
	11	12	13	14	15	16	17	18	19	20
“Cimarron”	1.63 a	1.43 a	1.37 a	1.34 a	1.32 a	1.30 a	1.29 a	1.26 a	1.24 a	1.24 a
“Lineño”	1.76 a	1.69 b	1.66 b	1.62 b	1.48 a	1.48 a	1.47 a	1.41 a	1.42 a	1.40 a
	21	22	23	24	25	26	27	28	29	30
“Cimarron”	1.16 a	1.13 a	1.07 a	1.06 a	1.04 a	0.99 a	0.97 a	0.93 a	0.89 a	0.78 a
“Lineño”	1.37 a	1.30 a	1.29 b	1.29 b	1.26 a	1.24 b	1.20 a	1.19 a	1.19 b	1.18 b

Numbers indicate the chromosome numbers of the monoploid chromosome set.

Same letters indicate no statistical difference using α = 0.05, with an ANOVA p < 0.0001.

Figure 3. Mean length of homologous chromosome pairs (x = 30) in Agave angustifolia “Cimarron” (+) and “Lineño” (x). Diploid populations (2n = 2x = 60) from Toliman, Jalisco State, Mexico.

Figure 4. Estimation of nuclear DNA content in Agave angustifolia “Cimarron” and “Lineño” using flow cytometry. (a) Simultaneous analysis of nuclei isolated from A. angustifolia “Cimarron” (2n = 2x = 60) and Zea mays cv. CE-777, used as standard for diploid A. angustifolia “Cimarron”. Peaks 1 and 3 represent G1 and G2 nuclei of Z. mays. Peaks 2 and 4 represent G1 and G2 of A. angustifolia “Cimarron”. (b) Simultaneous analysis of nuclei represents G1 and G2 nuclei of Z. mays. Peaks 2 and 4 represent G1 and G2 of diploid A. angustifolia “Lineño” (2n = 2x = 60) and Z. mays cv. CE-777, used as standard for “Lineño”.

Table 5. Nuclear DNA content and genome size from Agave angustifolia cultivars.

Cultivar	2C nuclear DNA content (pg)* ± SE	Tukey grouping	1Cx genome size (pg)^a	Tukey grouping	1Cx genome size (Mbp)	Tukey grouping
“Cimarron”	8.217 ± 0.0254	a	4.104	a	4013	a
“Lineño”	8.179 ± 0.009	a	4.093	a	4002	a

^a 1 pg = 978 megabase pairs (Mbp) (Dolezel et al. 2007b)

1Cx = value represents DNA content of one monoploid genome with chromosome number x (Greilhuber et al. 2005).

Dolezel J, Greilhuber J, Suda J. 2007b. Estimation of nuclear DNA content in plants using flow cytometry. Nat Protoc. 2(9):2233–2244.10.1038/nprot.2007.310

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