Phenotypic Correlation Between Traits of Studied Gladiolus Varieties

4.1.3.2. Phenotypic correlation between traits of studied gladiolus varieties

The correlation coefficient measures the degree of relationship between traits that ensures simultaneous improvement in two or more traits to achieve a compromise between the desired traits.

A high correlation coefficient between two traits indicates that selection for one trait leads to simultaneous improvement of the other trait.

Table 4.10. Phenotypic correlation of studied traits on gladiolus varieties

Traits

X1	X2	X3	X4	X5	X6	X7	X8	X9	X10
Length leaf	1
Number of leaves/plant	0.777 **	1
Length flower branch	0.890 **	0.654 **	1
Length flowering section	0.683 **	0.504 *	0.779 **	1
Branch condition flower	0.710 **	0.639 **	0.743 **	0.471 *	1
Number of flowers	0.808 **	0.513 **	0.913 **	0.720 **	0.814 **	1
Flower registration	0.448 *	0.502 *	0.490 *	0.441 *	0.707 **	0.607 **	1
Number of bulbs/bulb	-0.169 ns	-0.10 ns	-0.113 ns	-0.008 ns	-0.014 ns	0.090 ns	0.268 ns	1
Leaf World	0.125 ns	0.21 ns	0.261 ns	0.291 ns	0.072 ns	0.225 ns	0.309 ns	0.330 ns	1
Dry level leaf tip	-0.572 ns	-0.61 ns	-0.643 ns	-0.512 ns	-0.436 ns	-0.528 ns	-0.174 ns	0.176 ns	-0.052 ns	1

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Note:** Correlation is statistically significant at P < 0.01; * Correlation is statistically significant at P

< 0.05; Ns: Not significant. X1: Leaf length; X2: Number of leaves/plant; X3: Flower branch length; X4: Flower branch length; X5: Flower branch diameter; X6: Number of flowers; X7: Flower diameter; X8: Number of bulbs/bulb, X9: Leaf position, X10: Leaf tip dryness level

The results of the study showed that leaf length was positively and strongly correlated with most of the remaining traits. The correlation coefficient ranged from 0.683 to 0.890. This trait was insignificantly correlated with flower diameter, with a correlation coefficient of 0.448.

The number of leaves/plant is positively and moderately correlated with other traits. Along with leaf length, the number of leaves/plant shows a significant positive correlation with flower stem length and flower stem diameter. Thus, long leaves and a large number of leaves/plant will lead to large flower stem length and flower stem diameter.

The correlation coefficient showed that the flower stem length trait was directly proportional to the length of the flower-bearing segment, flower stem diameter and number of flowers at 0.743-0.913. However, it had a weak correlation with flower diameter and a negative, insignificant correlation with the number of bulbs/bulb.

Number of bulbs/bulb was negatively and statistically insignificantly correlated with most other traits. This trait was considered independent and not changed by influencing other traits. Leaf position and leaf tip dryness were recorded as insignificantly correlated with all other traits.

In summary, the traits of leaf length and number of leaves are closely and positively correlated with the length and diameter of flower branches. Traits related to flower branch quality (branch length, length of flower-bearing segment, branch diameter, number of flowers, flower diameter) all influence each other.

4.1.3.3. Direct and indirect effects of traits on gladiolus flower quality

Quantitative traits are determined by many factors. In practice, selection decisions based on correlation coefficients alone are not very effective because correlation coefficients provide limited information about the interrelationships between multiple traits. Correlation coefficients only show the relationship between two traits without the involvement of other traits that lead to that effect. The useful information that can be obtained from correlation coefficients can be improved by separating the direct and indirect effects for a set of interrelationships.

Analysis of the path coefficients of traits on flower branch length showed that: the traits of leaf length, number of leaves/plant, leaf posture, length of flower-bearing segment, number of flowers all have a direct positive effect on flower branch length; the remaining 3 traits of branch diameter, flower diameter and number of tubers have a direct negative effect on flower branch length. Also according to Choudhary & cs. (2011), the length of flower-bearing segment has a direct effect on flower branch length. This result is similar to the study of Patra & Mohanty (2015), improving the length of flower-bearing segment, leaf length and flower diameter can improve flower branch length.

Considering both direct and indirect effects, the trait with the greatest impact on flower stem length is the number of flowers/branch. Thus, choosing varieties with a high number of flowers/branch will increase the chance of improving flower stem length, which has the effect of lengthening the distance between flowers.

The traits of flower stem diameter and flower diameter both have insignificant direct and indirect effects and are all inversely related to the flower stem length trait from -0.1150 to -0.0004. Thus, improving flower stem diameter and flower diameter can be done in parallel without affecting flower stem length.

Table 4.11. Direct and indirect effects of traits on flower stem length

Indirect TT Direct TT

X1	X2	X3	X4	X5	X6	X7	X8
X1	0.1688	0.1051	0.0125	0.0910	-0.0007	0.5424	-0.0515	0.0224
%	16.98	10.57	1.26	9.15	0.07	54.54	5.18	2.25
X2	0.1312	0.1352	0.0211	0.0671	-0.0006	0.3443	-0.0577	0.0130
%	17.03	17.55	2.74	8.71	0.08	44.7	7.49	1.69
X3	0.0211	0.0285	0.1003	0.0387	0.0000	0.1511	-0.0355	-0.0438
%	5.03	6.8	23.94	9.24	0.0	36.06	8.47	10.45
X4	0.1152	0.0681	0.0291	0.1333	-0.0004	0.4833	-0.0507	0.0010
%	13.07	7.73	3.30	15.13	0.04	54.85	5.75	0.11
X5	0.1198	0.0864	0.0072	0.0628	-0.0009	0.5465	-0.0812	0.0018
%	13.2	9.53	0.79	6.93	0.09	60.28	8.95	0.19
X6	0.1363	0.0693	0.0225	0.0959	-0.0008	0.6714	-0.0698	-0.0119
%	12.64	6.43	2.08	8.89	0.07	62.28	6.47	1.1
X7	0.0756	0.0679	0.0387	0.0588	-0.0007	0.4074	- 0.1150	-0.0355
%	9.45	8.49	4.84	7.35	0.08	50.95	14.38	4.44
X8	-0.0284	-0.0133	0.0331	-0.0010	0.0000	0.0604	-0.0307	-0.1329
%	9.47	4.43	11.04	0.33	0	20.14	10.24	44.33

Note: 0.1688 is the direct effect of X1 on the flower stem length trait; 0.1051 is the indirect effect of X1 through X2 on the flower stem length trait. X1: Leaf length; X2: Number of leaves/plant; X3: Leaf position, X4: Length of flower-bearing branch; X5: Flower stem diameter; X6: Number of flowers; X7: Flower diameter;

X8: Number of balls/balls.

The effect of leaf length on flower spike length: directly is 0.1688; indirectly through the number of flowers and the number of leaves are 0.5424 and 0.1051 respectively; indirectly through other unusual traits is low -0.0515 to 0.09. The direct effect of the number of leaves on flower spike length is 0.1352 corresponding to 17.55%; indirectly through leaf length is 0.1312 (17.03%). It is clear that the development of the leaf set is very significant to the length of the flower spike.

The direct effect of the number of bulbs/bulb had a negative value of -0.1329, accounting for 44.33% of the effect. This trait had an indirect effect through other traits at a low level and was not significant.

The direct effects of traits on the number of flowers/branch were very different (Table 4.12). The group of traits with the largest impact were flower branch length, leaf length, number of leaves, and flower branch diameter. Of which, flower branch length had a positive direct effect of 0.5828 and number of leaves/plant had a negative direct effect of -0.3403. The remaining traits such as leaf position, length of flowering segment, flower diameter, and number of bulbs/bulb had insignificant effects. This result is also consistent with the publication of Patra & Mohanty (2015) that flower diameter, flower branch length had a positive direct effect and number of leaves had a negative direct effect on the number of flowers/branch.

Table 4.12. Direct and indirect effects of traits on number of flowers/branch

Indirect TT Direct TT

X1	X2	X3	X4	X5	X6	X7	X8
X1	0.2657	-0.2645	-0.0007	0.3979	0.0518	0.2674	0.0300	-0.0263
%	20.37	20.28	0.05	30.51	3.97	20.50	2.30	2.02
X2	0.2065	-0.3403	-0.0012	0.2936	0.0466	0.1698	0.0336	-0.0153
%	18.66	30.74	0.11	26.52	4.21	15.34	3.04	1.38
X3	0.0333	-0.0719	-0.0054	0.1694	0.0052	0.0745	0.0207	0.0515
%	7.71	16.65	1.25	39.22	1.20	17.25	4.79	11.92
X4	0.1814	-0.1715	-0.0016	0.5828	0.0343	0.2383	0.0295	-0.0012
%	14.62	13.82	0.13	46.98	2.76	19.21	2.38	0.10
X5	0.1885	-0.2175	-0.0004	0.2746	0.0729	0.2694	0.0473	-0.0022
%	17.57	20.27	0.04	25.60	6.80	25.11	4.41	0.21
X6	0.2146	-0.1745	-0.0012	0.4195	0.0594	0.3311	0.0406	0.0140
%	17.10	13.91	0.10	33.43	4.73	26.38	3.24	1.12
X7	0.1191	-0.1708	0.0387	0.257	0.0515	0.2009	0.0670	0.0418
%	12.58	18.04	4.09	27.14	5.44	21.22	7.08	4.41
X8	-0.0448	0.0335	-0.0017	-0.0045	-0.0010	0.0298	0.0179	0.1562
%	15.48	11.58	0.59	1.55	0.35	10.30	6.19	53.97

Note: 0.2657 is the direct effect of X1 on the number of flowers trait; -0.2645 is the indirect effect of X1 through X2 on the number of flowers trait. X1: Leaf length; X2: Number of leaves/plant; X3: Leaf position, X4: Flower branch length; X5: Flower branch length; X6: Flower branch diameter; X7: Flower diameter; X8: Number of bulbs/bulb.

Considering the impact of leaf length on the number of flowers/plant, it shows that: the coefficient value through branch length and branch diameter is larger than the direct value. This value is similar to the trait of flower-bearing segment length. Therefore, improving leaf length and flower-bearing segment length has a major impact through branch length and branch diameter on the number of flowers/plant.

Table 4.13. Summary of gladiolus varieties suitable for target traits

STT

Traits target	Value	Suitable sample
1	Quantity flower/branch	>10 flowers/branch	GL1, GL2, GL3, GL7, GL14, GL17, GL18, GL19, GL20, GL21, GL22, GL24, GL25
2	Length flower branch	>100 cm	GL2, GL7, GL14, GL17, GL18, GL19, GL20, GL21, GL22, GL24, GL25
3	Degree of dryness leaf tip	Level 1 - 3	GL2, GL3, GL4, GL6, GL7, GL14, GL16, GL20, GL21, GL22, GL24, GL25
4	Diameter flower	>10 cm	GL1, GL2, GL7, GL12, GL14, GL17, GL18, GL19, GL24
5	Diameter flower branch	>1.2 cm	GL2, GL14, GL17, GL24
6	Flower color	New, diverse	GL3, GL6, GL10, GL16

Based on the agronomic characteristics, genetic diversity and genetic composition of quantitative traits of the studied gladiolus varieties, and on the basis of the breeding objectives, 12 suitable varieties were identified for use as breeding materials: GL1, GL2, GL3, GL6, GL7, GL10, GL14, GL17, GL20, GL22,

GL24, GL25 have many outstanding advantages in terms of growth and development (plant height reaches from 100 - 142.8 cm), high flower quality (reaching 10.6 - 14 flowers/flower, flower diameter 10.3 - 11.5 cm, flower neck diameter 1.2 - 1.4 cm), diverse colors, not/less sensitive to dry leaf tips.

4.1.4. Morphological characteristics, vitality and quality of gladiolus pollen

4.1.4.1. Morphological characteristics of anthers and pollen grains of gladiolus flower varieties

In the process of breeding, research on reproductive organs is very important, which contributes to determining the pollination time and the success rate of a cross. This study evaluated the morphological characteristics of anthers and pollen grains of 25 gladiolus varieties.

The studied gladiolus varieties had anther lengths ranging from 1.02 to 1.38 cm. The varieties with the largest anther sizes were GL1, GL2, GL14, GL17, GL18, GL19 and GL24 with lengths ranging from 1.3 to 1.38 cm. The varieties with the shortest sizes were GL3, GL4, GL5, GL6, GL8, GL9, GL21, GL22 and GL23 with lengths ranging from 1.02 to 1.11 cm. The remaining varieties had anther lengths at an average of 1.15 to 1.27 cm. This result reflects the correlation between flower size and anther length is proportional, the larger the flower diameter of the variety, the longer the anther length tends to be.

The anther diameter of most gladiolus cultivars was over 2 mm. The cultivars with the largest diameter were GL2, GL6, GL14 and GL21 with 2.6 - 2.9 mm. The smallest diameter was 1.6 - 1.8 mm in cultivars GL3, GL9, GL13, GL16, GL18, GL22 and GL23.

The main color of the anther is quite similar to the color of the petals. Specifically, the GL2 (white) variety has white anthers, the GL3 (bright yellow) has light yellow anthers, etc. In the studied varieties, the anthers can have borders or be uniform. The border color is mainly darker than the main color, which is red or purple.

Table 4.14. Characteristics of anthers and pollen release time of gladiolus varieties

Sample

Anther length (cm)	Anther diameter (mm)	Main color	Border color	Natural blooming time	Pollen blooming time after autumn (hour)	Anther open rate (%)	Rate of malformed anthers (%)
GL1	1.31±0.05	2.1±0.08	Pink	Deep red	As soon as the petals open	17.5	100	0
GL2	1.34±0.04	2.6±0.03	White	White/light purple	As soon as the petals open	22.0	100	0
GL3	1.05±0.03	1.8±0.05	Light yellow	Purple	1 day after petals open	40.5	86.7	13.3
GL4	1.03±0.03	2.1±0.07	White	Light purple	As soon as the petals open	19.0	100	0
GL5	1.09±0.04	2.3±0.05	White	White	As soon as the petals open	22.0	100	0
GL6	1.04±0.02	2.9±0.03	Orange	Red	1 day after petals open	40.0	93.3	6.7
GL7	1.27±0.04	2.1±0.08	Light pink	Red	As soon as the petals open	19.0	100	0
GL8	1.11±0.02	2.3±0.11	White	Purple	1 day after petals open	37.5	100	0
GL9	1.02±0.02	1.6±0.04	Red	Red purple	1 day after petals open	40.0	100	0
GL10	1.15±0.05	2.3±0.07	Light red	Crimson	As soon as the petals open	19.0	100	0
GL11	1.24±0.04	2.6±0.08	Pink	Light purple	As soon as the petals open	21.0	100	0
GL12	1.23±0.03	2.1±0.10	White	Pink	As soon as the petals open	17.5	100	0
GL13	1.21±0.03	1.8±0.07	Yellow	Light purple	1 day after petals open	40.0	100	0
GL14	1.38±0.05	2.7±0.08	Light red	Crimson	As soon as the petals open	22.0	100	0
GL15	1.25±0.04	2.4±0.08	Light yellow	Light yellow	As soon as the petals open	22.0	73.3	26.7
GL16	1.18±0.03	1.7±0.04	White	White	As soon as the petals open	19.0	100	0
GL17	1.33±0.03	2.1±0.11	Light red	Crimson	As soon as the petals open	19.0	100	0
GL18	1.30±0.04	1.8±0.05	Light red	Red	As soon as the petals open	22.0	100	0
GL19	1.35±0.05	2.3±0.08	Light red	Red	As soon as the petals open	17.0	100	0
GL20	1.07±0.04	2.5±0.05	Light red	Red	As soon as the petals open	19.0	100	0
GL21	1.03±0.04	2.7±0.04	White	Light red	As soon as the petals open	19.0	100	0
GL22	1.06±0.02	1.8±0.06	Light pink	Light purple	1 day after petals open	40.5	100	0
GL23	1.02±0.03	1.7±0.05	Light yellow	Light yellow	1 day after petals open	40.0	56.7	43.3
GL24	1.36±0.06	2.4±0.03	Light pink	Red	As soon as the petals open	22.0	100	0
GL25	1.14±0.05	2.5±0.03	White	White	As soon as the petals open	17.0	100	0

Determining the natural pollen blooming time helps determine the exact pollen collection time and the time to remove the male. The main varieties have anthers blooming right after the petals open. Only two varieties GL3, GL6, GL8, GL9, GL13, GL22 and GL23 have pollen blooming time 1 day after the petals open.

After the anthers were separated from the flowers, the time for pollen opening varied considerably among gladiolus varieties. The varieties with the shortest pollen opening times were GL1, GL4, GL7, GL10, GL12, GL16, GL17, GL19, GL20, GL21 and GL25 with 17-19 hours, followed by GL2, GL5, GL11, GL14, GL15, GL18 and GL24 with 21-22 hours and the longest were GL3, GL6, GL8, GL9, GL13, GL22 and GL23 with 37.5-40.5 hours. The maximum opening rate was achieved in most varieties. In particular, the 4 varieties GL3, GL6, GL15 and GL23 had the corresponding malformed anther opening rates of 13.3%; 6.7%; 26.7%; 43.3%.

When studying the morphological characteristics of pollen grains of monocotyledonous species, Emel & cs. (2008) noted that gladiolus pollen grains are monochromatic, mostly elliptical in shape and medium to large in size with length from 47 - 95 µm and width from 41 - 82 µm.