Waxy corn, a single recessive gene (wx) was located on the short arm of chromosome 9, codes for the waxy endosperm of the kernel(Collins, 1909).These fresh waxy corn was a very popular food in Asian countries including Korea.
Hong (1994) suggested that it is necessary to study on waxy corn hybrids in order to improve its quality and nutritional composition cultivated traditionally. Zhu et al. (2014) reported that the pericarp mechanical properties of waxy corn inbred lines is one of important factors affecting the fresh corn eating quality. Besides, Lee et al. (2009) reported sugar content is also one among factors for increasing quality of edible waxy corn. Therefore, this study was conducted to gain the prospective hybrids through basic informations and to identify possible hybrids by assessing agronomic characteristics and physicochemical traits for the development of waxy cornhybrid with high table quality.
MATERIALS & METHODS
Plant Materials
This experiment used 23 hybrids developed in Genetics and Breeding Lab. of Chungnam Nat’l Univ. and five controls including Yeonnong1 as shown in Table 1.
Table 1.
Hybrids and their parents of waxy corn hybrids
Cultivation methods
In order to identify the botanical characteristics of colored corn hybrids, three kernels per hill were planted at Corn Genetic & Breed. Farm on April 28 and August 1 in 2011, respectively. Plant density was 70cm x 30cm. Herbicides after sowing and pesticides were applied at 5th leaf stage for ear worm control, and then followed by mulching. Also, they were thinned remaining one plant per hill at the 3th leaf stage. Fertilizer level of N-P2O2-K2O per 10a was 20-15-10kg. For pest control pesticides were injected at approximately 30 days after sowing.
RESULTS & DISCUSSION
Botanical characteristics
The major agronomic characteristics of the cultivated 23 hybrids are presented in Table 2 and 3. The stem height showed a range from 152.8 to 248.3cm. Those of CNU11H-4 and CNU11H-63 showed the highest value of 183.7cm at field and 248.3cm at greenhouse, respectively. But that of CNU11H- 8 was 152.8cm at field and CNU11H-6 was 191.6cm at greenhouse, which was the lowest value. Days to tasseling had average 65 days in hybrids grown at field, but that of hybrids grown at greenhouse was remarkably fast as 49days. About these facts, we thought that short days to tasseling results from increasing temperature of the greenhouse. Meanwhile, Chalok1 as a check which is representative of early maturing cultivar in 2000s, was average 56 days at the field and 41 days at the greenhouse. Compared to Chalok 1, other hybrids were approximately 8 days later than the field and the greenhouse. However, those of CNU11H-8 and CNU11H-11 were about 5-6 days faster than Yeonnong 1 as a control at the field. CNU11H-6 and CNU11H-31 grown in the greenhouse were similar to Chalok 1, About these facts, we thought that this hybrid will be advantageous in terms of cropping system. Range of ear height of used hybrids showed 35 to 107 cm. The ear height of CNU11H-8 at the field and CNU11H-34 at the greenhouse were lower than that of other hybrids. Meanwhile, the ear height of CNU11H-29 at the field and CNU11H-69 at the greenhouse were higher than other check. About these results, Ryu et al. (2001) suggested that stability to lodging of corn was good approximately 50% below in terms of the ratio of stem height to ear height.
Conclusion gained from this study was also evaluated as lodging resistance in most of hybrids grown in the field and the greenhouse. The relationships of stem height and ear height in 23 waxy corn hybrids are presented in Fig. 1.
Table 2.
Agronomic characteristics of waxy corn hybrids cultivated at the field in 2011
| Characters | Stem height (cm) | Ear height (cm) | Ear length (cm) | Ear dia. (mm) | Kernel setting (%) | Day to tassel. (days) | Kermel color |
|---|---|---|---|---|---|---|---|
| Hybrids | |||||||
| CNU11H-1 | 182ab±2.9* | 48bc±2.7 | 18.2abc±0.1 | 42.2ab±0.9 | 95 | 65 | Yellow |
| CNU11H-2 | 172ab±3.2 | 47bc±1.0 | 16.4a-d±0.7 | 38.4ab±0.5 | 97 | 68 | Yellow |
| CNU11H-4 | 183ab±3.9 | 46bcd±3.3 | 16.3a-d±1.3 | 36.8b±1.2 | 87 | 63 | Yellow |
| CNU11H-8 | 152c±5.0 | 35d±3.7 | 18.4ab±0.7 | 38.4ab±0.7 | 71 | 61 | Yellow |
| CNU11H-11 | 168bc±5.0 | 50bc±4.6 | 13.3cd±0.4 | 37.6ab±0.6 | 93 | 62 | Purple |
| CNU11H-29 | 171ab±4.4 | 52b±2.8 | 13.1d±1.1 | 37.8ab±1.3 | 75 | 70 | Purple |
| Chalok 1† | 150c±4.4 | 55ab±4.2 | 16.5a-d±1.1 | 37.0b±1.3 | 95 | 56 | White |
| Yeonnong1† | 177ab±0.8 | 39cd±1.2 | 14.8bcd±0.2 | 31.2c±0.4 | 98 | 67 | White |
| Daehackchal Gold† | 187a±6.0 | 58ab±2.4 | 21.2a±0.9 | 40.7ab±0.9 | 98 | 70 | Yellow |
| Mihuekchal† | 181ab±1.4 | 68a±2.3 | 17.4a-d±0.6 | 42.9a±0.5 | 97 | 68 | Purple |
| Mean | 172.7 | 50.1 | 16.5 | 38.3 | 90.6 | 64 | - |
| CV(%) | 6.11 | 15.18 | 10.82 | 4.53 | - | - | - |
Table 3.
Agronomic characteristics of waxy corn hybrids cultivated at greenhouse in 2011
| Characters | Stem height (cm) | Ear height (cm) | Ear length (cm) | Ear dia. (mm) | Kernel setting (%) | Day to tassel. (days) | Seed color |
|---|---|---|---|---|---|---|---|
| Hybrids | |||||||
| CNU11H-3 | 208b-g±4.1 | 63gh±2.4 | 12.6f-i±0.3 | 41.1a-e±1.1 | 95 | 43 | Yellow |
| CNU11H-6 | 191g±2.0 | 67e-h±4.9 | 13.1e-i±0.0 | 38.0c-h±0.2 | 70 | 42 | Yellow |
| CNU11H-12 | 205c-g±9.4 | 80d-h±4.2 | 9.9i±1.3 | 41.0a-e±1.2 | 82 | 45 | Yellow |
| CNU11H-17 | 230a-e±2.8 | 84c-h±3.7 | 18.1abc±0.2 | 41.5a-d±0.6 | 88 | 43 | Yellow |
| CNU11H-19 | 201fg±9.9 | 64fgh±0.6 | 17.1a-d±0.6 | 41.7abc±0.4 | 90 | 44 | Yellow |
| CNU11H-28 | 220a-g±9.5 | 95bcd±3.9 | 16.1b-e±0.1 | 37.8e-h±0.2 | 96 | 44 | Yellow |
| CNU11H-31 | 212a-g±3.4 | 80d-h±1.8 | 15.5c-f±0.2 | 39.4b-g±0.5 | 97 | 41 | Yellow |
| CNU11H-34 | 233a-d±2.8 | 62h±1.2 | 16.0b-f±0.7 | 43.3ab±0.2 | 77 | 43 | Yellow |
| CNU11H-38 | 209b-g±8.4 | 69e-h±2.6 | 15.3c-g±0.8 | 40.6a-f±1.1 | 98 | 48 | Purple |
| CNU11H-39 | 226a-f±0.3 | 84c-h±2.3 | 16.5b-e±0.5 | 41.1a-e±0.7 | 98 | 43 | Purple |
| CNU11H-53 | 226a-g±9.1 | 86b-g±2.5 | 12.0ghi±0.7 | 36.7fgh±0.9 | 86 | 56 | Purple |
| CNU11H-59 | 202d-g±4.4 | 82d-h±4.0 | 13.6e-h±0.5 | 39.6b-g±0.8 | 80 | 43 | Purple |
| CNU11H-63 | 248a±9.5 | 94bcd±2.1 | 15.0c-g±0.5 | 39.1b-g±0.4 | 73 | 46 | Purple |
| CNU11H-69 | 247a±1.4 | 107ab±5.6 | 15.0c-g±0.5 | 40.4b-f±0.4 | 92 | 48 | Purple |
| CNU11H-73 | 236ab±2.6 | 88b-e±2.1 | 14.3d-h±0.1 | 35.3gh±0.9 | 84 | 49 | Yellow |
| CNU11H-75 | 224a-g±1.1 | 87b-f±1.0 | 13.8d-h±0.1 | 37.8d-h±0.3 | 93 | 49 | Yellow |
| CNU11H-91 | 222a-g±6.3 | 98bcd±3.7 | 18.3abc±3.7 | 40.4b-f±0.2 | 88 | 50 | Yellow |
| Chalok 1† | 202efg±5.5 | 66e-h±10.3 | 11.1hi±1.4 | 38.9c-g±0.7 | 91 | 41 | White |
| Yeonnong1† | 221a-g±6.0 | 106abc±8.0 | 18.9ab±0.1 | 34.0h±0.3 | 95 | 48 | White |
| Daehackchal Gold† | 234abc±0.3 | 127a±7.8 | 20.3a±1.0 | 44.9a±0.5 | 92 | 49 | Yellow |
| Mihuekchal† | 216a-g±3.5 | 125a±5.5 | 17.8abc±0.4 | 39.8b-f±0.3 | 90 | 48 | White |
| Mean | 220 | 86 | 15.2 | 39.6 | 88 | 45 | - |
| CV(%) | 5.97 | 9.30 | 7.96 | 3.79 | - | - | - |
In order to compare productivity of used hybrids, ear length, ear diameter, and kernel setting were examined after drying the hybrids matured. The kernel setting ratio showed a range of 71~97% in hybrids grown in the field, and 70~98% at the greenhouse, respectively. That of CNU11H-2 among hybrids grown in the field was 97%, which was similar CNU11H-38 and CNU11H-39 grown in the greenhouse. Accordingly, we expected that productivity of these hybrids will be good at next planting. Pericarp thickness showed average 50 μm and 49 μm in hybrids grown at field (Table 4) and greenhouse (Table 5), respectively. The sugar content estimated average 13.6 brix and 15.3 brix in hybrids grown at the field(Table 4) and the greenhouse (Table 5). Among the hybrids, sugar contents of CNU11H-8 grown at the field and CNU11H-31 and CNU11H-75 grown at the greenhouse were higher than Yeonnong1 check hybrid.
Table 4.
Sugar content and pericarp thickness of waxy corn hybrids cultivated at the field
| Characters | Sugar content (brix%) | Pericarp thickness (µm) |
|---|---|---|
| Hybrids | ||
| CNU11H-1 | 11.6c±.0.1* | 48abc±1.0 |
| CNU11H-2 | 11.0c±0.7 | 52ab±2.0 |
| CNU11H-4 | 13.2bc±0.4 | 42c±1.0 |
| CNU11H-8 | 18.4a±0.8 | 49bc±0.0 |
| CNU11H-11 | 15.9ab±0.9 | 58a±2.0 |
| CNU11H-29 | 12.9bc±1.4 | 49bc±1.0 |
| Chalok 1† | 13.1bc±0.4 | 59a±1.0 |
| Yeonnong1† | 13.6bc±0.1 | 46bc±0.0 |
| DaehakchalGold† | 13.0bc±0.1 | 51ab±1.0 |
| Mean | 13.6 | 50 |
| CV(%) | 7.80 | 7.37 |
Table 5.
Sugar content and pericarp thickness of waxy corn hybrids cultivated at the greenhouse
| Characters | Sugar content (brix%) | Pericarp thickness (µm) |
|---|---|---|
| Hybrids | ||
| CNU11H-3 | 14.2fg±0.0* | 39gh±0.0 |
| CNU11H-6 | 12.4h±0.2 | 55b-e±0.1 |
| CNU11H-12 | 14.0fg±0.7 | 43fgh±7.2 |
| CNU11H-17 | 16.7bcd±1.2 | 45efg±4.6 |
| CNU11H-19 | 14.6ef±0.2 | 59abc±0.8 |
| CNU11H-28 | 14.5ef±0.3 | 48c-g±4.8 |
| CNU11H-31 | 18.3a±0.3 | 56a-e±0.0 |
| CNU11H-34 | 14.6ef±1.2 | 54b-f±0.8 |
| CNU11H-38 | 15.5de±0.3 | 32h±1.0 |
| CNU11H-39 | 13.1gh±0.7 | 38gh±1.0 |
| CNU11H-53 | 15.5de±0.3 | 63ab±0.5 |
| CNU11H-59 | 13.0gh±0.1 | 48c-g±0.0 |
| CNU11H-63 | 17.2bc±0.2 | 54b-f±3.6 |
| CNU11H-69 | 13.6fgh±0.0 | 46d-g±0.0 |
| CNU11H-73 | 16.0cd±0.1 | 53b-f±0.5 |
| CNU11H-75 | 18.8a±0.4 | 66a±2.0 |
| CNU11H-91 | 14.0fg±0.2 | 39gh±1.8 |
| Ilimchal† | 17.6ab±0.3 | 53b-f±0.5 |
| Chalok 1† | 14.4ef±0.4 | 40gh±1.0 |
| Yeonnong1† | 17.1bc±0.2 | 39gh±0.5 |
| DaehakchalGold† | 12.5h±0.2 | 59a-d±0.5 |
| Mean | 15.3 | 49 |
| CV(%) | 2.95 | 8.32 |
A pericarp thickness of CNU11H-4 was the thinnest as 42 μm among the hybrids grown at the field and had high sugar contentsas 13.2 brix (Table 4). Meanwhile, pericarp thickness of CNU11H-38 grown at the greenhouse had 32μm and sugar content was 15.5 brix. Zhu et al. (2014) and Teri et al. ( 2004) reported that the pericarp mechanical properties of waxy corn inbred lines are important factors affecting the fresh corn eating quality. We also estimated that these two hybrids will be good for the new cultivar of colored corn hybrid.
Edible corns including waxy corn go through many physical and chemical changes during silking and harvest stage, which greatly influences flavor and also keeping quality of the kernels (Garwood et al., 1976; Lee et al., 1987a). Sweet corn hybrids are harvested in 20 days after silking when sugar content is highest (Kientz et al., 1965). Generally, according to maturation advances, sugar content of sweet corns decreases, starch accumulates, and pericarp thickens. Kang et al. (1988), Lee et al. (1999) and Creech (1965) reported that waxy corn between 21 and 27 days after silking contained about 4% total sugars and decreased thereafter. But these results in CNU waxy hybrids showed large difference in both increased sugar contents and decreased pericarp thickness by the advanced methods.
