Corn has been and is regarded as an important crop not only as food for animals and humans but also as raw material for bioethanol. Recently, an attempt was made for growth enhancement and increased production of corn, but the goals were not achieved because of variable environmental conditions and cultivar limitations. Therefore, the development of corn hybrids with high productivity is required.
Domestic corn case also have been affected in cultivation and production because of low income and decreasing self-sufficiency rate of corn as livestock forage. To solve the problems, Cha (2010) suggested that the development of corn hybrids by heterosis was important to increase its yield.
Choi et al. (2011) reported that the advancement in domestic corn breeding was achieved by targeting for yield increase in white-colored corn. Furthermore, corn breeding in quality and quantity of corn were achieved by implementing the heterosis theory(Shull, 1908; Johnson et al., 1972; Tollenaar et al., 1992; Crow, 1998).
MATERIALS & METHODS
Plant materials
The 28 hybrids that were developed at the Corn Genetics and Breeding Laboratory of Chungnam National University (CNU) and four control hybrids including Mibak2 were used in this experiment. The pedigrees of these hybrids and their parents is shown in Table 1.
Table 1.
CNU hybrids and their inbred lines developed from the domestic collection corns.
| Hybrids | Seed Color | Pedigree of Cross Parent | |
|---|---|---|---|
| Female | Male | ||
| CNU13H-3 | White | CNU12’ - 145 Ⓧ | CNU12’- 245 Ⓧ |
| CNU13H-9 | CNU12’ - 248 Ⓧ | CNU12’- 345 Ⓧ | |
| CNU13H-16 | CNU12’ - 368 Ⓧ | CNU12’-1137 Ⓧ | |
| CNU13H-23 | CNU12’ - 480 Ⓧ | CNU12’- 368 Ⓧ | |
| CNU13H-24 | CNU12’ - 480 Ⓧ | CNU12’- 576 Ⓧ | |
| CNU13H-26 | CNU12’ - 517 Ⓧ | CNU12’- 558 Ⓧ | |
| CNU13H-27 | CNU12’ - 517 Ⓧ | CNU12’- 57 Ⓧ | |
| CNU13H-29 | CNU12’ - 519 Ⓧ | CNU12’- 668 Ⓧ | |
| CNU13H-34 | CNU12’ - 742 Ⓧ | CNU12’- 761 Ⓧ | |
| CNU13H-35 | CNU12’ - 655 Ⓧ | CNU12’- 663 Ⓧ | |
| CNU13H-36 | Yellow | CNU12’ - 659 Ⓧ | CNU12’- 651 Ⓧ |
| CNU13H-39 | CNU12’ - 668 Ⓧ | CNU12’- 593 Ⓧ | |
| CNU13H-40 | CNU12’ - 668 Ⓧ | CNU12’- 630 Ⓧ | |
| CNU13H-44 | CNU12’ - 683 Ⓧ | CNU12’- 604 Ⓧ | |
| CNU13H-46 | CNU12’ - 874 Ⓧ | CNU12’- 190 Ⓧ | |
| CNU13H-55 | CNU12’ - 571 Ⓧ | CNU12’- 780 Ⓧ | |
| CNU13H-69 | CNU12’ -1270 Ⓧ | CNU12’-1271 Ⓧ | |
| CNU13H-70 | CNU12’ -2460 Ⓧ | CNU12’-1646 Ⓧ | |
| CNU13H-71 | CNU12’ - 892 Ⓧ | CNU12’- 896 Ⓧ | |
| CNU13H-72 | CNU12’ - 952 Ⓧ | CNU12’- 975 Ⓧ | |
| CNU13H-73 | Purple | CNU12’ -1281 Ⓧ | CNU12’-1285 Ⓧ |
| CNU13H-74 | CNU12’ - 988 Ⓧ | CNU12’- 986 Ⓧ | |
| CNU13H-75 | CNU12’ - 724 Ⓧ | CNU12’- 651 Ⓧ | |
| CNU13H-77 | CNU12’ - 651 Ⓧ | CNU12’- 724 Ⓧ | |
| CNU13H-79 | CNU12’ - 532 Ⓧ | CNU12’- 651 Ⓧ | |
| CNU13H-80 | CNU12’ -2460 Ⓧ | CNU12’-1646 Ⓧ | |
| CNU13H-96 | CNU12’ - 975 Ⓧ | CNU12’- 939 Ⓧ | |
| CNU13H-97 | CNU12’ -2364 Ⓧ | CNU12’- 133 Ⓧ | |
| CNU13H-98 | CNU12’ - 61 Ⓧ | CNU12’- 801 Ⓧ | |
| Mibak 2†(White) | Ganwon Corn Expri.(2005) | ||
| Yeonnong†(White) | Choe et al. (2005) | ||
| Miheuckchal†(Purple) | Ganwon Corn Expri. (2004) | ||
| Daehackchal Gold1† (Yellow) | Lee et al. (2009) | ||
Cultivation methods
To identify the botanical characteristics of colored corn hybrids, 28 hybrids were planted two kernels per hill at the Corn Genetics and Breed farm on April 15, 2013. The plant density was 70 cm×30 cm. Pre-emergence herbicide treatment done and black-white combined vinyl mulching was practiced after sowing. To inhibit nematodes, soil pesticides were applied at a concentration of 2 kg/10a before mulching. These hybrids after sowing were thinned to one plant per hill at the three-leaf stage. The fertilizer level of N-P2O2-K2O per 10a was 20-15-10 kg. Pesticides for corn earworm control were injected about 65 days after germination and other cultivation managements were based on corn cultivation methods described in RAD.
Evaluation of botanical characteristics
To compare the botanical characteristics among hybrids, The major characters such as stem height and ear height were examined at tasseling stage. Ear characteristics related to marketability, such as ear length, ear diameter and kernel setting. Pericarp thickness related to edible corn were examined by Micrometer and sugar content did by Refractometer about 35 days after fertilization.
RESULTS & DISCUSSION
Major botanical characteristics
The major agronomic characteristics of the 28 hybrids were presented in Table 2. Stem height range appeared to be 115.0 cm to 239.3 cm and CNU13H-69 among hybrids showed the highest value, while that of CNU13H-79 was the lowest. Ear height ranged from 30.7 cm to 107.0 cm, and the purple Miheuckchal hybrid of them showed the highest value. Mean ear length of hybrids was 18.2 cm and the yellow Daehackchal Gold1 showed the highest value (23.0 cm). Mean of ear diameter was 43 mm. CNU13H-29 among these hybrids showed the highest value (47.2 mm). In days to tasseling and silking, CNU13H-24 were very fast as 60.7 days and 63.7 days, respectively.
Table 2.
Agronomic characteristics of waxy corn hybrids at each kernel color.
| Characteristics | Stem height (cm) | Ear height (cm) | Ear length (cm) | Ear diameter (mm) | Days to silking (days) | Days to tassel (days) |
|---|---|---|---|---|---|---|
| Hybrids | ||||||
| CNU13H- 3 | 197.7±4.0c | 77.0±1.7b | 19.3±0.6a-b | 37.9±1.9b | 71.0±1.7b | 69.0±0.0a |
| CNU13H- 9 | 181.7±5.5e-f | 31.3±0.6e | 17.4±0.7b-d | 44.0±1.8a | 67.3±0.6d | 64.3±0.6c |
| CNU13H-16 | 164.3±0.6g | 30.7±1.5e | 17.1±0.7c-d | 44.3±7.3a | 64.0±0.0g-h | 61.0±0.0e |
| CNU13H-23 | 197.3±1.2c | 46.3±0.6d | 18.3±2.2b-c | 41.3±1.7a-b | 65.3±0.6e-g | 62.3±0.6d |
| CNU13H-24 | 188.0±1.0d | 58.0±0.0c | 18.0±1.0b-c | 45.3±2.2a | 63.7±0.6h | 60.7±0.6e |
| CNU13H-26 | 186.3±0.6d-e | 58.7±0.6c | 15.5±1.5d | 41.3±0.4a-b | 64.3±0.6f-h | 61.3±0.6e |
| CNU13H-27 | 181.0±1.0f | 44.3±0.6d | 18.7±1.3a-c | 41.8±0.9a-b | 65.7±0.6e-f | 62.7±0.6d |
| CNU13H-73 | 231.3±3.2a | 46.7±1.5d | 17.2±0.2b-d | 43.9±2.4a | 66.0±1.0e | 63.0±1.0d |
| Mibak 2† | 203.3±2.9b | 86.7±1.5a | 18.7±0.6a-c | 42.7±1.6a-b | 69.0±0.0c | 66.0±0.0c-d |
| Yeonnong† | 182.3±2.1e-f | 86.3±2.9a | 20.8±1.2a | 40.2±1.1a-b | 72.7±0.6a | 69.7±0.6a |
| Mean / C.V(%) | 191.3 / 9.3 | 56.6 / 36.7 | 18.1 / 7.9 | 42.3 / 5.3 | 66.9 / 4.6 | 64.0 / 5.0 |
| CNU13H-29 | 226.7±5.8b | 58.0±1.0e | 17.8±0.5e-g | 47.2±1.1a-b | 67.7±1.5d-e | 64.7±1.5e-f |
| CNU13H-34 | 194.3±1.5e | 59.3±2.1e | 14.2±0.6i | 43.7±2.7b-d | 64.3±0.6g-i | 61.3±0.6i-j |
| CNU13H-35 | 183.3±1.5g | 44.7±0.6g | 16.7±0.5g-h | 43.1±1.7b-d | 63.7±0.6i | 60.7±0.6j |
| CNU13H-36 | 186.0±1.7f-g | 49.0±2.0f | 17.5±0.3f-g | 40.2±1.6d | 64.7±1.2f-i | 61.7±1.2h-j |
| CNU13H-39 | 164.3±4.0i | 41.3±0.6g | 15.6±1.1h-i | 42.5±3.3c-d | 64.7±0.6f-i | 61.7±0.6h-j |
| CNU13H-40 | 216.7±5.8c | 56.7±1.5e | 14.9±0.4i | 44.1±2.8b-d | 64.3±0.6g-i | 61.3±0.6i-j |
| CNU13H-44 | 208.7±1.5d | 58.0±1.0e | 19.1±0.4c-e | 40.5±2.0d | 64.7±0.6f-i | 61.7±0.6h-j |
| CNU13H-69 | 239.3±0.6a | 81.7±5.5b | 21.0±0.9b | 45.9±2.5a-c | 68.3±0.6c-e | 65.3±0.6e-f |
| CNU13H-70 | 195.7±3.1e | 68.3±4.6d | 19.2±1.1c-e | 45.1±3.2a-c | 68.3±0.6c-e | 65.3±0.6e-f |
| CNU13H-71 | 192.0±1.0e-f | 61.0±1.0e | 15.4±0.3h-i | 40.7±1.0d | 71.7±0.6a-b | 68.7±0.6a-b |
| CNU13H-96 | 216.7±7.6c | 90.7±2.3a | 20.4±1.1b-c | 42.4±3.4c-d | 71.0±0.0b | 68.0±0.0b |
| CNU13H-97 | 211.0±1.0c-d | 73.0±2.6c | 20.0±1.6b-d | 42.7±1.3c-d | 69.0±0.0c-d | 66.0±0.0c-d |
| CNU13H-98 | 206.0±4.6d | 74.7±2.1c | 18.5±0.9d-f | 43.1±0.9b-d | 69.3±0.6c | 66.3±0.6c-d |
| Daehackchal Gold1† | 176.3±1.2h | 87.3±1.5a | 23.0±0.6a | 48.7±0.9a | 71.7±0.6a-b | 68.7±0.6a-b |
| Mean / C.V(%) | 201.2 / 10.2 | 64.5 / 23.7 | 18.1 / 14.2 | 43.6 / 5.7 | 67.4 / 4.4 | 64.4 / 4.6 |
| CNU13H-46 | 136.3±0.6e | 31.7±1.2f | 15.9±0.3d | 41.3±5.4a | 69.0±0.0c-d | 66.0±0.0c-d |
| CNU13H-55 | 164.3±2.3d | 92.3±1.2b | 18.8±0.3b | 44.5±2.1a | 71.0±1.0b | 68.0±1.0b |
| CNU13H-74 | 210.7±0.6b | 59.0±3.5e | 19.4±0.4a-b | 43.1±1.6a | 66.0±0.0f | 63.0±0.0g |
| CNU13H-75 | 203.0±7.0b-c | 74.3±3.8d | 19.0±0.7a-b | 44.7±3.2a | 69.0±0.0c-d | 66.0±0.0c-d |
| CNU13H-77 | 230.3±0.6a | 84.3±4.7c | 17.3±0.1c-d | 43.0±0.8a | 69.7±1.2c | 66.7±1.2c |
| CNU13H-79 | 115.0±7.8f | 55.7±6.5e | 18.0±1.5b-c | 43.0±4.0a | 72.3±1.2a-b | 69.3±1.2a |
| CNU13H-80 | 199.3±15.0b-c | 71.3±6.0d | 19.0±1.3a-b | 41.9±2.3a | 68.7±0.6c-e | 65.7±0.6c-e |
| Miheuckchal† | 195.0±1.0c | 107.0±1.0a | 20.4±0.7a | 43.0±1.8a | 68.7±0.6c-e | 65.7±0.6c-e |
| Mean / C.V(%) | 181.8 / 21.8 | 72.0 / 32.6 | 18.5 / 7.5 | 43.1 / 2.7 | 69.3 / 2.7 | 66.3 / 2.8 |
| Overall mean | 193.2 | 63.9 | 18.2 | 43.0 | 67.7 | 64.7 |
| Total C.V(%) | 13.5 | 30.6 | 10.7 | 5.0 | 4.2 | 4.4 |
100-kernel weight showed range from 11.52 g to 21.74 g, and their mean was 17.6 g. Among hybrids CNU13H-9 was the heaviest and CNU13H-70 was the lightest.
In white hybrids, the first attached ear weight per plant was the highest in Mibak2, and followed by CNU13H-73 with an ear weight of 87.8g. This trend was similar to Yeonnongchal check hybrid. In yellow corn, Daehakchal Gold1 among the hybrids showed the highest ear weight as a 136.9 g (Lee et al., 2009).
In purple colored hybrids, CNU13H-79 showed the highest ear weight (132.6 g), but check Miheukchal showed an ear weight of 107.5 g. 100 kernel weight was the highest in CNU13H-9 as a 21.74 g and followed by CNU13H-3 and Mibak2 as 21.74 g and 21.62 g, respectively.
The fresh yield per 10a ranged from 198.4 kg to 658.8 kg. Check hybrid Daedukchal Gold 1 showed the highest yield (658.8 kg), while CNU13H-75 showed the lowest yield (198.4 kg).
Lodging degree of the used hybrids showed strong resistance and other environmental characteristics such as disease and insects were also showed medium to light strong resistance. We judged that these results of superior lines development from domestic corn genetic resources by Lee et al. (2009) since 2002.Table .3Fig .1
Table 3.
Characteristics related to yield and response on environmental stress of CNU waxy corn hybrids.
| Characteristics | Ear weight (g) | Cob weight (g) | 100 k. wt (g) | Lodging‡ | Disease & insects (1~9)‡ |
|---|---|---|---|---|---|
| Hybrids | |||||
| CNU13H- 3 | 79±5.9h-i | 11.4±4.3f-h | 21.68 | 2 | 3 |
| CNU13H- 9 | 80.4±4.8h-i | 15.1±5.0b-c | 21.74 | 2 | 3 |
| CNU13H-16 | 67.30±0.9k-l | 10.1±0.6g-h | 19.78 | 1 | 2 |
| CNU13H-23 | 68.4±1.7j-l | 10.6±2.1f-h | 16.75 | 1 | 3 |
| CNU13H-24 | 81.8±2.8g-h | 14.2±1.4j-l | 16.80 | 1 | 3 |
| CNU13H-26 | 76.7±3.1i-j | 14.2±2.4d-g | 18.56 | 3 | 3 |
| CNU13H-27 | 58±0.9m | 12.8±1.1e-g | 14.42 | 2 | 5 |
| CNU13H-73 | 87.8±3.0f-g | 13.1±1.7b | 15.38 | 2 | 3 |
| Mibak 2† | 96.6±1.5d-e | 17.5±0.9b-c | 17.74 | 1 | 3 |
| Yeonnong† | 89.8±1.8f | 10.3±2.8b-c | 21.82 | 1 | 5 |
| Mean | 78.9 | 14.2 | 18.5 | 1.6 | 3.3 |
| C.V (%) | 14.5 | 20.9 | 14.7 | 43.7 | 28.7 |
| CNU13H-29 | 112.3±0.5b | 22.1±0.3a | 19.23 | 2 | 5 |
| CNU13H-34 | 52.2±0.4n | 9.1±1.3h | 12.32 | 2 | 3 |
| CNU13H-35 | 45.1±2.4n | 13.3±4.8b-e | 12.60 | 1 | 3 |
| CNU13H-36 | 64.3±2.0l | 11.5±1.2e-g | 14.60 | 1 | 5 |
| CNU13H-39 | 100.1±5.3d | 13.2±3.5j-l | 15.20 | 1 | 1 |
| CNU13H-40 | 105.8±2.3c | 13.6±1.6c-f | 15.43 | 2 | 3 |
| CNU13H-44 | 72±1.4j-l | 17.8±2.5b-c | 14.52 | 1 | 3 |
| CNU13H-69 | 110.4±0.8b-c | 17.4±1.3b-c | 21.41 | 1 | 3 |
| CNU13H-70 | 50.8±1.6n | 17.8±2.5e-h | 11.52 | 1 | 3 |
| CNU13H-71 | 69.2±2.8k-l | 9.9±1.7e-h | 18.80 | 1 | 5 |
| CNU13H-96 | 110±2.3b | 17.6±1.6j-l | 19.35 | 2 | 3 |
| CNU13H-97 | 90.9±2.5e-f | 20.9±2.4b-c | 20.32 | 2 | 3 |
| CNU13H-98 | 111.4±3.5b-c | 21.7±2.3c-f | 20.76 | 3 | 3 |
| Daeduckchal Gold1† | 136.9±6.3a | 11.2±2.9a | 20.66 | 2 | 5 |
| Mean | 88.6 | 15.3 | 16.9 | 1.6 | 3.4 |
| C.V (%) | 32.1 | 26.1 | 19.3 | 40.3 | 33.8 |
| CNU13H-46 | 74.1±3.1j-k | 9.5±1.2g-h | 17.33 | 1 | 3 |
| CNU13H-55 | 95.9±2.8d-e | 14.7±4.3b-e | 17.37 | 1 | 3 |
| CNU13H-74 | 101.0±2.4d | 12±5.2b-d | 20.55 | 1 | 3 |
| CNU13H-75 | 40.9±1.6o | 13.8±4.6g-h | 13.16 | 2 | 5 |
| CNU13H-77 | 75.2±4.8i-j | 15.2±2.7e-h | 18.37 | 1 | 3 |
| CNU13H-79 | 132.6±3.1i-j | 15.3±2.0e-h | 16.39 | 1 | 5 |
| CNU13H-80 | 72.1±8.5j-k | 16.8±2.1g-h | 18.94 | 1 | 5 |
| Miheuckchal† | 107.5±1.9b-c | 11±1.9a | 15.99 | 2 | 3 |
| Mean | 87.4 | 13.4 | 17.3 | 1.3 | 3.8 |
| C.V | 32.0 | 32.6 | 12.8 | 37.0 | 27.6 |
| Total mean | 83.3 | 14.2 | 17.6 | 0.6 | 3.8 |
| Total C.V (%) | 26.9 | 24.9 | 17.0 | 41.5 | 30.2 |
Table quality-related characteristics
The sugar content and pericarp thickness were known as a evaluated standard of table qualities were analyzed in the 28 hybrids including control hybrids (Table 4). The sugar content of the CNU13H-73 among hybrid was 19.3 brix%, which was the highest. Next, CNU13H-55 and Mibak 2 followed with sugar contents of 19.1 brix% and 17.8 brix%, respectively.
Table 4.
Sugar content and pericarp thickness in CNU waxy corn hybrids.
| Characteristics | Sugar content (brix%) | Pericarp thickness (μm) | |||
|---|---|---|---|---|---|
| Hybrids | |||||
| CNU13H- 3 | 14.5±0.8c | 46.0±1.0f-j | |||
| CNU13H- 9 | 14.3±0.8c-d | 41.3±2.1f-k | |||
| CNU13H-16 | 11.3±0.5g | 45.7±3.5d-i | |||
| CNU13H-23 | 15.4±0.7c | 46.0±2.0f-j | |||
| CNU13H-24 | 13.8±1.3e-f | 45.7±3.1c-e | |||
| CNU13H-26 | 16.2±0.1b | 37.0±2.0h-k | |||
| CNU13H-27 | 12.0±0.9f | 46.0±3.6m-n | |||
| CNU13H-73 | 19.3±1.2a | 41.7±2.5d-g | |||
| Mibak 2† | 17.8±1.2a | 40.7±2.5j-l | |||
| Yeonnong† | 13.7±0.7d-e | 45.7±2.5b-d | |||
| Mean / C.V (%) | 14.8 / 16.6 | 43.6 /7.3 | |||
| CNU13H-29 | 13.9±0.8e-g | 42.0±3.6b-d | |||
| CNU13H-34 | 16.5±1.0a-b | 39.7±3.2m-n | |||
| CNU13H-35 | 13.9±1.2e-g | 40.0±3.6f-j | |||
| CNU13H-36 | 14.1±0.3d-f | 36.3±2.5g-k | |||
| CNU13H-39 | 17.4±1.0a | 43.3±2.5b-c | |||
| CNU13H-40 | 17.6±0.8a | 46.3±3.1d-f | |||
| CNU13H-44 | 15.7±1.5b-c | 41.0±2.0c-e | |||
| CNU13H-69 | 11.1±0.7h | 39.7±3.1o | |||
| CNU13H-70 | 9.1±0.8i | 44.0±2.0n | |||
| CNU13H-71 | 15.5±0.4b-d | 37.3±1.5f-j | |||
| CNU13H-96 | 12.4±0.3g-h | 39.7±1.5d-g | |||
| CNU13H-97 | 15.6±1.1b-d | 42.0±2.0e-j | |||
| CNU13H-98 | 14.8±0.3c-e | 35.7±1.5b | |||
| Daehackchal Gold1† | 12.8±0.9f-g | 41.0±0.0c-e | |||
| Mean / C.V (%) | 14.3 / 16.6 | 39.9 / 10.4 | |||
| CNU13H-46 | 15.6±0.6c-d | 35.5±0.6d-g | |||
| CNU13H-55 | 19.1±0.9a | 39.1±0.9a | |||
| CNU13H-74 | 17.5±0.4b | 40.3±1.2b-c | |||
| CNU13H-75 | 15.4±0.9c-d | 42.7±2.5a | |||
| CNU13H-77 | 13.6±0.3e | 37.7±1.5f-j | |||
| CNU13H-79 | 17.2±0.2b | 42.7±2.5e-j | |||
| CNU13H-80 | 14.9±0.6d | 40.0±1.7l-n | |||
| Miheuckchal† | 16.4±0.3b-c | 43.7±1.5k-m | |||
| Mean / C.V (%) | 16.2 / 10.5 | 35.2 / 32.0 | |||
| Total mean | 14.95 | 41.38 | |||
| C.V (%) | 15 | 9 | |||
Especially, CNU13H-40 hybrid had 17.6 brix%, which were higher than Daehackchal Gold 1 developed in 2009 (Lee et al). Additionally, that of CNU13H-55 as purple-colored hybrid was higher than control hybrids, Miheuckchal.
Lee et al. (2009) reported that pericarp thickness and sugar content in the development of new hybrids were the major factors determining taste quality, and also indicated that pericarp thickness was directly related to chewiness in edible corn. Among hybrids, CNUH13-46 was the thinnest as a 35.5 μm, followed by CNU13H-98 and CNU13H-36. Mean pericarp thickness in the used hybrids was 41.38 μm. The sugar content was the highest in CNUH13-73 and CNU13H-55, and their mean values was 14.95 brix%.
From this study, we found new hybrids for new variety development; CNU13H-79 of 28 hybrids was good in high yield, CNU13H-98 and CNU13H-73 were good in table quality such their pericarp thickness and high sugar contents than leading hybrids, respectively. These results were similar with contents reported by Richardson (1966), Lee et al. (1993), Cha (2010), and Choe et al. (1993).
Accordingly, these selected hybrids were will use for regional adaptability traits and yield test.
