Breeding of a Water-saving Drought-resistant Two-line Hybrid Rice Variety Wanliangyou 1008

Shimei WANG Yueming YI Wuyun FANG Qian ZHU Cunli GONG Jingde WU Liansong YANG

Abstract   Drought is one of the important factors limiting rice production， and the application of new water-saving rice varieties is urgently needed in rice production. Wanliangyou 1008 bred by Institute of Rice Research， Anhui Academy of Agricultural Sciences is a new two line hybrid rice variety with some good traits， including high drought resistance， high yield and good disease resistance. Wanlingyou 1008 was obtained by crossing drought-resistant high-quality restorer line DJ1008 and disease-resistant two-line sterile line Wan 25S. In this paper， the breeding process， characteristics and seed production technology of the variety were described in detail.

Key words   Drought resistance; Two-line hybrid rice; Wanliangyou 1008; Breeding

Rice is one of the main food crops in China， as well as a  major  water user in crops. The water consumption of rice production accounts for 70% of agricultural water consumption. Water resources are in short supply in China and even in the world. Therefore， cultivating water-saving drought-resistant hybrid rice varieties is one of the ways to alleviate the shortage of water resources in agricultural production and resist the reduction of rice production due to water shortage and drought. Wanliangyou 1008 is a new high-quality drought-resistant hybrid rice variety bred by Institute of Rice Research， Anhui Academy of Agricultural Sciences. It was approved by Anhui Provincial Crop Variety Approval Committee in 2021 under the approval number of 20211035. It has excellent characteristics of drought resistance， high quality and easy seed production.

Breeding Process 

CMS line Wan 25S

Wan 25S is an  indica  two-line sterile line bred by Institute of Rice Research， Anhui Academy of Agricultural Sciences by using 1892S as the female parent and the pi9 gene-carrying parent IRBL9-W introduced from International Rice Research Institute as the male parent through crossing， backcrossing with 1892S and molecular marker-assisted breeding and obtained after 7 years and 12 generations of selection. In 2018， it passed the technical  identification  of Anhui Province.

Drought-resistant restorer line DJ1008

The drought-resistant restorer line DJ1008 was bred through artificial crossing of Huanghuazhan as the female parent and  Shwewartun  as the male parent， followed by backcrossing with Huanghuazhan， and obtained after 6 years and 10 generations of selection. The drought resistance index is 0.96， and referring to NY/T2863-2015  Technical specification of identification and evaluation for rice drought resistance ， it has reached the second level of drought resistance.

The new hybrid combination， Wanliangyou 1008

Wanliangyou 1008 is a new mid-season  indica  hybrid rice combination bred by Institute of Rice Research， Anhui Academy of Agricultural Sciences and China Agricultural University. Combining was carried out in Bengbu City in the summer of 2014， and the yield and drought resistance identification was carried out in Hainan Province in winter. From 2015 to 2017， multi-point identification on rice quality， disease resistance， drought resistance and yield were carried out in Bengbu， Hefei， Lujiang， Fengyang， Huangshan， Jinggangshan and other places.  From 2018 to 2020， it participated in Rice Regional Experiment of the Anhui Hui， and in 2021， it was approved by Anhui Provincial Crop Variety Approval Committee （approval number： 20211035）.

Characteristics 

Botanical characteristics

Wanliangyou 1008 is a hybrid  indica  rice with moderate plant type， strong tillering ability， good stem elasticity and strong lodging resistance. It has high nitrogen use efficiency， and shows good color change in the later period. The average plant height was  130 cm;  the effective panicle was 2.565 million/hm 2; the panicle length was 26 cm; the total number of grains per panicle was about 220; the seed setting rate was about 80%; and the 1 000-grain weight was 23.7 g.

Growth period

Wanliangyou 1008 is a mid-season  indica  rice in Hefei，  Anhui  Province. It was sown in early May， and the average growth period was 134.3 d， which was 0.4 d shorter than that of the  control  II You 838.

Yield

In 2018， it participated in Rice Regional Experiment of the Anhui Hui， and the average yield per unit of nine experimental sites was 10.3 t/hm 2， which was 7.69% higher than that of the control variety （II You 838）， reaching a very significant level. In 2019， the regional test and a production test were carried out synchronously. The results showed that the average yield per unit area in the regional test was 10.7 t/hm 2， showing a significant increase of 4.44% compared with the control variety （II You 838）; and the  yield per unit in the production test of the same year was  9.8   t/hm 2，   exhibiting an increase of 2.60% compared with the control variety （II You 838）.

Quality

According to the inspection by Rice and Products Quality Supervision， Inspection and Testing Center of Ministry of Agriculture， in 2018， the rice quality was rated as the second class according to the ministerial standard， and in 2019， the rice quality was rated as the second class according to the ministerial standard as well.

Resistance

According to the resistance identification by the Institute of Plant Protection， Anhui Academy of Agricultural Sciences， in 2018， it was moderately susceptible to rice blast （comprehensive resistance index 4.8）， susceptible to rice false smut （rate of diseased panicles 18.8%）， and susceptible to bacterial blight; and in 2019， it was moderately resistant to rice blast （comprehensive resistance index 4.0）， susceptible to rice false smut （rate of diseased panicles 20.0%）， and susceptible to bacterial blight.

Key Points of Seed Production Technology 

Choose good planting fields and do a good job in isolation

The best choice for seed production is natural space isolation. There should be no other rice varieties within 350 m of the seed production field to prevent foreign pollen from flying in， so as guarantee the purity of hybrid rice.

Sow seeds at the right time based on the same growth period of the parents

The parents of Wanliangyou 1008 have the same growth period， so they are suitable for sowing at the same time. Two methods of seedling raising and transplanting and direct seeding can be  adopted.  In the summer system in Anhui， the flowering period is easily arranged in mid-August. For the method of seedling raising and transplanting， the seeds are generally sown between May 15 and 17 in Hefei. For direction seeding， the seeds are generally between May 17 and 20. The amount of seeds used in the female parent field is 18.7-22.5 kg/hm 2， and the amount of seeds used in the male parent field is generally 4.5 kg/hm 2. It is best to pre-germinate seeds by soaking for direct seeding， and the amount of seeds used is the same as that of the field.

Transplant sufficient basic seedlings at a reasonable density

The parents’ seedling age is generally within 25 d. The row ratio of the male parent to the female parent is 2∶ 10， and the row spacing between the male parent and the female parent is 26.4 cm. For the male parent， the spacing in the rows and between rows is 13.2 cm×16.5 cm; and two seedlings are inserted in each hole， and the basic seedlings are 186 700-356 000/hm 2. As to the female parent， the spacing in the rows and between rows is 13.2 cm×16.5 cm; and two seedlings are inserted in each hole， and the basic seedlings are 932 000-1 250 000/hm 2.

Fertilizer and water management

The fertilizers and water in the field for seedling raising and transplanting should be managed normally， and 450 kg/hm 2 of compound fertilizer （N∶ P2O5∶ K2O=15∶ 15∶ 15） and 225 kg/hm 2 of urea should be applied as the base fertilizer. At 7 to 10 d after transplanting， the water is naturally evaporated after the field turns green. After drying the field for about 7 d， small cracks will appear in the field， and 112.5 kg/hm 2 of urea is applied as the tillering fertilizer. Shallow water is adopted from the seedling stage to the booting stage. In directly-seeded fields， 600 kg/hm 2 of compound fertilizer （N∶ P2O5∶ K2O=15∶ 15∶ 15） and 225 kg/hm 2 of  urea  are applied as the base fertilizer， and water in the fields is managed normally.

Spray gibberellin （920）

Both parents are sensitive to gibberellin， and the total amount is 255-300 g/hm 2， sprayed in 2 times. When 5% of the panicles can be seen， the flag leaves are cut off by 1/2， and gibberellin is sprayed for the first time to the male parent alone within 4 h after cutting the leaves， with a dosage of 30.0-37.5 g/hm 2. On the second day， both parents are sprayed together， and the dosage of gibberellin is 195-225 g/hm 2.

Artificial pollination

Artificial pollination is carried out during the blooming period， generally with a tough rope having a diameter of about 1.5 cm. Generally， it starts at about 11∶ 00 on sunny days， and it is carried out according to the flowering time on cloudy and rainy days. Artificial pollination is performed twice a day， with an interval of  30 min ， continuously for about 7 d.

Focus on prevention and treatment of rice false smut

The female parent is susceptible to rice false smut， and it is necessary to focus on the prevention and control of rice false smut during seed production. It is recommended to spray the agrochemicals with little killing effect on stigmas and little effect on the  outcrossing  rate. The control time should be controlled. The first time of control should be in the rice break period， and the second time is 1 week later.

Removal of abnormal plants and harvesting

In seed production fields， abnormal plants should be strictly removed， and technical personnel should be organized to remove abnormal plants at the seedling stage， the jointing stage， the booting stage， the artificial pollination stage， and before harvesting. Especially， before and after heading of the female parent， technicians should be organized in time to remove abnormal plants， which include plants growing from fallen seeds， mutant plants and confounding plants. For the male parent， abnormal plants should be removed once before spraying gibberellin for the first time.

It is recommended to cut off the male parent one week after artificial pollination， and harvest the female parent in time about 28 d after the full bloom period. After harvesting， the seeds should be dried in time to reduce the moisture content to about 13%. When harvesting， attention should be paid to cleaning the harvesting tools to avoid artificial or mechanical mixing.

References

[1]  GAO H， ZHAO HY， NIE YY，  et al.  Research progress and application of water-saving and drought-resistant rice （WDR） on rice green production[J]. Acta Agriculturae Shanghai， 2017， 33（6）： 123-128. （in Chinese）.

[2] LI XH， WANG WK， YANG TW，  et al.  Development status， advantages and main problems to be resolved of water-saving and drought-resistant rice[J]. Journal of Huazhong Agricultural University， 2022， 41（1）：  84-91.  （in Chinese）.

[3]  YAO WY， GUO P， LI LT，  et al.  High-yielding seed production techniques of new hybrid combination Hanyou 116 of water-saving and drought-resistant rice[J]. Hybrid Rice， 2022， 37（1）： 101-102. （in Chinese）.

[4] WANG M， WANG ZH， HUANG CY，  et al.  Breeding and cultivation techniques of thermosensitive two-line hybrid rice variety Y Liangyou 098[J]. Bulletin of Agricultural Science and Technology， 2021（7）： 285-287. （in Chinese）.

 Editor： Yingzhi GUANG   Proofreader： Xinxiu ZHU