Breeding of High-quality Soft-grain Indica CMS Line Longfeng A

Meng ZHOU,Guofu DENG*,Haifu LIANG,Weiyong ZHOU,Gaoxing DAI,Lijun GAO,Weiwei CHEN,Gang QIN,Ronglin CHEN,Rentian CHEN,Shirong LIANG

1.Rice Research Institute,Guangxi Academy of Agricultural Sciences(RRI,GXAAS),Nanning 530007,China;

2.Plant Protection Institute,Guangxi Academy of Agricultural Sciences,Nanning 530007,China

Breeding of High-quality Soft-grain Indica CMS Line Longfeng A

Meng ZHOU1,Guofu DENG1*,Haifu LIANG1,Weiyong ZHOU1,Gaoxing DAI1,Lijun GAO2,Weiwei CHEN1,Gang QIN1,Ronglin CHEN1,Rentian CHEN1,Shirong LIANG1

1.Rice Research Institute,Guangxi Academy of Agricultural Sciences(RRI,GXAAS),Nanning 530007,China;

2.Plant Protection Institute,Guangxi Academy of Agricultural Sciences,Nanning 530007,China

Longfeng A,derived from the cross of Bo A/(Zhenshan 97B/Bo B F1//Bo B/Gui 2 F1),is a new high-quality indica CMS line with soft-grain characteristics in cooking rice.The CMS line is characterized by good agronomic traits,complete pollen sterility,stale fertility,favorable outcrossing habits,high combining ability and good grain quality.It was technically identified by Guangxi Crop Variety Appraisal Committee in June,2013.

Hybrid rice;CMS line;Longfeng A;Breeding

T he promotion and application of hybrid rice has made outstanding contributions to ensuring national food security.With the improvement of people’s living standards,the demand for high-quality rice grains has been increased year by year.The breeding of high-quality hybrid rice varieties has become an important goal for breeders.In terms of hybrid rice breeding,the Rice Research Institute,Guangxi Academy of Agricultural Sciences insists on the synchronized quality improvement strategies for male sterile line and restorer line,and it has made outstanding achievements.A series of highquality Simiao-type CMS lines have been bred,including Qi A,Qiu A,Mei A,Bai A and Fengtian 1A.Several high-quality hybrid rice combinations, such as Qiuyougui 99,Qiuyou 998, Qiuyou 1025,Meiyou 998,Meiyou 1025,Baiyou 838 and Fengtianyou 553,have been also bred,and they have passed the crop variety approval[1-10].The hybrid rice combinations have become the major rice cultivars planted in Guangxi and even Southern China.The large-scale cultivation of the high-quality hybrid rice combinations would meet the demand for high-quality rice grains.The F1generation of Gui 2×Bo B was crossed with the F1generation of Zhenshan 97B×Bo B,and then the offspring of Zhenshan 97B/Bo B//Gui 2×Bo B was backcrossed with Bo A continuously. Thus the CMS line Longfeng A was bred.The gel consistency and amylose content of Longfeng A were 82 mm and 11.9%,respectively.So the Longfeng A is a high-quality indica CMS line with soft-grain characteristics in cooking rice.

Breeding Processes

Though years of observation and

Main Characteristics and Features

Botanical characteristics

The average plant height of Longfeng A is 63.4 cm.Its plant type is moderate.The Longfeng A has vigorous growth and strong tillering ability.It is characterized by early germination and fast growth.There are about 16 effective panicles in average in each stump.The leaves are more upright, and the sheaths,auricles,leaf margin, apiculus and stigmas are all colorless. The length of flag leaf is about 30.3 cm,and of main panicle is about 23.2 cm.In the main panicle,the first branch number,secondary branch number and average grain number per spike are 11,30 and 159,respectively. The kilo-grain weight is 22.0 g.The grains are in length of 8.6 mm with length to width ratio of 3.2.The stigmas are developed,and the stigma exertion rate is 72.1%,among which the bilateral exertion rate is 49.3%. The plant height of Longfeng B is 70.8 cm.It has a large amount of pollen. The other traits of Longfeng B are similar to those of Longfeng A.

Growth period

In Nanning,the Longfeng A is sowed in early March,and there are 9-10 leaves in the main stem;it can also be sowed in late July,and the duration from seeding to heading lasts for about 53 d.

Flowering habits

For the population,the flowering lasts for about 14 d,and for single stump,the flowering lasts for 6-7 d. The flowering starts 1 d after the emergence of spikelets.The flowering time is relatively early and concentrated. The full flowering period starts 3-5 d after the starting of flowering.In sunny days,the flowering generally starts at 08:00,and it enters the peak period during 09:00 to 10:15.The pre-noon flowering rate accounts for 85.0%. Compared with that of the restorer line, the flowering time of the sterile line is brought forward by about 30 min.The spikelet opened angle ranges from 31° to 42°,which is lasted for 2-3 h.

Stigma vigor

In the morning before flowering in rice,the last-day flowered rice spikes were selected.The flowered spikelets and the spikelets with too young in panicle bases were cut off.For the remaining spikelets,one third of their husks were cut off.A total of 40 panicles were selected.After the cutting, they were bagged(2 spikelets per bag).From that day on,during the full flowering period(09:00-10:00)every day,for each bagged spikes,the anthers in the flowered spikelets were flicked off;the anthers in the un-flowered spikelets were picked out using a pair of tweezers without hurting the stigmas;the stigma of each spikelet was exposed outward.After cleaning the spikes,artificial pollination with enough pollen was carried out with two bags a day.Then the seed setting rate was observed 15-20 d after the pollination.According to the seed setting rate,the stigma vigor was judged.The results showed that the stigma vigor was highest on the starting day and the 3rdday since the flowering with outcrossing rate above 88.4%.Since then,the outcrossing rate was decreased gradually(Table 1).

Sterility

The appearance of agronomic traits was uniform in Longfeng A.Its sterility was stable.The sterile plant rate reached 100%.The anthers of Longfeng A were fine and white.The pollen abortion was complete,and the typical abortion was dominant.The pollen sterility reached 100%,among which the pollen sterilities caused by typical abortion,spherical abortion and stained reached 99.08%,0.91%and 0.01%,respectively.The bagged self sterility was 100%.

Table 1Stigma vigor of Longfeng A(Nanning,2013)

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Disease resistance

The disease resistance of Longfeng A was determined with artificial incubation method by the Plant Protection Institute and Microbiology Research Institute of Guangxi Academy of Agricultural Sciences.The results showed that the incidence degree of rice leaf blast in Longfeng A was 6thlevel,and of spikelet blast was 9thlevel with loss rate of 52.4%.The composite resistance index was 8.3. The Longfeng A was highly sensitive to rice leaf and spikelet blast.In terms of bacterial leaf blight,the incidence degree in Longfeng A was 7th-9thlevel. However,the rice blast and bacterial leaf blight did not occur in Longfeng A in large-scale fields.

Rice grain quality

The rice grains of Longfeng B collected in Nanning in late 2010 were sampled for grain quality analysis by the Rice Product Quality Inspection Supervision Testing Center(Hangzhou),Ministry of Agriculture(Table 2). The grain quality of Longfeng B was relatively good,and its brown rice rate, head rice rate,length to width ratio, chalky gain rate,chalkiness and gel consistency all met the national standards for high-quality rice grains.The rice grains of Longfeng A/Gui 139, Longfeng A/D3,Longfeng A/Hai 11 and Longfeng A/Haiyin all reached the three-grade national standards for high-quality rice grains.

Combining Application

The hybrid combinations of Longfeng A,which is test-crossed with middle-and late-mature restorer lines, show photo-sensitive characteristic.In recent years,the Longfeng A has been test-crossed with restorer lines Fuhui 838-1,Gui 811 and Gui 139.The combining ability of Longfeng A is found to be strong,and the heterosis is found to be obvious.The hybrid combinations have high quality and high yield.The yield is about 7.50 t/hm2. The cooking rice in hot and cold conditions all taste soft.

The Longfeng A/Fuhui 838-1(plot name of 62A/Fuhui 838)participated in the photosensitivity late-maturity group screening test of Guangxi Zhuang Autonomous Region in 2011.Its yield was 7.28 t/hm2,which was increased by 9.08%compared with that of Boyou 253(control).The yield-increased plot rate was 100%.In the regional test of photosensitivity late-maturity group in 2012,the yield of Longfeng A/Fuhui 838-1 was 7.83 t/hm2,which was increased by 7.62%compared with that of Boyou 253(control).The yield-increased plot rate was 100%.In 2013, its yield was 7.71 t/hm2,which was increased by 7.06%compared with that of Boyou 253(control).The yield of Longfeng A/Fuhui 838-1 was increased in all the test plots.In the same year,the average yield of Longfeng A/Fuhui 838-1 was 7.79 t/hm2in the production test,which was increased by 7.65%compared with that of Boyou 253(control).The grain quality of this combination was relatively good(Table 2).Its regional test has been completed in Guangxi,and its variety approval will be carried out in the near future.

The hybrid combination of Longfeng A/Gui 139(plot name of 62A/Gui 139)participated in the photo-sensitivity late-maturity group screening test of Guangxi Zhuang Autonomous Region in 2012.Its yield was 7.92 t/hm2,which was increased by 5.16%compared with that of Boyou 253(control).The yield-increased plot rate was 80%.In the photosensitivity late-maturity group regional test in 2013,the yield of Longfeng A/Gui 139 was also 7.92 t/hm2,which was increased by 9.07%compared with that of Boyou 253(control).The yield-increased plot rate reached 100%.The grain quality of this combination was relatively good,and it reached the third-grade standards for high-quality rice grains(Table 2).This combination will further take part in the regional test.

In addition,the hybrid combinations of Longfeng A/11L Fan 10,Longfeng A/11L Fan 12,Longfeng A/11L Fan 41 and Longfeng A/11L Fan 42 all participated in the comparative tests in the Rice Research Institute,Guangxi Academy of Agricultural Sciences in 2012 and late 2013.Their yields all exceeded that of Boyou 253(control) with increment ranging from 4.67%to 9.80%.

Main Points of CMS Line Multiplication and Seed Production Techniques

(1)Sowing time difference between male and female parents.For the multiplication,the sowing of Longfeng A is earlier than that of Longfeng B by 1.5 leaves.For the seed production in Nanning,in the early season,the total leaves number of Longfeng A is 9-10 leaves on the main stem;and in the autumn season, the duration from seeding to heading lasts for 53 d.

(2)Ratio between parental lines. For the multiplication,the ratio between parental lines is 2:(10-12);and for the seed production,the ratio between parental lines is 2:(12-14).

(3)Water and fertilizer management.Although Longfeng A has strong tillering ability,early germination and fast growth,its growth period is relatively short in the multiplication and seed production in autumn.Therefore, the basic fertilizer dressing should be increased appropriately;in the transplanting,seedlings should better carry some mud;the seedling damage should be reduced in order to accelerate the seedlings’green returning;the tillering fertilizer dressing should be applied early after transplanting,promoting effective tillering and construction of high-yielding population.For the male parents,1-2 times of additional fertilization should be carried out additionally so as to cultivate strong male plants,increase the spikelet number per unit area and increase the amount of pollen.Rational water management should be performed,and the diseases and pests all should be controlled timely.

(4)Spraying of GA3.The Longfeng A is sensitive to GA3.For the multiplication,the spaying amount of GA3 is 120-150 g/hm2;and for the seed production,the spaying amount of GA3 is 150-180 g/hm2.The first spaying of GA3 should be better carried out when about 20%of the female plants start their heading,and it should be completed in three consecutive days.

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Responsible editor:Tingting XU

Responsible proofreader:Xiaoyan WU

优质软米型籼稻不育系龙丰A的选育

周萌1，邓国富1*，梁海福1，周维永1，戴高兴1，高利军2，陈韦韦1，秦钢1，陈荣琳1，陈仁天1，梁世荣1
（1.广西壮族自治区农业科学院水稻研究所，广西南宁530007；2.广西壮族自治区农业科学院植保研究所，广西南宁530007）

龙丰A是以（珍汕97B/博B）F1为母本，（博B/桂2）F1为父本杂交制保后，再与博A测交并连续回交转育而成的优质软米型不育系。该不育系农艺性状优良，花粉败育彻底，育性稳定，异交习性好，配合力强，米质优，于2013年6月通过广西农作物品种审定委员会田间技术鉴定。

杂交水稻；不育系；龙丰A；选育measurement,it is found that the highquality rice line Gui 2 has advantages of strong retentivity,good grain quality, high stigma exertion rate,strong tillering ability and elongated grains,and it is a excellent parent for CMS line improvement.In early 1995,the widelyapplied rice varieties Bo B and Gui 2 (Bo B/Gui 2)and Zhenshan 97B and Bo B(Zhenzhan 97B/Bo B)were crossed with each other in the RRI, GXAAS.The F1of Bo B/Gui 2 and Zhenzhan 97B/Bo B was planted in late 1995.The F1of Bo B/Gui 2(♂) was crossed with the F1of Zhenzhan 97B/Bo B(♀).The F1of Zhenshan 97B/Bo B//Bo B/Gui 2 was cultivated in early 1996.The interior plants were eliminated,and the seeds were harvested mixedly.A total of 3 500 F2single plants were cultivated in late 1996, Finally,30 single plants with plant height of 60-90 cm,strong tillering capability,stigma exertion rate of more than 60%,elongate grains,kilo-grain weight of 18-22 g,almost no chalky grains and no or few glume-gapping seeds were selected.The F3was planted in early 1997.For each plant line,a total of 60 single plants were cultivated,and the target single plants were further selected.The F4was planted in late 1997,and the excellent single plants of the excellent line were selected and backcrossed with Bo A. The back-crossing F1was cultivated in early 1998.It was found that there were 5 back-crossing combinations in which the female parents had more sterile plants and higher sterility.The 5 back-crossing combinations were focused by backcrossing.From this generation afterward,the back-crossing combination with female parent having high sterility was selected,and the male plants were selected according to the appearance of target traits at last generation.Then the meritocratic backcrossing was carried out at a rate of two generations a year.In late 2003, after 10 generations of backcrossing, the male and female plants in the 62thbackcrossing plot showed similar traits,and the sterile female plants showed uniform growth,good plant and leaf type,strong tillering capacity, high sterility,high stigma exertion rate and strong heterosis in combinations. In early 2004,meritocratic backcrossing was further carried out for the parents selected from the 62thplot,and then the propagation was carried out. In late 2004,the BC12F1was cultivated. The meritocratic backcrossing was performed and the rice blast resistance was determined.In early 2005, the selected BC13F1was cultivated, and the rice blast resistance was determined again.At final,one pair of male and female lines was selected, and they were named as Longfeng A and Longfeng B.In June,2013, Longfeng A and Longfeng B passed the technical identification by the Crop Variety Approval Committee of Guangxi Zhuang Autonomous Region.

国家“十二五”农村领域科技计划项目（2012AA101201-2）；国家“十二五”科技支撑计划项目（2011BAD35B02-05）；国家国际科技合作专项项目（2012DF131220）；广西科学研究与技术开发计划项目（桂科攻1123001-4H、桂科攻1123001-4F）；广西壮族自治区八桂学者专项资金；广西自然科学基金项目（2010GXNSFA013085）；广西青年科学基金（桂科青0991054）；广西主席科技基金（11166-05）；广西农科院基本科研业务专项［200920（基）］。

周萌（1966-），女，广西陆川人，副研究员，从事水稻育种方面的研究，E-mail：zhoumeng@gxaas.net。*通讯作者，E-mail：dengguofu@gxaas.net。。

2015-02-11

修回日期 2015-05-17

Supported by National Rural Areas Project Application in the 12thFive-Year Period (2012AA101201-2);Key Project of the National 12thFive-Year Research Program of China(2011BAD35B02-05);Key Program for International S&T Cooperation Projects of China(2012DF131220);Guangxi Scientific Research and Technological Development Projects(GKG1123001-4H,GKG1123001-4F);"Bagui Scholars"Special Funds of Guangxi Zhuang Autonomous Region;Natural Science Foundation of Guangxi Zhuang Autonomous Region(2010GXNSFA013085);Youth Science Foundation of Guangxi Zhuang Autonomous Region(GKQ0991054);Chairman Science and Technology Fund of Guangxi Zhuang Autonomous Region(11166-05);Fundamental Research Funds of Guangxi Academy of Agricultural Sciences(200920F).

*Corresponding author.E-mail:dengguofu@gxaas.net

Received:February 11,2015 Accepted:May 17,2015