Breeding of Yuetang 08776, a New Sugarcane Variety Suitable for Mechanized Production

Fangyin PAN, Mingfu WEN, Lichong PENG, Qiru LIANG, Qingwen LUO

Bioengineering Institute, Guangdong Academy of Sciences, Guangzhou 510316, China; Zhanjiang Sugarcane Research Center, Guangzhou Sugarcane Industry Research Institute, Zhanjiang 524300, China

Abstract [Objectives] To study the breeding of a new sugarcane variety Yuetang 08776 suitable for mechanized production. [Methods] With Yuetang 96-86 as the female parent and Yuetang 99-66 as the male parent, Yuetang 08776 was bred by the Bioengineering Institute of Guangdong Academy of Sciences. It was approved as a non-major crop variety by the Ministry of Agriculture and Rural Affairs in December, 2019. Through many years of multi-pilot trials, the characters, traits and disease resistance of Yuetang 08776 were investigated, and the key points of its cultivation technique were summarized. [Results] Yuetang 08776 is characterized by medium maturity, high sugar content, high and stable yield, strong cold and drought resistance, large number of effective stems, strong ratooning ability and lodging resistance. Yuetang 08776 has excellent agronomic traits, and has been identified as moderately resistant to smut and mosaic disease. The average cane yield of Yuetang 08776 was 119.89 t/ha, 18.50 t/ha higher than that of CK, an increase of 18.25%. The average sugar yield was 17.15, 2.11 t/ha higher than that of CK, an increase of 14.03%. The average sucrose content of Yuetang 08776 in the early period (November to December) was 13.20%, 0.71 percentage points lower than that of CK; in the middle and late period (January to March of the following year), the average sucrose content was 15.23%, 0.22 percentage points lower than that of CK; and the average sucrose content of the whole period was 14.21%, 0.47 percentage points lower than that of CK. [Conclusions] Yuetang 08776 is a sugarcane variety with medium maturity, high sugar, high and stable yield, strong resistance and good ratooning. It is suitable for mechanized seeding, management and harvesting, and suitable for planting and popularizing in most sugarcane production areas of Guangdong, Guangxi and Yunnan.

Key words Mechanized production, New sugarcane variety, Yuetang 08776, Breeding

1 Introduction

Sugarcane is an important sugar crop and energy crop in China. As the industry develops and moves westward, sugarcane planting is mainly concentrated in three dominant production areas, central and southern Guangxi, southwestern Yunnan, and western Guangdong-northern Hainan. In China, the planting area of sugarcane is about 1.17 million ha, the annual total output of cane remains above 100 million t, and the annual output of cane sugar is more than 10 million t, accounting for more than 90% of China’s total sugar production. At present, the sugarcane production in China has the problems of single variety with wide adaptability, low mechanization, high production cost and "harvesting labor shortage", which are the main factors restricting the development of cane sugar industry in China. Seed is the core of agriculture, and the selection and breeding of sugarcane varieties is the foundation of the sustainable development of the sugarcane industry. In recent years, a large number of sugarcane varieties have been bred and promoted in China. However, due to issues such as adaptability, they can only be promoted and applied on a regional scale. In general, the proportion of new varieties is still relatively small. In particular, new varieties of sugarcane suitable for full mechanized production have fewer applications. Therefore, breeding and promoting high-yield, high-sugar, strong-ratooning, and strong-resistance sugarcane varieties suitable for full-process mechanized production, to achieve a diversified layout of varieties, is the top priority to ensure the healthy and sustainable development of the sugarcane industry.

Yuetang 08776 (Regional Trial Code: Yuegan No.50) is a new sugarcane variety bred by the Bioengineering Institute, Guangdong Academy of Sciences. After years of multi-site trials, it has exerted the characteristics of medium maturity, high sugar content, high and stable yield, strong cold and drought tolerance, large number of effective stems, strong ratooning ability and lodging resistance. Yuetang 08776 has excellent agronomic traits, and has been identified as moderately resistant to smut and mosaic disease, with potential for commercial use and promotion. In December, 2019, it was approved as a non-major crop variety by the Ministry of Agriculture and Rural Affairs.

2 Parent sources and breeding process

The female parent of Yuetang 08776 is Yuetang 96-86, which is an excellent parent for sugarcane with good shape, large stems, good vigor, high yield and good quality. This variety can be used for dual purposes, with early and medium maturity, high yield, and strong wind resistance. The male parent of Yuetang 08776 is Yuetang 99-66 (Yuetang 55) is an excellent parent with medium maturity, high sugar, strong ratooning ability, good drought resistance, good lodging resistance, and barren tolerance bred by Guangzhou Sugarcane Industry Research Institute. During 2007-2008, spica sexual hybridization was completed by Hainan Sugarcane Breeding Farm of Guangzhou Sugarcane Industry Research Institute. During 2008-2019, the variety participated in the five-nursery (hybrid nursery, selection nursery, identification nursery, comparison nursery and demonstration nursery)new planting and ratooning experiments at the Zhanjiang Sugarcane Research Center. During 2015-2017, the variety participated in sugarcane variety regional trials in Guangdong Province (5 pilots of Xinqiao of Suixi, Chiman of Zhanjiang, Heliu of Mazhang, Qujie of Xuwen and Yangqing of Suixi; two new planting and one ratooning trials for each pilot; a total of 15 trials including production trials). In 2016-2018, the variety participated in the 12round of joint regional trials of national sugarcane varieties (56 trials in 14 pilots in 5 provinces of South China).

3 Characteristics

3.1 Morphological characteristics

Yuetang 08776 has erect and high plant, and medium to large stems. Internodes are cylindrical, with shallow bud grooves. Shading part of canes is purple-red, and exposed part is purple. Wax powder bands are obvious. Canes are uniform, without water crack or aerial root. Buds are large and triangular. Base is near leaf scar, and top is above growth zone. There are 2-3 rows of root points, arranged irregularly. Leaves are green, medium in length and medium in width, with well-developed midrib. Heart leaf is upright. Leaf posture is straight. Plant is compact. Shading part of leaf sheath is yellow, and exposed part is light green. Leaves are easier to fall off. There is no hair group No.57. The inner and outer auricle is absent.

3.2 Biological characteristics

Yuetang 08776 sprouts quickly and neatly, with high germination rate, early tillering and strong tillering ability. During the whole growth period, it grows steadily, with strong vigor for the late period, without premature senescence. Stem diameter is uniform, with numerous effective stems. Yuetang 08776 is easier to defoliate, has no water crack or aerial root, and has strong ratooning ability. It is moderately resistant to smut and mosaic disease, and has strong cold and drought resistance and relatively strong lodging resistance. Sugarcane seeds are more resistant to transformation and storage. Yuetang 08776 is not easy to bloom or boot during the growth period.

4 Agronomic and economic traits and resistance

4.1 Agronomic traits

4.1.1

Seedling emergence and tillering. The results of many years of multi-pilot trials show that Yuetang 08776 has fast and neat emergence, with an average emergence rate of 61.32%, slightly higher than that of ROC22 (CK). The seedling emergence rate of ratoons was 132.31%, 23.83 percentage points higher than that of CK. The average tillering rate of 63-pilot/time trials was 159.74%, 39.92 percentage points higher than that of CK (Table 1). It suggests that Yuetang 08776 is a variety with strong tillering ability.

Table 1 Appearance of agronomic traits of Yuetang 08776

4.1.2

Composition of cane yield. As shown in Table 1, the average plant height of Yuetang 08776 was 273.60 cm, 22.60 cm lower than that of CK. Yuetang 08776 has thicker tip, while ROC22 (CK) has thinner tip (commonly known as "mouse tail"). Although Yuetang 08776 is not higher than ROC22 in plant height, the thicker tip at a certain level makes up for the lack of plant height. The average stem diameter of Yuetang 08776 is 2.72 cm, equivalent to that of CK, belonging to a medium-to-large-stem variety. Yuetang 08776 has a high stem-forming rate and a large number of effective stems. The average number of effective stems per hectare was 81 600, an increase of 21 200 stems/ha compared with that of CK.

4.2 Economic traits

4.2.1

Cane yield. In the 39-pilot/time trials, the average cane yield of Yuetang 08776 was 119.89 t/ha, 18.25% (18.50 t/ha) higher than that of CK, with a larger increase (Table 2).

4.2.2

Sugar output. As shown in Table 2, the average sugar output of Yuetang 08776 was 17.15 t/ha, 2.11 t/ha (14.03%) higher than that of CK, a larger increase. The sugar output of Yuetang 08776 was above 15 t/ha.

4.2.3

Sucrose content. During November-December, the average sucrose content of Yuetang 08776 was 13.20%; from January to March of the following year, the average sucrose content was 15.23%; and during the whole growth period, the average sucrose content was 14.21%. The sucrose content of Yuetang 08776 was 0.71 percentage points lower than that of CK in the early period (November-December), 0.22 percentage points lower than that of CK in the middle and late period (January-March), and 0.47 percentage points lower than that of CK during the whole growth period. Although Yuetang 08776 was slightly lower than CK in terms of sucrose content, it has good ratooning ability and high cane yield, so its sugar output and comprehensive benefits were higher than those of CK. Yuetang 08776 is a medium-maturing and higher-sugar variety, and is suitable for harvest in the middle stage for cane squeezing, with good prospects for popularization and application. The average gravity purity of Yuetang 08776 was 85.51%, equivalent to that of ROC22. The average fiber content of Yuetang 08776 was 11.00%, 0.52% lower than that of ROC22. In summary, Yuetang 08776 is suitable for squeezing by sugar mills.

Table 2 Cane yield, sugar output and sucrose content of Yuetang 08776

4.3 Disease resistance

In 2017, the National Sugar Industry Quality Supervision and Inspection Center was commissioned to identify the resistance of Yuetang 08776 to smut and mosaic disease. The results (Table 3) show that the incidence rate of smut in Yuetang 08776 under the condition of artificial inoculation was 21.28%; its disease resistance level was 5; and its disease resistance response type is moderate resistance. Under the condition of artificial inoculation, the incidence rate of mosaic disease in Yuetang 08776 was 17.43%, with disease resistance level of 3 and disease resistance response type of moderate resistance. However, the incidence rates of smut and mosaic disease in the control ROC22 were 44.13% and 55.37%, respectively, indicating that it is susceptible. In the breeding, region and production trials, no other serious diseases such as yellow leaf syndrome or tip rot were observed.

Table 3 Identification results of disease resistance of Yuetang 08776

5 Suitable planting areas and key points of cultivation technique

5.1 Suitable planting areas

The results of Guangdong Provincial regional trial and national joint regional trial show that the cane yield and sugar content of Yuetang 08776 growing in Kaiyuan, Lincang and Funing of Yunnan, Suixi of Guangdong, and Hechi and Laibin of Guangxi were all higher than those of ROC22. In Hechi, Guangxi, the sucrose content of Yuetang 08776 was higher than that of CK. In Lincang and Kaiyuan, Yunnan, the booting spikes bloomed at the mature stage. Thus, the most suitable planting areas for Yuetang 08776 are Kaiyuan, Lincang and Funing of Yunnan, Suixi of Guangdong, and Hechi and Laibin of Guangxi. In Zhangzhou of Fujian, Zhanjiang of Guangdong, Liuzhou of Guangxi and Danzhou of Hainan, the adaptability of Yuetang 08776 is moderate. In Baise and Chongzuo of Guangxi, and Baoshan and Dehong of Yunnan, the yield and sugar content of Yuetang 08776 reduced, so these areas are not suitable for planting Yuetang 08776.

5.2 Key points of cultivation technique

Yuetang 08776 is suitable for planting on dry slopes and paddy fields with medium or above fertility. It is recommended to be planted in winter or early spring (covered with plastic film). The planting density is recommended to be 45 000 double-sprout seedlings per hectare. Under the condition of artificial planting, the row spacing is 1.0-1.2 m. The wide-narrow row spacing suitable for small and medium-sized mechanized planting and harvesting is (1.4+0.45) m. The growth is slow in the early stage. In the seedling and tillering stage, water and fertilizer management should be strengthened, to promote effective early tillers, and suppress invalid tillers in the later stage, thereby increasing the rate of stem formation. Sufficient base fertilizer should be applied, and topdressing should be carried out early to meet the needs of growth in the early and middle period. The control of pests in the field should be strengthened to increase plant growth height. Ratoons are recommended to be mulched with plastic film, and fertilizer should be applied in one time to reduce intertillage links, reduce production cost, retain water and fertilizer, promote early and vigorous growth, and improve yield. Yuetang 08776 has good ratooning ability, and ratoons should be retained for more than two years to reduce planting cost and improve benefits.

6 Conclusions

The results of many years of new planting and ratooning trials show that the average cane yield, average sugar content and whole-period average sucrose content of Yuetang 08776 were 119.89 t/ha, 17.15 t/ha, and 14.21%, respectively, increased in varying degrees compared with those of ROC22. Yuetang 08776 is a new sugarcane variety with medium maturity, high sugar, high and stable yield, strong resistance and good ratooning. It is suitable for mechanized seeding, management and harvesting, and suitable for planting and popularizing in most sugarcane production areas of Guangdong, Guangxi and Yunnan.