A new late japonica rice variety Xiushui 110 achieves source-sink optimization through morphological type innovation
Xiushui 110 was bred by the Yao Haigen project team of the Jiaxing Academy of Agricultural Sciences in Zhejiang Province using the hybridization method, with the combination Jia 59 Tianza/Bing 95-13. In 2001 it passed variety approval by the Shanghai Municipal Variety Approval Committee, and in 2002 it passed variety approval by the Zhejiang Provincial Variety Approval Committee. In 2004 it received a post-variety subsidy from the Ministry of Science and Technology and the Ministry of Agriculture for the selection and breeding of new high-quality specialized crop varieties and research on breeding technology. In 2004 it won the first prize of the Zhejiang Provincial Science and Technology Award.
1 Morphological type innovation, achieving source-sink optimization
The greatest innovation of Xiushui 110 is that the plant is semi-dwarf type, while the panicle is dense-panicle type. Using the source of the semi-dwarf type to supply the sink of the dense-panicle type, it organically combines the characteristics of the semi-dwarf type, such as shortened internodes with leaf sheath wrapping, well-developed root system, good color conversion at the late stage, and high grain-filling quality (sufficient source), with the advantages of the dense-panicle type, such as large panicles and many grains (large sink), achieving source-sink optimization through morphological type innovation.
Rice plant-type breeding is a major hotspot in the field of modern rice cultivation science, and innovation in morphological types has played a huge role in the improvement and yield increase of rice varieties. The pioneer of plant-type breeding can be traced back to Donald's proposal of the concept of ideal plant-type breeding in 1968, after which many breeders directly carried out variety selection based on this theory. Rice varieties of different morphological types have different yield thresholds, so without a breakthrough in morphological type there can be no breakthrough in yield. Over the past more than 20 years in Zhejiang Province, the morphological types of main late japonica rice cultivars changed from the Nongken type to the Nonghu type, then were replaced by the semi-dwarf type and the dense-panicle type, and finally in recent years reached the source-sink optimized type in which the source of the semi-dwarf type supplies the sink of the dense-panicle type. It is precisely because of continuous innovation in morphological types that the yield level has continuously improved.
The semi-dwarf type varieties promoted in Zhejiang Province in the mid-1980s, such as Xiushui 27, Xiushui 11, Xiushui 1067 and Ning 67, had their main advantages in relatively short plants, compact plant type, leaf sheaths wrapping the internodes, upright flag leaves, long panicles with relatively sparse grain setting (the panicle type curved and drooping below the flag leaves, presenting the typical "grain below the leaves" form), high grain weight, well-developed root system, slow decline in root activity and leaf photosynthetic efficiency at the late stage, and therefore good color conversion, fast grain filling, consistent maturity among grains, and relatively small differences in grain weight and quality among grains at different positions on the panicle. However, because of sparse grain setting and fewer grains per panicle, it was difficult to further raise the yield level.
The dense-panicle type varieties promoted since the 1990s, such as Xiushui 17 and Xiushui 63, have erect or semi-erect panicle types, relatively dense grain setting, and relatively short and stiff flag leaves, with relatively superior ecological conditions in the population canopy. After heading and in the early and middle grain-filling stages, their flag leaf chlorophyll content, photosynthetic rate, specific leaf weight and root activity (root bleeding sap per plant) were all relatively high, and both dry matter accumulation before heading and dry matter production after heading (bleeding sap at the panicle neck per plant) were relatively high, and their panicles were large with many grains, so their yield-increasing potential was relatively great. However, because dense-panicle type varieties have short panicles with dense grain setting and short, narrow flag leaves, grain filling is slow. About 30 days after full heading, the decline in bleeding sap per plant (root activity) and net photosynthetic rate of flag leaves was significantly greater than in semi-dwarf type varieties. During the grain-filling stage, nutrient competition among strong, medium and weak grains on the panicle was intense, resulting in large differences in grain-filling rate and duration among different grain positions within the panicle, ultimately causing the grain weight and quality of weak grains to be obviously inferior to those of strong and medium grains, making maturity among grains uneven and affecting the improvement of overall quality.
In response to the respective advantages and defects of semi-dwarf type and dense-panicle type varieties, during the selection and breeding of new varieties we focused on strengthening the improvement of sink and source and the coordination and optimization of the sink-source relationship. Xiushui 110 not only maintains the excellent characteristics of semi-dwarf type rice, such as short stature with leaf sheath wrapping, vigorous root activity, long functional period of the top three leaves, high leaf photosynthetic efficiency and good color conversion at the late stage, but also has the panicle and grain structure of the dense-panicle type with large panicles and many grains. Xiushui 110 has short and sturdy plants, strong photosynthetic potential and strong root activity, especially obvious growth advantages of roots and leaves at the late stage, laying a physiological and ecological foundation for improving yield and quality. In addition, although Xiushui 110 has relatively high grain-setting density on the panicle, its number of primary branches is similar to that of Xiushui 63, and its large number of grains set mainly depends on an increase in the number of primary branches, so grain setting is relatively uniform and the phenomenon of asynchronous grain filling is lighter than in Xiushui 63. The differences in grain weight and quality among grains on the panicle, especially in appearance quality, are obviously smaller than in the dense-panicle type variety Xiushui 63, thus laying a morphological and physiological foundation for improving overall rice quality.
2 Main characteristics and traits
Xiushui 110 has short and sturdy plants, with a plant height of about 95 cm, 5-10 cm lower than the control variety Xiushui 63 in the national southern rice region late japonica regional trial. Its plant type is moderately compact and loose, with thick and sturdy stems, and upright, slightly wide leaves. The number of leaves on the main stem is 18-19. The leaves are slightly broad, light in color and upright, with leaf sheaths wrapping the internodes, and the flag leaves are upright. The root system is well developed and belongs to the upper-position root type, with good color conversion at the late stage. Tillering ability and effective panicle rate are moderate. Generally, the number of effective panicles per mu is 210,000-230,000, with 120-130 grains per panicle, a seed-setting rate of 85%-90%, and a 1000-grain weight of 25-26 g, belonging to the type that balances panicle and grain and tends toward large panicles. The panicle neck is thick and hard, the panicle type is relatively large, grain setting is uniform, and at maturity it presents a semi-erect panicle lower than the top of the flag leaves, with only slight secondary grain filling. Xiushui 110 is relatively strongly photoperiod-sensitive. When sown in northern Zhejiang from May 20-25, it reaches full heading from September 10-13 and is harvested at the end of October or the beginning of November, with a whole growth period of 155-160 days, making it a medium-maturity late japonica rice.
The rice quality is excellent and the taste is good. According to measurements by the Rice and Rice Products Quality Supervision, Inspection and Testing Center of the Ministry of Agriculture, and in accordance with the Ministry of Agriculture standard NY122-86 "High-quality edible rice," among 12 rice quality indicators, 9 indicators of Xiushui 110 reached the first-grade standard for high-quality rice: brown rice rate, milled rice rate, head rice rate, length-to-width ratio, chalkiness degree, alkali spreading value, gel consistency, amylose content and protein content. Two indicators, transparency and chalky grain rate, reached the second-grade standard for high-quality rice. Xiushui 110 has been rated by Shanghai as one of the city's five major high-quality late japonica varieties, and from 2001 to 2003 it was listed by the Zhejiang Provincial Department of Agriculture as one of the key recommended high-quality late japonica varieties.
Good stress resistance. According to identification by the Institute of Plant Protection of the Zhejiang Academy of Agricultural Sciences, its resistance to rice blast is significantly better than that of the control Xiushui 63, and its resistance to other major diseases and insect pests is better than or similar to that of Xiushui 63. It has strong lodging resistance and good ripening appearance at the late stage.
Based on Xiushui 110's short stature and short internodes, fertilizer tolerance and lodging resistance, relatively strong photoperiod sensitivity, and dual characteristics of semi-dwarf and dense-panicle types, it has wide adaptability. It is suitable for single-season direct seeding, seedling throwing and transplanting rice cultivation in the Hangzhou, Jiaxing and Huzhou areas of northern Zhejiang, as well as in Shanghai and southern Jiangsu, and in Ningbo, Shaoxing and other areas of Zhejiang. From 2001 to 2003, Xiushui 110 was listed as a key demonstration variety for Zhejiang Province's national-level high-yield demonstration of new rice varieties and the provincial grain and oil seed project demonstration bases, and performed well in demonstrations at national and provincial-level demonstration bases in Jiaxing, Jiashan, Changxing, Zhuji, Tongxiang and other places.
3 Yield performance
Xiushui 110 participated in the Jiaxing municipal regional trial in Zhejiang Province in 1999, 2000 and 2001, with average yields per mu of 536.8, 581.2 and 595.0 kg, increases of 4.62%, 3.46% and 8.91% over the control (Xiushui 63), ranking first, second and third respectively. In the Huzhou municipal regional trial in Zhejiang Province, the average yields per mu were 573.5 and 628.0 kg, increases of 4.7% and 6.44% over the control (Xiushui 63), ranking first for two consecutive years. In the Hangzhou municipal regional trial in Zhejiang Province, the average yields per mu were 542.1 and 591.7 kg, among which in 1999 it increased by 1.82% over Xiushui 63 and by 16.93% over Xiushui 11, and in 2000 it increased by 5.29% over Xiushui 63, ranking first for two consecutive years. In the 1999 variety comparison trial and 2000 regional trial in Shanghai, the average yields per mu were 527.7 and 596.7 kg, among which in 1999 it increased by 13.8% over Xiushui 17, and in 2000 it increased by 7.42% over Wuyunjing 7, ranking first for two consecutive years.
In 2002, the Zhejiang Academy of Agricultural Sciences used Xiushui 110 in a balanced fertilization cultivation experiment on 2.0 mu of single-season late rice in Mushan Town, Yuyao City. After provincial-level acceptance, the yield per mu reached as high as 812.5 kg, setting a small-area high-yield record for conventional late japonica rice in Zhejiang Province. In large-scale production trials and demonstrations in Jiashan County, Zhejiang Province, a 706-mu demonstration block in 1999 had a yield per mu of 577.7 kg, among which 159.0 mu of key demonstration fields had a yield per mu of 595.0 kg. In 2000, a 7,150-mu demonstration block had a yield per mu of 585.9 kg, among which 239.5 mu of key demonstration fields had a yield per mu of 607.8 kg. The demonstration block increased yield by 32.2 kg per mu over Xiushui 63, an increase of 5.8%. In 2000 in Huzhou City, Zhejiang Province, 120 mu were trial-planted and demonstrated in the Rishanwei Agricultural Park of Changchao Town, with an average yield per mu of 657 kg, an increase of 73 kg over the control Xiushui 63, or 12.5%. In the Shuanglin Town improved seed breeding base, 467 mu were demonstrated, with a yield per mu of 583.6 kg, and high-yield fields reached 647 kg per mu. In 2001, 4,300 mu were demonstrated in Changchao Township, with an average yield per mu of 567 kg, among which the central demonstration block of 312 mu had an average yield per mu of 675 kg, an increase of 81 kg over the control, or 13.63%. Among these, farmer Shi Jinfang's high-yield research field, with an area of 2.2 mu, reached a yield of 702 kg per mu, and farmer Zhou Wenjin's field, with an area of 1.8 mu, reached 680 kg per mu.
4 Application prospects
As a new high-quality, high-yield late japonica rice variety that achieves source-sink optimization through morphological type innovation, Xiushui 110 is the first short-stature, large-panicle single-season rice variety bred in Zhejiang Province in recent years. From 2002 to 2004, it was cumulatively promoted on about 7 million mu in Zhejiang Province, Shanghai and southern Jiangsu, creating enormous social and economic benefits. At present, Xiushui 110 has been used by many leading rice enterprises in Zhejiang Province, such as Jiashan County Ganyao Rice Industry Co., Ltd., Jiaxing City Hexin Rice Industry Co., Ltd. and Pinghu City Xindai Rice Industry Fine Co., Ltd., as the preferred variety for contract production, carrying out industrialized development of high-quality pollution-free rice. From 2002 to 2004, the three enterprises cumulatively carried out contract production of high-quality pollution-free rice on more than 800,000 mu, effectively promoting efficiency gains in grain farming and enhancing the market competitiveness of locally produced rice.
More notably, as a completely new late japonica rice type, Xiushui 110 has become an important excellent germplasm resource. Using Xiushui 110 as a parent, a series of new varieties, lines and hybrid combinations have been successfully bred: among them, 3 new varieties have passed variety approval in Zhejiang Province, including Jiahua 1, Xiushui 09 and Xiushui 03, and in particular Jiahua 1 reached a planting area of more than 1.2 million mu in Zhejiang Province in 2004. One late japonica male sterile line was successfully transferred and bred, namely Xiushui 110A, which has passed provincial identification. The new hybrid late japonica combination Xiuyou 5, successfully developed using Xiushui 110A, passed variety approval in Shanghai in 2005 and has been recommended to enter the national regional trial. In 2005 this combination became a key demonstration variety for hybrid late japonica rice in Zhejiang Province, Shanghai and other places, with many 100-mu blocks yielding up to 700 kg per mu, showing broad prospects for promotion and application.