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10 March 2020, Volume 34 Issue 2 Previous Issue    Next Issue
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Reviews and Special Topics

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Technology Exploration and Practice of Hybrid Rice Mechanized Seed Production Wenbang TANG, Guilian ZHANG, Huabing DENG 2020, 34(2): 95-103.  DOI: 10.16819/j.1001-7216.2020.9130 Abstract ( )   HTML ( )   PDF (920KB) ( )   The high cost of hybrid rice seed production has become one of the main factors restricting the popularization and application of hybrid rice. We analyzed the current situation of hybrid rice mechanized seed production at home and abroad, summarized the difficulties and problems existing in mechanized seed production. According to the current situation and the characteristics of farming system in China, and combined with many years of breeding practice, we proposed to utilize a small grain type sterile line suitable for hybrid rice mechanized seed production, and realized mechanized seed production in the whole process by using the difference of seed thickness of parents to realize mixed sowing, mixed harvest and mechanical separation. The characters and standards of small grain CMS lines suitable for mechanized seed production were put forward. According to this assumption, we have selected and bred the small grain CMS lines Zhuo 201S, Nan 3502S, Zhan 998S with excellent comprehensive characters, as well as a series of high-yield and high-quality hybrid rice combinations Zhuoliangyou 581, Zhuoliangyou 141, Nanliangyou 1998, and successfully realized the efficient mechanized seed production of these hybrid rice. The breeding of Zhuo 201S and other small grain sterile lines and a series of hybrid combinations is a major breakthrough in the breeding of hybrid rice combinations of mechanized seed production.

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Research Progress in Agronomic and Physiological Traits of Early Leaf Senescence Mutants in Rice Ke LI, Qing YU, Yunji XU, Jianchang YANG 2020, 34(2): 104-114.  DOI: 10.16819/j.1001-7216.2020.9078 Abstract ( )   HTML ( )   PDF (1075KB) ( )   Early leaf senescence greatly affects grain yield and quality in rice. Studies on the agronomic and physiological traits of the early leaf senescence mutants in rice would be beneficial to understanding the senescence process and its underlying mechanism in plants. We briefly summarized the characteristics and mechanisms of early leaf senescence, with focus on reviewing the agronomic and physiological traits of early leaf senescence mutants in rice and the regulation ways of delaying leaf senescence. Such a review would lay a theoretical basis for the breeding of anti-aging varieties and optimized cultivation practice in rice.

Research Papers

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Identification and Fine Mapping of Defective Pistil and Stamens 2 in Rice Changjian WANG, Long CHEN, Liping DAI, Xueli LU, Jinli HE, Long YANG, Jiang HU, Li ZHU, Guojun DONG, Guangheng ZHANG, Zhenyu GAO, Deyong REN, Guang CHEN, Lan SHEN, Qiang ZHANG, Longbiao GUO, Qian QIAN, Dali ZENG 2020, 34(2): 115-124.  DOI: 10.16819/j.1001-7216.2020.9122 Abstract ( )   HTML ( )   PDF (864KB) ( )   【Objective】 Identification and cloning of organ development-related genes can lay a foundation for further study on the molecular mechanism of rice flower development.【Method】The main agronomic traits and morphological characteristics of floral organs of wild type Chunjing 06 and dps2 (Defective pistil and stamens 2) mutant were compared under conventional planting conditions in field. The structure of anther was observed under a scanning electronic microscope by paraffin sectioning, and the fertility of pollen and embryo sac was observed by staining. Map-based cloning was used for the gene localization. Quantitative RT-PCR was performed to analyze the relative expression of genes associated with flower development in the wild type and the mutant. 【Result】 Longer heading date, abnormal flowering, shriveled pistils and stamens, increased anthers and stigmas were presented in the dps2 mutant. Further study revealed that the anther chamber of the dps2 mutant collapsed, and no microspores were found. Though some anthers had their chambers, there was no starch accumulation in the shriveled pollen grains, and the embryo sac fertility of dps2 was also affected. Genetic analysis indicated that the mutant’s phenotype of dps2 was controlled by a single recessive nuclear gene. The DPS2 gene was mapped to a 91.2 kb region on the short arm of chromosome 4. The expression levels of some genes associated with class B, C and E genes in ABCDE model were up-regulated in the mutant. 【Conclusion】 The abnormal development of stamens and pistils attributed to the complete infertility of the dps2 mutant, which indicated that DPS2 play an important role in third round of stamen development and the fourth round of pistil development.

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Fine Mapping of qGL1.1, a Minor QTL for Grain Length, Using Near Isogenic Lines Derived from Residual Heterozygotes in Rice Panpan LI, Yujun ZHU, Liang GUO, Jieyun ZHUANG, Yeyang FAN 2020, 34(2): 125-134.  DOI: 10.16819/j.1001-7216.2020.9125 Abstract ( )   HTML ( )   PDF (1562KB) ( )   【Objective】The objective of this study is to fine-map qTGW1.1b which was previously mapped in a 521.8-kb region on the long arm of rice chromosome 1.【Method】In this study, two BC2F9 plants carrying qTGW1.1 and qTGW1.2, respectively, was crossed and produced an F4 population. Three plants carrying sequential heterozygous segments in the interval Wn28826-RM1231 were selected and selfed to develop three sets of near isogenic lines (NILs) comprising the two homozygous genotypes. The NILs in F5:6 were planted in Hangzhou in 2017 and the 1000-grain weight, grain length and grain width were measured. The effect of qTGW1.1b was validated by two-way analysis of variance (ANOVA) using SAS program. Then six new sequential residual heterozygotes carrying smaller heterozygous segments overlapped in the interval Wn28826-RM1231 were identified. Six sets of pairwise NILs in F8:9 were planted in Lingshui in 2018 and the three traits were measured. Phenotypic differences between the two homozygous genotypic groups were analyzed using ANOVA.【Results】The allelic direction of qTGW1.1b remained consistent and the genetic effects were stable in the two trials. The Milyang 46 allele could significantly increase grain length and 1000-grain weight by 0.027 mm and 0.17 g with the contribution up to 27.12% and 19.09%, respectively.【Conclusion】Considering that qTGW1.1b stably showed significant effect to grain length but not to grain width in both previous and this study, qTGW1.1b was renamed as qGL1.1. As a result, qGL1.1 was delimited into a 76.8-kb region franked by Wn29077 and Wn29154 based on comparing of the segregating regions among the six sets of NILs.

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QTL Mapping for Heat Tolerance of Chalky Grain Rate of Oryza glaberrima Steud. Zhibin CAO, Yao LI, Bohong ZENG, Linghua MAO, Yaohui CAI, Xiaofeng WU, Linfeng YUAN 2020, 34(2): 135-142.  DOI: 10.16819/j.1001-7216.2020.9086 Abstract ( )   HTML ( )   PDF (620KB) ( )   【Objective】The objective of the research is to identify a QTL for heat tolerance of chalky grain rate, so as to provide support for the appearance quality breeding and analysis of genetic mechanism of rice high temperature tolerance of chalky grain rate. 【Method】 We developed a chalky grain rate heat-tolerant CSIL(chromosomal segment introgression lines), CSIL05-2, by backcrossing and marker assisted selection with African cultivated rice acc. IRGC102309 (Oryza glaberrima Steud.) as donor parent and Asian cultivated rice R9311 (O. sativa L. subsp. indica Kato) as recipient parent. And a QTL for insensitity of heat tolerance of chalky grain rate on chromosome 5 was analyzed using secondary populations from CSIL05-2.【Results】In a BC6F2 segregation populations, the SSR marker RM1200 on chromosome 5 showed significant correlation with heat tolerance of chalky grain rate by single marker analysis（P=0.0005）. Using Cartographer 2.5 and the composite interval mapping with BC6F3 and BC6F4 populations, we further anchored the quantitative trait loci (QTL) associated with heat tolerance of chalky grain rate at filling stage to the same position within a 1.3 cM interval, which was designed as qHTCGR and explained 11.4% and 17.5% of the phenotypic variances, respectively. Using homozygous recombinants screened from BC6F4 populations, qHTCGR5 was also detected in a ~333.4 kb region between RM11633 and RM11642.【Conclusion】 The QTL controlling the heat tolerance of chalky grain rate qHTCGR5 is a novel QTL.

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Detection and Analysis of Magnaporthe oryzae Avirulent Gene AVR-Pita and Its Homologous Genes in Heilongjiang Province Feng MENG, Yaling ZHANG, Xuehui JIN 2020, 34(2): 143-149.  DOI: 10.16819/j.1001-7216.2020.9085 Abstract ( )   HTML ( )   PDF (926KB) ( )   【Objective】We aim to investigate the distribution and variation of avirulent AVR-Pita family of Magnaporthe oryzae from Heilongjiang Province, and to understand the pathogenic phenotypes of avirulence alleles.【Methods】Specific primers of the three avirulent genes AVR-Pita1, AVR-Pita2 and AVR-Pita3 were used. 202 M. oryzae single-spore isolates were obtained from different regions of Heilongjiang Province, their DNA were PCR-amplified by using avirulent genes primers in 2017. PCR products of representative strains falling into different types and from different aresa were selected and sequenced by using agarose gel electrophoresis detection. The base and amino acid sequences were compared with those of the corresponding avirulent genes, and the rice resistant single gene line was used to verify the function of different strains of Magnaporthe oryzae.【Results】The frequency of AVR-Pita1 is 36.14%, and that of AVR-Pita3 is 59.41%. The target band of AVR-Pita2 could not be amplified from the DNA of 202 strains from Heilongjiang Province. Sequence analysis of some PCR products of AVR-Pita1 and AVR-Pita3 were carried out. Five variation types of AVR-Pita1 were detected; they were AVR-Pita1-1, AVR-Pita1-A, AVR-Pita1-B, AVR-Pita1-C and AVR-Pita1-D. Functional verification showed that AVR-Pita1-1, AVR-Pita1-A, AVR-Pita1-B and AVR-Pita1-D lost their function. No mutant strain was detected in the virulent gene AVR-Pita3. 【Conclusion】 AVR-Pita1 had strong mutation ability, which led to the loss of avirulent function of most strains, this should be used in conjunction with other resistant genes. AVR-Pita2 was not found in Heilongjiang Province. The sequence of AVR-Pita3 gene was stable in the strain.

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Effects of Different Concentrations of Paclobutrazol in Seedling Stage on Seedling Quality, Tillering Dynamics and Grain Yield of japonica Rice During Late Cropping Season in Southern China Chen CHENG, Kai LEI, Huihuang CHENG, Shengliang WANG, Bo ZHU, Zhanjun LU, Bingke GAO, Binqiang WANG, Qinghua SHI, Yongjun ZENG 2020, 34(2): 150-158.  DOI: 10.16819/j.1001-7216.2020.9064 Abstract ( )   HTML ( )   PDF (789KB) ( )   【Objective】Sufficient panicle number holds the key to higher yield of late japonica rice in southern China. Our goal is to achieve sufficient panicle number by paclobutrazol treatment so as to gain higher yield. 【Method】The split plot was designed with variety as main area and paclobutrazol concentrations as sub-area. Zhendao 11 and Yongyou 2640 were used as late japonica rice materials and H you 518 as control. Five concentrations of paclobutrazol (calculated by active component; A1, 0 mg/L, A2, 84 mg/L, A3, 120 mg/L, A4, 156 mg/L and A5, 192 mg/L) were used in the present field experiment. We investigated the effects of different concentrations of paclobutrazol on seedling quality, tillering dynamics and yield of late japonica rice in southern China between 2014 and 2015.【Result】The seedling height gradually decreased during the two years. The leaf age of seedling and SPAD of H you 518 and Yongyou 2640 gradually increased, while those of Zhendao 11 increased first and then decreased with increasing concentrations of paclobutrazol. The seedling root length, root number, tiller number, productive panicle number, seed setting rate, grain plumpness and yield of the three cultivars increased first and then decreased along with the rising concentrations of paclobutrazol. These indexes of H you 518 and Yongyou 2640 peaked at 156 mg/L of paclobutrazol, and Zhendao 11 at 120 mg/L of paclobutrazol. 【Conclusion】Rice seedling quality, panicle number and yield were significantly enhanced by applying suitable concentrations of paclobutrazol. The yield of H you 518 and Yongyou 2640 peaked at 156 mg/L of paclobutrazol, while Zhendao 11 reached the highest yield at 120 mg/L of paclobutrazol.

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Effect of Biodegradable Film Mulching on Growth and Quality of Mechanically Transplanted Rice (Oryza sativa L.) Guohui HU, Shunqi SONG, Jing XIANG, Defeng ZHU, Huizhe CHEN, Yikai ZHANG, Yaliang WANG, Yicheng XU, Zihao YI, Junke WANG, Yuping ZHANG 2020, 34(2): 159-170.  DOI: 10.16819/j.1001-7216.2020.9081 Abstract ( )   HTML ( )   PDF (1171KB) ( )   【Objective】Our aim is to reveal the effects of biodegradable film mulching on the growth and quality of mechanically transplanted rice in different ecological areas, and provid a method for the rice ecological planting.【Method】The biodegradable film mulching treatment was designed in early-season rice in southern area, single-season rice in northern area and single-season rice in southern area under mechanical transplanting with widely used Wuyoudao 4, Ezao 18 and Yongyou 538 as materials. We investigated the effects of biodegradable film mulching on soil temperature, mechanically transplanted rice growth and quality in different ecological areas.【Result】1) The effect of temperature increase: The film mulching had a better temperature increasing effect on mulched rice in northern area, which was mainly concentrated in the early period of growth, especially in the period from transplanting to panicle initiation; the average daily increase in soil temperature was 2.76℃. 2) Change of growth period: the growth period of rice was shortened in both northern and southern areas. The maturing stage of film-mulched rice was 7 days earlier in the norther area and 3 days earlier in the southern area. 3) Leaf age: biodegradable-film mulching promoted the growth of leaves and increased the rate of leaf emergence of rice in the northern and southern areas. In the early growth stage, the number of emerged leaves of the northern film mulched rice was 0.6~0.9 more than that of the control. 4) Plant height: the plant height of rice decreased in both northern and southern areas, while that of northern rice was significantly decreased by 5.7 cm. 5) Number of stems and tillers: the mulching treatment promoted the growth of rice tillers, and significantly increased the effective tillers number per hm2 of northern single-season rice by 357,000 compared with the control. 6) Shoot dry weight: the dry matter accumulation of single-season rice with biodegradable film mulched in northern area at panicle initiation stage, full heading stage and maturing stage was significantly higher than that of control, while that of early-season biodegradable film-mulched rice in southern area at maturing stage was significantly higher than that of control, that of single-season biodegradable film-mulched rice in southern area at full heading stage was significantly less than that of control. 7) Yield increasing effect: the yield of film-mulched rice in the northern and southern areas increased significantly. The yield of film-mulched single-season rice in northern area increased by 8.7%, early-season rice in southern area by 7.9%, and single-season rice in southern by only 4.1%. 8) Quality comparison: the brown rice, milled rice and protein contents were significantly improved by biodegradable film mulching in single-season rice in northern area, while the head rice was significantly increased in single-season biodegradable film-mulched rice in southern area, and the same results were obtained in southern early rice, but not significantly.【Conclusion】The planting mode of biodegradable film mulching and mechanical transplanting can promote the growth and development of rice and increase the yield of rice in both ecological regions. For rice quality, the northern film-mulched rice had improved milling quality of rice, but the eating quality decreased, and the southern film-mulched rice had improved milling quality, but the appearance quality became worse. The comparison between the northern and southern film-mulched rice showed that planting mode of biodegradable film mulching and mechanical transplanting had better promotion and yield-increasing effect on the northern rice, and reduced the environmental pollution caused by plastic film in the production of rice, and provide a new way for the green and high-quality production of rice.

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Variation of Plant Type, Yield and Quality of Hybrid Progenies of Chinese and Japanese Japonica Rice Varieties Under Nitrogen Reduction Practice and Their Interrelation Zhimin DU, Xiaolin LIU, Danlei SHAO, Nan ZHANG, Yiwei WANG, Jingbo WANG, Xiaokang WU, Tao HU, Yuanye XIA, Hai XU 2020, 34(2): 171-180.  DOI: 10.16819/j.1001-7216.2020.9051 Abstract ( )   HTML ( )   PDF (966KB) ( )   【Objective】Our aim is to study the variation of plant type, yield and rice quality of hybrid progenies of Chinese and Japanese japonica rice varieties under nitrogen fertilizer reduction and their interrelation.【Method】The recombinant inbred line (RIL) population constructed by crossing Liaojing 5, a typical erect panicle type rice variety in Northeast China with Akita Koizumi (curved panicle type), a good quality rice variety in Japan, was used as test material under two different fertilization modes of high nitrogen and low nitrogen levels. The changes of plant type, yield and rice quality and their relationship were analyzed. The common characteristics of rice varieties with high yield, stable yield and high taste value were summarized. 【Result】The full heading stage of RIL population was advanced, the plant height decreased, the flag leaf, top second leaf and top third leaf narrowed and shortened, the base angle of flag leaf decreased, the base angle of top third leaf increased, seed setting rate, 1000-grain weight, economic coefficient increased, panicle number and yield decreased, brown rice rate, milled rice rate and taste value increased. Compared with low-yield and low-taste rice type, high yield and high taste rice type has higher plants, longer leaves and panicles, higher seed setting rate on primary rachis branches, and lower grain density; high- and stable-yield type was featured by narrower leaves, larger base angle of flag leaves; high- and stable-yield and high-taste types were characterized by narrower flag leaves and the second leaf under the two fertilization patterns. 【Conclusion】Plant type characteristics can be used to indirectly select rice varieties with high yield, stable yield and high taste value.

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Effects of Brassinolide on Physiological Characteristics and Growth of Straw Substrate-cultured Rice Seedlings After Transplanting Sha LIAO, Xueming TAN, Muying LI, Kai HU, Xiaohua PAN, Qinghua SHI 2020, 34(2): 181-190.  DOI: 10.16819/j.1001-7216.2020.9089 Abstract ( )   HTML ( )   PDF (1313KB) ( )   【Objective】Our goal is to find the suitable application method and optimum dosage of brassinolide (BR) for straw substrate-cultured rice seedlings.【Method】The effects of three application patterns of BR (seed soaking, spraying, basal application at different concentrations) on physiological characteristics and growth in mechanized-transplanted early rice seedlings were estimated, with straw substrate-cultured Zhongzao 39 seedlings as test material.【Result】BR application could enhance antioxidant protective enzyme activities of seedlings, reduce MDA contents, increase soluble protein content, total sugar contents and C/N, increase root activity of seedlings by 13.24%-48.31%, which were conducive to the formation of robust seedlings with strong resistance. Spraying method had the best effect on increasing SOD, POD and CAT activities of seedlings, while basal application of BR had the best effect on reducing MDA content of seedlings. The right amount of brassinolide could also promote the growth of new leaves; new root and recovery after transplanting, spraying method had the best effect. The tillering ability per plant was enhanced by seeds soaking and spraying at 20-30 d after mechanized-transplanting.【Conclusion】BR application before sowing and after seedling emergence had favorable effects on cultivation of strong rice seedlings, turning green and tillering after transplanting, The concentration of 0.15 mg/L of brassinolide for seed soaking before sowing and 0.10 mg/L for spraying at 1.5 leaf age were better.