GENETIC RESEARCH AND BREEDING OF RAPESEED AT HUAZHONG AGRICULTURAL UNIVERSITY
The National key laboratory of crop genetics and improvement, Department of Agronomy, Huazhong Agricultural University, Wuhan 430070, P. R. China
Huazhong Agricultural University (HAU) is located in the middle range of Yangtze River, which is the major rapeseed production area in China. HAU is one of the key institutions for rapeseed research in China. We have combined basic research with applied research, discovered and developed many new germplasms, such as Polima cytoplasmic male sterility (CMS), yellow seeded Brassica napus, multisiliqua and so on, and bred more than ten cultivars during the past 50 years. Since 1990s especially, we have been doing cytogenetic and molecular genetic researches on rapeseed and its related germplasms. So far, we have registered one yellow seeded cultivar (B.napus), three canola cultivars (extended 100,000 hectares per year), and four canola hybrids (extended 400000 hectares per year).
KEY WORDS: Rapeseed; Genetics; Breeding.
There are 6-7 million hectares for planting rapeseed in China, which accounts for about one-third of the world’s Brassica oilseed acreage. The Yangtze River region is a major area. It produces 80% of rapeseed in China. HAU is located in Wuhan city which is in the centre of the Yangtze River region, and is within the jurisdiction of the Chinese Ministry of Agriculture.
The Institute of Rapeseed Genetics and Breeding, HAU, was found by Professor Dr. Houli, Liu in the early 1950s. It is one of the earlist units for rapeseed research in China. The rapeseed research and breeding in the past 50 years could be devided into the following stages:
(1) 1954-1969, our major activities were to collect, evaluate germplasm resources and develop conventional cultivars. In this stage, we assessed a large number of Brassica campestris landraces and introduced some B.napus cultivars. Professor Liu bred Huayou No.1, 2 by systematic selection, Huayou No.5, 6, 8, 9 by varietal hybridization and Huayou No.3, 11, 12, 13 by interspecific hybridization. These cultivars were extended widely in the Yangtze River region. In the meantime, we started to study the morphology and physiology related to the early maturity.
(2) 1970-1989, our main activities were concentrated on heterosis and qualities.
(3) 1990-now, we have started researches in cytogenetics and molecular genetics, and continue the researches and breeding in heterosis and qualities. Recently, the Chinese government sets up the National Key Laboratory of Crop Genetics Improvement, Rapeseed Propagation Base for Breeder’s Elite seeds, and Central China Research Centre for Development of Hybrid Rapeseed in our University
2. RESEARCH AND RECREATION OF NEW GERMPLASM RESOURCES
Embryo rescue technique was employed to recreate new materials from interspecific hybrids, such as B.napus×B.juncea, B.rapa×B.oleracea, B.napus×B.carinata, B.carinata×B.rapa, Moricandia arvensis×B.napus. Prof. Liu(1992), for example, found the yellow seed material in Huayou No.3 (B.napus) that was bred by an interspecific cross (B.napus×B.rapa) in 1975. Dr Chen et al(1988) developed a pure yellow seed line of B.napus by resynthesizing B.napus from B.rapa×B.alboglabra. Another kind of yellow seed material of B.napus was also developed by B.napus×B.carinata. Prof. Wu et al (1998) found dominant yellow seed material in Brassica napus. Dr. Meng et al (1995) got a new cms by B.juncea×B.napus. Prof. Wu et al (1996) obtained some multisiliqua lines of B.napus and B.rapa from the descendants of B.napus×B.rapa. Meanwhile, he also got some petalless materials.
Dr. Meng et al(1991) studied the interspecific compatibility between B.napus and B.juncea. The result from 366 combinations showed that the different compatibility rates related to the parent genotypes. Some high compatible lines, one from B.juncea, two from B.napus, were selected.
In order to transfer the C3-C4 characters into B.napus, Dr. Meng et al(1998) and Meng and Gan, 1998) conducted protaplast fusion between Moricandia nitens and B.napus, B.oleracea and B.campestris, respectively. He and his group have acquired some somatic cybrids and identified their heterogeneity with RAPD and RFLP markers.
Dr. Meng et al (1996) analysed the germplasm diversity of B.napus with RFLP markers, and also did the genetic diversity of B.juncea with RAPD markers. Chen(1998) identified two RAPD markers related to Sclorotinia stem rot among 860 primers.
Dr. Chen has collected many materials of B.juncea which originated from different parts of China.
From 1991 to 1995, efficiency of boron utilization was measured in 191 B.napus, 64 B.juncea and 24 B.campestris. The result showed that the efficiency of boron utilization in B.napus was the highest and that of B.campestris was the lowest. Eight cultivars with high boron efficiency were selected from 191 cultivars of B.napus (coefficien of boron efficiency>0.9). One was selected from 64 cultivars of B.juncea (Wang et al, 1995a, 1995b, Peng et al, 1995).
3. CYTOGENETIC RESEARCHES
Dr. Chen, under Prof. Heneen supervision in Swedish Agricultural University, got some B.campestris-alboglabra monosomic addition lines, and studied their cytogenetics (Chen et al, 1992, 1997). Dr. Cheng set up the mitotic karyotypes of B.campestris and alboglabra, respecitively. She used molecular marker technique to identify the B.campestris-alboglabra monosomic addition lines and established the chromosome specific linkage groups of the B.alboglabra genome, such as seed-coated figment gene with 19 RAPD markers in chromosome 1, erucic acid gene, white colour flower gene and LAP isozyme gene with 17 RAPD markers in chromosome 4 (Cheng, 1996).
Dr. Chen et al. (1988) also identified that white color flower gene and erucic acid gene were located on the same chromosome but had independent inheritance. In addition, he observed that GPI gene from C genome was expressed but that from A genome was switched off in B.napus (Chen et al., 1989).
Dr. Li et al(1995) discovered the phenomenon of genome separation in the decentant derived from B.napus ×Orychophragmus violaceus (2n=34). Based on his research, there are two parental types of cells and other cells with various chromosome numbers in the hybrid plant. Similarity was found in the other tetraploidy hybrids derived from O.violaceus×B.juncea and O.violaceus×B.carinata (Li et al, 1997).
4. GENETICS AND BREEDING IN QUALITY TRAITS
In this research section, our work included the content of oil and glucosinolates in seeds and fatty acid composition.
Since Prof. Liu found the yellowseed B.napus in 1975, we have investigated the relationship between this trait and high oil content. Xiao and Liu (1987) divided the seed color into eight grades from yellow to black seeds according the results of measuring 38 cultivars’ seed coat color with spectrum analyser. They identified that oil content of yellow seed, compared with that of black seeds, was 1.54-4.26% higher in average. With seed color decreasing one grade, seed oil content increased 0.65% accordingly. By measuring the thickness of seed coat, Chen and Liu (1985) thought that there was the same genetic basis in the lines with seed color of 1-2 grades (seed coat thickness:13-15mm), 3-5 grades (17-20mm) and 6-8 grades (23-24mm), respectively. There was a negative correlation between seed color and coat thickness. Furthermore, Wang and Liu analysed the oil content of the segregating generation from yellow seed×black seed of B.napus. The result showed that the oil content in embryo and coat of yellow seed individuals was 1.4-2.9% and 3.3-4.5% higher than these of black seed, respectively, but the coat ratio of the yellow seed was 2.3-3.5% less than that of the black seed.
In order to acquire good quality, high yield and disease resistant materials, Dr. Zhou(1989) set up a recurrent random mating population with a dominant genetic male sterile gene in B.napus. Up to now, he has conducted the fourth recurrent selection (Zhou and Wu, 1995; Zhou et al, 1996).
In recent ten years, we bred many high-quality cultivars. Huahuang No.1, which was a yellow-seed cultivar, was 4-6% more than the check cultivar in oil content and had over 85% yellow-seed rate. In addition, some canola cultivars were registered, such as Huashuang No.1 (1990), No.2 (1992) and No.3(1998). They were planted about 100 thousand hectares per year.
5. HETEROSIS AND HYBRID BREEDING
We developed hybrids with four systems including self-incompatibility (SI), cytoplasmic male sterility (CMS), genic male sterility (CMS) and ecotypical cytoplasmic male sterility (ECMS).
(1) SI system We bred three SI lines (211, 271, 219) and their hybrids of B.napus in 1975, and developed SI three-lines (SI line, SI maintainer and restorer) system for producing SI hybrids in 1980 (Fu, 1981b). In the meantime, we investigated saline solution spray for overcoming the self-incompatibility of SI line (Fu, 1984, 1992). Up to now, we have bred the double low three lines and have been able to select out some good combinations
(2) CMS system Since we found Polima cms in 1972(Fu, 1981a), the researches related to its inheritance (Yang et al, 1996a) and anatomy (Yu and Fu, 1990) were conducted. Dr. Yang tested the restoring and maintenance relationships between 10 different cms lines, observed their anatomic structures and identified their mtDNA polymorphism with RFLP markers(Yang et al, 1998). Yang et al(1996b) established a recurrent selection population to breed the Pol cms restorer with a dominant genic male sterile line. Yang and Fu (1993) introduced the genic male sterility gene into Pol cms line to reduce pollen production of Pol cms line. We registered four hybrids, Huaza No.2 (1992, low erucic acid), No.3 (1994, double low), No.4 (1998, double low) and Huaxie No.1 (SWH031, 1998, double low) which were planted over 400,000 ha. per year.
(3) GMS system We introduced two dominant GMS lines Yi-3AB and 9AB from Yibin Institute of Agricultural Science in Sichuan Province and Shanghai Academy of Agricultural Science, and two recessive GMS lines S45AB, 117AB from Sichuan University, Oil Crops Institute in Guizhou province, respectively. The genic relationship between S45AB, 117AB and 90-2441AB which was developed in my university were nestigated, and they were the same system geneticaly (Tu et al, 1997a). To utilize GMS system, a genetic marker of purple stem (Pur) was found to be tightly linked to the male fertile gene (MS1). By studying on this gene with RAPD markers, two markers UBC158.580 and UBC187.850 linked to Pur-MS1 on the same linkage group were obtained among 980 primers (Tu et al, 1997b).
(4) Ecotypic CMS system We bred an ecotypic CMS line AB1 of B.napus in 1990(Yang and Fu, 1990). This line had the polima male sterile cytoplasm(Yang et al, 1998). It was completely male sterile under the summer sowing condition to produce hybrid seeds, but it was completely male fertile under the fall sowing condition for self-propagation. This changes of ecotypic CMS was mostly determined by the environmental temprature and is not much influenced by the light length (Yang, et al, 1997). Some high yielding combinations are being selected.
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