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Magnitudes of genetic variation within each of major varietal groups of cultivated rice were surveyed in terms of isozyme polymorphism and allelic differentiation of hybrid sterility loci, both of which are considered to have litt le selective value. Allelic differences for 20 isozyme loci were examined in a total of 337 accessions, including Indica and Japonica rices. Aus cultivars from India, Javanica...
Recent genetic analyses on heading-time of rice indicated that almost all the well-adapted varieties in the temperate zone carry a strong photoperiod-sensitivity gene E1, a dominant allele of E1 locus. In order to identify the chromosome on which E1 is located, a trisomic analysis was made using two primary trisomic series originating from the japonica varieties, Nipponbare and Kinmaze, respectively...
Following anther culture of various F1 hybrids of indica restorer (R) lines/wide compatible varieties (WCVs) and japonica R lines/WCVs, the homozygous diploid plants (2n) generated were test-crossed with indica WA type cytoplasmic-genetic male sterile (CMS) line Zhanshan 97A (WA), indica testers Nanjing 11 and Nante, japonica BT CMS line Hanfeng A (BT), and japonica testers Balilla and Akihikari to...
Embryo-derived calli of four rice varieties cultivated at high altitude in Burundi — Facagro 57, Facagro 76, Kirundo 3 and Kirundo 9 — were submitted to different temperature regimes. The percentage of regenerating calli greatly varied depending on variety, length of culture and callus temperature treatment. The reduction of regeneration percentages induced by low temperature was more pronounced in...
Southern United States long grain rice (Oryza sativa L.) is a unique market type characterized by intermediate amylose content, gelatinization temperature, and amylograph viscosity profile characteristics. Rice breeders sometimes use long grain germplasm with differing amylograph viscosity profiles. The inheritance of rice amylograph viscosity profiles has not been ascertained and, thus, was the objective...
A selection procedure is described that isolated Al-resistant individuals from a sensitive rice (Oryza sativa L.) genotype. Somaclonal variation was used as the only source of variability and selection pressures were applied at both callus and regenerated plant levels. When 10 week-old, embryo-derived calli were submitted to different Al stresses for a period of 20 weeks. After this in vitro stress...
Two rice ecotypes, the so-called lowland and upland populations, which carry different isozyme genotypes mostly at a single locus, are cultivated in Japan. The aim of this study was to examine the origin and the mechanism for keeping these genetic differences. The upland population is cultivated in upland fields and carries a different allele for a particular isozyme gene, Pgd-1, which has never been...
Moderate to high heterosis for yield and ten related characters was studied in 45 crosses involving six indica (I) and four tropical japonica (J) varieties of rice under three (E1-optimum sowing and high fertility, E2-both optimum sowing and fertility and E3- late sowing and high fertility) environments. Trends of magnitude of heterosis for grain yield and plant height were I/J > I/I > J/J and...
High rough rice yields are important for the profitable production of rice (Oryza sativa L.). The value of rough rice is determined primarily by head rice (whole milled grains) and broken rice, together referred to as total milled rice. The objective of this study was to optimize selection for rough rice yield, head rice, and total milled rice using path-coefficient analysis and selection indices...
The rice (Oryza sativa L.) crop in Arkansas is seeded from late March through early June each year. Farmers need new rice cultivars that not only produce both high rough rice yields and high head rice across this range of seeding dates but do so consistently. Thus, a seeding date study was conducted during 1994 and 1995 at Stuttgart, Arkansas, to study seeding date effects on rough rice yield and...
A simple and efficient technique for in vitro unpollinated ovary culture in rice which is also applicable for indica genotypes was developed for breeding and genetic studies. Sampling explants at the auricle distance of 7–12 cm between the two uppermost leaves of a tiller, providing a chilling pretreatment and ovaries with 1/3 of the hulls intact gave optimum response to culture. For callus induction...
Plants were regenerated from protoplasts isolated from embryonic suspension cultures of N5047S, a photoperiod sensitive genic male sterile (PGMS) Japonica rice line. Flow cytometric analyses of nuclear DNA content identified some tetraploid regenerates whose agronomic traits could be distinguished from diploid regenerates. Pollen and female fertility of diploid protoplast-derived clones grown under...
Plants derived from unpollinated ovary culture of ten rice genotypes showed significant variability in agro-morphological characteristics. The ovary-derived plant (H1) populations were completely haploid, doubled haploid or haploid-doubled haploid mixture. Haploids had very drastic reduction in plant height, panicle length, grain length, breadth and number and spikelet fertility (0.0%–2.1%). Doubled...
We report the tagging of a brown planthopper (BPH) resistance gene (Bph–1) in rice using RAPD and RFLP markers. The Korean rice variety ‘Gayabyeo’ has dominant duplicate genes including Bph–1 conferring resistance to biotype 1 of BPH. Bulked segregant RAPD analysis was employed for rapid identification of DNA markers linked to resistance genes. For tagging these two genes, an F2F3 population from...
Ten microsatellite loci were analysed for 43 cultivars or breeding lines of rice. Polymorphism-Information-Content values ranged from 0.62 to 0.92. The microsatellite markers were found to be useful for cultivar identification and assessment of genetic relationships. Most of the cultivars could be uniquely identified by at least one microsatellite marker. Genetic heterogeneity was detected within...
A survey of the genetic diversity among the major cuban rice cultivars was conducted using isozyme, RAPD and AFLP markers. Polymorphisms were detected for esterases, peroxidases, alcohol dehydrogenases and polyphenoloxidases systems; 21 RAPD primers and four AFLP primer combinations. Heterozygosity arithmetic mean value (Hav(p)), the effective multiplex ratio (EMR) and the marker index (MI), were...
Root morphology under well-watered conditions sampled on two occasions and under low-moisture stress was studied in a randomly chosen subset of 56 doubled haploid lines derived from a cross between IR64 and Azucena at two growth stages during the vegetative stage. A molecular map of the same population served as the basis for locating QTLs controlling root morphology and associated traits. The region...
Marker-assisted selection (MAS) for resistance genes (R-genes), identified using molecular markers and quantitative trait loci (QTL) analysis, is now possible in many crops. MAS can be used to pyramid several R-genes into a single host genotype. However, this may not provide durable genetic resistance because the pathogen is exposed to a full homozygous pyramid during hybrid seed production and to...
We have examined the effectiveness of similar numbers of markers from four molecular marker systems (AFLP, isozymes, ISSR and RAPD) for revealing genetic diversity and discriminating between infraspecific groups of Oryza sativa germplasm. Each marker system classifies the germplasm into three major groups (most effectively with isozymes and AFLPs), but with differences (primarily with ISSR) between...
The genetic diversity of three salinity tolerant rice varieties Pokkali, Nona-Bokra and Bicol was investigated using random amplified polymorphic DNAs(RAPDs). High yielding susceptible variety IR29 was used as check for comparison. The salinity performance of these varieties were tested by using rapid screening techniques at seedling stage. One hundred primers tested of which 42 revealed differences...
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