Relationship between genetic divergence and hybrid performance in japonica rice grown in a cold water-irrigated field

The present study was carried out to evaluate genetic divergence among eleven japonica rice cultivars and to assess the relationship between genetic distance and hybrid performance in partial non-reciprocal crosses among them. The 44 F1 hybrids along with the eleven parents were evaluated for five cold tolerance-related traits; discoloration at seedling stage, days to heading, culm length, fertility, and spikelets per panicle in a cold water screening nursery (17 ^°C). The eleven parents were examined for DNA polymorphism using amplified fragment length polymorphisms(AFLPs). A total of 855 polymorphic variants were generated and based on the polymorphism data, genetic distances (GDs) ranged from 0.023 to0.524. Very little heterosis was observed in hybrids for most of the traits,whereas heterosis was high for fertility. The correlation values of GDs with F1 performance were mostly non-significant except for discoloration and fertility. The correlations of GDs with mid-parent and better-parent heterosis were not significant and proved to be of no predictive value. Our results indicate that GDs based on AFLP markers are not useful for predicting heterosis for cold tolerance in japonica hybrids. This revised version was published online in August 2006 with corrections to the Cover Date.     

Relationship between heterosis and genetic divergence in 'Tongil'-type rice

Improving grain yield and quality of ‘Tongil’‐type rice (indica/japonica) continues to be a major breeding objective in Korea. In this study, genetic divergence among 13‘Tongil’‐type rice cultivars was evaluated and the relationship between genetic distance and hybrid performance in all possible nonreciprocal crosses between them assessed. The 78 F₁ hybrids together with the 13 parents were evaluated for eight traits of agronomic importance, including yield, in a replicated field trial. The 13 parents were examined for DNA polymorphism using 71 micro‐satellite or simple sequence repeats and 46 random decamer oligonucleotide primers. A total of 319 polymorphic variants were generated and, based on the polymorphism data, genetic distances (GDs) ranged from 0.021 to 0.437. Cluster analysis based on GDs revealed associations among cultivars which was in agreement with the pedigree data. Heterosis was observed in hybrids for most of the traits, and yield exhibited the highest heterosis among the eight traits examined. The correlation values of GDs with F₁ performance were mostly nonsignificant, except for yield, culm length and spikelets per panicle. The correlations of GDs with midparent and better‐parent heterosis were not significant enough to be of predictive value. These results indicate that GDs based on the microsatellite and random amplified polymorphic DNA (RAPD) markers may not be useful for predicting heterotic combinations in ‘Tongil’‐type rice and support the idea that the level of correlation between hybrid performance and genetic divergence is dependent on the germplasm used.     

Effect of an oil heat treatment on the teachability and biological resistance of boric acid impregnated wood

Vegetable oils provide boron retention of about 30% of initial amount depending on oil drying properties. Linseed oil is the most efficient, followed by soybean oil and rapeseed oil. Durability of C. japonica and F. crenata wood specimens has been enhanced by application of linseed oil alone but not enough to reduce termite’s attack of Coptotermes formosanus. Treating wood with a 1.0% w/w boric acid solution prior to oil treatment protects C. japonica from termite and fungi degradations. Efficiency against termites is mainly due to boron retention by oil but hydrophobic oil also forms a barrier decreasing fungi penetration. Boron efficacy threshold around 0.7 kg/m³BAE, lower than classical boron treatments thresholds indicates that oil water-repellence reinforces boron biostatic effect.     

Laboratory evaluation of the termiticidal efficacy of copper HDO

A laboratory no-choice termite bioassay was conducted to evaluate the ability of copper HDO (CX-A or copper xyligen) to protect radiata pine (Pinus radiata D. Don) wood samples from attack by two subterranean termite species, Reticulitermes speratus and Coptotermes formosanus. A series of sapwood samples were pressure treated with either 0.25%, 0.50%, 0.75%, or 1.00% copper HDO solution. Samples treated with equivalent concentrations of a benchmark preservative, CCA-C, were used as treated controls. All samples (including controls) were subjected to an artificial weathering schedule before the bioassay. The samples were exposed to 30-day R. speratus tests and 3-week C. formosanus tests. Copper HDO was shown to deter termites from significant feeding on the treated wood. At a retention of 5.8 kg/m3 (treated with 0.75% solution) or higher, the mass loss from termite feeding did not exceed 3% for both the 30-day R. speratus tests and the 3-week C. formosanus tests. At each of the retentions tested, copper HDO performed comparably with equivalent retentions of CCA-C; however, field data are needed to validate these laboratory results. The preliminary findings are that copper HDO pressure treatment has potential as a viable method of protecting wood from attack by both termite species tested.     

Genetics and mapping of quantitative traits for nodule number, weight, and size in soybean (Glycine max L.[Merr.])

Soybean research has found that nodule traits, especially nodule biomass, are associated with N₂ fixation ability. Two genotypes, differing in nodule number per plant and individual nodule weight, KS4895 and Jackson, were mated to create 17 F₃- and 80 F₅-derived RILs. The population was mapped with 664 informative markers with an average distance of less than 20 cM between adjacent markers. Nodule traits were evaluated in 3-year field trials. Broad-sense heritability for nodule number (no. plant^?1), individual nodule dry weight (mg nodule^?1), individual nodule size (mm nodule^?1), and total nodule dry weight (g plant^?1) was 0.41, 0.42, 0.45, and 0.27, respectively. Nodule number was negatively correlated with individual nodule weight and size. Nodule number, individual nodule weight, and size are major components which likely contributed to increased total nodule weight per plant. Composite interval mapping (CIM) identified eight QTLs for nodule number with R² values ranging from 0.14 to 0.20. Multiple interval mapping (MIM) identified two QTLs for nodule number, one of which was located close to the QTL identified with CIM. Six QTLs for individual nodule weight were detected with CIM, and one QTL was identified with MIM. For nodule size, CIM identified seven QTLs with R² values ranging from 0.14 to 0.27. Five QTLs for total nodule weight were detected with CIM, one of which was located close to a QTL identified with MIM. These results document the first QTL information on nodule traits in soybean from field experiments utilizing a dense, complete linkage map.     

Discovery of single nucleotide polymorphisms in soybean using primers designed from ESTs

Discovery of single nucleotide polymorphisms (SNPs), including small insertions and deletions (indels), is one of the hot topics in genetic research. SNPs were surveyed using nine soybean genotypes from Korea. Sequence variations in a total of 110 genes from GenBank among the nine genotypes were studied using genomic DNA as a template. Direct fluorescent dideoxynucleotide sequencing data of PCR products from primers designed from soybean ESTs were analyzed by SeqScape software to ensure high accuracy. Approximately 70% of the primer sets produced a single PCR product from which reliable sequence data were obtained, and 23.6% of these had at least one SNP. Overall, a total of 110 ESTs for SNPs were screened in 33,262 bp, consisting of 16,302 bp from coding regions and 16,960 bp from adjacent non-coding regions (5 UTR, 3 UTR and introns). SNPs in coding and non-coding regions occurred at a frequency of 1 per 3,260 bp, corresponding to a nucleotide diversity () of 0.00011, and 1 per 278 bp ( = 0.00128), respectively. This suggested that the higher level of sequence variation in non-coding regions would make them good regions in which to search for SNPs. The SNPs in partial cDNA sequences could be valuable for gene-targeted map construction in soybean.     

Fingerprinting temperate <Emphasis Type="Italic">japonica</Emphasis> and tropical <Emphasis Type="Italic">indica</Emphasis> rice genotypes by comparative analysis of DNA markers

This paper describes the relative efficiency of three marker systems, RAPD, ISSR, and AFLP, in terms of fingerprinting 14 rice genotypes consisting of seven temperatejaponica rice cultivars, three indica near-isogenic lines, three indica introgression lines, and one breeding line of japonica type adapted to high-altitude areas of the tropics with cold tolerance genes. Fourteen RAPD, 21 ISSR, and 8 AFLP primers could produce 970 loci, with the highest average number of loci (92.5) generated by AFLP. Although polymorphic bands in the genotypes were detected by all marker assays, the AFLP assay discriminated the genotypes effectively with a robust discriminating power (0.99), followed by ISSR (0.76) and RAPD (0.61). While significant polymorphism was detected among the genotypes of japonica and indica through analysis of molecular variance (AMOVA), relatively low polymorphism was detected within the genotypes of japonica rice cultivars. The correlation coefficients of similarity were significant for the three marker systems used, but only the AFLP assay effectively differentiated all tested rice lines. Fingerprinting of backcross-derived resistant progenies using ISSR and AFLP markers easily detected progenies having a maximum rate of recovery for the recurrent parent genome and suggested that our fingerprinting approach adopting the ‘undefined-element-amplifying’ DNA marker system is suitable for incorporating useful alleles from the indica donor genome into the genome of temperate japonica rice cultivars with the least impact of deleterious linkage drag.     

Isolation of immunoglobulin from egg yolk by anionic polysaccharides

Isolation conditions of immunoglobulin in egg yolk (IgY) were optimized by the addition of various levels of Na-alginate (Alg), lambda-carrageenan (lambda-Cg), Na-carboxymethyl cellulose (CMC), and pectin (PC) to 6-fold diluted yolk. The mixtures were then reacted at pH 4.0-6.0 for 30 min. The optimal isolation conditions of IgY for Alg, lambda-Cg, and CMC were at the 0.1% level and at pH 5.0, while those for PC were at the 0.15% level and at the same pH. The remaining lipid and remaining protein in the supernatants thus obtained was 0.5-3.8% and 10-17%, respectively, and more than 90% of lipoproteins were precipitated. The IgY recovery was determined to be 33-74% by means of single radial immunodiffusion method when IgY was isolated under the optimal conditions. PC showed the best recovery of IgY, while lambda-Cg provided the least. The interactions between polysaccharides and lipoproteins were mainly ionic bonds, hydrophobic interactions, and hydrogen bonds as determined by the addition (0-2.0 M) of NaSCN or urea to the polysaccharide-lipoprotein precipitates.     

Isolation and antifungal and antioomycete activities of staurosporine from Streptomyces roseoflavus strain LS-A24

The actinomycete strain LS-A24 active against some plant fungal and oomycete pathogens was isolated from a soil sample of the Sunghwan Lake in Korea. The cell wall composition and spore shape of strain LS-A24 were LL-diaminopimelic acid and spiral type, respectively. On the basis of the physiological and biochemical characteristics and 16S ribosomal DNA sequence analysis, strain LS-A24 was identical to Streptomyces roseoflavus. An antifungal and antioomycete antibiotic was isolated from LS-A24 using various chromatographic procedures. The molecular formular of the antibiotic was determined to be C(28)H(26)N(4)O(3), and on the basis of the NMR data, the antibiotic was confirmed to be staurosporine, 2,3,10,11,12,13-hexahydro-10R-methoxy-9S-methyl-11R-methylamino-9S,13R-epoxy-1H,9H-diindolo[1,2,3-gh:3',2',1'-lm]pyrrolo[3,4-j][1,7]benzodiazonin-1-one. Staurosporine completely inhibited the mycelial growth of Colletotrichum orbiculare, Phytophthora capsici, Rhizoctonia solani, Botrytis cinerea, and Cladosporium cucumerinum with minimum inhibitory concentration (MIC) values of 1-50 microg/mL for MICs. Staurosporine also was active against Saccharomyces cerevisiae, Bacillus subtilis ssp. subtilis, and Xanthomonas vesicatoria. Staurosporine and the commercial fungicide metalaxyl inhibited the development of Phytophthora blight on pepper plants. However, the control efficacy of staurosporine against the Phytophthora disease was somewhat less than that of metalaxyl. This is the first study to isolate staurosporine from S. roseoflavus and demonstrate its in vitro and in vivo antioomycete activity against P. capsici.     

Isolation, antifungal activity, and structure elucidation of the glutarimide antibiotic, streptimidone, produced by Micromonospora coerulea.

The antibiotic Ao58A,which showed strong antifungal activity against some plant pathogenic fungi, was purified from the culture broth and mycelial mats of Micromonospora coerulea strain Ao58 using various chromatographic procedures. The molecular formula of the antibiotic Ao58A was deduced to be C(16)H(23)NO(4) (M + H, m/z 294.1707) by high-resolution FAB mass spectroscopy. Analyses of (1)H NMR, (13)C NMR, and 2D NMR spectral data revealed that the antibiotic Ao58A is the glutarimide antibiotic streptimidone, 4-(2-hydroxy-5, 7-dimethyl-4-oxo-6,8-nonadienyl)-2,6-piperidinedione. The antibiotic Ao58A was very effective in inhibiting growth of Phytophthora capsici,Didymella bryoniae, Magnaporthe grisea, and Botrytis cinerea in the range approximately 3-10 microg mL(-)(1) of MICs. In vivo evaluation of the antibiotic Ao58A under greenhouse condition showed strong control efficacies against the development of P. capsici, B. cinerea, and M. grisea on pepper, cucumber, and rice plants, respectively. The antibiotic Ao58A was equally as effective as metalaxyl, vinclozolin, and tricyclazole in the control of these plant diseases. However, it did not show any phytotoxicity on the plants even when treated with 500 microg mL(-)(1).