QTL mapping of <Emphasis Type="Italic">Sclerotinia</Emphasis> midstalk-rot resistance in sunflower

In many sunflower-growing regions of the world, Sclerotinia sclerotiorum (Lib.) de Bary is the major disease of sunflower (Helianthus annuus L.). In this study, we mapped and characterized quantitative trait loci (QTL) involved in resistance to S. sclerotiorum midstalk rot and two morphological traits. A total of 351 F₃ families developed from a cross between a resistant inbred line from the germplasm pool NDBLOS and the susceptible line CM625 were assayed for their parental F₂ genotype at 117 codominant simple sequence repeat markers. Disease resistance of the F₃ families was screened under artificial infection in field experiments across two sowing times in 1999. For the three resistance traits (leaf lesion, stem lesion, and speed of fungal growth) and the two morphological traits, genotypic variances were highly significant. Heritabilities were moderate to high (h²=0.55–0.89). Genotypic correlations between resistance traits were highly significant (P<0.01) but moderate. QTL were detected for all three resistance traits, but estimated effects at most QTL were small. Simultaneously, they explained between 24.4% and 33.7% of the genotypic variance for resistance against S. sclerotiorum. Five of the 15 genomic regions carrying a QTL for either of the three resistance traits also carried a QTL for one of the two morphological traits. The prospects of marker-assisted selection (MAS) for resistance to S. sclerotiorum are limited due to the complex genetic architecture of the trait. MAS can be superior to classical phenotypic selection only with low marker costs and fast selection cycles.     

Genetic effects on wood quality traits of plantation-grown white spruce (Picea glauca) and their relationships with growth

Clonal repeatabilities on individual tree (H_i² H_i^2 ) and clonal mean (H_{[`(C)]</sub> <sup>2</sup> H_{{\overline C }}^2 ) bases for growth (14-year height and volume), wood quality traits (latewood proportion, wood density, fiber length, and microfibril angle), and genotypic correlations among the traits were estimated, using 30 white spruce (Picea glauca [Moench] Voss) clones from six full-sib families (five per family). These families were selected from a clonally replicated test to represent different early growth categories: fast, moderate, and slow. Wood increment cores of the 30 clones were collected from two contrasting sites at age 19 years. For growth traits, in contrast to most wood quality traits, more genetic variation was accounted for by clone within family than by family within growth category. Both growth and wood quality traits appear to be under moderate genetic control, with [^(H)]<sub>i</sub><sup>2</sup> = 0.20 - 0.36 \widehat{H}_i^2 = 0.20 - 0.36 and [^(H)]<sub>[`(C)]} ² = 0.70 - 0.83 \widehat{H}_{{\overline C }}^2 = 0.70 - 0.83 . The only exception was microfibril angle ( [^(H)]_i² = 0.10  \textand  [^(H)]_[`(C)] ² = 0.34 \widehat{H}_i^2 = 0.10\;{\text{and}}\;\widehat{H}_{{\overline C }}^2 = 0.34 ). Generally, faster growth resulted in a significantly lower latewood proportion and lower overall wood density. Selection for faster growth does not appear to impact on either fiber length or microfibril angle. Among the wood quality traits, significant genotypic association was observed only between latewood proportion and wood density. Despite the generally negative association between growth and wood density among families, several fast-growing clones maintained above-average density. This implies that, by adopting multiclonal forestry, one can simultaneously improve growth and wood density.     

Quantitative genetics of growth and development in Populus. I. A three-generation comparison of tree architecture during the first 2 years of growth

One approach to gain an insight into the genetics of tree architecture is to make use of morphologically divergent parents and study their segregating progeny in the F₂ and backcross (B₁) generations. This approach was chosen in the present study in which material of a three-generation pedigree growing side by side in a replicated plantation, was analyzed. The pedigree included Populus trichocarpa (T) and P. deltoides (D) parents, their F₁ and F₂ hybrids and their B₁ hybrids to the D parent. The trees were grown in the environment of the T parent and measured for the first 2 years of growth. Nine quantitative traits were studied at the stem, branch and leaf levels of tree architecture, in which the original parents differed. Strong F₁ hybrid vigor relative to the better parent (T) was expressed in growth and its components. Most quantitative traits in the F₂ and B₁ hybrids were intermediate between the T and D parents but displayed a wide range of variation due to segregation. The results from the analysis of variance indicated that all morphometric traits were significantly different among F₂ and B₁ clones, but the B₁ hybrids were more sensitive to replicates than the F₂. Broad-sense heritabilities (H ²) based on clonal means ranged from moderately high to high (0.50–0.90) for the traits studied, with H ² values varying over age. The H ² estimates reflected greater environmental noise in the B₁ than in the F₂, presumably due to the greater proportion of maladaptive D alleles in those hybrids. In both families, sylleptic branch number and length, and leaf size on the terminal, showed strong genetic correlations with stem growth. The large divergence between the two original parents in the traits studied, combined with the high chromosome number in Populus (2n=38), makes this pedigree well suited for the estimation of the number of quantitative trait loci (QTLs) underlying quantitative variation by Wright's biometric method (1968). Variation in several traits was found to be under the control of surprisingly few major QTLs: 3–4 in 2nd-year height and diameter growth, a single QTL in stem diameter/height ratio.     

Genetic analysis for main length ratio associated with morphological traits in Japanese flounder Paralichthys olivaceus

The objective of this study was to estimate genetic parameters of main length ratios associated with morphological traits in Paralichthys olivaceus. At 180, 240 and 360 days of age, body length (L₁), head length (L₂), body depth (L₃), caudal peduncle depth (L₄) and caudal‐peduncle length (L₅) were observed in 4757–5224 individuals from 52 full‐sib families. Based on these observed traits, the main length‐ratio traits including L₃:L₁, L₂:L₁, L₅:L₁ and L₄:L₃ were constructed. Three single‐trait animal models were used to examine the phenotypic variation of length‐ratio traits and were compared using the likelihood ratio test. As a result, the optimal model for all the analysed traits was determined as the model with the fixed, additive genetic and full‐sib family effects. Using the optimal model, animal model analysis for single trait showed that heritabilities were estimated to be low, ranging from 0·122 to 0·276. The estimates for all length‐ratio traits decreased while the days of age increased except for L₃:L₁. Multivariate animal model analysis indicated that within and among days of age, genetic correlations between length‐ratio traits were different in the direction and magnitude. Genetic parameter estimation of main length ratios would be helpful for genetic improvement of body shape in P. olivaceus.     

Estimated genetic parameters for growth‐related traits in large yellow croaker Larimichthys crocea using microsatellites to assign parentage

To estimate the heritabilities of growth‐related traits in large yellow croaker, Larimichthys crocea, three independent full‐factorial crosses were created by crossing four males × four females, seven males × three females and four males × three females (set 1, set 2 and set 3). At 13 months post‐hatch, the juveniles were collected from three cross sets and measured for body mass (M), standard length (L_S) and body height (H_B). In addition, the parentage of the juveniles was assigned by genotyping six or seven polymorphic microsatellite loci. Out of the 959 juveniles, 99·6% could be assigned to a single parental pair. Heritabilities of growth‐related traits were estimated for individual and combined sets with the pedigrees reconstructed by using microsatellite genotypes. The heritability estimates at 13 month‐old were 0·02–0·30 for M, 0·02–0·25 for L_S and 0·03–0·36 for H_B. These results showed that the heritabilities of M, L_S and H_B were different among three sets, which suggested that different breeding strategies should be adopted for different sets.     

Plant regeneration from sorghum anther cultures and field evaluation of progeny

Summary Embryogenic calli were obtained from a hybrid line of Sorghum bicolor (L.) Moench anthers with mid to late uninucleate pollen cultured in N₆ medium supplemented with 3.0% sucrose, 2.0 mg/1 2,4-D, 0.8% agar and incubated at 30°C, which was the optimum temperature. The regeneration of embryos was obtained from the embryogenic calli cultured in modified MS medium supplemented with 3.0% sucrose, 2.0 mg/1 BAP combined with 0.3 mg/1 IAA and 0.8% agar. A total of 248 doubled haploids and 12 haploid plants were regenerated. In a subsequent field study, the selfed progeny from anther culture (designated as the anther culture-2, [A₂] generation) derived families was compared with both the F₂ and the F₁ for agronomic and morphological traits. Significant differences were noticed between the family means of both A₂ and F₂ for all the quantitative traits studied. The distinctive difference in the behavior of the A₂ families in comparison with the F₂ was established by within family variance, which was significant in F₂ for days to 50 per cent flowering, plant height, panicle length, leaf area index, dry matter production, harvest index and grain yield and was non-significant in A₂. Male sterility, one of the potentially important traits, currently exploited in the hybrid seed production of cereals, including CSH5 hybrid sorghum and the morphological traits (panicle shape, compactness, grain color, glume color and nature of the leaf sheath) segregated in the F₂. Such segregation was not observed within A₂ families and they bred true to their respective A₁ plants, indicating the rapid attainment of homozygosity/uniformity. The present study establishes the gametophytic origin of anther culture derived families and indicates the possibility of rapid production of homozygous lines which can be used as recombinant inbreds.Abbreviations N₆ Chu et al. (1975) - MS Murashige and Skoog (1962) - 2,4-D, 2 4-Dichlorophenoxyacetic acid - IAA Indole-3 -acetic acid - BAP Benzylaminopurine - A₁ regenerated plants - A2 selfed progeny from A₁     

Context‐dependent expression of sexual dimorphism in island populations of the common wall lizard (Podarcis muralis)

The condition‐dependent sexual dimorphism model explains the evolution and maintenance of sexual dimorphism in traits targeted by sexual selection, and predicts that the magnitude of sexual dimorphism depends on the variability of individual condition, male traits being more variable than female corresponding traits. Most convincing examples concern insects, while studies among vertebrates are scanty because manipulating condition often is not possible, and the time to reach sexual maturity may be too long. Islands offer a unique opportunity to compare how the environment affects the expression of sexual dimorphism, since they represent ‘natural experimental sets’ in which different populations of the same species may experience alternative environmental constraints. We investigated the occurrence of context‐dependent expression in sexual dimorphism of head shape in insular populations of the common wall lizards (Podarcis muralis) inhabiting the Tuscan Archipelago (Tyrrhenian Sea). Alternative models were formulated: H₀ assumes that the sexual dimorphism is uninfluenced by islands, H₁ assumes the only effect of phylogeny, H_2A and H_2B account for the biogeography of the archipelago (island size and distance from the mainland), while H₃ assumes island‐specific effects on sexual dimorphism. Models were compared using Akaike's information criterion adjusted for multivariate analyses. All hypotheses performed better than H₀, but H₃ largely outperformed all other alternative hypotheses, indicating that environmental features of islands play an additive effect to ontogenetic, biogeographic and genetic factors in defining variation in head shape sexual dimorphism. Our results support the hypothesis of a context‐dependent sexual dimorphism in common wall lizards. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 552–565.     

QTL mapping of resistance to Sclerotinia midstalk rot in RIL of sunflower population NDBLOSsel × CM625

Midstalk rot caused by Sclerotinia sclerotiorum is an important disease of sunflower in its main areas of cultivation. The objectives of this study were to (1) verify quantitative trait loci (QTL) for midstalk-rot resistance found in F₃ families of the NDBLOS_sel × CM625 population in recombinant inbred lines (RIL) derived from the same cross; (2) re-estimate their position and genetic effects; (3) draw inferences about the predictive quality of QTL for midstalk-rot resistance identified in the F₃ families as compared to those in the RIL. Phenotypic data for three resistance (leaf lesion, stem lesion, and speed of fungal growth) and two morphological traits (leaf length and leaf length with petiole) were obtained from 317 RIL following artificial infection in field experiments across two environments. For genotyping the 248 RIL, we selected 41 simple sequence repeat (SSR) markers based on their association with QTL for Sclerotinia midstalk-rot resistance in an earlier study. The resistance traits showed intermediate to high heritabilities and were significantly correlated with each other Genotypic correlations between F₃ families and the RIL were highly significant and ranged between 0.50 for leaf length and 0.64 for stem lesion. For stem lesion, two genomic regions on linkage group (LG) 8 and LG16 explaining 26.5% of the genotypic variance for Sclerotinia midstalk-rot resistance were consistent across generations. For this trait, the genotypic correlation between the observed performance and its prediction based on QTL positions and effects in F₃ families was surprisingly high The genetic effects and predictive quality of these two QTL are promising for application in marker-assisted selection to Sclerotinia midstalk-rot resistance.     

Synthesis of Streptovitacin-C2 Isomers

(2R*,4S*,6S*,αS*)- and (2R,4R,6R,αS)-Streptovitacin-C₂ (STV-C₂) (1a and 1b) were synthesized by an aldol condensation of (2R*,4S*)- or (2R,4R)-2,4-dimethyl-2-trimethylsiloxy-1-cyclohexanone (15a or 15b) with 4-(2-oxoethyl)-2,6-piperidinedione (16), which was followed by desilylation of the products. The stereochemistry of the synthesized STV-C₂ isomers (1a and 1b) was elucidated by NMR. STV-C₂ isomers (1a and 1b) did not show strong antimicrobial activity against Saccharomyces cerevisiae and Pyricularia oryzae.     

Genetic divergence between two forms of a tongue sole <Emphasis Type="Italic">Cynoglossus interruptus</Emphasis>

Genetic differences between trilinear and dilinear forms of a tongue sole, Cynoglossus interruptus, were examined by use of isozymes. Unequivocal differences were detected between the two forms, including complete replacement of alleles at the FBALD-2*, MDH-3*, PROT-1*, and SOD-1* loci, almost complete replacement at the AAT-3*, AH-1*, AH-2*, EST-3*, G3PDH-3*, GPI-2*, IDHP-1*, and MDH-1* loci, and extreme differences in allelic frequencies at the GPI-1* and PGDH* loci. The genetic distances (D values) between the two forms were 0.4207–0.4353, figures predicatively significant at the specific level. The considerable genetic differences strongly suggested that the two forms represent distinct species. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Genetic diversity and structure of the endemic Caesalpinia hintonii complex (Leguminosae: Caesalpinioideae) in Mexico

The Caesalpinia hintonii complex is formed by five endemic species (C. hintonii, C. laxa, C. macvaughii, C. melanadenia and C. epifanioi) occurring in central Mexico. This species complex is under incipient genetic divergence as by-product of local adaptations in reproductive and morphological traits to different habitats. We estimate the genetic variation and structure of populations of this species complex to assess the extent of genetic differentiation among populations and related species along its geographic distribution. Estimations of genetic diversity and structure were done based on ten enzymes and 18 loci. Mean number of alleles per locus ranged from 1.5 to 1.9. Polymorphic loci ranged from 42.1 to 68.4. Observed (H_o: range 0.191–0.275) and expected (H_e: range 0.205–0.317) heterozygosities in this complex were higher compared with other endemic and legume species. Neis genetic diversity estimates showed that most genetic variation was found within (H_S = 0.325) rather than among populations (D_ST = 0.085). Populations of the species C. hintonii showed a considerable genetic differentiation (F_ST = 0.207). The results of genetic diversity and structure within and among populations are in accord with the great morphological differentiation described for this species complex.     

Oxidative stress impairs autophagic flux in prion protein-deficient hippocampal cells

We previously reported that autophagy is upregulated in Prnp-deficient (Prnp^0/0) hippocampal neuronal cells in comparison to cellular prion protein (PrP^C)-expressing (Prnp^+/+) control cells under conditions of serum deprivation. In this study, we determined whether a protective mechanism of PrP^C is associated with autophagy using Prnp^0/0 hippocampal neuronal cells under hydrogen peroxide (H₂O₂)-induced oxidative stress. We found that Prnp^0/0 cells were more susceptible to oxidative stress than Prnp^+/+ cells in a dose- and time-dependent manner. In addition, we observed enhanced autophagy by immunoblotting, which detected the conversion of microtubule-associated protein 1 light chain 3 β (LC3B)-I to LC3B-II, and we observed increased punctate LC3B immunostaining in H₂O₂-treated Prnp^0/0 cells compared with H₂O₂-treated control cells. Interestingly, this enhanced autophagy was due to impaired autophagic flux in the H₂O₂-treated Prnp^0/0 cells, while the H₂O₂-treated Prnp^+/+ cells showed enhanced autophagic flux. Furthermore, caspase-dependent and independent apoptosis was observed when both cell lines were exposed to H₂O₂. Moreover, the inhibition of autophagosome formation by Atg7 siRNA revealed that increased autophagic flux in Prnp^+/+ cells contributes to the prosurvival effect of autophagy against H₂O₂ cytotoxicity. Taken together, our results provide the first experimental evidence that the deficiency of PrP^C may impair autophagic flux via H₂O₂-induced oxidative stress.     

Isolation of Amylase Inhibitor-producing Microorganism

An amylase inhibitor-producing microorganism was identified as a subspecies of Strepto- myces diastaticus from morphological and physiological studies and was named Streptomyces diastaticus subsp. amylostaticus No. 2476.

When this strain was aerobically cultured in a shaking flask containing 100 ml of medium consisting of 4% corn starch, 2% soy bean flake extract, 0.3 % NaCl, 0.1 % K₂HPO₄, 0.05% MgSO₄·7H₂O, 0.001% FeS0₄ · 7H₂O, 0.0001% CuSO₄-5H₂O, 0.0001% ZnSO₄·7H₂O, and 0.0001% MnS0₄ nH₂O (pH 7.0) at 30°C, the highest inhibitory activity was obtained after 70 ~ 80 hr of cultivation.

This amylase inhibitor (S-AI) had inhibitory activity on α-amylases and glucoamylase, but not on β-amylases and pullulanase.     

14个杉木家系主要用材性状表型多样性分析与评价

为了解杉木(Cunninghamia lanceolata)家系间用材性状的表型变异特征,采用方差分析、聚类分析、主成分分析等方法,对14个杉木家系的10个生长指标进行表型多样性分析和综合评价。结果表明,杉木家系主要用材性状的表型多样性指数为1.438～2.008,平均为1.735,最大的是树高,最小的是管胞长度。表型多样性丰富,其中,树高、胸径、单株材积、管胞长宽比和生材密度具有较强的遗传变异性,且各性状间具有一定相关性。家系遗传力(H2)为0.012～0.934,最大的是管胞长宽比,最小的是生材密度。表型变异系数为3.81%～39.90%,平均为15.03%,最大的是单株材积、最小是管胞腔径比,遗传改良潜力大。14个杉木家系可划分为3大类群,其中,类群Ⅲ的综合性状最优,类群I的生长量最佳。综合性状排名前3的家系是JX3、JX10和JX2。因此,10个主要用材性状的表型多样性丰富,筛选出的3个家系可作为优良材料用于杉木种质的保存与高效利用。     

QTL detection for stover yield and quality traits using two connected populations in high-oil maize

Both yield and quality traits for stover portion were important for forage and biofuel production utility in maize. A high-oil maize inbred GY220 was crossed with two normal-oil dent maize inbred lines 8984 and 8622 to generate two connected F_2:3 populations with 284 and 265 F_2:3 families. Seven yield and quality traits were evaluated under two environments. The variance components of genotype (σ_g²), environment (σ_e²) and genotype × environment interactions (σ_ge²) were all significant for most traits in both populations. Different levels of correlations were observed for all traits. QTL mapping was conducted using composite interval mapping (CIM) for data under each environment and in combined analysis in both populations. Totally, 45 and 42 QTL were detected in the two populations. Only five common QTL across the two populations, and one and three common QTL across the two environments in the two populations were detected, reflecting substantial influence of genetic backgrounds and environments on the results of QTL detection for stover traits. Combined analysis across two environments failed to detect most QTL mapped using individual environmental data in both populations. Few of the detected QTL displayed digenic epistatic interactions. Common QTL among all traits were consistent with their correlations. Some QTL herein have been detected in previous researches, and linked with candidate genes for enzymes postulated to have direct and indirect roles in cell wall components biosynthesis.     

Allozyme variability in Black Grouse (Tetrao tetrix), a tetraonid with lek behaviour

Summary The allozyme variability of 38 genetic loci coding for blood proteins was compared in up to 95 Black Grouse originating from Bavaria, the Netherlands and two sites in Sweden, bred to restock the Central European lowland populations. Polymorphisms are described forAda*,Pgd*, andPgm-1*, yielding an overall fraction of polymorphic loci of P=0.079, and an observed heterozygosity of H_o=0.015 (H_e=0.018). The genotype distributions at theAda* locus differed significantly between regional stocks, but unbiased standard distances measured D=0.0060 at most. Considering the inferred importance of genetic drift for Black Grouse microevolution, these slight genetic distances do not provide a basis for judging the validity of a suggested subspecies from the Netherlands. The weight differences of the eggs laid by grouse from different regional stocks reached statistical significance. A heterosis effect is inferred from the heavier eggs produced by F₁ crosses between parents originating from disparate geographic origins.

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Genetische Variabilität beim Birkhuhn (Tetrao tetrix), ein Hühnervogel mit Arenabalz

Zusammenfassung Die elektrophoretische Variabilität (38 Proteinloci) von Birkhühnern (Tetrao tetrix) wurde an Populationen aus Schweden, Bayern und den Niederlanden untersucht (n=95). Dabei handelt es sich um einige Gründertiere (teilweise Wildfänge) definierter geographischer Herkünfte für die Auswilderungszucht des Instituts für Wildtierforschung (Hannover) oder um deren Nachzuchten. Variabilität der EnzymeAda*,Pgd* undPgm-1* erbrachten einen Polymorphismus von P=0,079 und eine Heterozygotie von H_o=0.015 (H_e=0.018). Die Genotypenverteilung desAda*-Locus differenzierte regionale Populationen, jedoch betrugen die stichprobenkorrigierten genetischen Distanzen zwischen den Herkünften lediglich D=0.0060 oder waren geringer. Die geringe Mischerbigkeit wird hypothetisch mit relativ hoher genetischer Drift in Zusammenhang gebracht, weshalb sich Allozympolymorphismen beim Birkhuhn auch nur eingeschränkt zur Analyse von (unterartlichen) Populationsunterschieden eignen könnten, zumindest solange die Stichproben nicht erheblich ausgeweitet werden. Die Eigewichte von Hennen verschiedener regionaler Herkünfte unterscheiden sich signifikant, die Eier von Mischlingen zwischen Linien sind schwerer (Heterosiseffekt?). Die geringe Mischerbigkeit der untersuchten Birkhühner mag mit Faktoren der arteigenen Lebensweise (Arenabalz mit Polygynie, Varianz der Fruchtbarkeit unterschiedlicher Familien aufgrund hoher Kükensterblichkeit, Bestandesfluktuationen) erklärt werden. Die in den kleinen, isolierten Reliktbestände in Niedersachsen verbleibende genetische Variabilität dürfte sehr rasch verloren gehen, sofern die verbleibenden Habitate nicht durch Trittsteine verbunden werden, deren Abstände dem Ausbreitungsradius des Birkwildes Rechnung tragen.

     

Comparative effects of inbreeding and outbreeding on the ontogeny of Heliconius erato phyllis (Lepidoptera: Nymphalidae)

Inbreeding depression has been reported in various groups of organisms, including insects. Estimates of inbreeding consequences were obtained by comparing 12 life‐history and morphological traits among nine inbred families (F = 0.25) and 16 outbred families (F = 0) of the Neotropical butterfly Heliconius erato phyllis. A Student's t‐test showed statistically significant differences for pupal weight and right forewing area, both in males and in females, between inbred and outbred families. Survival during development, from egg hatching to adulthood, also differed significantly between inbred and outbred families. The average number of haploid lethal equivalents was 0.17 for pupal weight, 0.15 for forewing area and 0.71 for survival from hatching to adulthood. The results of this study confirm that the consequences of inbreeding are more deleterious to life history traits than to morphological ones.     

Hydrogen peroxide modulates meiotic cell cycle and induces morphological features characteristic of apoptosis in rat oocytes cultured <Emphasis Type="Italic">in vitro</Emphasis>

Hydrogen peroxide (H₂O₂) is known to induce cell cycle arrest and apoptosis in various somatic cell types cultured in vitro. We hypothesize that this reactive oxygen species (ROS) could modulate cell cycle and induce morphological features characteristics of apoptosis in oocytes cultured in vitro. To test this hypothesis, immature and mature oocytes were cultured in medium containing various doses of H₂O₂ with or without caspase-3 inhibitor for various times. The treatment of H₂O₂ induced germinal vesicle break down (GVBD) in all immature oocytes followed by initiation of shrinkage. Some of immature oocytes (but not mature oocytes) also showed membrane blebbing. On the other hand, H₂O₂ treatment inhibited first polar body emission in mature oocytes just prior to initiation of shrinkage. The cytoplasmic granulation and fragmentation into apoptotic bodies were observed in mature oocytes during later stages of H₂O₂ treatment. The shrinkage was induced by H₂O₂ in a dose- and time-dependent manner in both immature and mature oocytes. Although, H₂O₂-induced degeneration was observed in both immature and mature oocytes after 2.0 hrs of treatment, immature oocytes were more susceptible to undergo quick shrinkage, membrane blebbing and degeneration. Co-addition of caspase-3 inhibitor prevented shrinkage and degeneration of both immature and mature oocytes except membrane blebbing that was observed at higher doses of H₂O₂ after 1.0 hr of culture. Treatment of H₂O₂ induced bax protein expression (3 times), DNA fragmentation and caspase-3 activity (2.5 times) in oocytes undergoing morphological apoptotic changes. These findings clearly suggest that H₂O₂ induced GVBD in immature oocytes, inhibited first polar body extrusion in mature oocytes prior to initiation of morphological changes characteristic of apoptosis such as shrinkage, membrane blebbing and cytoplasmic fragmentation prior to degeneration.     

Identification and validation of QTL for Sclerotinia midstalk rot resistance in sunflower by selective genotyping

Midstalk rot, caused by Sclerotinia sclerotiorum (Lib.) de Bary, is an important cause of yield loss in sunflower (Helianthus annuus L.). Objectives of this study were to: (1) estimate the number, genomic positions and genetic effects of quantitative trait loci (QTL) for resistance to midstalk rot in line TUB-5-3234, derived from an interspecific cross; (2) determine congruency of QTL between this line and other sources of resistance; and (3) make inferences about the efficiency of selective genotyping (SG) in detecting QTL conferring midstalk rot resistance in sunflower. Phenotypic data for three resistance (stem lesion, leaf lesion and speed of fungal growth) and two morphological (leaf length and leaf length with petiole) traits were obtained from 434 F₃ families from cross CM625 (susceptible) × TUB-5-3234 (resistant) under artificial infection in field experiments across two environments. The SG was applied by choosing the 60 most resistant and the 60 most susceptible F₃ families for stem lesion. For genotyping of the respective F₂ plants, 78 simple sequence repeat markers were used. Genotypic variances were highly significant for all traits. Heritabilities and genotypic correlations between resistance traits were moderate to high. Three to four putative QTL were detected for each resistance trait explaining between 40.8% and 72.7% of the genotypic variance ( ). Two QTL for stem lesion showed large genetic effects and corroborated earlier findings from the cross NDBLOS_sel (resistant) × CM625 (susceptible). Our results suggest that SG can be efficiently used for QTL detection and the analysis of congruency for resistance genes across populations.     

The effects of hydrogen peroxide on metabolism in the coral Goniastrea aspera

Coral metabolism reflects the physiological condition of a coral colony. We studied coral metabolism using a continuous-flow, complete mixing (CFCM) experimental system. Small-size Goniastrea aspera coral colonies were incubated in the CFCM system with and without hydrogen peroxide (H₂O₂) added to the supplied seawater (0 µM H₂O₂ for 12 days; 0, 0.3, 3.0, and 30 µM H₂O₂ for 3 days, for each treatment) Without addition of H₂O₂, coral metabolism, including photosynthesis (gross primary productivity) and calcification, was relatively stable and there were no significant metabolic changes, suggesting that, without H₂O₂ added to the CFCM system, the corals did not suffer significant stress from the experimental system over a 12-day incubation period. When H₂O₂ was added, large decreases in photosynthesis and calcification were observed. The non-parametric Mann–Whitney U-test showed that there were statistically significant differences in photosynthesis after addition of 3.0 µM and 30 µM H₂O₂, compared with the control. We also found statistically significant differences in net calcification after addition of 30 µM H₂O₂. Thus, the incubation experiments suggest that higher H₂O₂ concentrations in seawater clearly influence coral metabolism. However, the results also suggest that the current seawater H₂O₂ level in Okinawa is not likely to pose significant acute effects on the metabolic activities of corals.