Assessment of Variation in Morpho-Physiological Traits and Genetic Diversity in Relation to Submergence Tolerance of Five Indigenous Lowland Rice Landraces

The present study evaluated submergence responses in 88 lowland indigenous rice(Oryza sativa L.) landraces from Koraput, India, to identify submergence-tolerant rice genotypes. In pot experiments, variations in survival rate, shoot elongation, relative growth index, dry matter, chlorophyll, soluble sugar and starch contents were evaluated in two consecutive years under well-drained and completely submerged conditions. Principal component analysis showed that the first three axes contributed 96.820% of the total variation among the landraces, indicating wide variation between genotypes. Major traits such as survival rate, relative growth index, soluble sugar and starch contents appeared to be important determinants of phenotypic diversity among the landraces. Phenotypic coefficient of variance was higher than genotypic coefficient of variance for all the traits and all showed high heritability(90.38%–99.54%). Five rice landraces(Samudrabali, Basnamundi, Gadaba, Surudaka and Dokarakuji) were the most tolerant to submergence. When submerged for up to 14 d, Samudrabali, Basnamundi and Godoba were notable for having greater survival rates than a standard submergence tolerant variety FR13 A, and also notable for elongating more vigorously and accumulating more biomass. These three landraces may therefore be especially useful in lowland rice growing areas that are affected by both moderate stagnant water and flash flooding. Molecular genotyping revealed that the submergence tolerance of Samudrabali, Basnamundi and Godoba is linked to the presence of one or more different Sub1 loci and it may well prove useful for breeding improved submergence tolerant rice varieties, thereby assising to improve yield stability in the rainfed lowland agro-ecosystem.     

Stability of soil plant analytical development (SPAD) chlorophyll meter reading (SCMR) and specific leaf area (SLA) and their association across varying soil moisture stress conditions in groundnut (<Emphasis Type="Italic">Arachis hypogaea</Emphasis> L.)

The complex nature of physiological traits associated with drought tolerance and the difficulties associated with their measurements in segregating populations and large number of genotypes inhibited their use in the past in developing water-use efficient genotypes in breeding programmes. With new knowledge of easily measurable surrogates of transpiration efficiency (TE), a trait associated with drought tolerance—specific leaf area (SLA) and soil plant analytical development (SPAD) chlorophyll meter reading (SCMR), it is now possible to integrate TE through the surrogates in breeding and selection schemes in groundnut (Arachis hypogaea L.). As a noninvasive surrogate of TE, SCMR is easy to operate, reliable, fairly stable and low cost. However, in a large-scale breeding program, it is difficult to complete SCMR observations within a specified time. The present study addressed the issue as to what extent the SCMR measurements can be spread over time by evaluating 18 diverse groundnut genotypes for two physiological traits, SCMR and SLA in two postrainy (Nov–Apr) seasons (2002/2003 and 2003/2004) in India. Observations were recorded at different times during and after the release of moisture deficit stress. There was general agreement in genotype and trait performance in both the seasons. Interaction between SCMR and time of observation was significant in only one season (2002/2003) but its variance relative to genotypes and time of observation was very small. ICGV 99029 and ICR 48, which recorded higher SCMR and lower SLA values in both the seasons, will make good parents for water-use efficiency trait in breeding programmes. Other good parents include ICGS 76, TCGS 647 and TCGP 6. SCMR recorded at three different times under differing soil moisture deficit in each season showed highly significant correlation with each other. Similarly, SLA at different times also correlated significantly with each other. SCMR and SLA were significantly negatively correlated with each other and the relationship was insensitive to time of observation. The results of the present study indicated that SCMR/SLA observations can be recorded at any time after 60 days of crop growth, preferably under moisture deficit conditions. This gives groundnut breeders a large flexibility to record these observations in a large number of segregating populations and breeding lines in the field. Thus, making it easy to incorporate these physiological traits associated with drought tolerance in breeding and selection scheme in groundnut.     

Accumulation of zinc and its effects on the growth, reproduction and life cycle of Drawida willsi (Oligochaeta), a dominant earthworm in Indian crop fields

 Accumulation of Zn and its effects on the growth, reproduction and life cycle of the earthworm Drawida willsi were determined. D. willsi did not reveal any significant changes in their mass at any of the concentrations of Zn (50, 200 and 400 mg kg^–1) compared to in untreated soils. The Zn concentrations in the exposed earthworms were significantly increased, but they were able to regulate their body content of Zn within a range of 116–125 mg kg^–1 (dry wt) in 200–400 mg kg^–1 Zn-treated soil. Reproduction was significantly reduced when the Zn concentration in soil exceeded 200 mg kg^–1. The drop in reproduction at elevated concentrations of Zn apparently resulted in a delay in completion of the life cycle and a decline in the total population. Received: 9 September 1998     

Variation in transpiration efficiency and its related traits in a groundnut (Arachis hypogaea L.) mapping population

Transpiration efficiency (TE) has been recognized as an important source of yield variation under drought stress in groundnut. Here the variation for TE is evaluated in a set of 318 recombinant inbred lines (RILs) of groundnut at F₈ generation, derived from a cross between a high TE (ICGV 86031) and a low TE (TAG 24) parent, and the value of specific leaf area (SLA), SPAD chlorophyll meter readings (SCMR) and carbon isotope discrimination (Δ¹³C) as surrogates of TE are measured. Transpiration efficiency was measured gravimetrically in the 318 RILs and parents under progressive soil drying in a pot culture in two post-rainy seasons. Large and consistent variation for TE existed among the RILs across years. The overall distribution of TE among the RILs indicated that TE was governed by dominant and additive genes. Surrogates SLA and SCMR, were measured prior, during and after completion of the drought period, whereas Δ¹³C was measured on the dried tissue after harvest. Transpiration efficiency was negatively associated with SLA after the completion of stress treatment (r² = 0.15) and Δ¹³C in leaves (r² = 0.13) and positively associated with SCMR during stress (r² = 0.17). These associations, all fairly weak, were significant only in 2004. None of these relationships was found in 2005. Although the heritability of SCMR during 2005 was relatively higher than that of TE, and although SCMR has previously been used to identify contrasting germplasm for TE, the stress-dependence of the relationship with TE, and the poor regression coefficients (r²) with that RIL population, do not confer that these surrogates are adequately robust enough in that population. Though more time consuming, a direct gravimetric evaluation for TE appeared to be more reliable.     

Genetic analysis of resistance to late leaf spot in interspecific groundnuts

Late leaf spot (LLS), caused by Phaeoisariopsis personata, is an important foliar fungal disease of groundnut (Arachis hypogaea L.), which causes significant economic losses globally to the crop. Inheritance of resistance to LLS disease was studied in three crosses and their reciprocals involving two resistant interspecific derivatives and a susceptible cultivar to refine strategy for LLS resistance breeding. The traits associated with LLS resistance, measured both in the field and under controlled conditions were studied following generation mean analysis. Results suggested that resistance to LLS is controlled by a combination of both, nuclear and maternal gene effects. Among nuclear gene effects, additive effect controlled majority of the variation. In JL 24 × ICG 11337 cross and its reciprocal only additive effects were important, while in JL 24 × ICG 13919 cross and its reciprocal, both additive and dominance effects contributed to the variation. Among digenic epistatic effects, additive × dominance interactions were significant. Additive–maternal effects were significant in both the crosses, while dominance–maternal effects also contributed to the variation in the crosses between the parents, JL 24 and ICG 13919. Due to significant contribution of additive effects of both nuclear and maternal inheritance to resistance to LLS, the parent, ICG 11337 would be a good donor in breeding programs. It would be worthwhile to use the resistance donor as female parent to tap maternal effects of resistance to LLS. Disease score is the best selection criterion in the field for use in breeding programs because of its high heritability and ease in measurement.     

近60年科尔沁沙地的气候变化

处于季风边缘带的科尔沁沙地气候变化具有复杂性和敏感性特征,文中采用线性倾向估计、非参数检验等方法探讨了其变化规律。结果表明:近60年研究区的年均气温呈上升趋势,变化速率为0.37℃/10a,尤其是20世纪80年代中后期以来增温趋势更为明显。且年际极端最高、最低气温也呈上升趋势。在季节变化中,春、冬季增温明显,夏季和秋季变化略小。而年降水量呈稳中有降的总趋势,变化速率为-13.54mm/10a。且年际、季节的降水日数也出现减少趋势。在季节变化中,除了春季以外其它季节均有减少趋势,与SPI变化一致。气温与降水量总体上呈负相关关系,即气温上升与降水的减少相对应,因而该区气候变化呈暖干化总趋势。夏季气候变化与东亚夏季风强弱有一定联系。     

Synthesis and solid-state NMR structural characterization of 13C-labeled graphite oxide

The detailed chemical structure of graphite oxide (GO), a layered material prepared from graphite almost 150 years ago and a precursor to chemically modified graphenes, has not been previously resolved because of the pseudo-random chemical functionalization of each layer, as well as variations in exact composition. Carbon-13 (13C) solid-state nuclear magnetic resonance (SSNMR) spectra of GO for natural abundance 13C have poor signal-to-noise ratios. Approximately 100% 13C-labeled graphite was made and converted to 13C-labeled GO, and 13C SSNMR was used to reveal details of the chemical bonding network, including the chemical groups and their connections. Carbon-13-labeled graphite can be used to prepare chemically modified graphenes for 13C SSNMR analysis with enhanced sensitivity and for fundamental studies of 13C-labeled graphite and graphene.     

Structure of Galphaq-p63RhoGEF-RhoA complex reveals a pathway for the activation of RhoA by GPCRs

The guanine nucleotide exchange factor p63RhoGEF is an effector of the heterotrimeric guanine nucleotide-binding protein (G protein) Galphaq and thereby links Galphaq-coupled receptors (GPCRs) to the activation of the small-molecular-weight G protein RhoA. We determined the crystal structure of the Galphaq-p63RhoGEF-RhoA complex, detailing the interactions of Galphaq with the Dbl and pleckstrin homology (DH and PH) domains of p63RhoGEF. These interactions involve the effector-binding site and the C-terminal region of Galphaq and appear to relieve autoinhibition of the catalytic DH domain by the PH domain. Trio, Duet, and p63RhoGEF are shown to constitute a family of Galphaq effectors that appear to activate RhoA both in vitro and in intact cells. We propose that this structure represents the crux of an ancient signal transduction pathway that is expected to be important in an array of physiological processes.     

Melanopsin (Opn4) requirement for normal light-induced circadian phase shifting

The master circadian oscillator in the hypothalamic suprachiasmatic nucleus is entrained to the day/night cycle by retinal photoreceptors. Melanopsin (Opn4), an opsin-based photopigment, is a primary candidate for photoreceptor-mediated entrainment. To investigate the functional role of melanopsin in light resetting of the oscillator, we generated melanopsin-null mice (Opn4-/-). These mice entrain to a light/dark cycle and do not exhibit any overt defect in circadian activity rhythms under constant darkness. However, they display severely attenuated phase resetting in response to brief pulses of monochromatic light, highlighting the critical role of melanopsin in circadian photoentrainment in mammals.     

Effect of different concentrations of metabolisable energy and protein on performance of White Leghorn layers in a tropical climate

1. An experiment was conducted to study the effects of feeding graded concentrations of metabolisable energy (ME) and crude protein (CP) on the performance of layers. Nine diets with three concentrations each of ME (10.04, 10.67 and 11.30 MJ/kg) and CP (150, 165 and 180 g/kg) in a 3 × 3 factorial arrangement of treatments were formulated.

2. A total of 5544 White Leghorn (WL) pullets (20 weeks of age) were housed in 4-bird colony cages and 22 adjacent cages constituted a replicate. Each diet was fed ad libitum to 7 replicates from 21 to 72 weeks of age. Production variables were recorded in 13 laying periods of 28 d each, and the data were pooled into three production phases, namely initial (21–32 weeks), peak (33–52 weeks) and post-peak (53–72 weeks).

3. No interaction was observed between ME and CP for egg production (EP), food intake (FI), food efficiency (FE), egg weight (EW), egg mass (EM) and body weight gain.

4. The EP, EW and EM during the initial phase of production were not affected by dietary ME concentrations, while the EW and EM improved with increasing concentrations of dietary CP from 150 to 165 g/kg.

5. During the peak production phase, improvements in EP (ME and CP), FI (ME), FE (ME, CP), EW (ME) and EM (ME, CP) were observed with increasing concentrations of energy and protein to 11.30 and 180 g/kg diet, respectively.

6. EP, EW and EM were unaffected by dietary variation in concentrations of ME and CP during post-peak production phase, but the FE improved and FI reduced with increasing dietary concentrations of these nutrients.

7. It is concluded that the optimum concentrations of ME for WL layers during the 21–32, 33–52 and 53–72 weeks of age are 11.30, 11.30 and 10.04 MJ/kg diet, respectively. The corresponding values for CP in diets are 180, 180 and 150 g/kg.