Provenance variations in seed-related characters and oil content of <Emphasis Type="Italic">Calophyllum inophyllum</Emphasis> L. in northern Australia and Sri Lanka

Seed morphometric characters and oil content were studied in multiple-use plant, Calophyllum inophyllum L. of two countries, Australia (southern hemisphere) and Sri Lanka (northern hemisphere). Seven provenances were selected which included three from northern Australia and four from Sri Lanka. Twelve Candidate plus trees (CPTs) each were selected from 2 to 3 different locations within each provenance based on the morphometric and qualitative traits (GBH > 100 cm). Seed collection in both hemispheres was carried out from May to August 2008. Calophyllum inophyllum L. provenances showed a distinct hemisphere variation in their seed-related characters and oil content. All provenances differed significantly (P < 0.05) with one another in seed length. Seeds from Anuradhapura, Sri Lanka and seeds from Cardwell Australia recorded the highest (≈57%) and the lowest oil (≈31%) content respectively. Strong correlations were found between seed morphometric characters. Relatively weaker correlations were found between seed morphometric characters and oil content. Variations in seed-related characters were largely attributed by the provenance contribution which shows the significance of the effect of genetic variability on above mentioned seed related characters.     

Minor pregnanes from Caralluma adscendens var. gracilis and Caralluma pauciflora

Phytochemical investigation of Caralluma adscendens var. gracilis and Caralluma pauciflora (Asclepiadaceae) whole plant extracts allowed to isolate one pregnane glycoside and two pregnanes characterized as 12β,20-O-dibenzoyl-5α,6-dihydrosarcostin β-oleandropyranosyl-(1→4)-β-cymaropyranosyl-(1→4)-β-digitoxypyranosyl-(1→4)-β-cymaropyranosyl-(1→4)-β-cymaropyranoside (1), 12β-O-benzoyl-3β,11α,14β,20R-pentahydroxy-pregn-5-ene (2), and 11α-O-benzoyl-3β,12β,14β,20R-pentahydroxy-pregn-5-ene (3), respectively. Their structural characterization was obtained on the basis of extensive NMR spectral studies. Three known pregnane glycosides along with lupeol and β-sitosterol were also isolated and characterized.     

Allelopathic Potential of Shoot and Root Leachates of Certain Weed Species

The allelopathic potential of shoot and root leachates of seven weed species was assessed using sorghum and blackgram as test crops. Weeds differed significantly among themselves in their allelopathic effect. Shoot leachates of weeds, in general, showed more allelopathic effect than their root leachates. Phenolic content of weed leachates has positive association with the allelopathic potential of the weed species.     

Genetic analysis and validation of quantitative trait loci associated with reproductive-growth traits and grain yield under drought stress in a doubled haploid line population of rice (Oryza sativa L.)

Drought is a major constraint for rice production and yield stability in rainfed ecosystems, especially when it occurs during the reproductive stage. Combined genetic and physiological analysis of reproductive-growth traits and their effects on yield and yield components under drought stress is important for dissecting the biological bases of drought resistance and for rice yield improvement in water-limited environments. A subset of a doubled haploid (DH) line population of CT9993-5-10-1-M/IR62266-42-6-2 was evaluated for variation in plant water status, phenology, reproductive-growth traits, yield and yield components under reproductive-stage drought stress and irrigated (non-stress) conditions in the field. Since this DH line population was previously used in extensive quantitative trait loci (QTLs) mapping of various drought resistance component traits, we aimed at identifying QTLs for specific reproductive-growth and yield traits and also to validate the consensus QTLs identified earlier in these DH lines using meta-analysis. DH lines showed significant variation for plant water status, reproductive-growth traits, yield and yield components under drought stress. Total dry matter, number of panicles per plant, harvest index, panicle harvest index, panicle fertility, pollen fertility, spikelet fertility and hundred grain weight had significant positive correlations with grain yield under drought stress. A total of 46 QTLs were identified for the various traits under stress and non-stress conditions with phenotypic effect ranging from 9.5 to 35.6% in this study. QTLs for panicle exsertion, peduncle length and pollen fertility, identified for the first time in this study, could be useful in marker-assisted breeding (MAB) for drought resistance in rice. A total of 97 QTLs linked to plant growth, phenology, reproductive-growth traits, yield and its components under non-stress and drought stress, identified in this study as well as from earlier published information, were subjected to meta-analysis. Meta-analysis identified 23 MQTLs linked to plant phenology and production traits under stress conditions. Among them, four MQTLs viz., 1.3 for plant height, 3.1 for days to flowering, 8.1 for days to flowering or delay in flowering and 9.1 for days to flowering are true QTLs. Consensus QTLs for reproductive-growth traits and grain yield under drought stress have been identified on chromosomes 1 and 9 using meta-QTL analysis in these DH lines. These MQTLs associated with reproductive-growth, grain yield and its component traits under drought stress could be useful targets for drought resistance improvement in rice through MAB and/or map-based positional analysis of candidate genes.     

Solid substrate for production of Alternaria alternata conidia: a potential mycoherbicide for the control of Eichhornia crassipes (water hyacinth)

Eichhornia crassipes (water hyacinth), a major aquatic weed in India, is one of the targets in a biological weed control research programme in India. A fungal pathogen, Alternaria alternata, is being evaluated as a biological control agent for this weed. The feasibility of solid substrate for the mass production of A. alternata has been examined. Conidia production and virulence of A. alternata were affected by temperature, light and incubation period. The highest number of conidia were produced on rice seed followed by wheat, sorghum, maize seeds and cornmeal at 20°C when exposed to near‐ultraviolet than on the other substrates, while the least conidia were observed on these substrates under light conditions. At 20°C, large numbers of virulent conidia were produced on rice seeds after 4 weeks of incubation under constant dark conditions. Henceforth, the use of rice seeds as a solid substrate for production of A. alternata could be a feasible method to produce conidia in a village co‐operative scenario in India.     

Release and Sorption Pattern of Monosilicic Acid from Silicon Fertilizers in Different Soils of Louisiana: A Laboratory Incubation Study

The amount of monosilicic acid (H₄SiO₄), which is the plant-available form of silicon (Si), released from fertilizers can be influenced by Si source and soil properties. A series of laboratory experiments were conducted using six soil series from Louisiana to document the differences in the release characteristics of H₄SiO₄ from wollastonite and slag. Monosilicic acid in solution released from slag declined with time while wollastonite consistently increased its concentration across all soil suspensions well above 40 µg mL^?1. Among these soil series, soils high in organic matter and clay were seen to have maximum percent sorption (up to 79%) with minimum polymerization of H₄SiO₄. The presence of ions like aluminum (Al) and magnesium (Mg) enhanced the process of H₄SiO₄ polymerization, which led to a decrease in H₄SiO₄ concentration in solution. Evident relationships were observed between H₄SiO₄ concentration in solution with added Si sources and sorbed quantity from soil solutions.     

基于远红外热成像的叶温变化与玉米苗期耐旱性的研究

 【目的】植物可以通过降低叶片气孔蒸腾来达到控制失水和增强抗旱的目的。蒸腾强度的变化会引起植物叶片温度的变化,利用远红外热成像仪研究遭受干旱胁迫时玉米自交系苗期叶温的变化与生物量耐旱系数间的关系,为筛选鉴定玉米耐旱自交系提供依据。【方法】以83个优良玉米自交系为材料,利用远红外热成像仪检测干旱胁迫条件下苗期叶片温度的变化,叶片的气孔导度、蒸腾强度采用气孔计Li-1600测定,同时测定植株的生物量。【结果】遭受干旱胁迫时,玉米苗期叶片的相对生物量变异幅度为0.271～0.997（生物鲜重）、0.338～0.969（生物干重）,叶温变异幅度为 -0.1～+0.5℃,均存在显著变异。耐旱玉米自交系的叶片温度显著上升,而敏感玉米自交系的叶片温度变化不明显。干旱胁迫与正常灌水条件下叶温的差值即叶温差与相对生物鲜重（0.283*,0.288**,n=83）及相对生物干重（0.239*,0.273**,n=83）间存在极显著的相关性。此外,叶温差与叶片气孔导度、蒸腾强度间也存在着显著的相关性。【结论】遭受干旱胁迫时,玉米苗期叶片温度变化可以显著反映玉米苗期的耐旱性,叶温差可以作为玉米苗期耐旱性初步筛选的一个指标,将远红外热成像技术运用于玉米耐旱育种存在可行性。