Availability and Utilization of Assimilates in Relation to Grain Growth Within the Ear of Wheat

The development of grains of different positions in the apical, middle and basal spikelets of wheat var. Kaly-ansona showed that beyond first two basal grains, the more distal a grain in a spikelet the lower its weight. The distal grains received less assimilates than the proximal grains as revealed from sugar concentration in the grains. The eflficiency of distal grains of kalyansona to synthesize reserves was, however, not inferior than the proximal grains in a spikelet. The depression in grain weight lowards extreme spikelet was lower compared to the depression in weight of individual grams towards a distal position in a spikelet. The study seems to suggest that in order to ensure better grain uniformity while maintaining a higher grain number per ear, the spikelet number per ear should be increased instead of increasing the grain number per spikelet.     

Modeling solute transport in sub-surface drained soil-aquifer system of irrigated lands

A two-dimensional finite element model of solute transport in a tile — drained soil — aquifer system has been applied to study the effects of the depth of impervious layer and quality of irrigation water on salt distribution during drainage of an initially highly saline soil. The model assumes steady state water movement through partially saturated soil and to drains in the saturated zone. The exact in time numerical solution yields explicit expressions for concentration field at any future time without having to compute concentrations at intermediate times. The model facilitates predictions of long-term effects of different irrigation and drainage practices on concentration of drainage effluent and salt distribution in the soil and groundwater. The model results indicated that the depth of impervious layer from drain level, d_I, does not significantly influence the salt distribution in the surface 1 m root zone of different drain spacings (drain spacing (2S)=25, 50, 75 m; drain depth (d_d)=1.8 m), its effect in the aquifer becomes dominant as drain spacing increases. It was also observed that d_I significantly governs the quality of drainage effluent. The salinity of drainage water increases with increasing d_I in all drain spacings and this effect magnifies with time. The model was also applied to study the effects of salinity of irrigation water in four drain spacing-drain depth combinations: (2S=48 m, d_d=1.0 m; 2S=67 m, d_d=1.5 m; 2S=77 m, d_d=2.0 m; 2S=85 m, d_d=2.5 m). The results indicated that a favorable salt balance can be maintained in the root zone even while irrigating with water up to 5 dS/m salinity in drains installed at 48 to 67 m spacing and 1.0 to 1.5 m depth. Further, irrespective of the quality of irrigation water, the deep, widely spaced drains (d_d=2.5 m, 2S=85 m) produced much saline drainage effluent during the initial few years of operation of the drainage system than the more shallow, closely spaced drains, thus posing a more serious effluent disposal problem.

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Résumé Considérant les conséquences potentiellement sérieuses de la pollution du sol et de l'eau souterraine dans l'agriculture irriguée, il est devenu absolument nécessaire de développer des modèles de simulation en vue d'évaluer les effects à long terme des méthodes agricoles modernes. Un modèle d'éléments finis à deux dimensions du transport en solution dans un système de sol aquifère drainé au moyen de tuyaux a été développé et validé sur le terrain (Kamra et al. 1991 a, b). Le modèle assume le mouvement de l'eau à régime constant à travers un sol partiellement saturé et jusqu'aux drains dans la zone saturée. La solution numérique exacte dans le temps produit des expressions explicites pour le champ de concentration à un temps future quelconque sans avoir à calculer les concentrations aux temps intermédiares. Le modèle facilite les prédictions des effets à long terme des diverses méthodes d'irrigation et de drainage sur la concentration des effluents de drainage et sur la distribution de la salinité dans le sol et dans l'eau souterraine. Les résultats du modèle relatifs aux effets de la profondeur de la couche imperméable et de la qualité de l'eau d'irrigation sur la distribution de la salinité lors du drainage d'un sol fortement salé à l'origine sont mentionnés dans la présente communication.Les résultats du modéle ont indiqué que la profondeur de la couche imperméable depuis le niveau du drain, d_I, n'influence pas d'une façon significative la distribution de la salinité dans la zone superficielle radiculaire de 1 m des divers écartements de drains (écartement de drains, 2S=25, 50, 75 m; profondeur des drains, d_d=1.8 m); son effet dans l'aquifère devient dominant à mesure que l'écartement de drains augmente. On a aussi constaté que le niveau du drain d_I influence d'une manière significative les effluents du drainage. La salinité de l'eau de drainage augmente à mesure que d_I augmente dans tous les écartements de drains et cet effet s'amplifie avec le temps. Le modèle a été aussi appliqué pour étudier les effets de la salinité de l'eau d'irrigation dans le cas de quatre conbinaisons d'écartement de drain et de profondeur de drain: (2S=48 m, d_d=1,0 m; 2S=67 m, d_d=1,5 m; 2S=77 m, d_d=2,0 m; 2S=85 m, d_d=2,5 m). Les résultats ont indiqué qu'un bilan de salinité favorable peut être maintenu dans la zone radiculaire même en irrigant avec de l'eau d'une salinité de 5 dS/m dans des drains installés à un écartement de 48 à 67 m et une profondeur de 1,0 à 1,5 m. De plus, indépendamment de la qualité de l'eau d'irrigation les drains profonds à grand écartement (d_d=2,5 m, 2S=85 m) produisaient une grande quantité d'effluents salés de drainage durant les quelques premières années de l'exploitation du système de drainage par rapport aux drains peu profonds à écartement serré, posant ainsi un problème plus sérieux d'évacuation des effluents.Les résultats du développement et de l'évaluation du modèle on montré qu'il peut être utilement employé en vue d'une évaluation judicieuse de la variation de temps escomptée dans la salinité des effluents de drainage lors de la mise en valeur des sols salins et peut ainsi aider à formuler son règlement plus sûr du point de vue environnement et les projects d'évacuation.

     

Analysis of genetic variability and agronomic performance of Indian lettuce (Lactuca indica L.)

Genetic Resources and Crop Evolution - Lactuca indica L. is an undomesticated medicinal crop in the Asteraceae family. The study was carried out to identify elite genotypes for lettuce cultivation...     

Landraces-potential treasure for sustainable wheat improvement

Genetic Resources and Crop Evolution - Agricultural production is facing serious threat from various biotic and abiotic stresses specifically under climatic challenges. It is becoming increasingly...     

Association of staygreen trait with canopy temperature depression and yield traits under terminal heat stress in wheat (Triticum aestivum L.)

The presence or absence of the staygreen trait was screened for 3 consecutive years in 963 wheat lines from various sources, including Indian and CIMMYT germplasm. Staygreen was assessed at the late dough stage by visual scoring (0–9 scale) and the leaf area under greenness (LAUG) measurement. Around 5.5 % of the lines were staygreen, 10.5 % were moderately staygreen, and the remaining lines showed little or no expression of the trait. One hundred lines showing diversity for the staygreen trait were sown under three different sowing dates (timely, late and very late) for 3 consecutive years in three replications to determine the association of staygreen with heat tolerance. There was a decline in yield, biomass, grain filling duration (GFD) and 1,000 grain weight (TGW) under late and very late sowing conditions owing to terminal stress at anthesis and later stages. However, the decline was relatively less in staygreen genotypes compared to the non-staygreen (NSG) ones. The correlation study showed that LAUG and canopy temperature depression (CTD) were strongly correlated. LAUG and CTD were also significantly associated with grain yield, GFD and biomass. To further confirm the association of the staygreen trait with terminal heat stress, individual F₂-derived F₇ progenies from the cross of the ‘staygreen’ lines with NSG were evaluated for yield and yield traits at the three sowing dates. In each cross, the staygreen progenies showed a significantly smaller decline in yield and TGW under heat stress than the NSG progenies. These results appear to suggest an association between the staygreen trait and terminal heat stress and, thereby, that the staygreen trait could be used as a morphological marker in wheat to screen for heat tolerance.     

Mining of rice blast resistance gene Pi54 shows effect of single nucleotide polymorphisms on phenotypic expression of the alleles

The rice blast resistance gene Pi54 (formerly Pi-k ^h ) isolated from indica rice line Tetep confers broad spectrum resistance to different strains of Magnaporthe oryzae in India. In this study, we performed PCR based allele mining for blast resistance gene Pi54 from six cultivated rice lines and eight wild rice species to understand its structural variation and its impact on the phenotypes. Sequence analysis indicates presence of more variation between cultivated and wild species (35–90 %) than variation found among cultivated species (1–20 %). Structural analysis of alleles showed presence of variable number of Open Reading Frames (0–2) principally having point mutations in the leucine rich repeats (LRR) regions. The Ka/Ks ratio of LRR region was >1, which shows the effect of selection pressure at this domain. The Pi54 alleles have 142 polymorphic sites with average nucleotide diversity of 0.04522. The K_a/K_s ratio of coding region ranged from 0 to >1 and Tajima’s D test showed negative as well as Darwinian selection within the alleles, which corresponded well with their phenotypic reaction to M. oryzae. The results obtained in this study shows divergent nature of Pi54 allele in wild species and land races of rice. The resistance alleles identified in this study can be used in effective management of rice blast disease through gene pyramiding.     

Comparative analysis of innate immune parameters of the skin mucous secretions from certain freshwater teleosts, inhabiting different ecological niches

The innate immune system of fish is considered first line of defense against a broad spectrum of pathogens. Being a component of innate immunity and lying at the interface between fish and the aqueous environment, skin mucus plays a frontier role in protecting fish from infections. In the present study, skin mucus of Cirrhinus mrigala, Labeo rohita, Catla catla, Rita rita and Channa punctata, inhabiting different ecological niches, was analyzed to characterize potential innate immune factors such as lysozyme, proteases, phosphatases, esterase and sialic acid. The enzyme activities were high in bottom dweller species, C. punctata and C. mrigala, and low in clean water inhabiting species, L. rohita and C. catla. An inverse relationship was observed between the level of enzyme activity and the sialic acid content in these fish species. In R. rita, however, the levels of all factors were found to be low. Zymographic analysis with labeled Micrococcus lysodeikticus revealed three isoforms of lysozyme in C. punctata and two in each species, C. mrigala, L. rohita and C. catla. In R. rita, lysozyme could not be detected. Gelatin zymography revealed that serine and metalloproteases were the major mucus proteases in all fish species investigated. In addition, trypsin-like protease and Ca(++)-specific serine proteases were observed in skin mucus. Increased knowledge of these parameters could be useful in understanding the role of skin mucus in the innate immune system of fish species inhabiting different ecological niches.     

Molecular characterization and SNP identification in HSPB6 gene in Karan Fries (Bos taurus x Bos indicus) cattle

Tropical Animal Health and Production - Heat shock proteins (HSPs) act as molecular chaperones which are preferentially transcribed in response to severe perturbations of the cellular homeostasis...     

西非Sudanian热带林地11个树种地上生物量异速生长预测

Allometric models are necessary for estimating biomass in terrestrial ecosystems. Generalized allometric relationship exists for many tropical trees, but species- and region-specific models are often lacking. We developed species-specific allometric models to predict aboveground biomass for 11 native tree species of the Sudanian savanna-woodlands. Diameters at the base and at breast height, with species means ranging respectively from 11 to 28 cm and 9 to 19 cm, and the height of the trees were used as predictor variables. Sampled trees spanned a wide range of sizes including the largest sizes these species can reach. As a response variable, the biomass of the trees was obtained through destructive sampling of 4 754 trees during wood harvesting. We used a stepwise multiple regression analysis with backward elimination procedure to develop models separately predicting, total biomass of the trees, stem biomass, and biomass of branches and twigs. All species-specific regression models relating biomass with measured tree dimensions were highly significant (p < 0.001). The biomass of branches and twigs was less predictable compared to stem biomass and total biomass, although their models required fewer predictors and predictor interactions. The best-fit equations for total above-ground biomass and stem biomass had R ² > 0.70, except for the Acacia species; for branches including twig biomass, R²-values varied from 0.749 for Anogeissus leiocarpa to 0.183 for Acacia macrostachya. The use of these equations in estimating available biomass will avoid destructive sampling, and aid in planning for sustainable use of these species.