Potassium fractions with other nutrients in crops: A review focusing on the tropics

Potassium (K), a plant nutrient with diverse roles to play in plant metabolism, is required in large amounts by most crops. It interacts with many other plant constituents to affect crop yield and quality. The magnitude of this interaction is high in areas of high cropping intensity, as in the tropics. The interaction of nutrients with K may be in the soil or in plant. Potassium modifies ammonium (NH₄ ⁺) ion fixation in soils to restrict nitrogen (N) availability. On the other hand, an antagonistic effect between K and NH₄ absorption has been suggested in which K absorption is restricted. Similarly, magnesium (Mg) or calcium (Ca) deficiency occurs from ion antagonism in acid soils following K fertilization and in soils with high exchangeable K. Sulfur (S) has been reported to increase K absorption and productivity of oilseed crops. With increasing levels of applied or soil K, the severity of phosphorus (P)‐induced zinc (Zn) deficiency in corn has been observed to decrease. Application of K decreases manganese (Mn) content and iron (Fe) toxicity in rice. Application of K has been reported to decrease B levels in plants and to increase incidence of boron (B) deficiency. Top‐dressing with K fertilizer was reported to lower the copper (Cu) content of alfalfa forage. In root, sugar‐producing, or fiber‐producing crops, the sodium (Na) and K relationship is important with the specific response to either element depending on which element is in low or high supply. Molybdenum (Mo) stimulated K uptake in alfalfa and com. In intensive agriculture with high‐yielding single crops or with multiple crops per year, farm management must include strategies to maintain substantial K reserves in the soil and to balance K nutrition with other fertilization practices.     

Accelerated development of quality protein maize hybrid through marker‐assisted introgression of opaque‐2 allele

Vivek Maize Hybrid 9‐ a popular single‐cross hybrid developed by crossing CM 212 and CM 145 was released for commercial cultivation in India. The parental lines, being deficient in lysine and tryptophan, were selected for introgression of opaque‐2 allele using CML 180 and CML 170 as donor lines through marker‐assisted backcross breeding. The opaque‐2 homozygous recessive genotypes with >90% recovery of the recurrent parent genome were selected in BC₂F_2, and the seeds with <25% opaqueness in BC₂F₃ were forwarded for seed multiplication. Vivek Quality Protein Maize (QPM) 9, the improved QPM hybrid, showed 41% increase in tryptophan and 30% increase in lysine over the original hybrid. The grain yield of the improved hybrid was on par with the original hybrid. The newly improved QPM maize hybrid released in 2008 will help in reducing the protein malnutrition because its biological value is superior over the normal maize hybrids. This short duration QPM maize hybrid has been adopted in several hill states of North Western and North Eastern Himalayan regions.     

Two major genes for seed size in chickpea (Cicer arietinum L.)

Summary Seed size as determined by seed weight, is an important trait for trade and component of yield and adaptation in chickpea (Cicer arietinum L.). Inheritance of seed size in chickpea was studied in a cross between ICC11255, a normal seed size parent (average 120 mg seed⁻¹) and ICC 5002, a small seed size parent (average 50 mg seed⁻¹). Seed weight observations on individual plants of parents, F₁, F₂, and backcross generations, along with reciprocal cross generations revealed that the normal seed size was dominant over small seed size. No maternal effect was detected for seed size. The numbers of individuals with normal, small and medium (average 150 mg seed⁻¹) seed sizes in F ₂ population were 1237, 323 and 111 fitting well to the expected ratio of 12:3:1 (χ² = 0.923, P = 0.630). The segregation data of backcross generations also indicated that seed size in chickpea was controlled by two genes with dominance epistasis. We designate the genotype of ICC 11255 as Sd ₁ Sd ₁ sd ₂ sd ₂, and ICC 5002 as sd ₁ sd ₁Sd₂ Sd ₂ wherein Sd ₁ is epistatic to Sd ₂ and sd ₂ alleles.     

Investigation on pre-zygotic barriers in the interspecific crosses involving Gossypium barbadense and four diploid wild species

Interspecific hybridisation has played significant role in the improvement of economically useful traits such as productivity, earliness, fibre quality and resistance to pests and diseases in cotton. However, wide crosses are often limited by the operation of either pre or/and post-fertilization barriers. The present study on pollen tube behaviour of four diploid wild species viz., G. triphyllum, G. davidsonii, G. thurberi and G. armourianum in the pistils of G. barbadense was taken up to determine the extent of pre-zygotic barriers operating in these crosses. High rate of pollen germination (∼80%) and normal growth of pollen tubes were observed upon selfing of both G. barbadense and four wild species. Pollen tubes reached the pistils and fertilization was accomplished within 8 HAP in all the five parental species. In the interspecific crosses, pollen germination was normal in the cross involving G. armourianum and drastically inhibited in the crosses involving G. triphyllum, G. davidsonii and G. thurberi. Even though delayed pollen tube growth was a general feature in all the four crosses, successful fertilization was observed only in the cross involving G. armourianum. In crosses involving G. triphyllum, G. davidsonii and G. thurberi, pollen tubes failed to reach the ovary even at 24 HAP due to the presence of strong stylar and ovarian incompatibility. Abnormalities in pollen tubes such as swelling, twisting, intense callose plug formation, breakage, branching and reverse orientation were frequently observed among the incompatible crosses.     

Recording and interpretation of cerebral magnetic fields

Contemporary brain research progresses along two main lines: the microlevel approach explores single neurons and subcellular elements, while macrolevel studies focus on more complex cerebral functions, including behavior. This review presents results obtained mainly in our laboratory by means of an intermediate method, magnetoencephalography (MEG), which reflects cortical activity of neuronal populations at the level fo cytoarchitectonic areas. Because it is completely noninvasive, MEG can be used to study brain functions that are characteristically human.     

Polymeric dyes based on thiadiazole derivatives

A series of polymeric dyes were synthesized by free radical addition polymerization of monomeric dyes. The 2-amino-5-mercapto-1,3,4-thiadiazole was diazotized and coupled with various N-arylmaleimides to give monomeric dyes. All the polymeric dyes were characterized by elemental analysis, infrared spectroscopy, visible absorption spectroscopy, viscometry, and thermogravimetric analysis. Color and dyeing properties of the polymeric dyes were discussed by comparing them with those of the corresponding monomeric dyes. The dyeing performance of these dyes was assessed on nylon fiber. These dyes were found to give various color shades with good to very good depth and levelness on the fiber. The dyeing of the monomeric dyes showed moderate fastness to light and good to excellent fastness to washing, perspiration and sublimation and their corresponding polymeric dyes showed excellent fastness properties. The dyebath exhaustion and fixation on nylon fiber has been found to be good.     

Improvement of Upland Rice Variety by Pyramiding Drought Tolerance QTL with Two Major Blast Resistance Genes for Sustainable Rice Production

Varalu is an early maturing rice variety widely grown in the rainfed ecosystem preferred for its grain type and cooking quality. However, the yield of Varalu is substantially low since it is being affected by reproductive drought stress along with the blast disease. The genetic improvement of Varalu was done by introgressing a major yield QTL, qDTY_12.1, along with two major blast resistance genes i.e. Pi54 and Pi1 through marker-assisted backcross breeding. Both traits were transferred till BC₂ generation and intercrossing was followed to pyramid the two traits. Stringent foreground selection was carried out using linked markers as well as peak markers (RM28099, RM28130, RM511 and RM28163) for the targeted QTL (qDTY_12.1), RM206 for Pi54 and RM224 for Pi1. Extensive background selection was done using genome-wide SSR markers. Six best lines (MSM-36, MSM-49, MSM-53, MSM-57, MSM-60 and MSM-63) having qDTY_12.1 and two blast resistance genes in homozygous condition with recurrent parent genome of 95.0%-96.5% having minimal linkage drag of about 0.1 to 0.7 Mb were identified. These lines showed yield advantage under drought stress as well as irrigated conditions. MSM-36 showed better performance in the national coordinated trials conducted across India, which indicated that improved lines of Varalu expected to replace Varalu and may have an important role in sustaining rice production. The present study demonstrated the successful marker-assisted pyramiding strategy for introgression of genes/QTLs conferring biotic stress resistance and yield under abiotic stress in rice.     

Development of Core Collection in Pigeonpea [<Emphasis Type="Italic">Cajanus cajan</Emphasis> (L.) Millspaugh] using Geographic and Qualitative Morphological Descriptors

Pigeonpea is an important pulse crop grown by smallholder farmers in the semi-arid tropics. Most of the pigeonpea cultivars grown to date are selections from the landraces, with a narrow genetic base. With the expansion of the crop to newer areas, problems of local importance are to be addressed. Hence, an economically feasible and faster germplasm evaluation mechanism, such as a core collection, is required. This article describes the development of core collection from 12,153 pigeonpea accessions collected from 56 countries and maintained at ICRISAT, Patancheru, India. The germplasm accessions from 56 countries were placed under 14 clusters based primarily on geographic origin. Data on 14 qualitative morphological traits were used for cluster formation by Ward’s method. From each cluster ≈10% accessions were randomly selected to constitute a core collection comprising 1290 accessions. Mean comparisons using Newman–Keuls test, variances’ comparisons by Levene’s test, and comparison of frequency distribution by χ²-test indicated that the core collection was similar to that of the entire collection for various traits and the genetic variability available in the entire collection is preserved in the core collection. The Shannon–Weaver diversity index for different traits was also similar for both entire and core collection. All the important phenotypic associations between different traits available in the entire collection were preserved in the core collection. The core collection constituted in the present study facilitates identification of useful traits economically and expeditiously for use in pigeonpea improvement.     

Effect of Continuous Application of Fertilizers,Farmyard Manure and Lime on Soil Fertility and Productivity of the Maize-Wheat System in an Acid Alfisol

A study on the long-term effect of fertilizers and amendments on crop productivity and changes in soil fertility in maize-wheat cropping system in an acid Alfisol was carried out in randomized block design (RBD) with 11 treatments. Continuous application of chemical fertilizers along with farmyard manure (FYM) or lime significantly influenced the grain and straw/stover yield and the uptake of nutrients by wheat and maize crops significantly. The organic carbon content increased from 7.9 to 12.1 g kg^?1, cation exchange capacity (CEC) from 12.1 to 14.6 cmol (p⁺) kg^?1 and available phosphorus from 21.9 to 75.2 kg ha^?1 through the integrated use of organic and fertilizers for the last 42 years while the status of available nitrogen (N) and potassium (K) declined over the years in all the treatments. Continuous application of urea alone resulted in a drastic decline in soil pH at both depths. Imbalanced use of fertilizers led to a significant reduction in the productivity of both crops and depleted the soil fertility.     

Empirical and optimal stomatal controls on leaf and ecosystem level CO2 and H2O exchange rates

Linkage between the leaf-level stomatal conductance (g_s) response to environmental stimuli and canopy-level mass exchange processes remains an important research problem to be confronted. How various formulations of g_s influence canopy-scale mean scalar concentration and flux profiles of CO₂ and H₂O within the canopy and how to derive ‘effective’ properties of a ‘big-leaf’ that represents the eco-system mass exchange rates starting from leaf-level parameters were explored. Four widely used formulations for leaf-level g_s were combined with a leaf-level photosynthetic demand function, a layer-resolving light attenuation model, and a turbulent closure scheme for scalar fluxes within the canopy air space. The four g_s models were the widely used semi-empirical Ball-Berry approach, and its modification, and two solutions to the stomatal optimization theory for autonomous leaves. One of the two solutions to the optimization theory is based on a linearized CO₂-demand function while the other does not invoke such simplification. The four stomatal control models were then parameterized against the same shoot-scale gas exchange data collected in a Scots pine forest located at the SMEAR II-station in Hyytiälä, Southern Finland. The predicted CO₂ (F_c) and H₂O fluxes (F_e) and mean concentration profiles were compared against multi-level eddy-covariance measurements and mean scalar concentration data within and above the canopy. It was shown that F_c comparisons agreed to within 10% and F_e comparisons to within 25%. The optimality approach derived from a linearized photosynthetic demand function predicted the largest CO₂ uptake and transpiration rates when compared to eddy-covariance measurements and the other three models. Moreover, within each g_s model, the CO₂ fluxes were insensitive to g_s model parameter variability whereas the transpiration rate estimates were notably more affected. Vertical integration of the layer-averaged results as derived from each g_s model was carried out. The sensitivities of the up-scaled bulk canopy conductances were compared against the eddy-covariance derived canopy conductance counterpart. It was shown that canopy level g_s appear more sensitive to vapor-pressure deficit than shoot-level g_s.