Soil respiration rate and its sensitivity to temperature in pasture systems of dry-tropics

Abstract

Tree clearing is a topical issue the world over. In Queensland, the high rates of clearing in the past were mainly to increase pasture production. The present research evaluates the impact of clearing on some soil biological properties, i.e. total soil respiration, root respiration, microbial respiration, and microbial biomass (C and N), and the response of soil respiration to change in temperature.

In-field and laboratory (polyhouse) experiments were undertaken. For in-field studies, paired cleared and uncleared pasture plots were selected to represent three major tree communities of the region, i.e. Eucalyptus populnea, E. melanophloia, and Acacia harpophylla. The cleared sites were chosen to represent three different time-since-clearing durations (5, 11–13, and 33 years; n=18 for cleared and uncleared plots) to determine the temporal impact of clearing on soil biological properties. Experiments were conducted in the polyhouse to study in detail the response of soil respiration to changes in soil temperature and soil moisture, and to complement in-field studies for estimating root respiration.

The average rate of CO₂ emission was 964 g CO₂/m²/yr, with no significant difference (P<0.05) among cleared and uncleared sites. Microbial respiration and microbial biomass were greater at uncleared compared with those at cleared sites. The Q ₁₀-value of 1.42 (measured for different seasons in a year) for in-field measurements suggested a small response of soil respiration to soil temperature, possibly due to the limited availability of soil moisture and/or organic matter. However, results from the polyhouse experiment suggested greater sensitivity of root respiration to temperature change than for total soil respiration. Since root biomass (herbaceous roots) was greater at the cleared than at uncleared sites, and root respiration increased with an increase in temperature, we speculate that with rising ambient temperature and consequently soil temperature, total soil respiration in cleared pastures will increase at a faster rate than that in uncleared pastures.     

Peptidase inhibitor from Mucuna pruriens seeds inhibits the growth and development of Zeugodacus cucurbitae larvae

Phytoparasitica - Zeugodacus cucurbitae (Coquillett) is an economically significant destructive pest of many vegetable and fruit crops. Peptidase inhibitors are a class of plant proteins that cause...     

Effect of different levels of nitrogen and farmyard manure on yield and quality of spinach (Spinacea oleracea L.)

The effect of different levels of nitrogen N₀(0kg/ha), N₁(30 kg/ha), N₂ (60 kg/ha), and N₃ (90 kg/ha) and farmyard manure F₀ (0 tonnes/ha), F₁ (10 tonnes/ha), and F₂ (20 tonnes/ha) on the yield and nutrient composition of spinach and its uptake was investigated on a sandy loam soil. Yield; phosphorus, iron, manganese, zinc, and copper uptakes; and ascorbic acid content increased with the application of both the inorganic nitrogen fertilizer and the farmyard manure, with a maximum at the N₃F₂ level, i.e. at 90 kg N/ha with 20 tonnes FYM/ha. However, the contents of protein, -carotene, and reducing sugars were maximum at the highest dose of nitrogen without the application of farmyard manure.     

Inheritance of alloplasmic fertility restoration in eggplant (Solanum melongena L.)

Cytoplasmic male sterility (CMS) system has been exploited worldwide in field and vegetable crops. In eggplant, alloplasmic CMS lines were developed through interspecific hybridization between Solanum aethiopicum L.?×?S. melongena L., while the restorer (R) lines were isolated from the reciprocal cross. The knowledge about inheritance of Rf gene is must for its further use in breeding and molecular studies. Therefore, four sets of CMS (D-CMS 291A, D-CMS 99A, D-CMS 5A and D-CMS 72A) and restorer (R 2-1, R 3-4, R 6-2 and R 2596-2) lines were used to develop F₁, F₂ and backcross progenies, to understand the inheritance mechanism. Phenotyping of all the populations and test of goodness of fit revealed involvement of a single dominant gene (Rf) for fertility restoration. The visual scoring of flowers for male sterility and fertility was further validated with the tests on pollen stainability, germination and index. Among others, media containing 0.5% agar?+?300 ppm calcium nitrate?+?5% sucrose?+?50 mg/l boric acid?+?400 mg/l PEG 4000 furnished the best results for in vitro pollen germination. Differences between and within male sterile and restorer lines were observed for pistil and stamen length and girth, pollen stainability and germination. Stable expression of CGMS and restorer lines in all the generation progenies confirmed their utility in future eggplant breeding programs.

     

Inheritance and molecular mapping of restorer‐of‐fertility (Rf) gene in A2 hybrid system in pigeonpea (Cajanus cajan)

Inheritance of fertility restorer gene in pigeonpea was studied using F₂ and BC₁F₁ populations derived from cross AL103A × IC245273. It was found to be controlled by single dominant gene. Out of 228 SSR primer pairs, 33 primer pairs showed parental polymorphism, while four primers were found polymorphic in bulk segregant analysis (BSA). These four primers viz., CcM 1615, CcM 0710, CcM 0765 and CcM 1522 were used for genotyping of F₂ population and were found to be placed at 3.1, 5.1, 28.1 and 45.8 cM, respectively. Two of them, CcM 1615 and CcM 0710, evinced clear and unambiguous bands for fertility restoration in F₂ population. The Rf gene was mapped on linkage group 6 between the SSR markers CcM 1615 and CcM 0710 with the distances of 3.1 and 5.1 cM, respectively. The accuracy of the CcM 1615 was validated in 18 restorers and six maintainer lines. The marker CcM 1615 amplified in majority of male restorer lines with a selection accuracy of 91.66%.     

Grain yield,nitrogen use efficiency and tillage intensity in wheat as affected by precision nutrient management

ABSTRACT

The present studies were conducted to evaluate the effect of different nutrient management practices under two tillage options in wheat. The experiments were laid out in split-plot design with a combination of two varieties (WH 1105 and HD 2967) and two tillage options (Conventional and No tillage) in the main plot and six precision nutrient management practices [absolute control, site-specific nutrient management with Nutrient Expert for wheat (SSNM-NE)(170 kg nitrogen (N)/ha), SSNM NE+GreenSeeker (GS)(153/158 N kg/ha), N₁₂₀ (120 kg N/ha) before irrigation, N₁₂₀ after irrigation and N Rich (180 kg N/ha)] in subplot replicated thrice. The grain yield and quality characters in no tillage (NT) and conventional tillage (CT) were similar but agronomic efficiency was higher in NT. Both the varieties (WH 1105 and HD 2967) gave similar grain yield and quality. Wheat variety WH 1105 recorded significantly higher sodium dodecyl sulfate sedimentation (SDS) and gluten index. The treatment SSNM NE+GS had resulted in 107.1% higher grain yield than no nitrogen control but similar to enriched N plot (180 kg N/ha). The grain protein, SDS and gluten index in need-based nutrient management (SSNM+GS) treatment were found to be similar as recorded in SSNM-NE (170 kgN/ha) and N enriched plot (180 kg N ha^?1). The agronomic efficiency and recovery efficiency in SSNM+GS were also better than SSNM NE.     

Development and Molecular Characterization of Wheat-Aegilops peregrina Introgression Lines with Resistance to Leaf Rust and Stripe Rust

A wild non-progenitor species from wheat (Triticum aestivum L.) tertiary gene pool, Aegilops peregrina (Hack.) Maire & Weiller accession pau3519 (UUSS), was used for introgression of leaf rust (caused by Puccinia triticina) and stripe rust (caused by Puccinia striiformis f. sp. tritici) resistance in bread wheat. The accession was crossed and backcrossed with hexaploid wheat line Chinese Spring Ph^I to develop two homozygous BC₂F₆ wheat-Ae. peregrina introgression lines (ILs), viz., IL pau16058 and IL pau16061, through induced homoeologous recombination. Homozygous lines were screened against six Puccinia triticina and two Puccinia striiformis f. sp. tritici pathotypes at the seedling stage and a mixture of prevalent pathotypes of both species at the adult plant stage. IL pau16061 showed resistance to leaf rust only, whereas IL pau16058 was resistant to both leaf and stripe rust pathotypes throughout plant life. Molecular profiling of these ILs with simple sequence repeat (SSR) markers indicated that alien introgressions were mainly terminal and very few were interstitial. Identification of linked markers with advanced genomic technologies will aid in marker-assisted pyramiding of alien genes in cultivated wheat background.     

Genetic analysis of persistency in HF crossbred cattle at an organized farm of northern India

The present study was undertaken to estimate effect of various genetic and non-genetic factors on persistency of milk production and to identify the most appropriate persistency method that fits best in our environment. In the present study, effects of different non-genetic factors, viz. year, season, days to attain peak yield, and genetic group based on the level of exotic inheritance on persistency of milk yield in crossbred cattle were studied. Data comprised of 686 first lactation daily milk yield records of crossbred cattle that were maintained at GADVASU dairy farm over a period of 25 years from 1991 to 2015 were utilized to calculate persistency coefficients by four methods, viz., Ludwick and Peterson method (P1), Mahadevan method (P2), ratio method (P3), and Prasad et al. method (P4). Overall least squares means for persistency by Ludwick and Peterson method (P1), Mahadevan method (P2), ratio method (P3), and Prasad et al. method (P4) were 0.896?±?0.096, 1.385?±?0.224, 187.207?±?26.398, and 0.621?±?0.098, respectively. Effect of sires was significant (P?<?0.05) on P2 and P4 methods. Effect of genetic group on all four methods was non-significant. Period of calving had significant (P?<?0.01) effect on persistency of milk yield (P2, P3, and P4 methods). Effect of season of calving on persistency of milk yield was found to be significant in all estimates obtained by the four methods. Summer and autumn calvers were most persistent whereas spring and winter calvers were least persistent for (P2, P3, and P4 methods). Persistency of milk yield was significantly (P?<?0.05) affected by days to attain peak yield in P1 and P2 methods. Maximum persistency was obtained in animals attaining peak at 41–57 days of lactation and minimum in <?41 days for Mahadevan method and ratio method. The highest heritability of persistency and minimum value of standard error was estimated as 0.275?±?0.11 for the Mahadevan method followed by the Prasad method (0.197?±?0.10) by half sib correlation method. The maximum coefficient of variation which indicates available variability was estimated as 20.788% for persistency by the Mahadevan method followed by 18.969% for the Prasad method. The highest correlation was also observed between P1 and P3 methods by Spearman’s and Pearson’s correlation for least squares breeding value of the sires. On the basis of heritability, standard error of heritability, and coefficient of variation, it can be concluded that the Mahadevan method followed by the Prasad method suits best to our environment for animals in first lactation as well as they can be utilized for effective selection for higher persistency in crossbred animals of Punjab.     

Differential Responses of Antioxidative Defence System to Long‐Term Field Drought in Wheat (Triticum aestivum L.) Genotypes Differing in Drought Tolerance

Drought is a severe abiotic stress and the major constraint on wheat (Triticum aestivum L.) productivity world wide. Deciphering the mechanisms of drought tolerance is a challenging task because of the complexity of drought responses, environmental factors and their interactions. The objective of this study was to evaluate the ability of the antioxidative defence system in imparting tolerance against drought‐induced oxidative stress and yield loss in two wheat genotypes, when subjected to long‐term field drought. Drought resulted in an increase in H₂O₂ accumulation and lipid peroxidation and decrease in ascorbate level in roots and leaves at different plant developmental stages. Drought‐tolerant genotype having higher antioxidative enzymes activities, and ascorbate level was superior to that of sensitive genotype in maintaining lower H₂O₂ content and lipid peroxidation and higher growth, yield and yield components under water deficit. Various antioxidative enzymes showed positive correlation with ascorbate and negative with H₂O₂ content. In developing grains, antioxidative defence response was nearly similar among both the genotypes under control condition; however, sensitive genotype failed to modulate the activities of antioxidative enzymes according to the ROS rush under field drought. Poor capacity of the antioxidative defence system in vegetative and reproductive tissues of sensitive genotype seems to be responsible, at least partly, for reduced yield potential under water deficit.     

Immunological relationship between strains of Theileria annulata Dschunkowsky and Luhs 1904

The immunological relationship between the Ludhiana and Hissar strains, and between the Uruli-Kanchan, Bangalore and Jaipur strains of Theileria annulata was studied. Calves were immunised against the Ludhiana strain by the infection-treatment method, against the Uruli-Kanchan strain by the infection-treatment method or by untreated low-grade infection and against the Jaipur strain by untreated low-grade infection. After 45 days, groups of immune calves and susceptible controls were challenged with 10-tick equivalent stabilates. The ensuing host responses, body temperature, swelling of the regional lymph node, appearance of schizonts in the regional lymph node and piroplasms in blood and mortality, were studied. All five strains proved very virulent and produced severe disease in susceptible calves. Immunisation with the Ludhiana, Uruli-Kanchan and Jaipur strains conferred absolute protection against severe homologous challenges. Immunisation with the Ludhiana and Uruli-Kanchan strains conferred substantial protection against heterologous challenges with the Hissar strain, and the Bangalore and Jaipur strains, respectively. Immunisation with the Uruli-Kanchan strain gave less protection against heterologous challenge with the Jaipur strain and vice versa as some of the challenged calves showed slight swelling of the regional lymph node, two had fever, all exhibited a low-grade parasitaemia and four developed anaemia.