Effects of arbuscular mycorrhizal fungus Rhizoglomus intraradices on active and passive pools of carbon in long-term soil fertility gradients of maize based cropping system

A potculture study was conducted in soils collected from long-term fertilizer experiment (LTFE) being kept up as far the past 40 years to determine whether arbuscular mycorrhizal fungus (AMF) Rhizoglomus intraradices colonization changes the active and passive pools of carbon in a maize (Zea mays) – finger millet (Eleusine crocana)- cowpea (Vigna sinensis) cropping sequence in the Experimental Farm of the Tamil Nadu Agricultural University, Coimbatore, India. Soil samples were processed, sterilized and maize plants were grown in various fertility gradients in the absence (M-) or presence (M+) of AMF (Rhizoglomus intraradices) inoculation. The data have clearly shown that M+ soils had consistently higher active pools such as water soluble carbon, hot water soluble carbon and biomass carbon (M- 189; M + 305 mg kg^?1), and passive pools such as soil organic carbon (M- 4.17; M + 4.31 mg g^?1) and total glomalin. Among the fertility gradients, 100% NPK + Farm Yard Manure (FYM) with or without mycorrhizal fungal inoculation registered higher values for both active and passive pools of C but the response was more pronounced in the presence AMF inoculation. Overall, the data suggest that mycorrhizal fungal inoculation assists in effective carbon sequestration in an intensive cereal-legume cropping system.Abbreviations: AMF: Arbuscular mycorrhizal fungi; DAS: Days After Sowing; LTFE: Long-Term Fertilizer Experiment; WSC: Water soluble organic carbon; HA: Humic acid; FA: Fulvic acid; HWSC: Hot water soluble carbon     

Isolation and characterization of a 6/85-like Mycoplasma gallisepticum from commercial laying hens

Eighty-three-week-old table egg layers with swollen sinuses were presented with a history of increased mortality. Serology revealed positive titers to Mycoplasma gallisepticum (MG). The birds were part of a flock in which some birds had been vaccinated with 6/85 live MG vaccine at 18 wk of age. Tracheal cultures were obtained from both vaccinated and unvaccinated birds within the flock. The cultures were indistinguishable from 6/85 vaccine by both random amplified polymorphic DNA analysis and DNA sequence analysis. Challenge studies were performed to compare the field isolates with 6/85 vaccine and the R strain of MG. The field isolates produced a greater antibody response by serum plate agglutination than did the 6/85 vaccine. The isolates effectively colonized the trachea without increasing the tracheal mucosal thickness; however, they did not extensively colonize the air sacs or cause airsacculitis in the experimental birds.     

Management of grain discoloration of rice with solvent-free EC formulations of neem and pungam oils

Neem and pungam oil-based emulsifiable concentrate (EC) formulations developed at Tamil Nadu Agricultural University were evaluated for their efficacy to inhibit the mycelial growth of the fungiHelminthosporium oryzae and Pyricularia oryzae causing grain discoloration on rice underin vitro conditions. All three formulations,viz., neem oil 60 EC (acetic acid), neem oil 60 EC (citric acid) and neem oil + pungam oil 60 EC (citric acid), inhibited mycelial growth of the pathogens; they were effective even after 9 months of storage. These formulations effectively controlled the grain discoloration on rice.     

A non-hypersensitive resistance in pepper to the bacterial spot pathogen is associated with two recessive genes

ABSTRACT The pepper genotype, ECW-12346, was developed with bacterial spot resistance derived from Pep13, PI 271322, and ECW123 (Early Calwonder containing Bs1, Bs2, and Bs3 genes). For genetic analysis of this resistance, ECW12346, ECW123, F(1), F(2), and backcrosses were inoculated with a pepper race 6 (P6) strain. Two recessive genes were identified that determined resistance. The genes are designated bs5 and bs6 for the resistance derived from PI 271322 and Pep13, respectively. In greenhouse and field studies, ECW12346 was highly resistant, whereas ECW123 had significant defoliation. In growth-room studies, electrolyte leakage and population dynamics were determined. Following infiltration of both genotypes with 10(8) CFU/ml of a P6 strain, there was no rapid increase in electrolyte leakage within 72 h, whereas a rapid increase in electrolyte leakage occurred within 24 h when a similar concentration of a P3 strain (containing the avrBs2 gene) was infiltrated into the intercellular spaces of the leaf. When 10(5) CFU/ml of a P6 strain was infiltrated into leaves, complete tissue collapse was evident in ECW123 10 days later as determined by visual assessment and electrolyte leakage data, but no confluent necrosis was detected in ECW12346. Internal populations were at least two logarithmic units higher in ECW123 than in ECW12346. Therefore, ECW12346 inhibits population build-up without inducing the typical hypersensitive reaction characterized by an increase in electrolyte leakage.     

Variation in total phenolics and antioxidant capacity among European plum genotypes

Our objective was to determine the amount of variation in total phenolics and antioxidants present in European plum fruits, so that it can be utilized in breeding programs to enhance the health benefits. Total antioxidant capacity and total phenolic content of the fruit, and the fruit skin color were determined in 20 genotypes, comprising of released varieties and advanced selections of European plums. Among the 20 genotypes, the total antioxidant capacity ranged from 105 to 424 mg ascorbic acid equivalents (AAE)/100 g fresh weight (FW) while the total phenolic content was 86–413 mg gallic acid equivalents (GAE)/100 g FW. The two parameters had a strong correlation of r² = 0.96. A direct correlation between skin color intensity and total phenolic content could also be observed. This study demonstrates that there is adequate variation in total phenolic compounds and antioxidants within European plums and hence there is potential for improvement towards enhancing these health-promoting phytochemicals in this fruit.     

Role of polyphenol oxidase and peroxidase in the generation of black tea theaflavins.

It has been reported earlier that when macerated tea leaf is fermented at lower pH, the resultant black tea contains increased levels of theaflavin, an important quality marker in black tea. In an attempt to investigate the biochemistry and chemistry underlying this observation, in vitro oxidation experiments using polyphenol oxidase (PPO) from fresh tea leaves, horseradish peroxidase (POD), and tea catechins, precursors for theaflavins, were carried out. In vitro oxidation experiments using crude tea PPO resulted in higher content of theaflavins at pH 4.5 in comparison with pH 5.5, the normal pH of the macerated tea leaf. When purified PPO was used in the in vitro system, surprisingly a reversal of this trend was observed, with more theaflavins being formed at the higher pH. A combination of pure tea PPO and POD led to an observation similar to that with the crude enzyme preparation, suggesting a possible role for POD in the formation or degradation of theaflavin. POD was observed to oxidize theaflavins in the presence of H(2)O(2), leading to the formation of thearubigin, another black tea pigment. This paper demonstrates that tea PPO, while oxidizing catechins, generates H(2)O(2). The amount of H(2)O(2) produced is greater at pH 5.5, the optimum pH for PPO activity, than at pH 4.5. Hence, an observed increase of theaflavins in black teas fermented at pH 4.5 appears to be due to lower turnover of formed theaflavins into thearubigins.     

Screening recently identified whitefly/spider mite‐resistant wild tomato accessions for resistance to Tuta absoluta

The tomato leaf miner (Tuta absoluta) is a serious pest of tomato (Solanum lycopersicum) in the tropics and subtropics. Previous World Vegetable Center studies identified selected accessions of S. galapagense, S. cheesmaniae and S. pimpinellifolium that were resistant to whitefly (Bemisia tabaci Genn.) and spider mite (Tetranychus urticae Koch). Here, we evaluated these accessions for resistance to T. absoluta based on the number of eggs from choice bioassays, and larval mortality and adults emerged percentages in no‐choice feeding bioassays at WorldVeg Eastern and Southern Africa (WorldVeg) and the International Centre for Insect Physiology and Ecology (icipe). At WorldVeg, S. galapagense VI063177 exhibited high resistance in both choice and no‐choice bioassays. There was strong negative correlation between larval mortality and adults emerged percentages in the no‐choice feeding bioassays. Results from the icipe experiments were consistent with those of the WorldVeg screening, except for S. pimpinellifolium accession VI030462 , which was susceptible at icipe. Tuta absoluta is rapidly spreading and the resistance sources reported here will be valuable in breeding tomato varieties resistant to this insect and others.     

Carbonic anhydrase and Na/K-ATPase activities during the molt cycle of low salinity-reared white shrimp <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>

Changes in hemolymph osmolality, ion concentrations, and enzymatic activities of carbonic anhydrase (CA) in the gills and epidermal tissue, and Na/K-ATPase in the gills during the molt cycle were investigated in the white shrimp Litopenaeus vannamei. Hemolymph osmolality was high in the intermolt and early premolt stages, but started to decrease prior to ecdysis through to postmolt stages A and B. Changes in Na⁺ and Cl⁻ ion concentrations paralleled those in hemolymph osmolality. CA activity levels in the anterior and posterior gills were low at intermolt stage C₀ and premolt stage D₀, and maximum at premolt stage D₃. In the epidermal tissue, activity was relatively high at intermolt stage C₀ and premolt stage D₀, but fluctuated towards premolt stage D₃ and postmolt stage A. On the other hand, Na/K-ATPase activity in the gills decreased between intermolt stage C₀ and premolt stage D₂, but increased at premolt stage D₃ and postmolt stage A. The changes in patterns of CA activity during the molt cycle suggest that CA may be involved in supplying counter-ions for Na⁺ and Cl⁻ uptake during molting. Branchial Na/K-ATPase appears to be involved in producing local osmotic gradients in order to support water influx across the epithelium.