Effects of pre- and post-inoculation photoperiod on the severity of Melampsora medusae leaf rust of Populus species

Disease severity, based on six parameters (time from inoculation to flecking, and eruption of uredinia, uredinial density and the amounts of urediniospoies produced), was assessed on leaf discs cut from four cultivars of Populus spp. raised with either a long (15 h) or a short (10 h) photoperiod. The discs were inoculated with race 4 of Melampsora medusae and subsequently incubated with either a long (15 h) or a short (10 h) photoperiod. While disease severity, based on most parameters, was lower in discs from the continuing long photoperiod (15 h pre- and 15 h post-inoculation) than from the continuing short photoperiod (10 h pre- and 10 h post-inoculation), maximum severity was developed by discs given a combination of a short pre- and a long post-inoculation photoperiod. The relative contribution of the cultivar, the pre- and the post-inoculation photoperiod and their second- and third-order interactions to variation in disease severity depended on the parameter employed to assess severity. The parameters used are elements of disease monocycles and their possible significance in modelling epidemics is discussed.     

Biological, serological and molecular characterization of a cucumber mosaic virus isolate from India

A. virus causing mosaic and leaf deformation of Physalis minima has been identified as an isolate of cucumber mosaic virus (CMV) on the basis of its transmission by aphids in a non-persistent manner, polyhedral particles of 29 nm diameter, molecular weight of coat protein subunits us 24-5 kDa. serological relationship with a CMV isolate and a tripartite single-stranded RNA genome with a subgenomic RNA4- Furthermore. cDNA representing coat protein gene was synthesized and cloned. Complete nucleotide sequences (890 nt) were obtained which showed a coat protein gene open reading frame of 657 residues. THE nucleotide sequences provided the 218 amino ACID sequences of the coat protein. Nucleotide as well as amino acid sequences revealed more than 90% identity with the CMV subgroup I strains.     

RADIOGRAPHIC DIAGNOSIS OF BOVINE HORN CANCER (SQUAMOUS CELL CARCINOMA)

Characteristic radiologic differences were observed between the normal and cancerous horns of five bullocks. In the latter, the horn core was replaced by a homogenous soft tissue mass without demarcating osseous landmarks. The horn appeared osteolytic in nature. It was evident that lysis of core started from the tip and progressed toward the base. Prognosis was favorable when the base was not involved.     

Occurrence of a strain of eggplant mottled crinkle virus in Solanum capsicastrum in India

Leaf crinkle symptoms, stem necrosis and stunting were observed in Solanum capsicastrum plants in India. A virus was isolated from these plants and identified as a strain of eggplant mottled crinkle virus based on host reactions, in vitro properties, icosahedral particle morphology, buoyant density (1.39 g cm³), molecular weight (41 ± 0.5 kDa) of coat protein subunits and serological relationships     

Wild onion (Asphodelus tenuifolius Cav.) interference in lentil and chickpea crops and its management through competitive cropping

The interference of wild onion with various densities of lentil and chickpea and its management through competitive cropping were studied under field conditions from 2001–2002 and 2002–2003 at Jabalpur, India. The observed yield loss and predicted yield loss related to wild onion indicated that wild onion was less competitive with chickpea than with lentil. As a result of intraspecies competition, the dry weight and number of seeds per plant for wild onion were reduced with increasing density. The suppressing effect of different crops on the seed rain of wild onion was in the order of pea > mustard > wheat > chickpea > linseed > lentil > French bean. Wheat, pea, and mustard were the most competitive crops against wild onion. The high shading ability of these crops was thought to contribute to the suppression of wild onion. French bean offered the least suppression while chickpea, linseed, and lentil showed moderate weed suppression.     

Influence of peach (Prunus persica Batsch) phenological stage on the short-term changes in oxidizable and labile pools of soil organic carbon and activities of carbon-cycle enzymes in the North-Western Himalayas

The labile organic carbon(C) and C-related enzymes are sensitive indicators capturing alterations of soil organic matter(SOM),even in a short-time scale.Although the effects of crop husbandry and land use change on these attributes have been well studied,there is no consensus about how plant phenology may impact them.This study aimed to determine the short-term effect of six distinct phenological stages(PS-1:full bloom;PS-2:fruit set;PS-3:pit hardening;PS-4:physiological maturity;PS-5:60 d after physiological maturity;and PS-6:fall) of peach on the changes in soil organic carbon(SOC) fractions of different oxidizability,labile C pools,and C-cycle enzyme activities in soils,for two consecutive years(2015 and 2016) in the North-Western Himalayas(NWH).Peach rhizosphere soils were sampled at the topsoil(0–15 cm) and subsoil(16–30 cm) layers,along with rhizosphere soils from adjacent perennial grasses,which served as a control.Values for most of the assessed parameters,including very labile C,labile C,microbial biomass C,permanganate oxidizable C,dissolved organic C,mineralizable C,amylase activity,and carboxymethyl-cellulase activity,were significantly(P ≤ 0.05) higher at PS-3 than at other phenological stages of peach.Conversely,a sudden decline in these soil variables was recorded at PS-5,followed by a slight buildup at PS-6,particularly in the topsoil of the peach orchard.Short-term changes in organic C fractions of different oxidizability,influenced by peach phenological stage,significantly(P ≤ 0.05) affected C management index,C pool index,and lability index.Both the C management index and lability index showed their highest values at PS-3 and their lowest values at PS-5,clearly indicating short-term accretion and depletion of SOC,in tandem with the peach phenological events.Principal component analysis suggested that a composite of soil indicators,including microbial biomass C,dissolved organic C,amylase,and invertase,could help detect short-term changes in SOC content.It is concluded that peach phenological events had a major impact on the short-term variations of the studied soil variables,which could be attributed to changes in the above-and belowground plant residues,as well as the extent of nutrients and water acquisition.     

Impact of irrigation regimes on regeneration and growth of Prosopis cineraria in arid areas of Indian Thar

An experiment was initiated in 2008 to evaluate the impact of irrigation regimes on germination and growth patterns of seedlings of Prosopis cineraria in the arid areas of Thar, India. Seeds collected from dried pods of P. cineraria were sown in polybags placed in nursery beds. Different irrigation regimes were provided to different beds and data regarding germination and growth were recorded to study natural regeneration. The study revealed that irrigation regimes significantly affected the germination and growth of P. cineraria under nursery conditions. The germination rate declined as the irrigation regime shifted from a daily to a fortnightly basis. Height of the seedlings also declined with a decrease in the intensity of irrigation. Thus, it can be concluded that germination and growth of seedlings of P. cineraria under nursery conditions can be enhanced by providing irrigation at regular intervals.     

Leaf-Litter Decomposition in an Oak-Conifer Forest in Himalaya: The Effects of Climate and Chemical Composition

The decomposition rates of certain dominant litter species inan undisturbed oak-conifer forest in the Kumaun Himalaya wereinvestigated by enclosing pre-weighed, newly senesced leavesin litter bags, placing these bags on the forest floor and determiningthe weight loss by recovering the bags at monthly intervals.Among the species examined, Daphne cannabina decomposed fastestand Cupressus torulosa decomposed most slowly. The former took6 months for complete decomposition, while Cupressus torulosadecomposed to about 72 per cent in 18 months. A linear combinationof rainfall and temperature explained 80 per cent of the variabilityin monthly weight loss. The rate of decomposition was also relatedto the initial chemical composition of the litter. Initially,several constituents showed a significant relation with decomposition;these are nitrogen, calcium, water soluble compounds, totalnonstructural carbohydrates, lignin, acid detergent cell wallcomponents and fibre. Of these, lignin and fibre contents showeda negative relation with weight loss while the others were positivelyrelated. As decomposition progressed, only nitrogen, lignin,ADCW and fibre content remained important. With further lapseof time only two constituents, nitrogen and lignin, remainedimportant. Among these the effect of nitrogen declined withtime while that of lignin increased. A linear combination ofnitrogen and lignin explained 59 per cent variability in theannual weight loss.