Isozyme Banding Pattern and Estimation of Genetic Diversity among Guinea Grass Germplasm

Isozyme banding pattern was studied in Guinea grass (Panicum maximum Jacq.), a widely cultivated grass having good fodder value. Similarity among 63 accessions collected from diverse sources was worked out using five enzyme systems (SOD, GOT, ACP, Esterase and Peroxidase) following horizontal starch gel electrophoresis. Biochemical markers such as isozymes are useful supplements in identifying the genetic variation present in any crop. A total of 35 clear and unambiguous bands were used for analysis of which 8 bands were monomorphic. Polymorphism exhibited by 27 bands from all five enzyme systems indicate presence of considerable diversity in this species. The dendrogram generated after UPGMA and SAHN cluster analysis using Jaccard genetic distance showed that 63 accessions from diverse geographical locations could be grouped in three main clusters, of which two could further be divided into sub-clusters. Although the clusters comprised members from different locations, most of the accessions from similar geographical locations tended to cluster in same group.     

Resource availability through rainwater harvesting influenced vegetation diversity and herbage yield in hillslope of Aravalli in India

Recent decline in biological diversity has stimulated the research on the effects of resource conservation on biodiversity and vice versa. We examined soil water and nutrients influenced by rainwater harvesting (RWH) in hillslope and its effects on herbage diversity and productivity at up (USP), middle (MSP) and lower position (LSP) in 75 plots, each of 700-m² area laid in < 10%, 10%–20% and > 20% slopes, respectively. The five RWH treatments were Contour trench (CT), Gradonie (G), Box trench (BT), V-ditch (VD) and control. Soil water content (SWC), species number, population, diversity and herbage yield increased (P < 0.05) downward suggesting positive relations between soil resource and diversity/productivity. The highest species number, population, richness and diversity in 10%–20% slope were associated with soil water usage and NO₃-N and NH4-N concentrations. SWC was 5.0%–19.0% greater in RWH areas than in control influencing herbage species, population, growth and yields. The increase in diversity and yields was the highest (P < 0.05) in V-ditch reinforced by soil fertility. The positive effect of diversity on yield increased with resources, and the effect was compositional rather than that of species richness. Conclusively, slope gradient and soil texture influenced herbage regeneration, diversity and productivity, which were positively affected by existing soil fertility and applied RWH and mobilizing soil water and nutrients. The effect of V-ditch was the highest on composition and yield. Thus, RWH enhanced herbaceous vegetation and restoration of degraded forest/rangelands. But long-term effects of diversity in restoring ecosystem productivity could be established through long-term data collections on optimum water/nutrient usage, diversity and productivity.     

Morphological and physiological responses of rice roots and shoots to varying water regimes and soil microbial densities

To understand the responses of rice roots and shoots to non-continuously-flooded soil–water regimes together with varied levels of soil microbial density, studies were conducted evaluating three different water regimes: intermittent flooding (IF) through the vegetative stage (IF-V), IF extended into the reproductive stage (IF-R), and soil maintained with no standing water (NSW); and three levels of soil microbial density: normal, reduced (autoclaved), and enhanced (EMS). At flowering, EMS-treated plants were found to have increased root-length density and greater root oxidizing activity rates under both IF-V and IF-R and more available soil nitrogen (ASN) under IF-V. Earlier senescence of plants grown with EMS was also observed under all water treatments. Water regime was seen to have a major effect on grain yield with a number of causal mechanisms involved. Significant relationships were observed between root oxidizing activity rate (ROA) and ASN, and between ROA and the chlorophyll content of lower leaves. The EMS effects were apparently not caused by microorganisms directly, but rather by differences in ASN facilitated by interaction between water regime and soil microbial activity. The latter would probably vary with different levels of soil organic carbon, but this additional parameter was not investigated. Further study on the role of soil organic matter under similar conditions is warranted for better understanding of these relationships, which have significant effects on rice grain yield.     

Effect of vertical mulch on moisture conservation and yield of sorghum in Vertisols

The intake rate of the local Vertisol is very low (0.08 cm/h). Vertical mulch was used from 1971 to 1976 in order to improve infiltration. Higher moisture contents were recorded near the mulch. The favourable effects of mulch extended to 1.5 m on either side of the mulch row. Vertical mulching exerted a greater influence on crop yields under dry conditions than in normal and above normal seasons. Compared with low yields in control plots (grain: 0.2 q/ha (20 kg/ha); straw: 9.5 q/ha (950 kg/ha)) mulches spaced at 2, 4 and 8 m produced 3.9 q/ha of grain and 19.0 q/ha of straw under the extremely dry conditions of 1972–1973. However, the increase in grain and straw yields under wet conditions in 1973–1974 was only 47.2 and 15.0%, respectively. Averaged over dry and wet years, vertical mulching resulted in 45.1 and 37.9% higher grain and straw yields. The favourable effects of vertical mulching were found to last for 4 years. Considering dry and wet years, a spacing of 4 m was found to be ideal. Placing sorghum stubble as a vertical mulch to the top of the salt zone (30 cm) was found to be as good as placing it to a depth of 90 cm.     

Toxicity of selected chromium compounds in microbial bioassay system

The short term acute toxicity of potassium chromate, potassium dichromate and chromium sulphate has been compared in a simple microbial bioassay. The test parameters were, decrease in viability, genotoxicity and metal uptake. The LC₅₀ values of Cr(III), dichromate Cr(VI) and chromate Cr(VI) for Escherichia coli were 16, 10 and 1.2 μg mL^?1, respectively. Among the test substances potassium chromate was most toxic and showed no bioaccumulation while potassium dichromate was less toxic but resulted in significant bioaccumulation. Chromium sulphate was least toxic. As evident from loss of plasmid, genotoxicity was exhibited only by Cr (VI).     

Immune responses to hemagglutinin-neuraminidase protein of peste des petits ruminants virus expressed in transgenic peanut plants in sheep

Peste des petits ruminants (PPR) is an acute, highly contagious disease of small ruminants caused by a morbillivirus, Peste des petits ruminants virus (PPRV). The disease is prevalent in equatorial Africa, the Middle East, and the Indian subcontinent. A live attenuated vaccine is in use in some of the countries and has been shown to provide protection for at least three years against PPR. However, the live attenuated vaccine is not robust in terms of thermotolerance. As a step towards development of a heat stable subunit vaccine, we have expressed a hemagglutinin-neuraminidase (HN) protein of PPRV in peanut plants (Arachis hypogea) in a biologically active form, possessing neuraminidase activity. Importantly, HN protein expressed in peanut plants retained its immunodominant epitopes in their natural conformation. The immunogenicity of the plant derived HN protein was analyzed in sheep upon oral immunization. Virus neutralizing antibody responses were elicited upon oral immunization of sheep in the absence of any mucosal adjuvant. In addition, anti-PPRV-HN specific cell-mediated immune responses were also detected in mucosally immunized sheep.     

Harnessing mutant donor plants for microspore culture in Indian mustard [Brassica juncea (L.) Czern and Coss]

Haploid mutagenesis offers several advantages over conventional (seed) approach. However, its potential has not been utilised for Brassica juncea, an important oilseed. In this study, mutant donor plants of three Indian B. juncea genotypes, generated by ethyl methanesulfonate (EMS) and ethyl nitrosourea (ENU), were used for microspore culture. The response of mutant donor plants was about 100 times lower than non-mutant controls; a total of 9,411 embryos were produced from the EMS treated donor plants, while microspores isolated from ENU treated donors did not yield any embryos. The lethality of induced mutations demonstrated itself mainly as the induction of abnormal embryos (80%), failure of germination (70%) and failure of plantlet development (70%). Nine doubled haploid (DH) mutant lines and three non-mutant DH lines obtained through this approach were tested for agronomic and biochemical variation over two growing seasons. High variability was observed and stable mutants were recovered for reduced height (125 vs. 168 cm for the control), appressed pod character, altered fatty acid composition higher protein proportion in de-oiled meal (48%) and a lower glucosinolate content in de-oiled meal (59.5 μM/g) relative to controls. The approach demonstrates that despite severe reduction in efficiency of the DH line production, valuable mutants can be recovered from mutated donor plants.     

Production of Eruca-Brassica Hybrids by Embryo Rescue

Allied species of crop Brassicas have potential value as donors of useful nuclear/organelle genomes. Eruca sativa, a member of subtribe Brassicineae, is resistant to white rust and well adapted to drought. Attempts to hybridize it with Brassica campestris by conventional methods were unsuccessful. However, hybrids were obtained by embryo rescue and the hybrid embryos were found to produce numerous secondary embryos in upto 7 to 8 subcultures. Plantlets developed from them exhibited morphological characteristics of both parents. The chromosome number of 2n = 42 showed that they were amphidiploids. The plants were allotctraploids (2n = 42) and showed 21 bivalents at M₁ of meiosis. Hybridization of total DNA of the hybrids with two probes, a B. campestris tandem repeat DNA and 18s ribosomal DNA of wheat showed that it was derived from the genome of both parents. The hybrids are self-fertile and show the same high fertility even in A³ generation. They were selfed or crossed with B. juncea, B. campestris and B. nigra to screen for useful agronomical traits. Six more embryos of E. saliva × B. campestris have been obtained and their growth is being studied. Preliminary small scale field trials indicate that the selfed hybrid is comparable in yield with a high yielding commercial variety of B. juncea.     

First natural co-occurrence of tomato leaf curl New Delhi virus DNA-A and chili leaf curl betasatellite on tomato plants (<Emphasis Type="Italic">Solanum lycopersicum</Emphasis> L.) in India

Tomato leaf curl disease (ToLCD) affected 25% of the tomato crop in Chitrakoot, India and symptomatic leaves were collected for molecular assay. The complete sequences of bipartite begomovirus DNA-A and a betasatellite DNA were amplified. In a sequence analysis, begomovirus DNA-A and betasatellite shared highest sequence identity (91–99%) with Tomato leaf curl New Delhi virus (ToLCNDV) DNA-A and chili leaf curl betasatellite (ChLCB), respectively. The virus was transmitted by whitefly to tomato plants and caused ToLCD symptoms with 70% transmission rate. To our knowledge, this is the first report of the natural occurrence of ToLCNDV and ChLCB in India.     

An unprecedented cluster of Australian bat lyssavirus in Pteropus conspicillatus indicates pre‐flight flying fox pups are at risk of mass infection

In November 2017, two groups of P. conspicillatus pups from separate locations in Far North Queensland presented with neurological signs consistent with Australian bat lyssavirus (ABLV) infection. These pups (n = 11) died over an 11‐day period and were submitted to a government laboratory for testing where ABLV infection was confirmed. Over the next several weeks, additional ABLV cases in flying foxes in Queensland were also detected. Brain tissue from ABLV‐infected flying foxes during this period, as well as archived brain tissue, was selected for next‐generation sequencing. Phylogenetic analysis suggests that the two groups of pups were each infected from single sources. They were likely exposed while in crèche at night as their dams foraged. This study identifies crèche‐age pups at a potentially heightened risk for mass ABLV infection.