Genome characterization of a new strain of peanut chlorotic streak virus causing chlorotic vein banding disease of groundnut (Arachis hypogaea L.) in India

The double-stranded DNA of the chlorotic vein banding isolate of peanut chlorotic streak caulimovirus (PC1SV-CVB), isolated from purified virus, resolved into circular and linear molecules similar to those of other caulimoviruses. A physical map of viral DNA was constructed, which showed the PCLSV-CVB DNA to be circular and composed of approximately 8.2 kbp. A number of restriction sites were found to be shared with a similar caulimovirus, PCLSV. Nevertheless, several differences between physical maps of the 2 viruses suggested that PCLSV-CVB should be considered as a distinct strain of PCLSV. Bam HI-cleaved PCLSV-CVB DNA was cloned into pUC 118 and was infectious when cleaved from the cloning vector and inoculated onto Vigna unguiculata [cowpeas]

Groundnut

Groundnut, a crop rich in nutrients, originated in South America and spread to the rest of the world. Cultivated groundnut contains a fraction of the genetic diversity present in their closely related wild relatives, which is not more than 13 %, due to domestication bottleneck. Closely related ones are placed in section Arachis , which have not been extensively utilized until now due to ploidy differences between the cultivated and wild relatives. In order to overcome Arachis species utilization bottleneck, a large number of tetraploid synthetics were developed at the Legume Cell Biology Unit of Grain Legumes Program, ICRISAT, India. Evaluation of synthetics for some of the constraints showed that these were good sources of multiple disease and pest resistances. Some of the synthetics were utilized by developing ABQTL mapping populations, which were screened for some biotic and abiotic constraints. Phenotyping experiments showed ABQTL progeny lines with traits of interest necessary for the improvement of groundnut

Serological methods for detection of Polymyxa graminis, an obligate root parasite and vector of plant viruses

A purification procedure was developed to separate Polymyxa graminis resting spores from sorghum root materials. The spores were used as immunogen to produce a polyclonal antiserum. In a direct antigen coating enzyme-linked immunosorbent assay (DAC ELISA), the antiserum could detect one sporosorus per well of the ELISA plate. In spiked root samples, the procedure detected one sporosorus per mg of dried sorghum roots. The majority of isolates of P. graminis from Europe, North America, and India reacted strongly with the antiserum. Interestingly, Fl graminis isolates from the state of Rajasthan (northern India), from Pakistan, and an isolate from Senegal (West Africa) reacted weakly with the antiserum. The cross-reactivity of the serum with I! betae isolates from Belgium and Turkey was about 40% of that observed for the homologous isolate. There was no reaction with common fungi infecting roots or with the obligate parasite Olpidium brassicae. However, two isolates of Spongospora subterranea gave an absorbance similar to that observed with the homologous antigen. The DAC ELISA procedure was successfully used to detect various stages in the life cycle of P. graminis and to detect infection that occurred under natural and controlled environments. A simple procedure to conjugate antibodies to fluorescein 5-isothiocyanate (FITC) is described. Resting spores could be detected in root sections by using FITC-labeled antibodies. The potential for application of the two serological techniques for studying the epidemiology of peanut clump disease and for the characterization of Polymyxa isolates from various geographical origins is discussed

Indian peanut clump virus (IPCV) infection on wheat and barley: symptoms, yield loss and transmission through seed

Wheat and barley crops were shown to be susceptible to Indian peanut clump virus (IPCV) under field conditions. In wheat, the Hyderabad isolate of IPCV (IPCV-H) induced symptoms resembling the rosette caused by soil-borne wheat mosaic virus, and these were apparent only three weeks after emergence. Early-infected plants were severely stunted and dark green, with chlorotic streaks on the youngest leaves, which turned necrotic as the plants aged; most of these plants died. Late-infected plants were also stunted and were conspicuous in the field because of their dark green appearance as a result of delayed maturity. The virus was detected by ELISA and nucleic acid hybridization in all plants with symptoms. These plants usually produced fewer tillers than healthy ones. Spikes were malformed, often did not emerge from the flag leaf, and they contained few shrivelled seeds. Grain yield was decreased, on average, by 58%. In barley, IPCV-H caused severe stunting and general leaf chlorosis. As the plants aged, the leaves became necrotic and the few infected plants that reached maturity produced small spikes. IPCV-H antigens were detected by ELISA in every wheat seed from infected plants and the virus was transmitted through wheat seed at a frequency of 0.5-1.3%. Storage at 4 degrees C for more than a year did not affect seed transmission frequency. The virus was detected in leaves and roots of seed-transmitted plants. Seed transmission was not detected in barley. The Durgapura isolate (IPCV-D) was detected in wheat crops (cv. RR-21) at 3 different locations in Rajasthan State, India. Infected plants showed reduced growth without any overt symptoms

Severe stunting of wheat caused by the Indian peanut clump virus (IPCV), possibly vectored by Polymyxa sp

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