Spatiotemporal Separation of Groundnut Rosette Disease Agents

Abstract

Analysis by triple-antibody sandwich enzyme-linked immunosorbent assay of groundnut samples from fields in two seasons from different regions of Malawi showed the absence of groundnut rosette assistor virus (GRAV) from some plants showing groundnut rosette disease symptoms and the presence of GRAV in some symptomless plants. Viruliferous Aphis craccivora collected from fields transmitted either GRAV alone, groundnut rosette virus (GRV) with its satellite RNA (sat RNA), or all three agents together, in different proportions. More plants became infected with all three agents when increasing numbers of potentially viruliferous aphids were used per plant, suggesting a dosage response. Electrical pentration graph studies of aphid stylet activities indicated successful transmission of GRV and its sat RNA during both the "stylet pathway phase" and salivation into sieve elements, whereas GRAV was transmitted only during the latter phase. Aphids transmitted all three agents together only during the salivation phase. Reverse-transcriptase polymerase chain reaction testing of viruliferous aphids and of inoculated plants revealed no correlation between the presence of all three agents in prospective aphid vectors and their simultaneous transmission to groundnut plants. These results show that separation of the groundnut rosette disease agents occurs over time and space.

Genetic control of resistance to rosette virus disease in groundnut (Arachis hypogaea L.)

“…An indirect triple antibody sandwich-enzyme -linked immunosorbent essay method which entails the usage of beet western yellow virus (Luteovirus) antiserum was used for the detection of GRAV antigen in the various samples (Naidu et al, 1999b). Purified polyclonal antiserum (LgG) (AS-0049) raised against purified preparation of GRAV was diluted at recommended dilution in coating buffer, 200 µl was added to each well of a microliter plate.…”

The Effect of Groundnut rosette assistor virus on the Agronomic Performance of Four Groundnut (Arachis hypogaea L.) Genotypes

“…A colony of non‐viruliferous A. craccivora , derived from a single aphid (Naidu et al., 1999b), was maintained on healthy groundnut plants (cv. Malimba) in the glasshouse fitted with a desert cooling system to maintain a daytime temperature of 30°C ± 5°C at the International Crops Research Institute for the Semi‐Arid tropics (ICRISAT) facilities at Chitedze Agricultural Research Station, Malawi.…”

“…Malimba) in the glasshouse fitted with a desert cooling system to maintain a daytime temperature of 30°C ± 5°C at the International Crops Research Institute for the Semi‐Arid tropics (ICRISAT) facilities at Chitedze Agricultural Research Station, Malawi. The plants used for rearing the aphid colony was routinely monitored for freedom from groundnut rosette disease symptoms and tested by a triple‐antibody sandwich enzyme‐linked immunosorbent assay (TAS‐ELISA) for the presence of GRAV (Naidu et al., 1999b) as described below.…”

“…Two months after transplanting, plants were tested individually for the presence of GRAV by TAS‐ELISA (Naidu et al., 1999b). Fully expanded leaves at the same position were collected from individual plants to minimize sample variation between plants.…”

“…Thus, GRAV plays a crucial role in the epidemiology and perpetuation of groundnut rosette disease. However, GRV and its sat RNA do not require GRAV for replication and spatial and temporal separation of the latter from the other two agents can occur under natural conditions in groundnut, depending on the feeding behaviour of the aphid vector (Naidu et al., 1999b). Consequently, a single aphid vector can transmit either GRAV or GRV plus sat RNA separately, even though the individual aphid acquires all three disease agents.…”