RICE AND WEED HOSTS OF RICE TUNGRO-ASSOCIATED VIRUSES AND LEAFHOPPER VECTORS

Transmission of rice tungro bacilliform virus (RTBV) and rice tungro spherical virus (RTSV) to rice and weeds by Nephotettix virescens, N. nigropictus, N. malayanus, and Recilia dorsalis was compared. N. virescens was the most efficient vector of both viruses to rice and retained them for 4 days after an acquisition access period on infected rice. N. nigropictus was less efficient but retained both viruses for 5 days. N. malayanus and R. dorsalis were the least efficient and retained both viruses for only 1 day. Young seedlings or rhizomes of Eleusine indica, Echinochloa crusgalli, E. glabrescens, E. colona, Leptochloa chinensis, Leersia hexandra, Panicum repens, and Cyperus rotundus were infected with RTBV and RTSV, either together or separately, when exposed to the four leafhopper species that had fed on doubly infected rice plants. N. nigropictus transmitted both viruses from doubly infected E. crusgalli, P. repens, or C. rotundus plants to rice seedlings, whereas other leafhopper species failed to transmit the viruses from these infected weed plants to rice seedlings. On rice, N. virescens fed mainly from the phloem and showed high adult longevity, nymph survival, and population growth, indicating a high level of its biological relationship. N. virescens fed from the xylem on all the weed hosts, showing a low level of its biological relationship with the weeds. N. nigropictus showed its relationship with E. crusgalli, E. glabrescens, E. colona, L. hexandra, and C. rotundus. N. malayanus showed its relationship only with L. hexandra, and R. dorsalis, with rice. These results indicate that N. nigropictus has a potential for dispersing RTBV and RTSV in weeds in idle fields.