Maize Iranian mosaic virus (MIMV) and maize rough dwarf virus (MRDV) are two important viruses in maize production regions throughout Iran. These virus are transmitted by small brown plant-hopper, Loadelphax striatellus (Hem., Delphacidae) in a circulative-propagative manner. L. striatellus is a polyphagous pest on rice, maize, wheat, barley and oat. The circulative- propagative plant viruses can affect their vectors directly or indirectly. In this research, we surveyed the effects of different hosts, MIMV and MRDV on development and fecundity of L. striatellus by using fertility-life table parameters. Virus infected plant-hoppers were investigated in two grou inoculated and non- inoculated insect. Specific primers and RT-PCR used for detection of MIMV and MRDV in insect and plants. According to fertility life table results maize, nymphs and adults did not survive for a long time on maize and females did not lay eggs on maize, it seems maize isn’t a suitable host for this plant-hopper. Barley is more suitable host than wheat as the intrinsic rate of increase, the finite capacity and the reproductive rate were determined 39.08±1.02 day -1 , 0.13±0.006 day -1 , 1.14±0.007 day -1 and 221.67±42.2 nymphs, respectively for barely and 36.97±0.58 day -1 , 1.12±0.003 day -1 , 1.13±0.004 day -1 and 100.54±15.45 nymphs, respectively for wheat. MIMV infection increased the growth rate of nymphs whereas their fecundity was decreased. The mean duration of oviposition in inoculated females were dropped to half (13.52 day) of the control. The intrinsic rate of increase, the reproductive rate and the finite capacity were determined 0.11 day -1 , 50.45 nymphs, 1.12 day -1 respectively in inoculated and 0.08 day -1 , 19.53 nymphs, 1.09 day -1 , respectively in non- inoculated plant-hoppers. Transmission efficiency of MIMV was estimated about 47.76%. In MRDV inoculated plant-hoppers, nymphal development time and adult fecundity were decreased. The intrinsic rate of increase, the reproductive rate and the finite capacity were 0.10 day -1 , 30.04 nymphs, 1.1, day -1 , respectively in MRDV inoculated and were 0.11 day -1 , 50.28 nymphs, 1.12 day -1 , respectively in non- inoculated plant-hoppers. Transmission efficiency of MRDV was estimated about 33.33%. MRDV inoculated population had more macropterous adults than control causing to spread virus. These results will be useful to understand virus- vector- host plant relationship and will be beneficial for monitoring and controlling these viral disease. Key words : Reoviridae, Rhabdoviridae, Intrinsic rate of increase, Virus transmission, Wheat, Barley.
