Russian wheat aphid causes greater reduction in phloem transport capacity of barley leaves than bird cherry-oat aphid.

Abstract

The effects of feeding by Russian wheat aphid (RWA), Diuraphis noxia Mordvilko and the Bird cherry-oat aphid (BCA), Rhopalosiphum padi L on the transport capacity of barley Hordeum vulgare L leaves were investigated and compared with a view to relate these effects to the visible symptoms shown by the respective infested plants. RWA is known to cause extensive chlorosis and necrosis on infested plant whereas BCA gives no observable symptoms. Our results using the xenobiotic, phloem mobile fluorophore, 5, 6 carboxyfluorescein diacetate (5,6-CFDA) revealed striking differences in damage to the transport of assimilates through the phloem by these two aphids. The result clearly suggests that short-term feeding by RWA causes a reduction in transport of assimilates and a more severe reduction or perhaps permanent cessation of transport occurs during long-term feeding. In contrast, feeding by BCA does not lead to a markedly decrease in transport during short-term feeding period, however, a reduction in the transport was recorded during long-term feeding activities. These results perhaps suggest that damage to transport capacities of the barley leaves appears to be partly responsible for the observed symptoms in RWA-infested plants and lack of such symptoms during BCA infestations as reduction or cessation in transport of assimilates to growing tissues may lead to such observable symptoms.