Studies on Sequential Parasitism by Orobanche and Cuscuta on Petunia hybrida

Abstract

Parasitism by Cuscuta and Orobanche on Petunia hybrida resulted in decreased choline kinase activity and phospholipids in the host shoots. The Cuscuta-infected host roots suffered a dedine in phospholipid concentration with no appreciable change in enzyme activity, whereas the roots of the Orobanche-infected plants exhibited a substantial increase in phospholipid concentration despite a marked lowering in enzymic activity. Superimposition of infection by Cuscuta on Orobanche-infected plants resulted in an increase in both enzyme activity and phospholipid in host shoots; the host roots recorded a decline in phospholipid, although enzyme activity was increased. As compared to the ffiaments infecting singly, Cuscuta, in sequential infection, registered an increase in phospholipid concomitant with a fall in enzyme activity, whereas the root parasite revealed a lowered enzyme activity and a slight decrease in phospholipid. It is hypothesized that a physiological response to infection by root parasite was an accumulation of phospholipids at the region under infection, and to that by shoot parasite was an uptake of phospholipids by the parasite from the host; this was effected not by de novo synthesis but rather by mobilization from distal regions. This laboratory has been engaged now for over a decade and a half in studies on the biochemical effects on plants infected by some angiosperm parasites; such studies have generally been made under conditions of infestation by single parasites (8,15). In the present investigation, studies were undertaken on the biochemical alterations consequent on infection by Cuscuta (the shoot parasite) of Petunia hybrida which was already under the active influence of infection by Orobanche (the root parasite). This experiment permitted a comparison of infection of the same host separately, and in combination, with the shoot and root parasite. Some of the studies made with these plants have already appeared; for example, the decreased dry solids, protein, and phosphorus contents in Orobanche-infected plants was counteracted by secondary infection by Cuscuta (11). Singh (13,14), studying starch and nucleic acid metabolism, observed that the influence of the two parasites was not confined to the region immediately infected but was transmitted over the entire host plant, sometimes being more prominent in the distal region. The two parasites, when infecting together, in addition to modifying I

Host Resistance to Parasitic Plants—Current Knowledge and Future Perspectives

“…What is missing here is a systemic approach of studying the response of a single host to two different (root and stem) parasitic plants. The existing scientific literature is not abundant in such reports [ 100 ] and there seems to be a clear differentiation between Orobanchaceae and Cuscuta spp.-affected crop plants. However, the possibility that a single host could be infected by both root and stem parasites simultaneously, and most importantly, that the resistance to one of them would confer resistance to the other, could be of special interest.…”

Convolvulus dorycnium L. (Convolvulaceae) as a new host for Orobanche mutelii F. Schultz (Orobanchaceae)

“…ex E. Vilm. (Mattoo and Mattoo, 1977); also attacks Nicotiana (Hibberd, et. al., 1999); O. aegyptica attacks Helianthus annuus L. (Eizenberg, et.…”