A time‐course study of early establishment stages of parasitic angiosperm Striga asiatica on susceptible sorghum roots

Abstract

A time-course study of the early establishment stages of Striga asiatica was carried out on a susceptible sorghum hybrid, CSH 1, using polyethylene bags and whole-root clearing and staining techniques. Preconditioned Striga seeds were applied to different aged segments of primary root but the results did not differ for these different aged segments. Most of the Strzga seeds (63%) germinated within 24 h of inoculation on the host roots. The attachment of Striga radicles to host root was rapid and it occurred between 36 and 48 h after inoculation. Only 9% of the germinated Striga seeds attached to the host root but 659; of these attachments successfully penetrated through the epidermis and entered the host cortex within 72 h. Penetration through the cortical cells was difficult; only 17% of attachments were able to reach the endodermis. Penetration took from 12 to 43 h after the first appearance of haustorial cells in the cortex; a total of 84 to 120 h after inoculation on the host root. Penetration through the endodermis and establishment on the host stele was relatively easier, as most of the haustoria reaching the endodermis were able to establish on the host stele. But this is a slow proces. taking a minimum of 24 h, and a maximum of 60 h after first contact of haustorial cells with the endodermis. The minimum time taken from inoculation of ungerminated Striga seed on the host root to establishment is about 108 h. The results are discussed in relation to published reports on other parasitic species such as Agalinis purpurea.

Response of Alectra vogelii Benth to Different Crop Root Exudates

“…Furthermore A vogelii seeds contain only small or very limited food reserves such that they only survive for a few days after their germination unless they reach host root and xylem [24] hence maybe the low attachments levels observed in Nyanda, pearl millet, sorghum and maize could be due to the fact the germinated seeds quickly ran out of food reserves before reaching the host root.…”

“…attachment formation, such as failure of the xylem connection [17] and compatible interaction or connection between the parasite and host root and avoidance through root architecture as shown in a previous study where a maize variety [19]. seeds contain only small or very limited food reserves such that they only survive for a few days after their germination h host root and xylem [24] hence maybe the low attachments levels observed in Nyanda, pearl millet, sorghum and maize could be due to the fact the germinated A. vogelii seeds quickly ran out of food reserves before nt counts observed in some of the varieties could also be due to the failure of radicles to respond to chemotropism and also due to host root tissue which may stagger the haustorial cell till mechanical barrier. This is because varieties differ in their morphological characteristics such as wall thickness and therefore screening of host varieties with regard to their resistance to penetration via the various root tissues maybe…”

Striga gesnerioidesParasitising Cowpea: Development of Infection Structures and Mechanisms of Penetration

“…In Striga species, differentiation of the radicle tip into a host attachment organ can be seen as a switch from a limited vegetative phase to an expansive parasitic and reproductive phase. A system of chemical signalling between host and parasite is involved in the formation of this attachment organ (Chang and Lynn, 1986 ;Timko, Florea and Riopel, 1989 ;Ramaiah, Chidley and House, 1991 ;Magnus, Stommen and Zwanenburg, 1992 ;Riopel and Timko, 1992).…”

Combining host plant defence with targeted nutrition: key to durable control of hemiparasitic Striga in cereals in sub‐Saharan Africa?

“…This article is protected by copyright. All rights reserved and establish a parasitic relation with suitable host plants within that time frame leads to death of the seedlings (Berner et al, 1995;Ramaiah et al, 1991;Runo & Kuria, 2018).…”

“…These mechanisms impair Striga germination or attachment to host roots and thereby prevent parasitism. Striga endosperm resources can only support seedling growth for 3–7 d after germination and failure to attach and establish a parasitic relation with suitable host plants within that time frame leads to death of the seedlings (Ramaiah et al ., 1991; Berner et al ., 1995; Runo & Kuria, 2018).…”