Germination ecology, emergence and host detection in Cuscuta campestris

Abstract

Trials were carried out to study the germination and dormancy of Cuscuta campestris Y. (dodder) seeds and factors influencing the success of early parasitisation of sugarbeet. Primary dormancy can be removed by seed scarification. Germination was negligible at 10°C and optimal at 30°C, while it was not influenced by light. Seed burial induced a cycle of induction and breaking of secondary dormancy. Seedling emergence was inversely proportional to the depth of seed burial and only seed buried within 5 cm of the soil surface emerged. Storage of C. campestris seeds in a laboratory for 12 years resulted in the loss of primary dormancy, enabling the germination of all viable seeds. Host infection (i.e. protrusion of parasite haustoria from host tissue) was heavily influenced by host growth stage. Tropism towards a host was due to the perception of light transmitted by green parts of sugarbeet plants. Insertion of a transparent glass sheet between host leaves and parasite seedlings did not modify this response. This phototropism permitted Cuscuta to identify host plants with high chlorophyll content as a function of the lower red/far red ratio of transmitted light.

Temperature effects on Cuscuta campestris Yunk. seed germination

“…The authors concluded that the overwintering period or storage at low temperature had broken dormancy. Benvenuti et al (2005) examined the influence of temperature on C. campestris germination and found that 60% and 80% of the seeds scarified with sulphuric acid germinated at 20ºC and 30ºC, respectively, while the germination of unscarified seeds was significantly lower (20%). Figure 2.…”

“…The growth of weed seedlings could be affected by different factors, such as temperature, light, depth to which seeds are embedded in soil, seed storage conditions, soil bacteria and seed vigour (Haidar et al, 1997;Walters, 1998;Benvenuti et al, 2005;Li and Kremer, 2006). The growth C. campestris seedlings depends on seed vigour, which also determines whether a successful parasitic bond with the host plant will be established (Walters, 1998).…”

“…In C. campestris, secondary dormancy occurs at the end of summer and it prevents germination during the following autumn and winter in order to avoid the season in which potential hosts of the temperate region would be scarce due to low temperatures. Secondary dormancy ends at the end of winter when temperature begins to grow and overall conditions for germination and growth of host plants improve (Benvenuti et al, 2005). Physical dormancy has been reported for seeds of several Cuscuta species: C. campestris (Benvenuti et al, 2005;Hutchison and Ashton, 1980), C. trifolii (Lados, 1999), C. monogyna and C. planiflora (Salimi and Shahraeen, 2000), C. chinensis (Marambe et al, 2002), C. gronovii, C. umbrosa, C. epithymum andC.…”

“…Secondary dormancy ends at the end of winter when temperature begins to grow and overall conditions for germination and growth of host plants improve (Benvenuti et al, 2005). Physical dormancy has been reported for seeds of several Cuscuta species: C. campestris (Benvenuti et al, 2005;Hutchison and Ashton, 1980), C. trifolii (Lados, 1999), C. monogyna and C. planiflora (Salimi and Shahraeen, 2000), C. chinensis (Marambe et al, 2002), C. gronovii, C. umbrosa, C. epithymum andC. epilinum (Costea andTardif, 2006).…”

Field dodder - how to control it?

“…Its seeds retain vitality in soil over 10 years or more. A single plant is able to form up to 15.000 seeds, and their abundance constitutes the main mode of survival of that parasite in the environment (Benvenuti et al, 2005). Its reproduction may also be vegetative through segmentation of its treadlike stem.…”