Physiology of the parasitic association between maize and witchweed (<i>Striga hermonthica</i>): is ABA involved?

Taylor, Andrew; Martin, John M.; Seel, W. E.

doi:10.1093/jxb/47.8.1057

Cited by 75 publications

(72 citation statements)

References 28 publications

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“…As we found previously (Taylor et al, 1996), host plant height appeared to be a highly sensitive indicator of infection by S. hermonthica even before emergence of the parasites. Figure 1 shows the height of control and infected maize plants throughout the association.…”

Section: Growth and Biomass Accumulationsupporting

confidence: 81%

“…In addition, leaves of infected plants exhibited lower stomatal conductance than uninfected controls. Furthermore, we also found that, as is often the case with droughted plants, leaf abscisic acid (ABA) concentrations were higher in maize plants infected with S. hermonthica than in control plants (Taylor et al, 1996). Similar findings have been made concerning sorghum infected with S. hermonthica (W. E. Seel, M. C. Press & I. Cechin, unpublished ;Frost et al, 1997).…”

Section: supporting

confidence: 80%

“…This not only ensures that xylem sap is diverted to the parasite from the host, but could also deplete the water supply around the host roots to which the Striga is attached. We have studied the effects of parasitism by S. hermonthica on the growth and stomatal conductance of maize (Taylor, Martin & Seel, 1996), and observed that many of the symptoms exhibited by the host are similar to those which occur in drought-stressed plants. For example, in comparison with uninfected maize, Strigainfected host plants were shorter but had greater root growth (especially early in the association), both of which contributed to an increase in the root : shoot ratio.…”

Section: mentioning

confidence: 99%

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Do Striga hermonthica‐induced changes in soil matric potential cause the reduction in stomatal conductance and growth of infected maize plants?

Taylor

Seel

1998

New Phytologist

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Maize (Zea mays L.) plants parasitized by the root hemi-parasitic angiosperm, Striga hermonthica (Del.) Benth., consistently display a range of symptoms similar to those found in droughted plants. The mechanisms by which these changes occur are largely unknown. However, S. hermonthica has unusually high rates of transpiration, and stomata which are relatively insensitive to water deficit. Consequently, it has often been suggested that the parasite might cause a severe depletion of the available water in the host's rooting zone. To determine whether the lower stomatal conductance and retarded growth of infected plants could be a result of parasite-induced water deficit, we have monitored the matric potential of the growth medium, water use, growth and stomatal conductance of infected vs. uninfected maize plants.Host plant height and stomatal conductance of parasitized plants were significantly lower than those of control plants from 31 or 37 d after planting (d.a.p.) respectively. However, there was no indication of an increase in the rate of water depletion in the rooting zone of infected plants until approx. 63 d into the parasitic association. In fact, from 39 until 59 d.a.p. infected plants used less water than uninfected control plants, probably the result of the plants having fewer expanded leaves during part of this period, combined with the lower stomatal conductance exhibited by the infected plants from day 37 onwards. Leaf RWC of infected plants was unchanged in comparison with that of uninfected plants, therefore the change in stomatal conductance was not a response to dehydration of the leaf tissue. Our results indicate that parasitism by S. hermonthica does not cause an increase in water uptake\use in the host until well after most of the symptoms of infection have become fully established. It is highly unlikely, therefore, that the observed effects on the host are primarily due to soil water deficit.

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Section: Growth and Biomass Accumulationsupporting

confidence: 81%

Section: supporting

confidence: 80%

Section: mentioning

confidence: 99%

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Do Striga hermonthica‐induced changes in soil matric potential cause the reduction in stomatal conductance and growth of infected maize plants?

Taylor

Seel

1998

New Phytologist

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“…Although S. hermonthica acts as a sink, the difference in biomass between infected and uninfected plants cannot be accounted for by parasite biomass (Graves et al, 1989). This raises the possibility that S. hermonthica alters host metabolism by other mechanisms, for example, introduction of novel compounds active at low concentrations (Parker & Riches, 1993) or influence on growth regulators in the host (Drennan & El Hiweris, 1979 ;Taylor et al, 1996 ;Frost et al, 1997). If the effects of infection are mediated through changes in host metabolism, these might be of less consequence in a larger host.…”

Section: mentioning

confidence: 99%

Infection time and density influence the response of sorghum to the parasitic angiosperm Striga hermonthica

1999

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Two cultivars of sorghum (CSH-1 and Ochuti) were grown in the presence and absence of the root hemiparasite Striga hermonthica in uniform conditions in the field in Kenya, Africa. S. hermonthica had a marked influence on growth and photosynthesis of ' CSH-1 ' ; however, ' Ochuti ' showed a less severe response to infection and tolerance of the parasite. The variation in genotype response might be partly explained by later attachment of the parasite and a lower level of infection. Laboratory studies were used to determine the importance of both variables in determining host response to infection. Early infection by S. hermonthica had a more negative effect on the host than late infection. The level of parasite biomass supported by the host also influenced host productivity but the relationship was nonlinear. Low degrees of parasite infection had a proportionately much greater effect on host grain weight than at greater parasite loading. Early infection of ' Ochuti ' in laboratory conditions resulted in lower stem dry weight than in uninfected plants but not in smaller total plant biomass or lower rates of photosynthesis.In conclusion, the time of parasite attachment affected host performance and might explain much of the variation in host sensitivity both within and between studies. The level of parasite infection affected host performance to a lesser extent. In addition, late attachment and low levels of infection might have implications for control management strategies.

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“…Striga parasitizes on the host root, subtracting host carbon assimilates (Rogers and Nelson 1962;Okonkwo 1966;Press et al 1987a), water, nutrients (nitrate) and amino-acids (Pageau et al 2003). However, the main part (80-84%) of the yield loss is caused by a pathogenic effect and its attendant decreased levels of cytokinins and giberellic acid (Drennan and El Hiweris 1979), and increased levels of abscisic acid (ABA) in the infected host plant (Drennan and El Hiweris 1979;Taylor et al 1996;Ackroyd and Graves 1997;Frost et al 1997). The latter cause reduced stomatal conductance, one of the reasons for reduced CO 2 -assimilation of infected hosts (Prabhakara Setty and Hosmani 1981;Press and Stewart 1987;Graves et al 1989;Gurney et al 1995;Smith et al 1995;Gurney et al 1999).…”

mentioning

confidence: 99%

CO2-assimilation and chlorophyll fluorescence as indirect selection criteria for host tolerance against Striga

Rodenburg¹,

Bastiaans²,

Schapendonk

et al. 2007

Euphytica

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Striga hermonthica (Del.) Benth. is a parasitic weed on tropical cereals causing serious yield losses in Africa. The use of host crop varieties with improved resistance and tolerance against this parasite is a key component of an integrated control strategy. Breeding for tolerance is however seriously hampered by the absence of reliable and yet practical selection measures. The observation that the photosynthetic rate of tolerant genotypes is less sensitive to Striga infection was used as a starting point to search for suitable selection measures. In a greenhouse pot experiment the effect of Striga infection on the photosynthesis of four sorghum (Sorghum bicolor [L.] Moench) genotypes, differing in Striga tolerance level, was measured at three moments in time (26, 48 and 75 days after sowing). Genotypes were CK60-B, E36-1, Framida and Tiémarifing. Measurements involved CO 2 -assimilation (A) and three chlorophyll fluorescence characteristics (electron transport rate through photosystem II [ETR], photochemical [Pq] and non-photochemical quenching [NPq]). Striga infection negatively affected A, ETR and Pq. Based on A and Pq, genotypes with superior levels of tolerance (Tiémarifing) could be discriminated from genotypes with superior level of resistance (Framida). Both A and Pq showed high heritabilities and consequently clear and predictable differences between genotypes. Using discriminative ability, heritability and cost effectiveness as main criteria, photochemical quenching (Pq) was concluded to possess the highest potential to serve as indirect selection measure for host plant tolerance to Striga. Screening should preferably be conducted at relatively high Striga infestation levels, between Striga emergence and host plant flowering.

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Physiology of the parasitic association between maize and witchweed (Striga hermonthica): is ABA involved?

Cited by 75 publications

References 28 publications

Do Striga hermonthica‐induced changes in soil matric potential cause the reduction in stomatal conductance and growth of infected maize plants?

Do Striga hermonthica‐induced changes in soil matric potential cause the reduction in stomatal conductance and growth of infected maize plants?

Infection time and density influence the response of sorghum to the parasitic angiosperm Striga hermonthica

CO2-assimilation and chlorophyll fluorescence as indirect selection criteria for host tolerance against Striga

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