Mineral Nutrition and the Parasite-Host Relationship of Witchweed

Abstract

The influence of mineral nutrition on the parasite-host relationship of witchweed (Striga luteaLour.) and sorghum (Sorghum vulgarePers. ‘Texas Bighead’) was investigated in greenhouse and growth chamber studies. Sorghum was grown in Eustis loamy sand, either infested or not infested with witchweed, and treated with one of three levels of mineral nutrients. Witchweed reduced host-shoot yields by about 70% at the low nutrient levels and by about 45% at the highest nutrient level. Witchweed produced seed at all nutrient levels, whereas the host produced seed at the highest level only. Increased nutrition also increased witchweed yields. Regardless of nutrient level, an early attack by witchweed was more destructive to the host than a late attack. Growth of witchweed in soil also was studied after the parasite was detached from the host or the host shoot was removed. When only the host shoot was removed, (a) witchweed growth was inhibited; (b) feeding of sucrose to witchweed did not restore parasite growth; (c) mineral nutrients were toxic to the parasite; and (d) high relative humidity around witchweed protected it from the nutrient toxicity. High relative humidity enhanced survival of the detached parasite but markedly inhibited growth of witchweed in the intact parasite-host relationship.

Effects of Nitrophoska and Atrazine on relations betweenSorghum bicolorandStriga hermonthica

“…The translocation of minerals, photosynthate, organic compounds and eosin dyes from host to parasite have been reported by Rogers and Nelson (1962) and Okonkwo (1966). Egley (1971), working on the parasite-host relations of witchweed (striga) and sorghum under greenhouse and growth chamber conditions, has also shown that mineral nutrients were toxic to witchweed attached to host roots without a shoot and highly toxic to isolated witchweed.…”

GROWTH AND BIOMASS PARTITIONING OF MAIZE DURING VEGETATIVE GROWTH IN RESPONSE TO STRIGA HERMONTHICA INFECTION AND NITROGEN SUPPLY

“…Doggett (1984;1988) reported that the addition of N fertilizers reduced Striga emergence on fertile soils but increased infestation levels on infertile soils. In contrast, Egley (1971) and Parker (1984) observed that high N levels in the soil enhanced the growth of both the host and parasite. Cechin and Press (1993) found that the response of sorghum (Sorghum bicolor) to infection changed depending on the concentration of N in the rooting medium.…”

Water relations, temperatures, and mineral nutrients in Pedicularis dasyantha (Scrophulariaceae) from Svalbard, Norway

“…The high transpiration rate reported for boreal (Press et al 1988), temperate (Hartel 1956) and tropical (Egley 1971) hemiparasitic Scrophulariaceae were also found in P. dasyantha and P. hirsuta. The diffusion resistance for water vapour during the cuticular transpiration phase for these species is within the range of diffusion resistances in the stomatal phase for mesophytic species (Gates 1980, Stoner andMiller 1975).…”