Histological Studies of Ditylenchus africanus Within Peanut Pods.
Ditylenchus africanus entered the immature pegs and pods of peanut (Arachis hypogaea cv. Sellie) at the peg-connection and subsequently invaded the parenchymatous regions of the hull exocarp and endocarp, and eventually the seed testa. The nematode caused malformations of the cells of infected tissues, cell wall breakage, and cell collapse. The damage appeared to be due to enzymatic activity. In some testae the entire parenchyma region, which aids in protection of the seed, was destroyed. In immature pods, the nematodes moved across the fibrous region of the mesocarp into the hull endocarp. In mature pods, however, the fibrous mesocarp of the hull was lignified and apparently was a barrier to penetration of the inner pod tissues. In late-harvested pods, increased numbers of eggs and anhydrobiotes were found in the hull tissues, and eggs in the seed testa, suggesting the onset of winter survival mechanisms of the nematode.
Reproductive and Damage Potential of Ditylenchus destructor on Peanut.
The reproductive and damage potential of Ditylenchus destructor on peanut, Arachis hypogaea cv. Sellie, was determined in greenhouse tests. Final nematode population densities (Pf) in roots, hulls, and seeds increased (P = 0.01) as a function of increasing initial population (Pi). Final population densities were higher in hulls than in seeds and roots. Final densities in hulls and seeds were positively (P = 0.01) correlated. Fresh root and hull weight and number of pods and seeds per plant were not affected by D. destructor. Second generation germination and pod and seed disease severity increased (P = 0.01), whereas fresh seed weight decreased (P = 0.01) as a function of increasing Pi, and Pf in seeds and Pf in hulls. At Pi 250 and higher, 10-25% of seeds germinated into second generation seedlings before harvest. At Pi 250 and higher, fresh weight of harvested seed was suppressed 20-50%. At Pi 50 or Pf greater than 20 per seed, pod disease severity was 3-7 (on a scale of 1 to 10) and 15-80% of seeds were blemished or unsound.
Anhydrobiosis in nematodes: Evaporative water loss and survival
1Nematodes, Aphelenchus avenae, can be induced to become anhydrobiotic by drying in aggregates (pellets) (>90 mg wet weight) at 97% relative humidity (RH). When the rate of weight loss exceeds 3% hr−1 survival is low. 
2The number of animals in a pellet that survive exposure to dry air increases with time at 97% RH. 
3The time required for recovery is shortened by rehydration at high humidities before the animals are placed in water and advances with the length of time they are in dry air. 
4The proportion of animals recovering in water that will survive rapid dehydration decreases with the time they are in water. 
5A hypothetical scheme for the events of the induction of anhydrobiosis and recovery is presented.