Interactions of concomitant species of nematodes and Fusarium oxysporum f. sp. vasinfectum on cotton

Meloidogyne incognita, Hoplolaintus galeatus, and North Carolina and Georgia populations of Belonolaimus longicaudatus were introduced singly and in various combinations with Fusarium oxysporum f. sp. vasinfectum on wilt-susceptible 'Rowden' cotton. Of all the nematodes, the combination of the N. C. population of B. longicaudatus with Fusarium promoted greatest wilt development. H. galeatus had no effect on wilt. With Fusarium plus M. incognito or B. longicaudatus, high nematode levels promoted greater wilt than low levels. The combination of either population of B. longicaudatus with M. incognita and Fusarium induced greater wilt development than comparable inoculum densities of either nematode alone or where H. galeatus was substituted for either of these nematodes. Nematode reproduction was inversely related to wilt development. Without Fusarium, however, the high inoculum level resulted in greater reproduction of all nematode species on cotton. Combining M. incognita with B. longicaudatus or H. galeatus gave mutually depressive effects on final nematode populations. The interactions of H. gateatus with B. longicaudatus varied with two populations of the latter.

The influence of Trichoderma harzianum on the root-knot Fusarium wilt complex in cotton

Wilt-susceptible cultivar 'Rowden' cotton was inoculated wilh Meloidogyne incognita (N), Trichoderma harzianum (T), and Fusarium oxysporum f. sp. vasinfectum (F) alone and in all combinations in various time sequences. Plants inoculated with F alone or in combination with T did not develop wilt, Simultaneous inoculation of 7-day-old seedlings with all three organisms (NTF) produced earliest wilt. However, plants receiving nematodes at 7 days and Fusarium and Trichoderma at 2 or 4 weeks later (N-T-F, N-TF) developed the greatest wilt between 49-84 days after initial nematode inoculation. During the same period, Fusarium added 4 weeks after initial nematode inoculation (N-F) and Fusarium added 4 weeks after initial simultaneous inoculation of nematode and Trichoderma (NT-F) produced the least wilt. The addition of Fusarium inhibited nematode reproduction. Simultaneous inoculation with nematodes and Trichoderma (NT-) resulted in the greatest root gall development, whereas nematodes alone produced the greatest number of larvae. In comparison with noninoculated controls (CK), treatments involving all three organisms inhibited plant growth, plants inoculated with the nematode alone (N-) or with nematodes and Trichoderma (NT-) simultaneously had greatest root weight. Any treatment involving the nematode resulted in fewer bolls per plant and greater necrosis on roots than the noninoculated checks.

Effects of light intensity and quality effects on reproduction of plant-parasitic nematodes

Growing cotton in a greenhouse with 12-h of supplemental light [8,608 lux (800 ft-c) from combination of mercury and Lucalux lamps] resulted in 2 x to > 3 x greater reproduction of Meloidogyne incognita and Belonolaimus longicaudatus as compared to natural light alone. Rate of increase of Hoplolaimus galeatus was affected little in this experiment. In a second experiment under controlled conditions in a phytotron, light source and intensity had greater influence on the reproduction of Heterodera glycines and Pratylenchus penetrans on soybean than on B. longicaudatus. Fluorescent plus incandescent and metal halide light sources resulted in the greatest nematode reproduction. Lucalux lamps resulted in much lower rates of nematode increase than other light sources. Rates of nematode increase on soybean under the different light sources in the phytotron generally were positively related to plant growth.

Effects of N2-O2 and CO2-O2 tensions on growth of fungi isolated from damaged flue-cured tobacco

Ten fungi, Aspergillus niger, A. flavus, A. ochraceus, A. ruber, A. repens, A. amstelodami, Alternaria tenuis, Penicillium brevi-compactum, Cladosporium herbarum, and Chaetomium dolicotrichum, were isolated from moldy flue-cured tobacco and grown in various mixtures of N(2)-O(2) or CO(2)-O(2). A 1 to 5% concentration of O(2) in an N(2) atmosphere caused the greatest change in growth of the nine species, and a 10 to 20% concentration of O(2) for A. flavus. All species, except A. amstelodami and A. ruber, grew faster in air than in mixtures containing 10% O(2). High O(2) concentrations generally inhibited furrow production in the mycelial mats. In an atmosphere of 5 to 40% O(2) in the N(2) atmosphere, furrows formed in mycelial mats between 5 and 40% O(2) in the species except for A. ruber, A. repens, and A. amstelodami, which produced none in any concentration. As O(2) decreased below 20%, spore production was progressively decreased, colony color faded to white, and cleistothecia formation was suppressed. In CO(2)-O(2) mixtures radial growth of all species increased with each quantitative decrease of CO(2). All species except A. niger grew faster in air than in 10% CO(2). In contrast to N(2)-O(2) mixtures, the fungi formed furrows, sporulation and cleistothecial formation were suppressed, and colony color changed to white in higher O(2) concentrations.

Action of proteolytic enzymes on wheat gluten

Papain and trypsin partially hydrolyzed wheat gluten dispersed in 10% sodium salicylate, and pepsin partially hydrolyzed gluten dispersed in aluminium lactate. Trypsin was considerably less effective than either papain or pepsin. Papain produced non-protein nitrogen most rapidly during early stages of hydrolysis but pepsin produced the largest total after 48 h. The rate of release of terminal amino nitrogen was similar for papain and pepsin, and release was not complete after 48 h. The mean size of polypeptides was larger in papain than in pepsin hydrolysates during early stages of hydrolysis but definitely smaller after 48 h. Only pepsin released appreciable amounts of free amino acid nitrogen. Leucine and phenylalanine made up over 50% of the free amino acids after 48 h but several other amino acids were found in significant quantities.