The food habits of the collared peccary (Pecari tajacu) were determined from three locations in south Texas. From September 1976 through August 1978, peccaries' food preferences on the Zachry Ranch in Jim Hogg and Zapata Counties were 74.7% cacti, 15.3% woody plants, 5.1% forbs, 2.3% grasses, 2.3% unknown plants, and 0.3% animal matter. Pricklypear pads comprised the bulk of the diet from October through March, whereas pricklypear fruit and mesquite pods were the most important foods from April through September. During the fall and early winter period, peccaries' food preferences were determined on the Gonzalez Ranch in Starr County and the Yturria Ranch in Kenedy and Willacy Counties. Food preferences on the Gonzalez Ranch were 81.5% cacti, 13.6% forbs, 2.0% woody plants, 0.6% grasses, 2.3% unknown plants, and 0.1% animal matter, whereas food preferences on the Yturria Ranch were 48.1% forbs, 32.5% cacti, 8.3% woody plants, 5.7% grasses, 5.3% unknown plants, and 0.1% animal matter. Pricklypear had a relatively low density on the Yturria Ranch in comparison with higher densities on the Zachry and Gonzalez Ranches. This study indicated that pricklypear was the preferred food of peccaries in south Texas, but in areas of low pricklypear density, forbs are highly utilized.

The potential for using cell-free culture filtrate (CFCF) and toxin (phaseolinone) from Macrophomina phaseolina for rapid and efTective screening procedures for charcoal rot resistance in guayule (Parthenium argentatum) germplasm was assessed. The CFCF and partially purified phaseolinone were incorporated into modified Murashige and Skoog solid medium at the rates of 0-100% (v/v) and 0-1000^g ml"', respectively. The medium pH was adjusted to 5.8 before solidifying with 0.8% agar. Fourweek-old seedlings of 10 guayule genotypes were planted in the medium, incubated and rated for phytotoxic symptoms and tissue damage over a 15-day period. In a greenhouse study, seedling growth, phytotoxicity and damage severity were compared in 12-week-o!d guayule seedlings root-inoculated with M. phaseolina microsderotia. There were significant differences (P = 0.05) in genotypic responses to the fungus, the filtrate and the toxin inoculations. Time until phytotoxic symptoms developed was inversely related to the concentrations of CFCF and the toxin. Phytotoxic symptoms were produced 6 days after exposure to 50% CFCF and 48 h after exposure to 1000/jg ml"' of partially purified phaseolinone. A comparison of photomicrographs of the control and toxintreated root tissues revealed no damage to the control roots and extensive damage to epidermal layers of the treated roots, which was evident 48 h after exposure to lOO^g ml"' level of phaseolinone. Significant correlations were found between tolerance to the fungus and insensitivity to the culture filtrate (r = 0.89, P = 0.05) and the toxin (r = 0.95, P = 0.001) suggesting the possibility of screening for resistance to M. phaseolina using CFCF or phaseolinone. The genotypic reactions to the CFCF were also correlated with reactions to the toxin {r = 0.90, P = 0.05). Guayule breeding lines 'UCIOT and 'P3-r exhibited the greatest tolerance to the pathogen and insensitivity to the CFCF or the toxin whereas 'Cal6', 'Cal7', 'N576', 'N9-5', M1605' and 'N6-5' were very susceptible to the pathogen and sensitive to the CFCF or the toxin. Zusammenfassung Unterscbiedliche Reaktionen von Guayole-Genotypen {Par-themum argentatum Gray) gegenuber dem Kulturflltrat and dem Toxin von Macrophomina pkaseolina (Tassi) GoidanichUntersucht wurde die mogliche Anwendung von zellfreiem Kulturfiltrat (CFCF) und dem Toxin (Phaseolinon) von Macrophomina phaseolina in einem schnellen und zuverlassigen Verfahren bei der Resistenzprtlfung in Guayule {Parthenium argentatum). Das CFCF und das teilgereinigte Phaseolinon wurden dem modifizierten Murashige und Skoog-Agarmedium in den Konzentrationen 0 bis 100% (v/v) bzw. 0 bis 1000 /ig/ml beigemischt. Der pH-Wert des Mediums wurde bei 5,8 eingestellt und anschlieBend mit 0,8% Agar versehen. Vier Wochen alte Samlinge von 10 Guayule-Genotypen wurden in diesen Medien gepflanzt, inkubiert und bonitiert auf phytotoxische Symptome und Gewebezerstorung uber einem Zeitraum von 15 Tagen. Das Samlingswachstum, die Phytotoxizitat sowie die Befallsintensitat wurden in Gewachshausversuc...

Effects on herbaceous plant species composition of two mechanical brush manipulation treatments (rootplowing and front-end stacking) with and without grass seeding were investigated in the Rio Grande Plain of Texas. Clearing of brushy rangeland by either rootplowing or front-end stacking increased native grass and forb diversity. During the first year after treatment, forbs accounted for about 70% of plant species composition based on density, but by the third and fifth year, they decreased to 2950. Plots seeded to native or introduced grasses established good stands, and by the second year, desirable forage had increased. Buffelgrass (Cenchrus ciliaris), an introduced seeded species, was the most aggressive species. Five years after mechanical brush manipulation, this species accounted for a major portion of the plant composition in both seeded and nonseeded treatments.

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