Effects of Certain Fungicides on Seed Germination and Seedling Establishment of Range Forage Plants

Abstract

of thesis submitted in partial juljillment of the requirements for the degree of Master of Science, Department o j Range and Forestry, Agricultural and Mechanical College of Texas, 1955. Plants of different strains of hairy grama (Bouteloua hirsuta Lag.) were collected in Texas and Mexico and grown under uniform nursery conditions during the summer of 1954 through the summer of 1955. Morphological and cytological studies were made to determine characteristics for the delineation of strains. Three-week and sixweek drought treatments were used to observe possible differences in drought resistance between strains. Strains observed could be classified according to morphological and cytological characteristics into two distinct groups. Group one, consisting of four of the five strains observed (A, B, E and F) was typified by plants with many spreading and decumbent seed culms, fine roots and cauline leaves. Chromosome numbers in this group were n = 12, 14, and cu. 28. Group two, consisting of one strain (C-D), was typified by plants with strictly erect seed culms, rachis terminated by a reduced spikelet, coarse roots, and basal leaves. The chromosome number of plants in this group was n = 10. Ten plants of each strain were transplanted into three-gallon pots in the spring of 1955 for the purpose of testing drought resistance. Four plants of each strain were subjected to a six-week period without additional watering, four were subjetted to a three-week drought period and two were treated as controls. Differences in responses of plants during drought treatments were recorded by observations of temporary and permanent wilting. Readings were made periodically with a Colman soil moisture meter to determine percent soil moisture. Visible characterstics of temporary and permanent wilting were considered more dependable than the soil moisture readings in estimating moisture content of soil. After four weeks of adequate watering, the percent of basal area recovering was recorded for all plants. The method for testing drought resistance used in this study was effective in showing differences between strains of hairy grama. Although plants of strain A were collected in Menard and Kimble Counties, critical drought areas, they appeared less drought resistant than plants in any other strain. Plants in strain B were collected in Brazos and Burleson Counties, the highest rainfall areas in which collections were made. This strain was considered low in drought resistance. Plants in strain C-D were collected in Hayes, Travis and Bexar Counties. This strain exhibited the highest drought resistance of those tested. Plants of strain E, collected in the states of Durango and Chihuahua, Mexico, were variable in their response to the drought treatments. Individual plants proved to be highly drought resistant while others proved to be highly susceptible. Plants in strain F, collected in the Cross Timbers Region of Texas during critical drought conditions exhibited intermediate drought resistance.-Roger Q. Landers Jr., Menard, Texas.