No genetic estimates for turfgrass characteristics in bermudagrass, Cynodon dactylon (L.) Pers., are currently available in the literature. Therefore, the objectives of this investigation were to evaluate genetic variation among bermudagrass clones and their polycross progenies and to estimate heritability values for several turfgrass characteristics. Parental clones and polycross progenies were established in a randomized complete block design with four replications in 1981. The parental clones differed (P < 0.01) for all characteristics evaluated during 1981 and 1982. Polycross families differed (P < 0.05) for 13 of the 18 characters evaluated. Broad‐sense heritability estimates for a single year ranged from 0.83 to 0.99. Narrow‐sense heritability estimates based on the polycross family analyses ranged from 0.06 to 0.94. Heritability estimates from the parent‐offspring covariance analyses ranged from 0.00 to 1.22. For a number of characters, additive genetic variation accounted for a significant portion of the total genetic variation. Data over a 2‐year period were combined for leaf length and leaf width. Broad‐sense heritability estimates were moderately high with values of 0.94 and 0.83 for leaf length and leaf width, respectively. Narrow‐sense heritability values for leaf length and leaf width were 0.83 and 0.62 from the progeny analysis and 0.57 and 0.43 based on parent‐offspring covariance, respectively. For characteristics which had moderate‐to‐high narrow‐sense heritability values, breeding methods which involve no progeny testing should be suitable for genetic gain to be realized.

Three field inoculation experiments, two in Florida and one in New Mexico, were conducted with Azospirillum brasilense Cd. Each of the Florida experiments evaluated two crop species. One species in each of the Florida experiments responded to inoculation with a significant dry matter yield increases of 11 to 24% and nitrogen yield increases of 9 to 39%. No inoculation response was noted in the New Mexico experiment. The responding species were Sorghum bicolor (L.) Moench (sorghum) and the interspecific hybrid between Pennisetum americanum (L.) K. Schum. (pearl millet) and P. purpureum Schumach. (napiergrass). Nonresponding species were pearl millet (Florida) and Sorghum sudanense (Piper) Staph. (New Mexico). Acetylene reduction activity of inoculated plots in Florida was low, showing no increase over the natural uninoculated background rates and, in one case, was negatively correlated with yield. Acetylene reduction activity was not measured in New Mexico. In Florida, A. brasilense populations were found to decline from 5 × 10 3 to 5 × 10 2 bacteria g of soil −1 in about 3 weeks (quadratic regressions). Continued decline to less than 10 2 by week 5 indicated that the inoculated bacteria did not become established in the soil in high numbers. The A. brasilense population declined at about the same rate in the New Mexico experiment. The erractic inoculation responses in these experiments are similar to those observed in earlier work at the University of Florida. The lack of acetylene reduction activity response to inoculation and the rapid population decline of the inoculated bacteria suggest that N 2 fixation is not the major mechanism causing yield responses after inoculation.

The rate of N fixation by leguminous plants depends on both the effectiveness of the Rhizobium strain and the genotype of the host plant. Most of the previous work has involved attempts to improve the bacterial strain. The objective of this study was to determine the variability in ‘Mesilla’ alfalfa (Medicago sativa L.) for plant characteristics considered to be indices of N fixation and to determine the response of these indices to selection based on acetylene reduction rate. Alfalfa seedlings were grown for a 10‐week period in a N‐free sand culture. Before planting, seeds were inoculated with a commercial peat base alfalfa inoculum. Data were obtained on nodulation score, nodule color score, root score, dry weight of the top growth, % N in the top growth, total N in the top growth, and acetylene reduction rate. Considerable variation existed for all traits measured among 278 plants of the cultivar Mesilla. Plants selected for high rates of acetylene reduction were higher in nodulation score, nodule color score, root score, dry weight of top growth and total N in the top growth than the original cultivar. Fifteen plants with high acetylene reduction rates and 15 with low acetylene reduction rates were selected. These plants were intercrossed within groups by hand pollination without emasculation. Progeny of the high selections showed an 82% increase in acetylene reduction, a 57% increase in dry weight of the top growth, and a 60% increase in total nitrogen in the top growth as compared to the original cultivar. These progeny also had a significant increase in nodulation. Nodule score and root score were highly correlated with each other and with dry weight of the top growth. Dry weight of the top growth was more closely correlated with total nitrogen in the top growth than percent nitrogen in the top growth. Dry weight of the top growth and total nitrogen in the top growth were highly correlated with acetylene reduction rates. A selection procedure for nilnitrate conditions was suggested involving 1) a 10‐week growth period, 2) initial selection on the basis of dry weight of the top growth, and 3) acetylene reduction assays of selected plants.