THE GENECOLOGY OF LAWN WEEDS

SUMMARY An examination of variation in Poo. annua L. provided evidence for population differentiation between two bowling greens and their adjacent flower beds. The bowling green populations consisted almost entirely of prostrate individuals, whereas the flower bed populations were more heterogeneous, containing both erect and prostrate growth forms. Family trials indicated that vegetative and floral erectness, and time from sowing to anthesis were under genetic control. Erect families came into flower significantly quicker than prostrate families. Moreover, there were significant differences, both between and within families, for each of the two growth forms in mean number of days from sowing to anthesis. An investigation was conducted using gel electrophoretic techniques to examine the genetic structure of these populations of P. annua , and to estimate the amount of natural out crossing. The esterase enzyme system was found to consist of multiple molecular forms. No apparent banding differences were found which distinguished erect and prostrate growth forms. Heterogeneity of banding patterns was discovered within both growth form groups, suggesting that each of the prostrate and erect growth forms consisted of more than one genotype. Evidence that the observed banding patterns were under genetic control was obtained from the examination of four families derived from selfed heterozygotes, which yielded segregating patterns within families. Both erect and prostrate growth forms, in the area under study, had the chromosome number 2n= 28.