CYTOLOGY AND REPRODUCTIVE CHARACTERISTICS IN PENNISETUM SETACEUM

A green ecotype of fountaingrass, Pennisetum setaceum (Forsk.) Chiov., was found to be triploid (3x = 27) with 9 II + 9 I at metaphase I. Meiotic behavior of the bivalents was normal, but the univalents lagged and divided precociously at anaphase I. The univalent halves lagged at anaphase 11 and were distributed at random. Micronuclei were common, and stainable pollen was approximately 40%. The green type produced four progeny with 54 chromosomes. A purple strain of P. setaceum was found to be hexaploid (6x = 54) with varying chromosomal associations. Meiotic behavior was highly irregular and stainable pollen was almost zero. Megasporogenesis was initiated in both types, but the megaspores degenerated and nucellar and integument cells developed into four-nuieleate, aposporous embryo sacs. Following self-pollination, the green type set approximately 10% seed and the purple type set 0.05%0 seed. Purple fountaingrass set as high as 18% seed following the application of pollen from Pennisetum ciliare (L.) Link (4x = 36), exemplifying a rare form of pseudogamy between two species. Improvement of P. setaceum throlugh a standard breeding program appears uinlikely. PENNISETUM SETACEUM (Forsk.) Chiov. is a warm-season perennial bunch grass which originated in East Africa (Bailey, 1947). This species, called fountaingrass, is often referred to in the literature by the synonym P. ruppelii Steud. (Hitchcock, 1950) and is used primarily for ornamental purposes. Two distinct types of fountaingrass are known: a green type with narrow green leaves and light purple inflorescences; and a purple type with broad purple leaves and dark purple inflorescences. Both types are low in fertility and have relatively little cold tolerance. The green type, though generally quite uniform, has a tendency to produce aberrants among its progenies. This investigation was conducted to learn more about the genus Pennisetum, and to determine the feasibility of a breeding program designed to improve cold tolerance, uniformity and fertility in P. setaceum. Avdulov (1931) reported green fountaingrass to be triploid (3x = 27), and Hrishi (1952) stated that the most common chromosomal I Received for publication 23 May 1968. Cooperative investigations at College Station, Texas, of the Crops Research Division, ARS, U. S. Department of Agriculture, and the Department of Soil and Crop Sciences, Texas Agricultural Experiment Station, College Station. Based on a thesis submitted to the Graduate College, Texas A&M University, by the senior author in partial fulfillment of the requirements for the degree of Master of Science, 1966. 2 Present address: Texas Agricultural Experiment Station, Stephenville. associations were 13 II + 1 I. Hrishi (1952) observed progeny from self-pollinated plants which had 26, 27, 28, 36 and 54 chromosomes. From this information he concluded that green P. setaceum reproduced by sexual means. Narayan (1953) later reported metaphase I associations of green P. setaceum which were entirely 9 II + 9 I. Raman, Nair, and Krishnaswami (1954) confirmed Narayan's findings. Narayan (1953) gave an extensive account of embryo sac orientation but did not report on megasporogenesis and embryo sac initiation. He concluded that P. setacemn (green type) was an obligate apomict reproducing bv apospory. It seemed that the discrepancy between Hrishi and Narayan's reports might be clarified by an investigation of megasporogenesis and embryo sac development in fountaingrass. We found no information in the literature on cytology or method of reproduction of purple P. setaceum. Gustafsson's (1946-47) interpretation of the terminology on apomixis will be followed in this paper. MATERIALS AND METHODS-In October, 1963, 15 P. setaceum plants of the green type were obtained from the Floriculture Department, Texas A&M University. These plants were selfpollinated and at least 10 progeny from each parent were grown in the field. One purple type P. setaceum plant was obtained from the same source. Only five seeds were recovered from self-pollinating this plant. Plants of both types and their