APOMIXIS AND SEXUALITY IN THEMEDA FORSSK. AT DIFFERENT PLOIDY LEVELS (GRAMINEAE) SP. BIRARI* Cytogenetics Laboratory, College of Agriculture, Pune, Maharashtra State, India Received January 1, 1979 /Accepted November 15, 1979 The twenty-chromosome, diploid species Themeda Emery (1957) in a 2n = 40 chromosomal race of anathera (Nees) Hack., T. tremula Nees ex Steud., T. Themeda triandra from India. According to them, the strigosa (Ham) A. Camus, T. hookeri (Griseb.) A. tetraploid cytotype of T. triandra with moderate Camus, T. mooneyi Bor and two forty-chromosome, meiotic irregularities is a facultative apomict. Merewe tetraploid species, T. villosa (Nees) A. Camus and T. (1957) published on tile embryology of T. triandra caudata (Nees) A. Camus with normal meiosis, are from South Africa. Without any mention of chromo- sexual. Two more tetraploids, T. quadrivalvis (L.) O. some number and type of meiosis, he recorded T. Ktze and T. triandra Forssk., one fifty-chromosome triandra to be sexual and apomictic. Woodland (1964) pentaploid, T. longispatha Raiz et Jain, two sixty- undertook studies on the mode of reproduction in chromosome hexaploids, T. dacruzii Birari and T. diploid and tetraploid T. australis from Australia. arundinacea (Roxb.) with moderate degrees of meiot- According to him, diploid T. australis is sexual and ic irregularities, are facultative apomicts. Eighty-, the tetraploid a facultative apomict. Tlfis paper re- ninety- and one-hundred-and-ten-chromosome, octo-, ports on file mode of reproduction in the diploids nona- and 11 -ploids of T. triandra with severe meiotic T. anathera, T. tremula, T. strigosa, T. hookeri, T. irregularities are obligate apomicts. Sexual species mooneyi, the tetraploids T. villosa, T. caudata, T. produce reduced 8-nucleate bipolar Polygonum-type quadrivalvis, T. triandra, the pentaploid T. longispatha, of embryosacs in the ovules. In the facultative apo- the hexaploids T. dacruzii, T. arundinacea and in micts, most of the ovules exhibit the simultaneous octo-, 9- and 11-ploid cytotypes of T. triandra, in development of unreduced, 4-nucleate monopolar relation to chromosome number (ploidy) and chro- Panicum type and reduced, 8-nucleate Polygonum mosomal association in meiosis. type embryosacs. In a few cases the sexual embryo- sacs degenerated and only Panicum type matured. In obligate apomicts there was early degeneration of Material and methods MMC, dyads and, in few instances, mature sacs of the Polygonum type and only four-nucleate Panicum The material included 37 accessions (Tab. 1) collected type embryosacs developed. The ovules in this group from 7 states of India, and belonging to 12 species of of cytotypes produced 1 to 5 embryosacs of the Themeda as identified by the author and subsequent- Panicum type. ly confirmed by the Director, Botanical Survey of India Calcutta, and the Director, Royal Botanic Introduction Gardens, Kew, England. The specimens of all acces- sions were deposited in the herbarium of tile Regional Studies on the mode of reproduction in relation to Botanist, Botanical Survey of India, Western Circle, chromosome number were reported by Brown & Pune. Embryological preparations were made by the * Present address: Head, Dept. of Agricultural Botany, traditional microtome method and by Bradley's mod- Konkan Krishi Vidyapeeth, Dapoli 415712, Maharashtra, ified ovule squash technique (D'Cruz & Reddy, India 1967). Flemnfing's triple stain technique was used for Genetica 54, 133-139 (1980). 0016-6707/80/0542-0133 $1.40. 133 © Dr. W. Junk B.V. Publishers, The Hague. Printed in The Netherlands. Table 1 Species studied and collecting data Species Accession Location Date of Number collection Themeda anathera 1-773 Shivalik, Uttar Pradesh Dec 1969 Themeda tremula 1-731 Foot of Pratapgar, Maharashtra Nov 1968 Themeda strigosa 1-777 Gorakhpur, Uttar pradesh Jan 1970 Themeda hookeri I-775 Raisily Koraput, Orissa Jan 1970 Themeda mooneyi 1-776 Nelpada-Koraput, Orissa Jan 1970 Themeda villosa 1-686 Ranchi, Bihar Jan 1969 1-687 Shillong Assam Jan 1969 1-689 Gauhatti-Assam Jan 1969 1-772 Shivalik, Uttar Pradesh Dec. 1969 Themeda caudata 1-778 Mussory, Uttar Pradesh Dec. 1969 Themeda quadrivalvis 1-641 Pune, Maharashtra Sep. 1968 1-647 Carla Cave, Maharashtra Sep. 1968 1-648 Khopoli, Maharashtra Sep. 1968 1-651 Kamshet, Maharashtra Sep. 1968 1-657 Palghar, Maharashtra Oct. 1968 1-664 MRA Panchgani, Maharashtra Nov. 1968 1-668 Mahabaleswar, Maharashtra Nov. 1968 I-674 Satpura, Maharashtra Nov. 1968 1-690 Gauhatti, Assam Jan. 1969 1-766 Palamau, Bihar Nov. 1969 1-767 Laxmipur, Orissa Jan. 1970 1-768 Rajendranagar,, Hyderabad Jan. 1970 Therneda longispatha 1-779 Dehra Dun, Uttar Pradesh Dec. 1969 Themeda dacruzii 1-774 Mussory hills, Uttar Pradesh Dec. 1969 Themeda arundinacea 1-780 Sastradhara, Uttar Pradesh Dec. 1969 Themeda triandra 1-897 Tamil Nadu, Madras Jan. 1970 1-638 Panhala Fort, Maharashtra Jan. 1970 1-683 Ooty, Tamil Nadu Nov. 1968 I-691 Hazaribag, Bihar Jan. 1969 1-770 Laxmipura, Orissa Jan. 1970 I-771 Raisily, Orissa Jan. 1970 1-637 Purandar Fort, Maharashtra Nov. 1968 1-688 Netherhat, Bihar Jan. 1969 1-640 Panchagani, Maharashtra Apr. 1968 1-665 Mahabaleswar, Maharashtra Nov. 1968 1-673 Pratapgar, Maharashtra Nov. 1968 staining the sectioned material (Johansen, 1940). detailed report on meiotic behaviour in diploid and Ovule squashes were stained in 1% acetocarmine. polyploid species of Themeda will be given else- where. However, to elaborate the observed rela- tions between the mode of reproduction and type Observations of meiosis encountered, the data on chromosome association at metaphase I and the type of re- Meiosis production have been summarized in Table 2. These data reveal that all diploids (2n = 20) and two tetra- Meiosis in the species and cytotypes of Themeda ploids, T. villosa and T. caudata (2n = 40)form bi- varied from essentially normal to highly irregular. A valents only, while the other two tetraploids T. qua- 134 Table 2 Chromosome association at meiotic metaphase I, tetrad formation and type of reproduction in species of Themeda Species Chromosome + Average chromosomal configu- Reproduction number rations per cell at metaphase I 2n and types of tetrad Themeda anathera 20 ! 0 II, normal tetrads sexual Themeda tremula 20 10 II, normal tetrads sexual Themeda strigosa 20 10 II, 0-3 B, abnormal tetrads and sexual triads Themeda hookeri 20 10 11, 0-3 B, normal tetrads sexual Thimeda rnooneyi 20 10 II, 0-3 B, normal tetrads sexual Themeda villosa 40 20 11, normal tetrads sexual Themeda caudata 40 20 II, normal tetrads sexual Themeda quadrivalvis 40 3 I + 13.5 II + 0.69 III+ 2.00 IV, facultative apomictic tetrads with or without micronuclei Themeda triandra 40 2.40 1 + 15.20 II + 1.80 IV + 2 B, facultative apomictic tetrads always with micronuclei 80 0.40 I + 30.40 I1 + 2 IV + 1.80 VI, obligate apomictic tetrads always with micronuclei 90 5.0 I + 26.84 II + 1.50 III + 1.83 IV obligate apomictic + 0.33 V + 1.67 VI + 0.50 VII + 0.17 VIII + 0.33 IX; tetrads always with micronuclei 110 3.13 I+31.8011+ 1.75 111+4.90 obligate apomictic IV + 2.50 VI + 0.38 1X tetrads with micronuclei Themeda longispatha 50 7.60 1 + 12.40 II + 2.04 III + 1.72 facultative apomictic IV + 0.92 V, tetrads with or without micronuclei Themeda dacruzff 60 16.40 II + 2.0 III + 2.12 IV + 2.12 facultative apomictic VI, tetrads with or without micronuclei Themeda arundinacea 60 1.40 I + 25.00 I1 + 1.00 1II facultative apomictic + 1.40 IV, tetrads with or without micronuclei +Averages based on more than 50 PMC examined. drivalis and T. triandra, the pentaploid T. longi- Mode of reproduction spatha and the hexaploids T. dacruzii and T. arun- dinacea form multivalents and univalents. Forma- The ernbryosac formation was normal in T. anathera, tion of higher associations appears the characteristic T. tremula, T. strigosa, T. hookeri, T. mooneyi, T. vil- feature of the 2n = 80, 2n = 90 and 2n = 1 I0 cyto- losa and T. caudata. In each ovule of these species, a types of T. triandra. Thus in the species of Themeda primary subepidermal cell derived from an archespo- chromosome association ranged from normal to rium differentiated into a megaspore mother cell highly irregular, with intermediate behaviour in two (MMC). It underwent first meiotic division and form- out of four 2n = 40 species and in the 2n = 50 and ed a linear tetrad. Three megaspores of file tetrad at 2n = 60 cytotypes. the micropylar end degenerated wl~e the chalazal 135 one developed. An enlarged chalazal megaspore under- were examined. Of these, 22 (17%) had single, well- went three successive mitotic divisions and formed developed Polygonum type sacs with underdeveloped two, four and eight nuclei respectively. The unorien- uni.nucleate aposporous cells, while 53 (35.70%) ted 8-nucleate embryosac oriented its nuclei at the ovules had both Polygonum and Panicum type sacs time of anthesis. The mature 8-nucleate reduced em- developed simultaneously. In 38 of these ovules, Po- bryosac with oriented nuclei was a typical bipolar lygonum and Panicum type sacs occurred in a 1:1 Polygonum type. A day after anthesis, the antipodals proportion, in 15 in a 1:2 proportion. In the third were found to divide into six nuclei and these antipo- group (55 ovules), there were only one to three dais underwent further successive mitotic divisions Panicum type of sacs. In pentaploid T. longispatha, and formed an antipodal complex. of the 100 ovules examined, 21 had a single Polygo- The normal sequence of megasporogenesis and num type embryosac with one or two nucleate apo- gametogenesis as described above was disturbed in sporous cells, while 70 (70%) ovules possessed both most of the ovules in T. quadrivalvis, T. triandra, T. sacs, well developed.