Abstract
Cytomorphological studies were carried out on some Cynodon species and their hybrids. The number of whorls in the inflorescences of the interspecific hybrids was found to be intermediate between those of the parents. The seedset of the hybrids was generally poor, ranging from 0.04% in the hybrid between C. coursii (A. Camus) Harlan and de Wet var. africanus and C. robustus Clayton and Harlan, to 5.99% in the hybrid, C. dactylon (L.) Pers. var. dactylon × C. coursii var. coursii. Only one of the triploid hybrids was sterile; all the tetraploid and diploid hybrids, except C. robustus × C. aethiopicus Clayton and Harlan and C. dactylon var. laxus × C. coursii var. africanus, were fertile. Some hybrids such as IB-8, C. plectostachyus (K. Schum.) Pilger × C. coursii var. coursii, and C. dactylon var. laxus × C. coursii var. alricanus clearly exhibited hybrid vigour for leafiness and leaf size. Chromosome numbers and meiotic behaviour were not correlated with the low fertility. All the Cynodon materials studied had chromosome numbers in multiples of 9. Based on this and reports in the literature, the base chromosome number (genome), x = 9 is well established for most Cynodon species and hybrids; the existence of a second genome, x = 10, remains questionable.
