Breeding of Zoysia Grass

1. Collection of Genetic Resources and General View of their Characteristics

Abstract

For the last twenty years, germplasm collection of Zoysia species for genetic resources has been carried out all over Japan and Korea, China, Taiwan, Nepal, Thailand, Australia and New Zealand. Presently, 788 germplasms of seven Zoysia species are reserved at Kyushu Tokai University.
Wide genetic variations in terms of morphological characteristics exist among these Zoysia species. Leaf length of Z. japonica can be more than 30 cm, leaf width of Z.japonica can be more than 8 mm, respectively. On the other hand, leaf length of Z. minima can be 1 cm, and leaf width of Z.tenuifolia is less than 1 mm.
Genetic variations are also observed within each species, especially in Z, matrella, which has the widest variations in terms of leaf length, leaf width, stem length, shoot type, internode length, etc. Many characteristics of the ecotypes in the Southwest Islands of Japan have wide variations. Some ecotypes which have characteristics of two species or uncertain species have been found. They seem to be natural interspecilic hybrids. The chromosome number of all collected ecotypes was 2 n=40, and could be crossbred each other.
Among these collections, various interesting characteristics may be useful as genetic resources for breeding. For example, an ecotype from a small island in Japan can be grown under seawater during high tide. This ecotype is considered to be useful as a genetic resource for salt tolerance in saline soils. Some Z. macrostachya produces hull-less seeds which germinate well in low temperatures under dark conditions, while common seeds of Zoysia germinate in high temperatures and light. This ecotype is useful resources for breeding new varieties which establish turf by seeding. Z. minima, collected in New Zealand, has very small leaves, although its stolon is rather big. It seems to be an important genetic resource for special ornamental or turf varieties.