Theme 2: Forage--Oral Sessions

Description

Perennial warm-season grasses share several agronomic characteristics, such as marked seasonal growth, cold susceptibility and photoperiod sensitivity. Breeding efforts in South America have been focused on attempting to improved cool-season growth, cold tolerance and also adaptation to the alternation of flooding and drought periods. Warm-season grasses also have in common that most of them are polyploid and some have very low fertility. Apomixis is also a common trait among these species. For polyploid species with limited seed yield, which commonly have stolons or rhizomes, F1 hybrids are created and released as cultivars. Acroceras macrum and Hemarthria altissima will be used as examples. For polyploid species without seed fertility issues, such as Setaria sphacelta, recurrent phenotypic selection (RPS) is used to generate improved populations adapted to these transition zones. For polyploid and apomitic species, such as Paspalum spp. and Brachiara spp., several breeding approaches are now available. The generation of F1 apomictic hybrids is currently used. It has been recently observed that the efficiency of this breeding method can be improved if the genetic distance among parents is considered. There is also new information indicating the great potential of using apomixis-linked molecular markers for the early identification of apomictic hybrids. Population-breeding approaches, such as RPS and selection based on combining ability, can also be used to assess the generation of superior apomictic hybrids. Finally, the challenge of breeding perennial warm-season grasses for the subtropics mainly relates to improving adaptation to extreme conditions (cold winters and warm summers and alternation of flooding and drought), developing specific breeding techniques for polyploid or apomictic species.

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Breeding Perennial Warm-Season Grasses for the Subtropical Belt in South America

Perennial warm-season grasses share several agronomic characteristics, such as marked seasonal growth, cold susceptibility and photoperiod sensitivity. Breeding efforts in South America have been focused on attempting to improved cool-season growth, cold tolerance and also adaptation to the alternation of flooding and drought periods. Warm-season grasses also have in common that most of them are polyploid and some have very low fertility. Apomixis is also a common trait among these species. For polyploid species with limited seed yield, which commonly have stolons or rhizomes, F1 hybrids are created and released as cultivars. Acroceras macrum and Hemarthria altissima will be used as examples. For polyploid species without seed fertility issues, such as Setaria sphacelta, recurrent phenotypic selection (RPS) is used to generate improved populations adapted to these transition zones. For polyploid and apomitic species, such as Paspalum spp. and Brachiara spp., several breeding approaches are now available. The generation of F1 apomictic hybrids is currently used. It has been recently observed that the efficiency of this breeding method can be improved if the genetic distance among parents is considered. There is also new information indicating the great potential of using apomixis-linked molecular markers for the early identification of apomictic hybrids. Population-breeding approaches, such as RPS and selection based on combining ability, can also be used to assess the generation of superior apomictic hybrids. Finally, the challenge of breeding perennial warm-season grasses for the subtropics mainly relates to improving adaptation to extreme conditions (cold winters and warm summers and alternation of flooding and drought), developing specific breeding techniques for polyploid or apomictic species.