A comparison of apomictic reproduction in eastern gamagrass (Tripsacum dactyloides (L.) L.) and maize-Tripsacum hybrids

Abstract

The expression of gene(s) governing apomictic reproduction in Tripsacum provides the best foundation for comparing the effectiveness of apomictic reproduction in a series of maize-Tripsacum hybrids. Several 38-chromosome, apomictic maize-Tripsacum hybrids are available which possess the gene(s) conferring apomictic reproduction from Tripsacum. Without a base line for comparison, studies directed towards discerning the successful transfer or effectiveness of gene expression in a maize background are hampered. The objectives of this study are to compare the reproductive features found in apomictic Tripsacum with those in apomictic maize-Tripsacum hybrids. In addition, this study determined the feasibility of utilizing these maize-Tripsacum hybrid materials to continue an attempt to transfer the genes into a pure maize background. The frequency and occurrence of five unique reproductive features found in apomictic accessions of Tripsacum dactyloides were compared to the reproductive behaviours exhibited in the maize-Tripsacum hybrids. Results indicate the genes controlling apomixis in tetraploid Tripsacum are fully functional in maize-Tripsacum hybrids with diploid and triploid maize constitutions. The ability of the Tripsacum apomictic genes to retain full expression provides evidence to continue their transfer to a diploid or tetraploid maize background.

Apomixis in Crop Improvement

“…The long arm of Tripsacum chromosome Tr16, on which a nucleolus organizing region is located, was shown to be required for apomictic reproduction in maize-Tripsacum hybrids, but apomixis was only observed when the hybrids had at least eight other Tripsacum chromosomes (Kindiger et al 1996 ). Leblanc et al ( 1995b ) identifi ed three restriction fragment length polmorphic (RFLP) markers linked to diplospory in maize-Tripsacum hybrids that were also found to be linked in the maize genetic map supporting the single-locus hypothesis.…”

Apomixis for crop improvement

“…The F1 hybrid (2n = 46) obtained from the crosses of the two species, has been backcrossed repeatedly to maize, and apomictic backcross progenies with 20 maize chromosomes and 2-6 chromosomes of T. dactyloides have been selected. The localization of the apomictic gene ("apo" locus) on the long arm of Tripsacum chromosome 16 (Tr16L), and its translocation to the long arm of maize chromosome 6 (Mz6L) represent important achievements towards the isolation of apomictic gene(s) (Kindiger et al 1996). An association between linkage group "I2' of the Tripsacum molecular map and Tr16 has been established, and some randomly amplified polymorphic DNA markers were cloned to use for the screening of apomixis (Kindiger et al 1996).…”

“…The localization of the apomictic gene ("apo" locus) on the long arm of Tripsacum chromosome 16 (Tr16L), and its translocation to the long arm of maize chromosome 6 (Mz6L) represent important achievements towards the isolation of apomictic gene(s) (Kindiger et al 1996). An association between linkage group "I2' of the Tripsacum molecular map and Tr16 has been established, and some randomly amplified polymorphic DNA markers were cloned to use for the screening of apomixis (Kindiger et al 1996). The apomictic maize x T. dactyloides hybrid derivatives produced after backcrossing with maize showed low male and female fertility, poor seed quality (shrunken seeds) and seed set.…”

“…Modification or avoidance of female meiosis and promoting autonomous embryo development in the ovule are the key steps for apomictic reproduction. Several laboratories are using various molecular strategies for the isolation and transfer of genes for apomixis or its components , Khush et al 1994, Savidan et al 1993, Liu et al 1994, Hanna 1995, Jefferson and Bicknell 1996, Kindiger et al 1996, Vielle Calzada et al 1996, Carman 1997, Grimanelli et al 1998, Grossniklaus et al 1998a, Maheshwari et al 1998. Mapping populations have been developed in Pennisetum squamulatum and in Tripsacum dactyloides • maize hybrids for studying genetics of apomixis (Grimanelli et al 1998, Ozia-Akins et al 1998).…”

Somaclonal Variation and Induced Mutations in Crop Improvement

“…Currently, severallaboratories are engaged in the isolation and transfer of genes for apomixis, for example in Pennisetum, maize and Brachiaria Hanna, 1995a,b;Savidan et al , 1993;Liu et al , 1994;Kindiger et al , 1996). Currently, severallaboratories are engaged in the isolation and transfer of genes for apomixis, for example in Pennisetum, maize and Brachiaria Hanna, 1995a,b;Savidan et al , 1993;Liu et al , 1994;Kindiger et al , 1996).…”