Genomic behavior of hybrid combinations between elephant grass and pearl millet

Fernando Ferreira Leão,Antonio Vander Pereira,Lisete Chamma Davide,Fernanda de Oliveira Bustamante,José Marcello Salabert de Campos

doi:10.1590/s0100-204x2011000700006

Abstract

The objective of this work was to evaluate the genomic behavior of hybrid combinations between elephant grass (Pennisetum purpureum) and pearl millet (P. glaucum). Tetraploid (AAA'B) and pentaploid (AA'A'BB) chromosome races resulting from the backcross of the hexaploid hybrid to its parents elephant grass (A'A'BB) and pearl millet (AA) were analyzed as to chromosome number and DNA content. Genotypes of elephant grass, millet, and triploid and hexaploid induced hybrids were compared. Pentaploid and tetraploid genomic combinations showed high level of mixoploidy, in discordance with the expected somatic chromosome set. The pentaploid chromosome number ranged from 20 to 34, and the tetraploid chromosome number from 16 to 28. Chromosome number variation was higher in pentaploid genomic combinations than in tetraploid, and mixoploidy was observed among hexaploids. Genomic combinations 4x and 5x are mixoploid, and the variation of chromosome number within chromosomal race 5x is greater than in 4x.

Highlights

The genus Pennisetum is widely used in grass forage production
The objective of this work was to evaluate the genomic behavior of hybrid combinations between elephant grass and pearl millet
All genomic combinations showed variable levels of mixoploidy (Figure 1 and Table 2), and the number of cells observed with the full chromosome complement was reduced, it was more frequent in the genomic combination HCM‐6x‐2

Summary

Introduction

Among the species with an important role in forage grass production, elephant grass (Pennisetum purpureum Schumach; 2n = 4x = 28, A’A’BB) and pearl millet (P. glaucum L.R.Br.; 2n = 2x = 14, AA) are the ones of greatest economic importance within the genus. Hybrid production between these two species (2n = 3x = 21, AA’B) is a common strategy used in elephant grass breeding programs to combine the most favorable millet characteristics (resistance to drought, tolerance to diseases, and seed size) with the hardness, aggressiveness, and high dry matter production of elephant grass (Pereira et al, 2003). Mixoploidy with cells containing between 14 and 42 chromosomes has been reported in these experiments

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Results