Genetic stability in interspecific hybridizations of wheat populations determined by meiotic index and pollen viability

Patrícia Frizon,Sandra Patussi Brammer,Amanda Chechi,Maria Imaculada Pontes Moreira Lima,Carolina Cardoso Deuner,Pedro Luiz Scheeren

doi:10.5007/2175-7925.2021.e79666

Patrícia Frizon, Sandra Patussi Brammer + Show 4 more

Open Access

https://doi.org/10.5007/2175-7925.2021.e79666

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Abstract

The objective of this study was to evaluate genetic stability by determining the meiotic index (MI) and pollen viability in F1RC2 segregating populations, obtained by the crosses between wheat commercial cultivars and synthetic wheat, aimed at introgression/genetic resistance. For MI, three ears were collected per genotype, before anthesis, and they were fixed in Carnoy’s solution. The cytological slides were prepared by crushing the anthers and staining with 1% acetocarmine, and the normal tetrads and the ones with micronuclei were observed under a light microscope. For pollen viability, the ears were collected at the stage of mature pollen grain. The methodological procedure was similar to that of the tetrads, evaluating the pollen grains as viable, with little starch, with two pores, different sizes and non-viable. The pollen grain size was measured by the Axion Vision software. All the segregating populations with MI above 90% and high pollen viability (above 85%) reflected a stable meiotic behavior. About the variation in size, the CIGM90.909/BRS 179 cross showed pollen grains with 58.43 μm and CIGM93.298/BRS Guamirim, 47.15 μm. According to the results, wheat segregating populations were considered meiotically stable and suitable for use in wheat breeding programs and for incorporation of new important genes.

Highlights

The hexaploid wheat (Triticum aestivum L.) is one of the most important cereals in the world, and there have been several cytogenetic, molecular and evolutionary studies on the genetic and genomic structure of the species of the group (Aegilops, Amblyopyrum and Triticum) and about the relationships between various wild relatives and between them and domesticated species as well (MIRZAGHADERI; MASON, 2019).Among the species that contributed to the evolution of wheat, the species Aegilops tauschii stands out, being considered a valuable genetic resource for the improvement of cultivated wheat (ARORA et al, 2018), mainly because its genome has important commercial features such as tolerance/resistance to biotic and abiotic stresses
The development of a synthetic hexaploid wheat is a way to obtain potential resistance genes from Ae. tauschii for wheat breeding programs (OGBONNAYA et al, 2013). Such synthetic wheats are obtained from artificial crosses between the tetraploid species Triticum turgidum or T. durum and the wild relative Ae. tauschii, followed by in vitro immature embryo culture and colchicine application, aimed at chromosome duplication and fertility in regenerated seedlings to restore the hexaploid condition (OGBONNAYA et al, 2013)
This is considered ideal, since in cytogenetic studies, meiotic index (MI) is the parameter that allows the inference of genetic stability

Summary

Introduction

Among the species that contributed to the evolution of wheat, the species Aegilops tauschii stands out, being considered a valuable genetic resource for the improvement of cultivated wheat (ARORA et al, 2018), mainly because its genome has important commercial features such as tolerance/resistance to biotic and abiotic stresses. The development of a synthetic hexaploid wheat is a way to obtain potential resistance genes from Ae. tauschii for wheat breeding programs (OGBONNAYA et al, 2013). Such synthetic wheats are obtained from artificial crosses between the tetraploid species Triticum turgidum or T. durum (genome AABB, 2n = 28) and the wild relative Ae. tauschii (genome DD, 2n = 14), followed by in vitro immature embryo culture and colchicine application, aimed at chromosome duplication and fertility in regenerated seedlings to restore the hexaploid condition (OGBONNAYA et al, 2013). It is noteworthy that some of the germplasms derived from synthetic wheat have been used successfully to develop commercial varieties of wheat, such as the highproducing variety Chuanmai 42’ (YANG et al, 2009) and insect resistant varieties “TAM 110” (LAZAR et al, 2004) and “TAM 112” (RUDD et al, 2014)

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