Genetic and molecular characterization of multiflorous spikelet in oat

Abstract

ABSTRACT. Multiflorous spikelets are found in several grass species of agricultural and economic interest. In oat, this morphological characteristic is associated with the production of naked grains. Although many genetic studies have been performed over the past century, the inheritance of the multiflorous spikelet trait is not fully understood in oat. The objectives of this study were to evaluate environmental effects on the multiflorous spikelet trait, to estimate the number of genes controlling the trait, and to clone and characterize sequences of the AP2 gene in oat. Two genetic populations of recombinant inbreed lines were screened for the multiflorous spikelet trait from different years and sowing dates under field experiments. Normal, multiflorous, and mosaic spikelets were analyzed in the whole panicle for both years and sowing dates. Specific primer pairs for the AP2 gene was utilized to amplify and clone oat sequences. The results demonstrate that under higher temperature and day-length conditions, the variable expressivity of the multiflorous spikelet trait was less pronounced in both populations. Genetic analyses indicated the action of one major gene and two or three modifying genes controlling the expression of the multiflorous spikelet trait in oat, depending on the genetic background. Sequences with similarity to the AP2 gene were isolated from the oat lines UFRGS 017004-2 and URS Taura, and genetic polymorphisms were identified, which are valuable to confirm the action of AP2 on the multiflorous spikelet trait. Our results provide information to assist in the development of future studies of the multiflorous spikelet trait in oat.

Variable expressivity and heritability of multiflorous spikelets in oat panicles

“…These genetic factors must come from the hulled parental lines, once both naked ones share the same cross 'Coker 492/Starter-1//UFRGS 8'. Recently, genetic analyses demonstrated the action of one major gene and three modifying genes acting in multiflorous spikelet formation in the 'U01B/U006' population, while one major gene and only two modifying genes best fit in the 'UTau/U017' population (Zimmer et al, 2017). The major gene was associated with the growth pattern definition (determinate or indeterminate), while the modifying genes would interact with the major gene according to the environmental stimuli.…”

“…In this way, miR172 could be a strong candidate modifying gene, once the expression of this gene is regulated by environmental conditions (Jung et al, 2007;Lee et al, 2010) and its target genes, which are AP2 gene family members, are highly associated with indeterminate spikelets in grasses (Chuck et al, 2008;Lee et al, 2007;Poursarebani et al, 2015). Nucleotide sequences showing similarity to an AP2 gene family member were isolated from 'URS Taura' and 'UFRGS 017004-2' parents, where different genetic polymorphisms and a putative miR172 target site were identified (Zimmer et al, 2017). However, these genetic polymorphisms detected in AP2 candidate sequences were not validated in RILs derived from the cross 'URS Taura' by 'UFRGS 017004-2'.…”

“…Recently, oat nucleotide sequences showing similarity to an AP2 gene family member were isolated from the 'URS Taura' and 'UFRGS 017004-2' lines, which are contrasting for the multiflorous spikelet formation. Important genetic polymorphisms and a putative miR172 target site were identified in these sequences, indicating its putative involvement in multiflorous spikelet formation in oats (Zimmer et al, 2017). The miR172 expression is regulated by environmental stimuli, including temperature and day length (Jung et al, 2007;Lee et al, 2010).…”

“…byzantina (C. Koch) Romero Zarco], which have hulled spikelets with two or three fertile florets per spikelet (Valentine, 1995). To date, indeterminate spikelets/inflorescences have been studied in several grasses, such as barley (Brown and Bregitzer, 2011;Poursarebani et al, 2015), wheat (Poursarebani et al, 2015), rice (Lee et al, 2007), maize (Chuck et al, 1998(Chuck et al, , 2007a(Chuck et al, , 2008 and oat (Zimmer et al, 2017).…”