Natural Genetic Variation Underlying Tiller Development in Barley (Hordeum vulgare L)

Abstract

In barley (Hordeum vulgare L.), lateral branches called tillers contribute to grain yield and define shoot architecture, but genetic control of tiller number and developmental rate are not well characterized. The primary objectives of this work were to examine relationships between tiller number and other agronomic and morphological traits and identify natural genetic variation associated with tiller number and rate, and related traits. We grew 768 lines from the USDA National Small Grain Collection in the field and collected data over two years for tiller number and rate, and agronomic and morphological traits. Our results confirmed that spike row-type and days to heading are correlated with tiller number, and as much as 28% of tiller number variance was associated with these traits. In addition, negative correlations between tiller number and leaf width and stem diameter were observed, indicating trade-offs between tiller development and other vegetative growth. Thirty-three quantitative trait loci (QTL) were associated with tiller number or rate. Of these, 40% overlapped QTL associated with days to heading and 22% overlapped QTL associated with spike row-type, further supporting that tiller development is associated with these traits. Some QTL associated with tiller number or rate, including the major QTL on chromosome 3H, were not associated with other traits, suggesting that some QTL may be directly related to rate of tiller development or axillary bud number. These results enhance our knowledge of the genetic control of tiller development in barley, which is important for optimizing tiller number and rate for yield improvement.

Identification of novel plant architecture mutants in barley

“…These results suggest that genetic control of tillering at later developmental stages may at least in part be distinct from earlier stages. This idea is consistent with results from a recent genome-wide association study of tillering in a collection of 768 barley lines: tiller number at later time points was associated with more quantitative trait loci (QTLs) compared to early time points (Haaning et al 2020). Mutants M07.5478 and M08.0589 were especially interesting as they started tillering early resulting in higher numbers of fertile tillers.…”

INTERMEDIUM-C mediates the shade-induced bud growth arrest in barley

“…However, in barley, little is known about the genetic mechanisms acting inside tiller buds to cause growth arrest. Although a quantitative trait locus (QTL) study revealed several genes associated with tiller number ( Haaning et al , 2020 ), the fact that some tillering genes do not overlap with identified QTLs point toward the complex involvement of environmental influence. Here, we show that the bHLH transcription factor gene INT-C is involved in the integration of different branching signals mediating a suppressive effect on bud outgrowth ( Fig.…”

“…As the association of tiller formation and yield or fertile tillers is also dependent on the developmental stage and environmental condition, only a modulation of INT-C function might be helpful. As INT-C was not detected among the genes in tiller QTLs ( Haaning et al , 2020 ), an easy association of the presence or absence of the gene with yield or fertile tillers is not possible.…”

“…In particular, breeding of new elite varieties with optimized shoot architecture, such as tiller number, will allow the maintenance of high yield potential in unfavorable environments. The effect of genetic factors on this trait was described recently ( Haaning et al , 2020 ). In many countries, particularly at very high latitudes or on shaded slopes, light is a limiting factor affecting crop growth and yield.…”

Four-Year and Five-Developing-Stage Dynamic QTL Mapping for Tiller Number in the Hybrid Population of Agropyron Gaertn.

“…The TN is controlled by multiple genes ( Haaning et al, 2020 ). At present, several candidate genes associated with TN have been reported in barley ( Bai et al, 2021 ), and several single genes that control TN have been identified in wheat ( Peng et al, 1998 ; Spielmeyer and Richards, 2004 ; Kuraparthy et al, 2007 ; Zhang et al, 2013 ; Wang et al, 2021 ).…”