Morphological analysis of laxatum barley mutants

Larsson, Håkan

doi:10.1111/j.1601-5223.1985.tb00508.x

“…The recessive laxatum-a (lax-a) mutant exhibits a pleiotropically altered spike architecture characterized by (1) extended rachis internodes conferring a relaxed inflorescence architecture, (2) a broadened base of the lemma awns, (3) thin and exposed grains due to an impaired palea development, as well as (4) a homeotic conversion of the lodicules into two additional stamens, which are smaller and have only two locules instead of four in the regular three stamens (Larsson, 1985;Laurie et al, 1996).…”

mentioning

confidence: 99%

A homolog of Blade-On-Petiole 1 and 2 (BOP1/2) controls internode length and homeotic changes of the barley inflorescence

Jost

¹

,

Taketa

²

,

Mascher

³

et al. 2016

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Inflorescence architecture in small-grain cereals has a direct effect on yield and is an important selection target in breeding for yield improvement. We analyzed the recessive mutation laxatum-a (lax-a) in barley (Hordeum vulgare), which causes pleiotropic changes in spike development, resulting in (1) extended rachis internodes conferring a more relaxed inflorescence, (2) broadened base of the lemma awns, (3) thinner grains that are largely exposed due to reduced marginal growth of the palea and lemma, and (4) and homeotic conversion of lodicules into two stamenoid structures. Map-based cloning enforced by mapping-by-sequencing of the mutant lax-a locus enabled the identification of a homolog of BLADE-ON-PETIOLE1 (BOP1) and BOP2 as the causal gene. Interestingly, the recently identified barley uniculme4 gene also is a BOP1/2 homolog and has been shown to regulate tillering and leaf sheath development. While the Arabidopsis (Arabidopsis thaliana) BOP1 and BOP2 genes act redundantly, the barley genes contribute independent effects in specifying the developmental growth of vegetative and reproductive organs, respectively. Analysis of natural genetic diversity revealed strikingly different haplotype diversity for the two paralogous barley genes, likely affected by the respective genomic environments, since no indication for an active selection process was detected.The inflorescence is the most prominent part of smallgrain cereal plants, producing the carbohydrate-rich grains that are harvested for food, feed, and fiber. However, our understanding of the genetic factors that regulate inflorescence architecture remains limited. What is clear is that the appearance and shape of the inflorescence has been under constant visual selection since early domestication and is still ongoing in modern plant breeding due to the impact of inflorescence architecture on crop yield. For instance, in barley (Hordeum vulgare), strong selection has been exerted on spontaneously occurring alleles of nonbrittle rachis1 (btr1) and btr2 that prevent dehiscence of the rachis at maturity (Pourkheirandish et al., 2015), six-rowed spike1 (vrs1) that determines whether the inflorescence exhibits two or six rows of grain (Komatsuda et al., 2007), and nudum (nud) that controls whether the grain is hulled or hull-less (Taketa et al., 2008). Ultimately, knowing all of the genes that control cereal inflorescence architecture will provide targets for understanding and exploiting natural or induced genetic diversity toward improving both yield potential and end-use characteristics.The barley inflorescence or spike forms an unbranched main rachis carrying triplets of sessile single-floreted

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“…Other mutants with spike branching and extra spikelets, such as compositum1 and poly‐and‐branched‐row spike also increase lateral spikelet development (Larsson, ; Shang et al ., ) that, taken with the results here, suggest a profound link between control of LSM growth and spikelet and floret identity. Dixon et al .…”

Section: Discussionmentioning

confidence: 99%

Interaction between row‐type genes in barley controls meristem determinacy and reveals novel routes to improved grain

Zwirek

¹

,

Waugh

²

,

McKim

³

2018

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Summary Hordeum species develop a central spikelet flanked by two lateral spikelets at each inflorescence node. In ‘two‐rowed’ spikes, the central spikelet alone is fertile and sets grain, while in ‘six‐rowed’ spikes, lateral spikelets can also produce grain. Induced loss‐of‐function alleles of any of five Six‐rowed spike ( VRS ) genes ( VRS 1‐5 ) cause complete to intermediate gains of lateral spikelet fertility. Current six‐row cultivars contain natural defective vrs1 and vrs5 alleles. Little information is known about VRS mechanism(s). We used comparative developmental, expression and genetic analyses on single and double vrs mutants to learn more about how VRS genes control development and assess their agronomic potential. We show that all VRS genes repress fertility at carpel and awn emergence in developing lateral spikelets. VRS 4, VRS 3 and VRS 5 work through VRS 1 to suppress fertility, probably by inducing VRS 1 expression. Pairing vrs3 , vrs4 or vrs5 alleles increased lateral spikelet fertility, despite the presence of a functional VRS 1 allele. The vrs3 allele caused loss of spikelet identity and determinacy, improved grain homogeneity and increased tillering in a vrs4 background, while with vrs5 , decreased tiller number and increased grain weight. Interactions amongst VRS genes control spikelet infertility, determinacy and outgrowth, and novel routes to improving six‐row grain.

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“…A more precise description of induction data will be published elsewhere (LARSSON 1986 b). Studies of the morphology and the genetics of the lax mutants are presented earlier in this volume (LARSSON 1985a and b).…”

Section: Methodsmentioning

confidence: 99%

“…It has also a more diversified morphology (LARSSON 1985a) and heterogeneous allelic background (LARSSON 1985b). This is the third paper in a series dealing with the lax type mutant of barley (LARSSON 1985a andb, 1986a).…”

mentioning

confidence: 99%

“…It has also a more diversified morphology (LARSSON 1985a) and heterogeneous allelic background (LARSSON 1985b). This is the third paper in a series dealing with the lax type mutant of barley (LARSSON 1985a andb, 1986a). Preliminary reports on linkage have been issued before about the genes accordoid basal rachis internodes, abrl (= lax 3, lax 12 and lax 337) and cornpositurn, comla (synonymous to branching, inflorescent rachilla, birla = lax 270) (LARSSON 1981 and1983).…”

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confidence: 99%

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Linkage studies with genetic markers and some laxatum barley mutants

Larsson

¹

2008

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Linkage was studied in 38 lax-spiked (laxaturn) mutants from Bonus (20) and Foma (18) barley. The mutant genes were first localized to chromosome arms by a cytogenetic tester set that indicated linkage to semisterility factors.In preliminary tests, 20 of the lax mutants were found unsuitable owing to sterility, presence of translocations, variable penetrance of indistinguishable morphology, alone or in combination. Of the other 18 mutants, 5 gave no linkage indications, mostly owing to varying penetrance in different tester combinations. 5 other mutants showed association with more than one chromosome arm. 8 mutant genes were localized to chromosome arms and the distances of 4 of them to known markers were estimated by two-and three-point tests: abrl was located to the short arm of chromosome 2; lax-6 and lax-c were 27.3 cM apart in the long arm of chromosome 6; and coml (synonymous to birl) was located to the long arm of chromosome 7, < 1 cM from the previously studied locus lax-a. In chromosome 7, negative interference (y=1.83) was found in connection with err-n.In the 14 lax loci (including lax-a) where linkage was detected, 8 are associated with chromosome 7. As nocompleteallelism test wasdone withthemutantsinvolved. there are.maybe.fewerthan8loci.Theskewness also may be induced by the bias in the cytogenetic tester set applied, where breakpoints in chromosome 7 are represented in 7 translocation lines out of 11.

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Morphological analysis of laxatum barley mutants

Cited by 13 publications

References 20 publications

A homolog of Blade-On-Petiole 1 and 2 (BOP1/2) controls internode length and homeotic changes of the barley inflorescence

A homolog of Blade-On-Petiole 1 and 2 (BOP1/2) controls internode length and homeotic changes of the barley inflorescence

Interaction between row‐type genes in barley controls meristem determinacy and reveals novel routes to improved grain

Linkage studies with genetic markers and some laxatum barley mutants

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