Genomic variation within the maize stiff-stalk heterotic germplasm pool

The stiff-stalk heterotic group in Maize (Zea mays L.) is an important source of inbreds used in U.S. commercial hybrid production. Founder inbreds B14, B37, B73, and, to a lesser extent, B84, are found in the pedigrees of a majority of commercial seed parent inbred lines. We created high-quality genome assemblies of B84 and four expired Plant Variety Protection (ex-PVP) lines LH145 representing B14, NKH8431 of mixed descent, PHB47 representing B37, and PHJ40, which is a Pioneer Hi-Bred International (PHI) early stiff-stalk type. Sequence was generated using long-read sequencing achieving highly contiguous assemblies of 2.13–2.18 Gbp with N50 scaffold lengths >200 Mbp. Inbred-specific gene annotations were generated using a core five-tissue gene expression atlas, whereas transposable element (TE) annotation was conducted using de novo and homology-directed methodologies. Compared with the reference inbred B73, synteny analyses revealed extensive collinearity across the five stiff-stalk genomes, although unique components of the maize pangenome were detected. Comparison of this set of stiff-stalk inbreds with the original Iowa Stiff Stalk Synthetic breeding population revealed that these inbreds represent only a proportion of variation in the original stiff-stalk pool and there are highly conserved haplotypes in released public and ex-Plant Variety Protection inbreds. Despite the reduction in variation from the original stiff-stalk population, substantial genetic and genomic variation was identified supporting the potential for continued breeding success in this pool. The assemblies described here represent stiff-stalk inbreds that have historical and commercial relevance and provide further insight into the emerging maize pangenome. © 2021 The Authors. The Plant Genome published by Wiley Periodicals LLC on behalf of Crop Science Society of AmericaOpen access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Somaclonal variation in micropropagated Heliconia bihai cv. Lobster Claw I plantlets (Heliconiaceae) Variação somaclonal em mudas micropropagadas de Helicônia, Heliconia Bihai cv. Lobster Claw I (Heliconiaceae)

The occurrence of somaclonal variation is described in various cultures of agronomic interest. Such variation can be of benefit in the development of new flower varieties. In this study, the occurrence of somaclonal variation in micropropagated changes of Heliconia bihai cv. Lobster Claw I was investigated. Stem apexes were introduced in MS culture media with the addition of 2.5 mg L-1 of benzylaminopure (BAP) and 500 mg L-1 of sodium cefotaxime. After selecting the apex stem, it was sub-cultivated in MS media and supplemented with 4.0 mg L-1 of BAP to induce side buds. To conduct the trial, 2,000 plants were selected and compared with plants originated from rhizomes. To calculate the percentage of the variants, the plant stature, the form and color of leaves and pseudostem were evaluated. The plants with buds presenting the same type of variation were considered as variants. The occurrence of three types of somaclonal variants was observed: Variation of the Chlorophyll in the Leaf, Low Stature Variant and Pseudostem and Petiole Color Variant, the latter with ornamental potential. The somaclonal variation rate for Heliconia bihai cv Lobster Claw I, under the proposed conditions, was 61.40%.<br>A ocorrência de variação somaclonal é descrita em diversas culturas de interesse agronômico. A floricultura pode beneficiar-se dessa variabilidade, com a obtenção de novas variedades. Nesse trabalho, estudou-se a ocorrência de variação somaclonal em mudas micropropagadas de Heliconia bihai cv. Lobster Claw I. Ápices caulinares foram introduzidos em meio de cultivo MS com adição de 2,5 mg L-1 de benzilaminopurina (BAP) e 500 mg L-1 de cefotaxima sódica. Após a seleção do ápice caulinar, o explante foi subcultivado em meio MS suplementado com 4,0 mg L-1 de BAP para indução de brotações. Foram selecionadas, ao acaso, 2.000 mudas e comparadas com mudas originadas de rizomas, para compor o ensaio. No cálculo da porcentagem dos variantes avaliaram-se as características: estatura da planta, a forma e coloração das folhas e pseudocaule. Consideraram-se como variantes as plantas cujos perfilhos também mostravam o mesmo tipo de variação. Constatou-se a ocorrência de três tipos de variantes somaclonais, VCF (Variação da Clorofila na Folha), VPB (Variante de Porte Baixo) e VCPP (Variante da Coloração do Pseudocaule e Pecíolo), este último com potencial ornamental. A taxa de variação somaclonal para Heliconia bihai cv Lobster Claw I, nas condições propostas, foi de 61,40 %

Somaclonal variation on in vitro callus culture potato cultivars Variação somaclonal in vitro em cultura de calos de cultivares de batata

Synthetic seeds can be an alternative for those species in which botanical seeds are not viable. One of the major problems of in vitro plant cultivation is the high level of somaclonal variation. The most common factors affecting somaclonal variation are genotype, explant source, in vitro period and cultivation conditions in which the culture is established. In this work, calli were induced using leaf and stem explants of the commercial potato cultivars Achat, Baraka, Baronesa, Bintje, and Contenda in MS culture media supplemented with 1.65 mM of picloram and 11.5 mM of 2,4-D. Seventy and 90 days after induction, DNA samples of 40 calli were compared concerning the effects of the two explant (leaf and stem) and two growth regulator sources on five potatoes cultivars. A total of 20 arbitrary sequence primers were evaluated. The RAPD pattern generated by these primers suggested a high percentage of polymorphic fragments among the five genotypes, indicating a high level of genetic variation among cultivars. Cultivar Baronesa showed the highest number of polymorphic fragments for all treatments. The cultivar Contenda showed the smallest somaclonal variation, for most of the treatments, except for the treatment which consisted of stem explants, picloram (1.65 mM) application, and a 70-day period of callus formation. 'Contenda' is, therefore, the most suitable cultivar for synthetic seed production.<br>A produção de sementes sintéticas pode ser uma altenativa para culturas, cuja produção de sementes botânicas não é viável. Um dos principais problemas do cultivo de planta in vitro é o alto nível de variação somaclonal resultante. Os fatores mais comuns que afetam a variação somaclonal são genótipo, fonte de explante e duração e condições de cultivo. Neste trabalho, calos foram induzidos utilizando explantes de folha e caule das cultivares comerciais de batata Achat, Baraka, Baronesa, Bintje e Contenda em meio de cultura MS, suplementado com 1.65 µM de picloram ou 11.5 µM de 2,4-D. Após 70 e 90 dias de indução, amostras de DNA de 40 calos foram analisadas por meio de RAPD, em um estudo comparativo entre os efeitos das duas fontes de explante e os dois reguladores de crescimento nas 5 cultivares. Para este propósito, 20 primers de seqüência arbitrária foram testados. No padrão RAPD gerado por estes primers observou-se alta porcentagem de fragmentos polimóficos entre os 5 genótipos, indicando alto nível de variação genética entre as cultivares. A cultivar Baronesa apresentou o mais alto número de fragmentos polimórficos para os tratamentos. A cultivar Contenda apresentou a menor variação somaclonal genética entre os genótipos e tratamentos utilizados, exceto para o tratamento que consistiu de caule como explante, uso de picloram (1.65 mM) e 70 dias para formação de calos. Portanto, 'Contenda' é a cultivar mais adequada para a produção de sementes sintéticas