Abstract
Allium sativum L. is an herb of the Alliaceae family with a specific taste and aroma and medicinal and nutraceutical properties that are widely marketed in several countries. Brazil is one of the largest importers of garlic in the world, despite of its production is restricted and limited to internal consumption. Thus, explore the genetic diversity of commercial garlic conserved at germplasm banks is essential to generate additional genetic information about its economically important crop. A suitable tool for this purpose is the cytogenetic characterisation of these accessions. This study aimed to characterise the cytogenetic diversity among seven accessions of garlic from a Germplasm Bank in Brazil. The karyotypes were obtained by conventional staining and with chromomycin A3 (CMA) and 4,6-diamidino-2-phenylindole (DAPI) fluorochromes. All accessions analysed showed chromosome number 2n = 16, karyotype formula 6M+2SM, symmetrical karyotypes, reticulate interphase nuclei, and chromosomes with uniform chromatin condensation from prophase to metaphase. The fluorochromes staining showed differences in the amount and distribution of heterochromatin along the chromosomes and between accessions studied. Based on the distribution pattern of these small polymorphisms, it was possible to separate the seven accessions into three groups. It was also possible to differentiate some of the accessions individually. One of the results obtained showed a heteromorphic distension of the nucleolar organiser region observed on the chromosome pairs 6 or 7 with peculiar characteristics. It was suggested for example, that the heteromorphic block of heterochromatin (CMA+++/DAPI-) on chromosome 6 of the "Branco Mineiro Piauí" accession can be used as a marker to identify this genotype or may be associated with some character of economic interest.
Highlights
The genus Allium L. contains over 700 species, including Allium sativum L., which is a temperate climate species widely used for seasoning in food preparation (Jayaswall et al, 2019)
The successful selection of new cultivars depends on the ability to identify the existing genetic diversity among accessions from a germplasm bank and the ability to measure this diversity using tools such as biochemical, molecular, and cytogenetic markers, among others
The interphase nucleus exhibited a reticulate structure, with dense and evenly distributed chromatin and evident small knobs possibly corresponding to small amount and densely compacted heterochromatin that were more clearly visualised by fluorochromes (Figure 3D)
Summary
The genus Allium L. contains over 700 species, including Allium sativum L. (garlic), which is a temperate climate species widely used for seasoning in food preparation (Jayaswall et al, 2019). In Brazil, garlic has socioeconomic importance and, in some states, has been produced as a source of income in family farming systems for small and medium-size farmers, where local or land races garlic cultivars are predominantly used (Santos and Gomes, 2012; Landau et al, 2020). These cultivars exhibit genetic diversity that can be exploited for the selection of improved genotypes for production and commerce, because production has decreased considerably in recent decades due to competition with garlic imported mainly from China and Argentina (Paladini, 2019). The successful selection of new cultivars depends on the ability to identify the existing genetic diversity among accessions from a germplasm bank and the ability to measure this diversity using tools such as biochemical, molecular, and cytogenetic markers, among others
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