Banana leaf anatomy characteristics related to ploidy levels

Abstract

Many important crops have cultivars with different ploidy and provide a diverse choice of materials for breeding programs. Therefore, it is essential to accurately assess the ploidy of all breeding materials. Increased DNA content is known to have various effects on external and internal morphology, an effect known as the “nucleotypic effect”. Thus, anatomical assessment can be used as a tool for determining ploidy in plants, making the chromosome counting technique or flow cytometry unnecessary. This study aimed to evaluate the leaf anatomical characteristics of banana cultivars and understand the relationship between these features and ploidy levels. Thirteen accessions were evaluated, including diploid, triploid, and tetraploid genotypes, and cultivars, resulting from in vitro propagation after 90 days of acclimatization. Five fully expanded young leaves were collected from each cultivar, fixed in FAA70 (formaldehyde–acetic acid–ethanol) and preserved in 70% alcohol. Transverse and paradermal sections of the abaxial and adaxial regions were taken, and variables such as size and stomatal density, leaf thickness in the midrib and fourth vascular bundle region, and thickness of the epidermis, hypodermis, and parenchyma were measured. Results for leaf thickness, stomatal size, and density proved to be appropriate parameters for characterizing banana ploidy levels.

Ploidy estimation and pre-selection of banana autotetraploids after in vitro polyploidy induction

“…Thus, the trend of control plants, which were entirely made up of diploid plants, to present a lower mean value of leaf fresh mass was confirmed (Figure 1). Higher stomatal density was also verified in these plants since one of the nucleotide effects associated with increased ploidy is the increase in stomatal size and, therefore, polyploid plants tend to have lower stomatal density than diploid ones (MANDAIL et al, 2022). However, a parabolic behavior is observed in this variable as a function of antimitotic doses.…”

“…Vandenhout et al (1995) analyzed the correlation between stomatal density and ploidy of banana hybrids and found a significant negative association but with a low correlation coefficient (r=−0.49). The authors also found that the variability of stomata (size and density) is influenced by the genotype, even at the same ploidy level, a result corroborated by Mandail et al (2022). Thus, there are no reports of the use of stomatal density as a method to effectively pre-select presumably tetraploid plants.…”

“…However, time and resources can be optimized using indirect methods to estimate ploidy and pre-select possible polyploids when dealing with hundreds and even thousands of obtained plants. Morphological and anatomical traits are associated with polyploid plants because they have larger cells and organs and are usually more robust than diploid ones (COSTA et al, 2011;JESUS et al, 2016;MANDAIL et al, 2022). Parameters such as leaf blade thickness, which can be indirectly measured by leaf disc mass, cell size, and stomata size and density (GANGA; CHEZHIYAN, 2002;FOSCHI et al, 2013;TOMÉ et al, 2016), can be used to considerably reduce the number of plants to be analyzed for ploidy determination, facilitating polyploidization research.…”