Meiotic Behavior of Male and Hermaphrodite Genotypes of Papaya (<i>Carica papaya</i> L.)

Abstract

SummaryThe aim of this study was to analyze the meiotic behavior and to estimate the meiotic index and the pollen grain viability of three papaya genotypes, male (Cariflora) and hermaphrodite (Golden and UENF/CALIMAN01). In considering of the fact that the genotypes have different flower sizes, initially, meiotic stages were defined in relation to bud size, and, after that, meiosis was observed in the three genotypes. To observe meiosis, flower buds of different sizes were collected and the length of each bud was measured using graph paper. Once the measurements had been taken, two slides were prepared for each flower bud by squashing the anthers in 1% acetic carmine solution. Slides were observed under an optical microscope and for each bud, size was determined as indicating one of three stages, depending on meiotic phase: pre-meiotic, meiotic stage, or post-meiotic stage. In this way, meiosis was observed for the three genotypes, with particular attention given to possible irregularities in cell division in relation to prophase I. It was observed that there is a relation between flower bud size and meiosis. In general, meiosis was normal, but all genotypes showed some meiotic irregularity, with laggard chromosome being the most common. The Cariflora (male) genotype had a higher frequency of irregularities compared to the hermaphrodite genotypes. The meiotic indices estimated for the Golden, UENF/CALIMAN01, and Cariflora genotypes were 92.6%, 91% and 76.9%, respectively; however, the pollen grain viability, on average, was higher than 90%. In conclusion, the meiotic behavior of male and hermaphrodite genotypes was similar, and all three genotypes had some degree of meiotic abnormality. Papaya (Carica papaya L.) is a diploid species with nine pairs of chromosomes (Damasceno Jr. et al. 2010). It is trioecious with female, male, and hermaphrodite plants, and is considered to be sexually polymorphic. The cultivars are ginoandromonoicas, consisting of female and hermaphrodite plants. Key wordsThe most accepted theory for sex determination in papaya plants is that the sex of plants is determined by a gene with three allelic forms (M 1 , M 2 , m); so, the genotype of the female plants is mm, that of the male is M 1 m and that of the hermaphrodite is M 2 m (Hofmeyr 1938, Storey 1938. However, Liu et al. (2004) formulated another theory that the sex of the plants is due to the presence of an incipient sex chromosome pair differentiated by a small male-specific region of the Y chromosome (MSY). According to Ming et al. (2007) there are two Y chromosomes in papaya, a controlling male designated as Y and the other, controlling the sex hermaphrodite, designated as Y h . The female plant is homogametic with XX chromosome constitution, the male is XY, and the hermaphrodite is XY h .

Cytological Characterization of Brazilian Green Dwarf Coconut (<i>Cocos nucifera</i> L.) <i>via</i> Meiosis and Conventional and Differential Karyotyping

“…The samples of plant material used in this study were obtained from 10 plants (seedlings) of the green Dwarf coconut group, which were kept in the field. Flower buds from different developmental stages were collected, fixed in a 3 : 1 solution (ethanol : acetic acid) and stored at 4 C. The slides were prepared using the squash technique in an acetic carmine solution at 1% to verify the different stages of meiosis (Freitas et al 2013). The recombination index (RI) was estimated according to Darlington (1958), verifying the number of chiasmata in ring and rod bivalents at diakinesis.…”