Meiotic behavior and pollen fertility in triploid and tetraploid natural populations of Campuloclinium macrocephalum (Eupatorieae, Asteraceae)

Abstract

Campuloclinium macrocephalum DC. is a perennial herb widely distributed in the New World and introduced in South Africa, where it is commonly called ''pompom weed''. This species is considered one of the most important weeds of Brazil and one of the problematic invasive plants of South Africa. The meiotic system can be studied to assess the ability of a weed to spread, but only few studies on C. macrocephalum have been realized. In this study, we examined the meiotic behavior and pollen fertility of 14 natural populations of C. macrocephalum from Argentina and Uruguay. Meiotic analysis revealed 2 triploid (2n = 3x = 30), 11 tetraploid (2n = 4x = 40) and 1 mixed population (2n = 2x = 20, 2n = 4x = 40). Both, triploid and tetraploid specimens showed a widely variable meiotic behavior with irregular chromosome pairing showing univalents, bivalents, trivalents (in triploids) and tetravalents (in tetraploids) at diacinesis of first meiotic division. Different abnormalities were observed, such as: laggard chromosomes, chromatin bridges, and out of plate chromosomes at metaphase I. During meiosis I (prophase), some cells showed the phenomenon of cytomixis or chromatin transfer between pollen mother cells. The meiotic indexes suggest that only four populations were normally fertile (over 90 % of fertile pollen), indicating meiotically stable plants. The remaining populations share variable pollen fertility, with triploids ranging from 46.64 to 54.83 % and tetraploids varying from 3.54 to 45.30 %. We suggest that polyploidy seems to be recurrent in C. macrocephalum, promoting partial sterility of pollen grains, generating large numbers of individuals by apomixis promoting invasion of crop fields. This study presents the meiotic behavior of this weed, these could be useful for future studies of biological control in areas with no natural enemies.

Abnormal meiosis in an intersectional allotriploid of Populus L. and segregation of ploidy levels in 2x × 3x progeny

“…The frequency of precocious chromosome migration in metaphase I, laggard chromosomes or bridge formation in anaphase I, the presence of micronuclei in telophase I and II, and the number of parallel, fused and tripolar spindles in anaphase II were analyzed together with the variation of sporad types. The meiotic index was calculated as the fratio of the number of normal sporads to the total number of sporads analyzed per hybrid multiplied by 100 [ 43 ].…”

Pollen variation as a response to hybridisation in Populus L. section Aigeiros Duby

“…More than 900 sporads for each genotype were observed in the meiotic products to determine the proportion of tetrads, triads, and dyads. The meiotic index was calculated as the ratio of the number of normal sporads to the total number of sporads analysed per hybrid, multiplied by 100 (Farco and Dematteis 2014).…”

Meiotic behaviour and pollen fertility of F1, F2 and BC1 progenies of Iris dichotoma and I. domestica

“…Pollen fertility analysis of different cross combinations in this study indicated that meiotic abnormalities, such as non-congression, lagging chromosomes, unequal separation and abnormal spindle fibres orientation, led to low pollen fertility. As previously reported, pollen viability is closely associated with meiosis of pollen mother cells, and meiotic abnormalities affect pollen development (Boff and Chifino-wittmann, 2002;Zha et al, 2007;Farco and Dematteis, 2014;Usandizaga et al, 2020). The relationship between meiotic abnormalities and fertility has been studied in many plant species, including Musa and Brassica (Adeleke et al, 2004;Yang et al, 2020).…”