Mode of reproduction and meiotic chromosome behavior in Acroceras macrum

Abstract

Acroceras macrum Stapf is a high‐quality C3 grass species adapted to the subtropics. It is a valuable forage resource in frequently flooded environments. The objectives were to analyze the type of polyploidy, mode of reproduction, and estimate seed and pollen fertility. A living collection of 22 tetraploid and five hexaploid genotypes of A. macrum was analyzed. Type of polyploidy was analyzed from chromosomal pairing at diakinesis and prometaphase I, and meiotic irregularities were evaluated during the microsporogenesis. Pollen viability was also examined. Bivalents predominated in tetraploids and trivalents in hexaploids. Meiotic abnormalities were more frequent in hexaploids than in tetraploids, and they were mainly related to mechanisms of chromosome nondisjunction. The reproductive mode was determined by cytological analysis of megasporogenesis and megagametogenesis, seed fertility under different pollination methods, and molecular progeny tests. In both tetraploid and hexaploid races, only the development of single meiotically derived embryo sacs was observed. Greater seed production in outcrossing compared with selfing indicated a primarily allogamous matting system. Progenies from crosses between genetically different tetraploid genotypes amplified male‐specific molecular markers, indicating a hybrid origin and solid evidence of sexual reproduction. Population breeding approaches developed for sexual cross‐pollinated species are suited for improving A. macrum.

Microsporogenesis associated with seed yield in Urochloa sexual polyploid hybrids

“…The percentage of irregular microspore tetrads in Medicago sativa L. was negatively correlated with seed fertility only when irregularity levels were high (Smith and Murphy 1986). According to Usandizaga et al (2020), meiotic irregularities are closely correlated with pollen fertility, although they do not appear to be a limiting factor for the fertility of crosses in Acroceras macrum. In the same study, pollen viability of tetraploid cytotypes with open pollination was positively correlated with the seed set (r = 43, p = 0.0034).…”

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).…”

Plant reproduction research in Latin America: Toward sustainable agriculture in a changing environment

“…However, there are multiple examples of applied research in the field of meiosis, as shown by the cytogenetic work in Mexico of Ruvalcaba‐Ruiz and Rodríguez‐Garay (2002) in blue agave, in which structural rearrangements reduce pollen fertility; the work of Usandizaga et al. (2020) in Argentina with tetraploid and hexaploid lines of forage grass Acroceras macrum Stap. ; and the work of Sattler et al.…”