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Understanding the reproductive mechanisms of invasive alien species can lay the foundation for effective control measures. Praxelis clematidea is a triploid neotropical Asteraceae species that is invasive in China and other countries. However, few studies have focused on its reproductive biology. In this study, flow cytometric seed screening (FCSS) was used to identify and confirm the reproductive mode of the species. The development of ovules, anthers, and mega- and microgametophytes was observed using a clearing method and differential interference contrast microscopy. Pollen viability was measured using the Benzidine test and Alexander's stain. Pollen morphology was observed via fluorescence microscopy after sectioning the disk florets and staining with water-soluble aniline blue or 4′6-diamidino-2-phenylindole nuclei dyes. Controlled pollination experiments were conducted on four populations in China to examine the breeding system and to confirm autonomous apomixis. The reproductive mode was found to be autonomous apomixis without pseudogamy, according to FCSS. Megaspore mother cells developed directly into eight-nucleate megagametophytes without meiosis, conforming to Antennaria -type diplospory. The unreduced egg cells developed into embryos through parthenogenesis, while the endosperm was formed by the fusion of two unreduced polar nuclei. Pollen viability was very low (0.82 ± 0.57 % and 0.36 ± 0.44 %) as measured by the Benzidine test and Alexander's stain, respectively. The majority of the pollen grains were empty and had neither cytoplasm nor nuclei. The seed set was >90 % for all treatments of open pollination, bagging and emasculated capitula. Mature cypselae developed in capitula that were emasculated before flowering, which confirmed that the breeding system of P. clematidea was autonomous apomixis. The present study is the first report of autonomous apomixis in P. clematidea in China. Antennaria -type autonomous apomixis in P. clematidea greatly increases the probability of successful colonisation and dispersal of P. clematidea into new areas, which likely contributes to its high invasion potential. Effective control measures should be implemented to prevent autonomous (pollen-independent) seed production. [ABSTRACT FROM AUTHOR]

Chromosome number, meiotic behavior and pollen viability were evaluated in a collection of 53 Paspalumnicorae Parodi accessions, which are part of a breeding project of the species. All accessions are tetraploid, with 2n=4x=40.Despite the invariable chromosome numbers, there was variation among accessions in the frequencies of different chromosomeconfigurations at diakinesis and metaphase I, such as univalents, trivalents and quadrivalents. Other abnormalities asbridges and laggards were also observed at anaphase and telophase I. Meiotic indexes ranged from 82.00 to 99.50% andpollen viability from 88.99 to 95.06%. As the species is pseudogamous apomictic, fertile pollen is necessary for endospermformation. Results show that all plants are meiotically stable and have enough fertile pollen to be used as male parents incontrolled crosses.

We analyzed anaphase I configurations and pollen viability in aposporous and sexual tetraploid (2 n = 4 x = 40) cytotypes of Paspalum notatum. Five natural aposporous accessions and three experimentally obtained sexual individuals were used. In addition, 16 (8 aposporous and 8 sexual) F hybrids, previously classified by their mode of reproduction, were analyzed. Cytogenetic observations revealed normal and abnormal anaphase I configurations in both aposporous and sexual genotypes. Anaphase I abnormalities were mainly laggard chromosomes, chromatin bridges, and micronuclei. On average, 44.36 % of aposporous meiocytes and 29.66 % of sexual ones showed abnormal anaphase I configurations. The total numbers of normal and abnormal anaphase I were highly significantly different between aposporous and sexual strains. The pollen viability test indicated that aposporous individuals had significantly more non-viable pollen than sexual ones; a positive correlation ( r = 0.71; r = 0.50) between the variables was detected. Analysis of aposporous and sexual hybrids confirmed differences in the numbers of normal and abnormal anaphase I patterns in the aposporous and sexual parents. However, similar proportions of viable pollen were produced by both groups of hybrids. In this case, the variables were not correlated ( r = 0.23; r = 0.05). Data from this study indicated that aposporous strains had a genetic rearrangement affecting meiosis that was absent in the experimentally obtained sexual individuals and that it was transmitted to the progeny. The possible association between meiotic abnormalities and the inheritance of apospory is discussed. [ABSTRACT FROM AUTHOR]

The study in relation to loral biology conducted at Ludhiana (central plain region of Punjab, India) exhibited that Jatropha curcas lowered for two seasons viz. April till June and July till November. Male and female lowers opened 7 to 10 days after bud formation. Fruiting was visible 26.5 to 30.2 days after bud formation. Fruit setting ranged from 37.0 to 61.6% and the anthesis of male and female lowers occurred between 0600 to 0700 hours and 0700 to 0800 hours respectively. Anther dehiscence was observed after 0800 hours. Flowers were unisexual and male and female lowers were produced in the same inlorescence but female lowers were bigger. The male to female ratio was 13.4:1. Mean number of pollen per anther was 122.3 and ranged from 61.9 to 195.1. Mean pollen viability was 71.6%. Results of the breeding system showed fruit setting of 93.2, 72.2, 36.2 and 79.2% in cross pollination, self pollination, apomixis and open pollination respectively. [ABSTRACT FROM AUTHOR]