Traditional sugarcane cultivars (Saccharum officinarum) proved highly susceptible to diseases, and this led breeders to progress to interspecific crosses resulting in disease resistance. A backcrossing program to S. officinarum was then required to boost sucrose content. Clonal selection across generations and incorporation of other germplasm into cultivated backgrounds established the (narrow) genetic base of modern cultivars (Saccharum spp.), which have a man-made genome. The genome complexity has inspired several molecular studies that have elucidated aspects of sugarcane genome constitution, architecture, and cytogenetics. However, there is a critical shortage of information on chromosome behavior throughout meiosis in modern cultivars. In this study, we examined the microsporogenesis of a contemporary variety, providing a detailed analysis of the meiotic process and chromosome association at diakinesis, using FISH with centromeric probes. Chromosomal abnormalities were documented by examining high quality preparations of pollen mother cells (700 in total). Approximately 70% of the cells showed abnormalities, such as metaphase chromosomes not lined up at the plate, lagging chromosomes and chromosomal bridges, and tetrad cells with micronuclei. Some dyads with asynchronous behavior were also observed. Due to the hybrid composition of the sugarcane genome, we suggest that bivalent incomplete pairing may occur in the first prophase leading to univalency. The presence of rod bivalents showing the lagging tendency is consistent with a reduction in chiasma frequency. Finally, the presence of chromatin bridges indicates the indirect occurrence of chromosomal inversions, although chromosome fragments were not clearly recognized. Possible reasons for such meiotic abnormalities and the large prevalence of bivalent formation are discussed.

The modern cultivars of sugarcane (Saccharum spp.) are highly polyploid and accumulate aneuploidies due to their history of domestication, genetic improvement and interspecific hybrid origin involving the domesticated sweet species Saccharum officinarum (‘noble cane’) and the wild Saccharum spontaneum, both with an evolutionary history of polyploidy. The first hybrids were backcrossed with S. officinarum, and selection from progenies in subsequent generations established the genetic basis of modern cultivars. Saccharum genome complexity has inspired several molecular studies that have elucidated aspects of sugarcane genome constitution, architecture and cytogenetics. Herein, we conducted a comparative analysis of the meiotic behaviour of representatives of the parentals S. officinarum and S. spontaneum, and the commercial variety, SP80‐3280. S. officinarum, an octoploid species, exhibited regular meiotic behaviour. In contrast, S. spontaneum and SP80‐3280 exhibited several abnormalities from metaphase I to the end of division. We reported and typified, for the first time, the occurrence of peri‐ and paracentric inversions. Using in‐situ hybridisation techniques, we were able to determine how pairing association occurred at diakinesis, the origin of lagging chromosomes and, in particular, the mitotic chromosome composition of SP80‐3280. Interestingly, S. spontaneum and recombinant chromosomes showed the most marked tendency to produce laggards in both divisions. Future attempts to advance knowledge on sugarcane genetics and genomics should take meiotic chromosome behaviour information into account.

The modern cultivars of sugarcane (Saccharum spp.) are highly polyploid and accumulate aneuploidies due to their history of domestication, genetic improvement and interspecific hybrid origin involving the domesticated sweet species S. officinarum ('noble cane') and the wild S. spontaneum, both with an evolutionary history of polyploidy. The first hybrids were backcrossed with S. officinarum, and selection from progenies in subsequent generations established the genetic basis of modern cultivars. Saccharum genome complexity has inspired several molecular studies that have elucidated aspects of sugarcane genome constitution, architecture and cytogenetics. Herein, we conducted a comparative analysis of the meiotic behavior of representatives of the parentals S. officinarum and S. spontaneum, and the commercial variety, SP80-3280. S. officinarum, an octoploid species, exhibited regular meiotic behavior. In contrast, S. spontaneum and SP80-3280 exhibited several abnormalities from metaphase I to the end of division. We reported and typified, for the first time, the occurrence of peri- and paracentric inversions. Using in-situ hybridization techniques, we were able to determine how pairing association occurred at diakinesis and, in particular, the chromosome composition of SP80-3280. Our findings have implications for sugarcane genetic mapping, genomics, and for studies on resynthesized polyploids.

There is an error in the Funding statement. The correct number for Fundação de Amparo a Pesquisa do Estado de São Paulo (FAPESP) is "2008/03969-4." The authors apologize for this error and state that this does not change the scientific conclusions of the article in any way. The original article has been updated.

Tamarindus indica L. é uma espécie exótica de origem africana que se estabeleceu em diversos países tropicais. Esta cultura possui importância econômica nas áreas alimentícia, medicinal e ornamental. Analisando a carência de estudos citogenéticos com espécies arbóreas de leguminosas. Desse modo, este trabalho objetivou identificar o número, morfologia e região organizadora nucleolar dos cromossomos de tamarindo, assim como avaliar o índice meiótico e a viabilidade polínica do mesmo. Dez plantas do perímetro urbano de Alta Floresta-MT foram escolhidas de forma aleatória para a obtenção do material necessário para as análises. A espécie avaliada apresentou 2n = 18 cromossomos, distribuídos na fórmula cariotípica 3m + 5sm + 1a. Referente ao bandeamento AgNOR evidenciou-se a presença nos pares homólogos 1, 4 e 9 de NOR positivas. O índice meiótico da população foi superior a 70% com a ocorrência de células anômalas tríades e díades. A viabilidade polínica apresentou um índice considerável, sendo superior a 75%. O corante que proporcionou melhor resultado para estimar a viabilidade do pólen foi o reativo de Alexander.