Meiotic behavior of economically important plant species: the relationship between fertility and male sterility

Abstract

Meiosis is an event of high evolutionary stability which culminates in a reduction of chromosome number. The normal and harmonious course of meiosis ensures gamete viability. The cytologic events of gametogenesis are controlled by a large number of genes that act from premeiotic to postmeiotic mitosis. Mutations in these genes cause anomalies that may impair fertility, and many abnormalities affecting plant fertility or causing total male sterility have been detected during the evaluation of meiotic behavior in some species. Some of these abnormalities have been frequently described in the literature, while others have not been previously reported. The most frequent abnormalities found in the species analyzed were irregular chromosome segregation, cytomixis, chromosome stickiness, mixoploidy, chromosome fragmentation, syncyte formation, abnormal spindles, and failure of cytokinesis. Uncommon abnormalities, such as chromosome elimination during microsporogenesis, were found in one species. Original meiotic mutations affecting different steps of meiosis were also observed in these species, especially in maize, Paspalum and soybean. Some mutants present characteristics that may be exploited successfully in breeding programs because they cause total male sterility.<br>A meiose é um evento de alta estabilidade evolucionária que culmina na redução do número de cromossomos. O curso normal e harmonioso da meiose garante a viabilidade gamética. Os eventos citológicos da gametogênese são controlados por um grande número de genes que atuam desde as mitoses pré-meióticas até as pós-meióticas. Mutações nestes genes causam anomalias que podem afetar a fertilidade. Durante a avaliação do comportamento meiótico em algumas espécies de plantas, muitas anormalidades que afetaram a fertilidade ou causaram total macho-esterilidade foram detectadas. Algumas das anormalidades encontradas já eram descritas na literatura, enquanto outras eram totalmente desconhecidas. As anormalidades mais freqüentes nas espécies analisadas foram segregação irregular de cromossomos, citomixia, aderências cromossômicas, mixoploidia, fragmentação cromossômica, formação de sincícios, fusos anormais e falta de citocinese. Eliminação de cromossomos, uma anormalidade meiótica rara, foi observada em uma espécie de Paspalum. Mutantes meióticos nunca antes descritos, afetando diferentes passos da meiose, foram observados em algumas espécies, especialmente em milho, soja e Paspalum. Alguns mutantes apresentam características que podem ser exploradas com sucesso em programas de melhoramento, pois causam total macho-esterilidade

Meiotic analysis of interspecific hybrids between Capsicum frutescens and Capsicum chinense

“…According to Pagliarini (2000), the most common meiotic abnormalities observed in several species is the irregular chromosome segregation, characterized by early migration or laggard chromosomes at metaphase I and anaphase I. Considering that the meiotic behavior of a plant is directly related to their degree of fertility, the changes observed during cell division may be reflected in the viability of pollen grains (Defani-Scoarize et al 1996).…”

Meiotic behavior during microsporogenesis of Alchornea triplinervia (Sprengel) Müller Argoviensis

“…The stickiness is characterized as a chromosome grouping during some phases of the cellular cycle that according to PAGLIARINI (2000), may be caused by environmental causes as well as genetic control. GAULDEN (1987) suggest that chromosome stickiness its caused by a failure in the functioning of one of the two non-histone proteins involved in the process of chromosome separation and segregation.…”

Male Meiotic Studies in Some Accessions of <i>Boswellia serrata</i> (Roxb.) Ex. from the Aravali Region of Rajasthan, India

“…It is interesting to note that the PMCs with unequal distribution of chromosomes due to the presence of laggards, however, did not exceed 10-15% of the total PMCs analyzed at AI. Unpaired chromosomes (univalents) in diploid taxa are reported to be the main factor resulting in the abnormal distribution of chromosomes at anaphase I and/or II (Singh 1993, Rao 1990, Pagliarini 2000, Kumar and Rao 2003. Gill et al (1979) and Gill and Singhal (1988a, b) have reported that the occurrence of accessory chromosomes (B) is a regular feature of many woody tree species.…”