Apomixis maintains heterosis and avoids transmission of systemic pathogens which accompany vegetative propagation of cassava. An embryonic study of cleared ovules of two cassava clones in toto showed them to be of aposporic nature. Cytogenetic analysis of the two clones revealed an aneuploid structure (2n + 1) in apomictic individuals, whereas it was 2n in the sexually reproduced plants.
. Molecular and embryonic evidence of apomixis in cassava interspecific hybrids (Manihot spp.). Can. J. Plant Sci. 78: 349-352. In cassava, apomixis could fix hetereozygosity and prevent the transmission of systemic pathogens which complicate vegetative propagation of the crop. Evidence from maternal inheritance of RAPD markers and the structure of the embryonic sac in large progeny sets of two distinct genotypes have further confirmed that apomixis occurs in cassava. Here, we have built on an earlier report of apomixis in cassava in four ways (1) we estimated the rate of faculative apomixis in the range of 2% (2) we detected the occurrence of apomixis in a second genotype, derived form a different interspecific cross; (3) apomictic behavior was demonstrated in an F 1 individual and (4) embryonic evidence showed that the mode of apomixis is aposporic. Since apomixis was detected in an F 1 interspecific hybrid it is possible that genes for apomixis could be transferred directly to cultivated cassava from a wild relative. Chez le manioc, l'apomixie pourrait être un moyen de fixer l'hétérozygotie tout en évitant la transmission des pathogènes systémiques qui rendent compliquée la propagation végétative de la culture. Les indications obtenues à partir de la transmission maternelle de marqueurs RAPD et à partir de la structure du sac embryonnaire dans de grandes populations issues de 2 génotypes distincts, permettent de confirmer que l'apomixie existe dans le manioc. Dans la présente communication, qui s'appuie sur une communication antérieure, nous avons 1°estimé aux alentours de 2 % le taux d'apomixie facultative, 2°décelé la présence d'apomixie dans un second génotype dérivé d'un croisement interspécifique distinct, 3°mis en évidence un comportement apomictique dans une plante F 1 et 4°mis en évidence une preuve embryonnaire que le mode d'apomixie est aposporique. Vu que l'apomixie a été décelée dans la F 1 d'un hybride interspé-cifique, les gènes commandant l'apomixie pourraient être transférés au manioc cultivé directement à partir d'une espèce sauvage apparentée. Mots clés: Manioc, hybride interspécificCassava (Manihot esculenta) also named yuca, mandioca or manioc, is the most important staple crop in the tropics and subtropics, being a food staple for more than 600 million people (Food and Agriculture Organization, 1994). Cassava is propagated vegetatively by stem cuttings which perpetuate superior genetic combinations, but allow viral and bacterial diseases to be accumulated. These reduce productivity and may eventually lead to the extinction of superior genotypes. Systemic pathogen contamination could be avoided by seed propagation of the crop. However, this approach has not been possible because the genetic superiority of individual clones breaks down due to genetic segregation in the progeny.The heterozygosity responsible for vigor could be efficiently fixed by apomixis in cassava. This phenomenon is defined as a process in which plants produce seeds without fertilization. This would bypass female meiosis...
ABSTRACT. Lychnophora ericoides and Lychnophora pinaster are species used in popular medicine as analgesic or anti-inflammatory agents to treat contusions, rheumatism, and insect bites. In this study, 21 simple sequence repeat loci of L. ericoides were developed and transferred to L. pinaster. Three populations of L. ericoides and 2 populations of L. pinaster were evaluated; they were collected in the State of Minas Gerais. Population parameters were estimated, and the mean values of observed and expected heterozygosity were 0.297 and 0.408 (L. ericoides) and 0.228 and 0.310 (L. pinaster), respectively. Greater genetic variability was observed within populations than between populations of L. ericoides (62 and 37%) and L. pinaster (97 and 2.8%). These results provide information for genetic conservation and taxonomic studies of these endangered species.
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