Abstract:Polyploidy was induced in two Musa species and their hybrid by means of immersing newly germinated diploid seedlings in 0.5% aq. colchicine solution. Tetraploid M. balbisiana plants were taller and more robust but had slower growth rate, droopier leaves, fewer suckers, and scantier root systems than the diploids. Tetraploidy affected fruit size and shape in M. balbisiana and in M. acuminata. Tetraploidy did not affect bunch size (the number of fruit‐bearing nodes) in M. acuminata banksii but caused great reduc… Show more
“…Alternative breeding strategies based on colchicine-induced autotetraploids have been proposed as a means of introducing disease resistance into breeding programs (Vakili 1967;Stover and Buddenhagen 1986). By using improved, disease-resistant diploid bananas, and inducing autotetraploids from these, !greater genetic diversity can be introduced into a breeding population.…”
Alternative breeding strategies, based on colchicine-induced autotetraploids, have been proposed as a means of introducing disease resistance into banana breeding programs. This paper describes techniques for the in vitro induction of banana autotetraploids by the use of colchicine on cultured explants. The technique can be readily applied and large numbers of autotetraploids produced. The optimum treatment involved immersing shoot tips in a 0.5% w/v colchicine solution for 2 h under aseptic conditions. Dimethyl sulfoxide (DMSO) was applied with the colchicine treatments to increase cell permeability and so absorption of colchicine, resulting in the optimum treatment unchanged at 0.5% colchicine, but including the addition of 2% v/v DMSO. Of the shoot tips treated over 30% were induced to the autotetraploid level.Methods for in vitro selection of induced tetraploids from treated diploid plantlets were also developed. Tetraploid plants were more robust with thicker pseudostems, roots and broader leaves than diploids and they could be selected on these morphological characteristics. Mean stornatal lengths of diploid banana plants growing in vitro were significantly smaller (16.0 pm) than the tetraploids (26.9 pm) and were used as a more reliable indicator of ploidy than morphological criteria alone. A root tip squash technique using carbol fuchsin was developed for positive confirmation of ploidy change by chromosome counts. Although chimerism and reversion to the diploid form occurred, it was not considered a problem because of the large number of autotetraploids induced. Stable autotetraploids were recovered and established in the field and were characterised by their large, drooping leaves and thick pseudostems. They have retained these characteristics for more than 3 years in the field.
“…Alternative breeding strategies based on colchicine-induced autotetraploids have been proposed as a means of introducing disease resistance into breeding programs (Vakili 1967;Stover and Buddenhagen 1986). By using improved, disease-resistant diploid bananas, and inducing autotetraploids from these, !greater genetic diversity can be introduced into a breeding population.…”
Alternative breeding strategies, based on colchicine-induced autotetraploids, have been proposed as a means of introducing disease resistance into banana breeding programs. This paper describes techniques for the in vitro induction of banana autotetraploids by the use of colchicine on cultured explants. The technique can be readily applied and large numbers of autotetraploids produced. The optimum treatment involved immersing shoot tips in a 0.5% w/v colchicine solution for 2 h under aseptic conditions. Dimethyl sulfoxide (DMSO) was applied with the colchicine treatments to increase cell permeability and so absorption of colchicine, resulting in the optimum treatment unchanged at 0.5% colchicine, but including the addition of 2% v/v DMSO. Of the shoot tips treated over 30% were induced to the autotetraploid level.Methods for in vitro selection of induced tetraploids from treated diploid plantlets were also developed. Tetraploid plants were more robust with thicker pseudostems, roots and broader leaves than diploids and they could be selected on these morphological characteristics. Mean stornatal lengths of diploid banana plants growing in vitro were significantly smaller (16.0 pm) than the tetraploids (26.9 pm) and were used as a more reliable indicator of ploidy than morphological criteria alone. A root tip squash technique using carbol fuchsin was developed for positive confirmation of ploidy change by chromosome counts. Although chimerism and reversion to the diploid form occurred, it was not considered a problem because of the large number of autotetraploids induced. Stable autotetraploids were recovered and established in the field and were characterised by their large, drooping leaves and thick pseudostems. They have retained these characteristics for more than 3 years in the field.
“…Ortiz & Vuylsteke (1992) reported that locus P1 segregated in trisomic ratios in plantain-derived diploid test-crosses derived by crossing triploid 'French' plantains and 'Calcutta 4'. Simmonds (1976), based on Vakili (1967), explained that fruits of triploid Musa cultivars grow faster and larger than diploids. Indeed, in natural banana germplasm, triploids have heavy bunches of big fruits whereas diploids have bunches with small fruits.…”
Plantain and banana (Musa spp. AAB and AAA groups) are perennial giant herbs of the tropics which develop parthenocarpic fruits. At least three independent but complementary dominant genes control vegetative parthenocarpy in Musa. One of these genes, F1, segregates in euploid hybrid progenies derived from crosses between triploid 'French' plantains and a wild nonedible diploid banana. Linear correlation and regression analyses revealed that bunch weight and fruit weight and size were positively influenced by both ploidy increases and change of recessive to dominant alleles at the P1 locus. Moreover, significant multiple regression models, including ploidy and number of copies of the P1 allele as independent variables, accounted for most of the phenotypic variation for bunch and fruit traits. The coefficients of determination of the multiple regression analyses were always smaller than estimates of broadsense heritability for each trait. This implies that ploidy and the effect of allele substitution did not explain all the genetic variation for bunch and fruit traits. Hence, other genetic factors may explain the remaining portion of genetic variation. The potential for indirect marker-assisted selection in the seedling nursery, through the utilization of predictive multiple regression
“…Assim sendo, para cada espécie e tipo de material a ser tratado, a concentração do alcalóide deve ser determinada (VAKILI, 1969 Tabela 1. Valores médios da taxa de sobrevivência, porcentagem de plântulas com múltiplas brotações, primeira medição de altura de parte aérea das plântulas (três meses após tratamento com colchicina) (cm) e segunda medição de altura de parte aérea das plântulas (sete meses após tratamento com colchicina) (cm) de Cattleya tigrina, tratadas com diferentes concentrações de colchicina (g.L -1 ) e diferentes intervalos de tempo (horas).…”
ResumoNas orquidáceas, a poliploidia produz características desejáveis, que se traduzem em aumento das peças florais, grau de suculência, intensificação do colorido, durabilidade e maior resistência das flores. A colchicina como agente indutor de poliploidia em cultura de plantas in vitro tem suas limitações, pois em elevadas concentrações ou tratamentos muito prolongados, torna-se tóxica. O objetivo do trabalho foi avaliar a influência da concentração e do tempo de exposição à colchicina, na sobrevivência e no desenvolvimento in vitro de Cattleya tigrina. Protocormos foram tratados com colchicina em concentrações de 0,5 e 1g.L -1 durante 24, 48 e 72 horas. Foram avaliados taxa de sobrevivência dos protocormos (%), porcentagem de plântulas com múltiplas brotações e altura após três e sete meses. Com o aumento da concentração e do tempo de exposição à colchicina houve maior mortalidade e aumento do número de plântulas com múltiplas brotações e altura reduzida. Palavras-chave: Cattleya tigrina, poliploidia, protocormos
AbstractPolyploidy produces desirable characteristicsin orchids that are represented by increase of the floral pieces, succulency degree, intensification of color, durability and larger resistance of flowers. The colchicine as polyploidy inductor agent in in vitro culture of plants has limitations, because when in high concentrations or very long treatments, it becomes poisonous for the vegetal tissues. The objective of this research work was to evaluate the influence of concentrations and times of exposition to the colchicine, on the survival and on the in vitro development of Cattleya tigrina. Protocorms were treated with colchicine in the concentrations of 0.5 and 1g.L -1 during 24, 48 and 72 hours. There were evaluated the tax of survival of the protocorms (%), percentage of plantlings with multiple buds and plant height after three and seven months. The increase of the concentration and of the time of exposition to colchicine caused a larger plant mortality and an increase of plantlings with reduced height.
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