5 research outputs found
Effect of self-pollination with heat-treated pollen on parthenocarpy and homozygosity in cassava
Cassava\u2019s ( Manihot esculenta Crantz) high heterozygosity
complicates its genetic improvement via selective breeding. Double
haploid (DH) technology can be used to improve the crop\u2019s
heterozygosity, thereby improving the capacity for genetic improvement.
The objective of this study was to evaluate the effect of
self-pollination using heated pollen on pollen tube penetration, fruit
set, seed and haploid embryo development in cassava genotypes for the
production of haploid cassava. Pollen from two cassava genotypes, NASE3
and NASE14, was heated at 40, 50 and 60 oC for 0.5, 1.0 and 2.0 hr
each. The heated pollen was used in six rounds of self-pollinations.
Pollen tube penetration was monitored by fluorescent microscopy,
followed by early embryo rescue and ovule culture. Ploidy and zygosity
were assessed using flow cytometry and single-nucleotide polymorphism
analysis, respectively. Pollen germinated on the stigma, grew within
the style through the nucellar beak, but did not reach the embryo sac,
thus achieving no fertilisation in all the 5756 self-pollinated
flowers. There was a reduction in pollen germination (in vitro and in
vivo), pollen tube penetration and fruit set with increasing
temperature. Heat-treated pollen stimulated division of the egg cell
and induced development of parthenocarpic fruits. Up to 6 embryoids per
ovule were observed and all regenerated plantlets were diploid, with up
to 93.0% increased homozygosity. For the first time, plant regeneration
from ovules, pollinated with fresh pollen at 14 days after pollination,
was achieved indicating improved speed in plant regeneration. The data
generated are important for the development of protocols for cassava DH
plant production.La forte h\ue9t\ue9rozygotie du manioc ( Manihot esculenta
Crantz) complique son am\ue9lioration g\ue9n\ue9tique par
s\ue9lection s\ue9lective. La technologie d\u2018 haplo\uefde
double (DH) peut \ueatre utilis\ue9e pour am\ue9liorer
l\u2019h\ue9t\ue9rozygotie de la culture, am\ue9liorant ainsi la
capacit\ue9 d\u2019am\ue9lioration g\ue9n\ue9tique.
L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer
l\u2019effet de l\u2019auto-pollinisation \ue0 l\u2019aide de
pollen chauff\ue9 sur la p\ue9n\ue9tration du tube pollinique, la
nouaison, le d\ue9veloppement des graines et des embryons
haplo\uefdes dans les g\ue9notypes de manioc pour la production de
manioc haplo\uefde. Le pollen de deux g\ue9notypes de manioc, NASE3
et NASE14, a \ue9t\ue9 chauff\ue9 \ue0 40, 50 et 60 oC pendant
0,5, 1,0 et 2,0 heure (s) chacun. Le pollen chauff\ue9 a
\ue9t\ue9 utilis\ue9 dans six cycles d\u2019auto-pollinisation.
La p\ue9n\ue9tration du tube pollinique a \ue9t\ue9
surveill\ue9e par microscopie fluorescente, suivie d\u2019un
sauvetage pr\ue9coce des embryons et d\u2019une culture
d\u2019ovules. La plo\uefdie et la zygosit\ue9 ont \ue9t\ue9
\ue9valu\ue9es \ue0 l\u2019aide de la cytom\ue9trie en flux et
de l\u2019analyse du polymorphisme mononucl\ue9otidique,
respectivement. Le pollen a germ\ue9 sur le stigmate, s\u2019est
d\ue9velopp\ue9 dans le style \ue0 travers le bec nucellaire,
mais n\u2019a pas atteint le sac embryonnaire, n\u2019obtenant ainsi
aucune f\ue9condation dans toutes les 5756 fleurs autogames. Il y
avait une r\ue9duction de la germination du pollen (in vitro et in
vivo), de la p\ue9n\ue9tration du tube pollinique et de la nouaison
avec l\u2019augmentation de la temp\ue9rature. Le pollen trait\ue9
thermiquement a stimul\ue9 la division de l\u2019ovule et induit le
d\ue9veloppement de fruits parth\ue9nocarpiques. Les 6
embryo\uefdes par ovule ont \ue9t\ue9 observ\ue9s et toutes les
plantules r\ue9g\ue9n\ue9r\ue9es \ue9taient diplo\uefdes,
avec 93,0% d\u2018augmentation d\u2019homozygotie. Pour la
premi\ue8re fois, la r\ue9g\ue9n\ue9ration des plantes \ue0
partir des ovules, pollinis\ue9es avec du pollen frais 14 jours
apr\ue8s la pollinisation, a \ue9t\ue9 r\ue9alis\ue9e,
indiquant une vitesse am\ue9lior\ue9e de
r\ue9g\ue9n\ue9ration des plantes. Les donn\ue9es
g\ue9n\ue9r\ue9es sont importantes pour l\u2019\ue9laboration
de protocoles de production de plantes de manioc de DH
Fruit set and plant regeneration in cassava following interspecific pollination with castor bean
The increasing demand for cassava ( Manihot esculenta Crantz) for
food and non-food uses in the tropics necessitates that its breeding
for increased root productivity be made faster. The characteristic long
breeding cycle and heterozygous nature of this crop, pose a major
obstacle to its rapid genetic improvement. This study aimed at
inter-pollinating cassava with castor bean ( Ricinus communis ), with
a purpose of inducing and regenerating cassava doubled haploids (DHs).
A total of 3,349 flowers from twelve elite cassava varieties were
inter-pollinated with caster bean. A total of 803 fruits were harvested
for early embryo rescue and/or ovule culture. Of these, three were
dissected to obtain seven unique embryos, while 800 were dissected to
obtain 1312 young ovules, all of which were cultured in vitro. Overall,
82 (6.25%) of the cultured ovules formed callus that originated from
the embryosac region, which is haploid. Four out of seven rescued
embryos (57.1%) regenerated into plantlets. Ploidy analyses of 24
samples using flow cytometry revealed that 23 of the analysed samples
were diploid. However, one callus sample was anueploid. Only one sample
had an exceptionally high level of homozygosity ( 84.2%). These
findings lay a foundation for future research aimed at induction of
haploids in cassava.La demande croissante de manioc (\ua0 Manihot esculenta
\ua0Crantz\ua0) \ue0 usage alimentaire et non alimentaire dans
les tropiques\ua0n\ue9cessite que sa reproduction pour une
productivit\ue9 accrue des racines soit faite plus
rapidement.\ua0Le long cycle de reproduction et le caract\ue8re
h\ue9t\ue9rozygote de cette plante constituent un obstacle majeur
dans la rapidit\ue9 de son am\ue9lioration
g\ue9n\ue9tique.\ua0Cette \ue9tude visait \ue0
inter-polliniser le manioc avec le haricot (\ua0 Ricinus communis
\ua0), dans le but d\u2019induire et de r\ue9g\ue9n\ue9rer le
manioc d\u2019haplo\uefdes doubl\ue9 (HD).\ua0Un total de 3 349
fleurs de douze \ue9lites vari\ue9t\ue9s de manioc ont
\ue9t\ue9 inter-pollinis\ue9es avec le haricot.\ua0Un total de
803 fruits ont \ue9t\ue9 r\ue9colt\ue9s pour les embryons
pr\ue9matur\ue9s qui etaient sauves et\ua0/ ou la\ua0culture
d\u2019ovules\ua0.\ua0Parmi ceux-ci,\ua0trois ont \ue9t\ue9
diss\ue9qu\ue9s pour obtenir sept embryons
uniques\ua0,\ua0tandis que 800 ont \ue9t\ue9
diss\ue9qu\ue9s pour obtenir 1312 jeunes ovules, qui ont tous
\ue9t\ue9 cultiv\ue9s\ua0in vitro\ua0.\ua0Un total de 82
(6,25%) des ovules en culture ont form\ue9 des cals provenant de
la\ua0r\ue9gion\ua0embryonnaire\ua0, qui est haplo\uefde.
Quatre parmi sept embryons sauv\ue9s (57,1%) se sont
r\ue9g\ue9n\ue9r\ue9s en plantules.\ua0Les analyses de
plo\uefdie de 24 \ue9chantillons par cytom\ue9trie en flux ont
r\ue9v\ue9l\ue9 que 23 des \ue9chantillons analys\ue9s
\ue9taient diplo\uefdes.Cependant, un \ue9chantillon de cals
\ue9tait anueplo\uefde.\ua0Un seul \ue9chantillon
pr\ue9sentait un niveau d\u2019homozygotie exceptionnellement
\ue9lev\ue9\ua0(84,2\ua0%).\ua0Ces r\ue9sultats sont les
bases des recherches dans le futur sur la cause des haplo\uefdes dans
le manioc
Effects of gamma irradiation and ethyl methane sulphonate on morphometric traits and prevalence of common viral diseases and whiteflies in cassava
Cassava ( Manihot esculenta Crantz) is an important staple and food
security crop for millions of people in Africa. However, its
nutritional value is limited; yet its productivity is constrained by
several pests and diseases. Induced mutagenesis is one approach with
the potential to overcome such biotic stresses. The objective of this
study was to assess the variability in morphometric traits and
prevalence of common viral diseases and whiteflies in cassava to
different doses and concentrations of gamma irradiation and ethyl
methane sulphonate (ems) treatments. The effects were assessed on seed
germination and growth of stakes, as well as foliar viral disease
symptoms and whitefly counts. Radio-sensitivity tests revealed LD50 for
sprouting as 37.6Gy for \u3b3-irradiation and 0.08% for EMS treatment.
There was notable decrease in sprout, epicotyl length, shoot height,
petiole length and number of leaf lobes, with increasing \u3b3-ray
doses and EMS concentrations. Contrastingly, total chlorophyll content
increased with increasing doses of \u3b3-rays and EMS concentrations.
Basing on foliar whitefly counts and disease symptoms, there was a
general increase in susceptibility to whitefly infestation and cassava
mosaic disease (CMD) incidence. Significantly varying levels of
resistance or tolerance to whiteflies and CMD were observed among
plantlets derived from irradiated and EMS treated stems, compared to
the controls. These findings lay a foundation for more future research
on breeding for various traits, including disease resistance in cassava
using induced mutagenesis approach.Le manioc ( Manihot esculenta Crantz) est une culture de base et de
la s\ue9curit\ue9 alimentaire importante pour des millions de
personnes en Afrique. Cependant, sa valeur nutritionnelle est
limit\ue9e; pourtant, sa productivit\ue9 est limit\ue9e par
plusieurs ravageurs et maladies. La mutagen\ue8se induite est une
approche ayant le potentiel de surmonter de tels stress biotiques.
L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer la
variabilit\ue9 des traits morphom\ue9triques et la pr\ue9valence
des maladies virales courantes et des aleurodes du manioc en raison de
l\u2019exposition \ue0 diff\ue9rentes doses et concentrations des
traitements par l\u2018 irradiation gamma et \ue9thyl m\ue9thane
sulfonate (EMS). Les effets ont \ue9t\ue9 \ue9valu\ue9s sur la
germination des graines et la croissance des tuteurs, ainsi que sur les
sympt\uf4mes de la maladie virale foliaire et le nombre des
aleurodes. Les tests de radiosensibilit\ue9 ont r\ue9v\ue9l\ue9
que la DL50 pour la germination \ue9tait de 37,6 Gy pour
l\u2019irradiation et de 0,08 % pour le traitement EMS. Il y avait une
diminution notable de la pousse, de la longueur de
l\u2019\ue9picotyle, de la hauteur des pousses, de la longueur du
p\ue9tiole et du nombre des lobes foliaires, avec
l\u2019augmentation des doses de rayons et des concentrations EMS. En
revanche, la teneur totale en chlorophylle augmentait avec
l\u2019augmentation des doses de rayons et des concentrations EMS. Sur
la base des d\ue9nombrements foliaires des aleurodes et des
sympt\uf4mes de la maladie, il y avait une susceptibilit\ue9
g\ue9n\ue9ralement accrue \ue0 l\u2019infestation des aleurodes
et \ue0 l\u2019incidence de la maladie de la mosa\uefque du manioc
(CMD). Des niveaux significativement variables de r\ue9sistance ou de
tol\ue9rance aux aleurodes et \ue0 la CMD ont \ue9t\ue9
observ\ue9s parmi les plantules d\ue9riv\ue9es de tiges
irradi\ue9es et trait\ue9es par EMS, par rapport aux t\ue9moins.
Ces r\ue9sultats jettent les bases des autres recherches futures sur
la s\ue9lection pour les divers caract\ue8res, y compris la
r\ue9sistance aux maladies du manioc en utilisant une approche de
mutagen\ue8se induite
Fruit set and plant regeneration in cassava following interspecific pollination with castor bean
The increasing demand for cassava (Manihot esculenta Crantz) for food and non-food uses in the tropics necessitates that its breeding for increased root productivity be made faster. The characteristic long breeding cycle and heterozygous nature of this crop, pose a major obstacle to its rapid genetic improvement. This study aimed at inter-pollinating cassava with castor bean (Ricinus communis), with a purpose of inducing and regenerating cassava doubled haploids (DHs). A total of 3,349 flowers from twelve elite cassava varieties were inter-pollinated with caster bean. A total of 803 fruits were harvested for early embryo rescue and/or ovule culture. Of these, three were dissected to obtain seven unique embryos, while 800 were dissected to obtain 1312 young ovules, all of which were cultured in vitro. Overall, 82 (6.25%) of the cultured ovules formed callus that originated from the embryosac region, which is haploid. Four out of seven rescued embryos (57.1%) regenerated into plantlets. Ploidy analyses of 24 samples using flow cytometry revealed that 23 of the analysed samples were diploid. However, one callus sample was anueploid. Only one sample had an exceptionally high level of homozygosity ( 84.2%). These findings lay a foundation for future research aimed at induction of haploids in cassava
Effects of gamma irradiation and ethyl methane sulphonate on morphometric traits and prevalence of common viral diseases and whiteflies in cassava.
Cassava (Manihot esculenta Crantz) is an important staple and food security crop for millions of people in Africa. However, its nutritional value is limited; yet its productivity is constrained by several pests and diseases. Induced mutagenesis is one approach with the potential to overcome such biotic stresses. The objective of this study was to assess the variability in morphometric traits and prevalence of common viral diseases and whiteflies in cassava to different doses and concentrations of gamma irradiation and ethyl methane sulphonate (ems) treatments. The effects were assessed on seed germination and growth of stakes, as well as foliar viral disease symptoms and whitefly counts. Radio-sensitivity tests revealed LD50 for sprouting as 37.6Gy for g-irradiation and 0.08% for EMS treatment. There was notable decrease in sprout, epicotyl length, shoot height, petiole length and number of leaf lobes, with increasing g-ray doses and EMS concentrations. Contrastingly, total chlorophyll content increased with increasing doses of g-rays and EMS concentrations. Basing on foliar whitefly counts and disease symptoms, there was a general increase in susceptibility to whitefly infestation and cassava mosaic disease (CMD) incidence. Significantly varying levels of resistance or tolerance to whiteflies and CMD were observed among plantlets derived from irradiated and EMS treated stems, compared to the controls. These findings lay a foundation for more future research on breeding for various traits, including disease resistance in cassava using induced mutagenesis approach