Highest Multiplication Rate Research Articles

In vitro propagation of the endangered plant Centaurea ultreiae: assessment of genetic stability by cytological studies, flow cytometry and RAPD analysis

The effect of different cytokinins on multiple shoot regeneration from shoots of Centaurea ultreiae was studied. The culture system consisted of solid basal half-strength Murashige and Skoog medium supplemented with one of four cytokinins [6-benzyladenine (BA), zeatin, kinetin, or N6-(2-isopentyl) adenine (2-iP)] at each of five different concentrations. The highest multiplication rate (5.52 shoots per explant) was obtained in the medium supplemented with 4.44 μM BA. Shoots were successfully rooted (91% success) by dipping the basal end into a solution containing 10 M 1-naphthaleneacetic acid for 30 s. Genetic stability of the regenerated plants was assessed by random amplified polymorphic DNA (RAPD) analysis and flow cytometry. In the initial randomly selected plant material (control) and 20 of its regenerants, 2,688 bands were generated by RAPD with 12 different primers, and the same banding profiles were exhibited. Molecular and cytological analyses did not reveal genomic alterations in any of the regenerated plants obtained on medium containing 4.44 μM BA. The success of acclimatization to environmental conditions—100% of plants were successfully acclimatized—suggests that the micropropagation system described is a reliable method for propagation of C. ultreiae.

Mass propagation of Vaccinium corymbosum in bioreactors

Two kinds of bioreactors were evaluated for in vitro propagation of Vaccinium corymbosum: a temporary immersion system (RITA®) and a permanent immersion reactor. Results were compared with the system currently used of micropropagation in semi-solid medium, used as control for this study. Two varieties, ‘O’Neal’ and ‘Georgia Gem’, of the triple hybrid Vaccinium corymbosum, V. ashei and V. darrowii were employed. Explants were cultured in WPM medium (Lloyd and Mc Cown, 1981) containing 0.01mM ascorbic acid, 0.22mM adenine sulphate, 2% sucrose and 20μM 2iP. To minimize hyperhydricity of explants, the effect of ancymidol (0.4, 0.9 and 2.0 µM) as growth retardant and phloroglucinol (0.32mM) as promoter of lignin biosynthesis was tested. The highest multiplication rates were 28 and 24 shoots per bud for the varieties ‘O’Neal’ and ‘Georgia Gem’ respectively, and were achieved in the permanent immersion system containing phloroglucinol. Light microscopy of the shoots showed a more developed and lignified xylem in the phloroglucinol-derived plants. Shoots obtained from the multiplication system that were 3 or more centimeters long were rooted ex vitro in a mixture of soil, peat and perlite (1:1:1) resulting in 80% rooting. Plants acclimatized well and exhibited normal development in the greenhouse. Abbreviations: IBA – Indol-3-butyric acid, 2iP – 6-(γ, γ-dymethilamino) purine, WPM – Woody Plant Medium (Lloyd and McCown, 1981).

Desempenho in vitro e agronômico de cultivares micropropagadas de morangueiro em vários subcultivos

O morangueiro é uma espécie multiplicada vegetativamente, o que facilita a progressão de viroses a partir de mudas infectadas. A utilização de matrizes provenientes do processo de cultivo in vitro tem sido uma prática na obtenção de mudas isentas de patógenos. Diversos protocolos de micropropagação recomendam a utilização de quatro subcultivos, para preservar a identidade genética dos clones e manter alta taxa de multiplicação. Desta forma, visando a elevar a eficiência do processo de micropropagação, foram utilizadas duas cultivares de morangueiro Oso Grande e Vila Nova, submetidas a nove subcultivos, sendo avaliadas a taxa de multiplicação e a variação somaclonal. Durante o cultivo in vitro, foi avaliada a taxa de multiplicação, a altura e o número de folhas por propágulo. Na aclimatização, determinaram-se a taxa de sobrevivência, a área foliar, a massa fresca e seca da parte aérea e da raiz. As mudas obtidas a partir de matrizes também foram avaliadas quanto ao comportamento agronômico, em ambiente protegido. A maior taxa de multiplicação foi observada durante o 2º e o 3º subcultivos com média de sete a oito propágulos/ explante, respectivamente. Não foram observadas alterações fenotípicas nas duas cultivares, durante as fases de micropropagação, aclimatização e crescimento em ambiente protegido. A cv. Oso Grande apresentou maior desempenho agronômico que a 'Vila Nova'.

Genetic Stability in Long-Term Micropropagated Plants ofGentiana Kurroo—An Endangered Medicinal Plant

The present investigation was carried out to study genetic stability of micropropagated plants of Gentiana kurroo using randomly amplified polymorphic DNA (RAPD) and karyotype analysis. A large number of micropropagated plantlets of G. kurroo developed from nodal segment explants started more than 10 years ago were assessed for genetic variations. Similarly, the donor mother plant maintained in the arboretum was also subjected to genetic analysis. Out of 20 RAPD primers, 5 displayed the same banding profile within all the micropropagated plants and donor mother plant. The karyotypic analysis showed no chromosomal variations in the plants micropropagated through nodal segment culturing. High multiplication rate of healthy plant material associated with molecular and karyotypic stability ensures the efficacy of the protocol to be used across a long period for in-vitro propagation of this important medicinal plant species.

Rapid in vitro propagation of Holarrhena antidysenterica using seedling cotyledonary nodes

A rapid in vitro propagation of Holarrhena antidysenterica has been developed. Seedling cotyledonary nodes on Murashige and Skoog medium (MS) containing 2 mg dm-3 N6-benzyladenine (BA) produced highest number of multiple shoots. The shoot numbers were increased further upon subculture on MS medium supplemented with 0.5 mg dm-3 BA. By repeated subculture of derived shoots, a high multiplication rate was established. The excised shoots were rooted on MS basal medium without growth regulators. The in vitro formed shoots were also rooted ex vitro by dipping them in 2 mg dm-3 of indole-3-butyric acid (IBA) solution for 2 min before transferring them onto the hardening medium. Successful hardening and further establishment (survival 90 %) of micropropagated plants under natural conditions was observed.

Ovulation induction outcomes: analysis of more than 1500 cycles

OBJECTIVE: To evaluate the outcomes of a large cohort of patients undergoing ovulation induction cycles.DESIGN: A retrospective cohort study of 1525 ovulation induction cycles performed in 694 patients between August 1998 and December 2008.MATERIALS AND METHODS: Patients underwent ovulation induction cycles with gonadotropins then timed intercourse or intrauterine insemination. Clomiphene citrate or a GnRH antagonist were used in about 10% of the cycles. Strategies used to reduce multiple gestations included low gonadotropin doses, and cancellation in high risk patients for more than three follicles > 16 mm or high estradiol levels.RESULTS: Per cycle pregnancy rate was 12.4% with a per cycle live birth rate of 7.5%. There was a trend towards higher per cycle pregnancy rate and live birth rate in younger patients (P=.0002). Multiple pregnancy rate was 12.7% with 10.1% twins and 2.6% triplets. Miscarriage rate was 25.8%, after excluding biochemical pregnancies, with a trend towards decreased miscarriages in younger patients (P=.004). The use of a GnRH antagonist decreased the risk of miscarriage (AOR .26, 95% CI .07-.91). Patients with hypothalamic ovarian dysfunction were associated with the highest per cycle pregnancy rate and live birth rate of 37.5% (no miscarriages) followed by PCOS. The lowest per cycle live birth rates were in women with diminished ovarian reserve, recurrent miscarriages, and uterine myomas (2%). The birthweight of a singleton from a pregnancy with a vanishing twin (n=8) was significantly lower than the birthweight of a singleton without a vanishing twin (2882 gm vs 3250gm, P=.013).CONCLUSIONS: Reducing multiple pregnancy with ovulation induction remains an important and challenging goal although there are no strict universal guidelines. In this cohort of patients, the high order multiple pregnancy rate was limited to 2.6% by using certain strategies. Risks of multiple pregnancy include a lower birthweight of the surviving singleton originating from a twin pregnancy. OBJECTIVE: To evaluate the outcomes of a large cohort of patients undergoing ovulation induction cycles. DESIGN: A retrospective cohort study of 1525 ovulation induction cycles performed in 694 patients between August 1998 and December 2008. MATERIALS AND METHODS: Patients underwent ovulation induction cycles with gonadotropins then timed intercourse or intrauterine insemination. Clomiphene citrate or a GnRH antagonist were used in about 10% of the cycles. Strategies used to reduce multiple gestations included low gonadotropin doses, and cancellation in high risk patients for more than three follicles > 16 mm or high estradiol levels. RESULTS: Per cycle pregnancy rate was 12.4% with a per cycle live birth rate of 7.5%. There was a trend towards higher per cycle pregnancy rate and live birth rate in younger patients (P=.0002). Multiple pregnancy rate was 12.7% with 10.1% twins and 2.6% triplets. Miscarriage rate was 25.8%, after excluding biochemical pregnancies, with a trend towards decreased miscarriages in younger patients (P=.004). The use of a GnRH antagonist decreased the risk of miscarriage (AOR .26, 95% CI .07-.91). Patients with hypothalamic ovarian dysfunction were associated with the highest per cycle pregnancy rate and live birth rate of 37.5% (no miscarriages) followed by PCOS. The lowest per cycle live birth rates were in women with diminished ovarian reserve, recurrent miscarriages, and uterine myomas (2%). The birthweight of a singleton from a pregnancy with a vanishing twin (n=8) was significantly lower than the birthweight of a singleton without a vanishing twin (2882 gm vs 3250gm, P=.013). CONCLUSIONS: Reducing multiple pregnancy with ovulation induction remains an important and challenging goal although there are no strict universal guidelines. In this cohort of patients, the high order multiple pregnancy rate was limited to 2.6% by using certain strategies. Risks of multiple pregnancy include a lower birthweight of the surviving singleton originating from a twin pregnancy.

Mass propagation of Vaccinium corymbosum in bioreactors

Two kinds of bioreactors were evaluated for in vitro propagation of Vaccinium corymbosum : a temporary immersion system (RITA®) and a permanent immersion reactor. Results were compared with the system currently used of micropropagation in semi-solid medium, used as control for this study. Two varieties, ‘O’Neal’ and ‘Georgia Gem’, of the triple hybrid Vaccinium corymbosum, V. ashei and V. darrowii were employed. Explants were cultured in WPM medium (Lloyd and Mc Cown, 1981) containing 0.01mM ascorbic acid, 0.22mM adenine sulphate, 2% sucrose and 20iM 2iP. To minimize hyperhydricity of explants, the effect of ancymidol (0.4, 0.9 and 2.0 µM) as growth retardant and phloroglucinol (0.32mM) as promoter of lignin biosynthesis was tested. The highest multiplication rates were 28 and 24 shoots per bud for the varieties ‘O’Neal’ and ‘Georgia Gem’ respectively, and were achieved in the permanent immersion system containing phloroglucinol. Light microscopy of the shoots showed a more developed and lignified xylem in the phloroglucinol-derived plants. Shoots obtained from the multiplication system that were 3 or more centimeters long were rooted ex vitro in a mixture of soil, peat and perlite (1:1:1) resulting in 80% rooting. Plants acclimatized well and exhibited normal development in the greenhouse. Abbreviations : IBA – Indol-3-butyric acid, 2iP – 6-(a, a-dymethilamino) purine, WPM – Woody Plant Medium (Lloyd and McCown, 1981).

Simulation of soil organic carbon response at forest cultivation sequences using 13C measurements

When deforestation is followed by continuous arable cropping, a permanent decline of between 22% and 42% in the soil organic carbon (SOC) has been reported. This systematic loss of soil carbon (C) is mainly attributed to the loss of physically protected SOC. The Rothamsted Carbon model (RothC) does not include a description of the processes of physical protection of SOC and so losses of C during continuous cultivation of previously uncultivated land are not likely to be accurately simulated. Our results show that in the first years following deforestation, RothC does not capture the fast drop in forest derived soil C. However, the model does satisfactorily simulate the changes in SOC derived from the following crops. Uncertainty in input data and accounting for erosion, does not explain the underestimation of decomposition after deforestation by RothC. A simple approach to increase decomposition by multiplying rate constants is evaluated. This approach needs high multiplication rates and leads to an overestimation of plant input values to sustain SOC equilibrium levels. However, the ability of RothC to simulate changes in the forest derived SOC can be greatly improved with an implementation of a simple approach to account for SOC dynamics due to the loss of physically protected C. This approach implements a new soil carbon pool into RothC which represents the labile but protected carbon fraction which builds up under minimally disturbed land uses, and which loses its protection once the soil is disturbed. The new pool is calibrated using 13C natural abundance analysis in conjunction with soil fractionation.

In vitro propagation of Pimelea spicata R.Br (Thymelaeaceae), an endangered species of the Sydney region, Australia

Micropropagation was assessed as an ex situ conservation strategy for the endangered Australian plant Pimelea spicata (Thymelaeaceae). Although regeneration of this species was achieved, several physiological problems were observed and examined. Explants of P. spicata had a higher multiplication rate on MS medium, than on ½ MS, but there was a significantly higher percentage of necrotic shoot tips on the higher salt medium. Increasing calcium concentration and gas exchange exacerbated shoot-tip necrosis. A number of hyperhydrated shoots were produced in all treatments, the cause of which could not be determined, although less hyperhydicity was observed in the ½ MS treatment. Shoots, rooted in vitro on ½ MS in the absence of plant growth regulators, were successfully acclimatised to greenhouse conditions, while direct rooting of microshoots using IBA gel treatment proved unsuccessful. This is the first report of tissue culture propagation of this endangered species.

Bacteriophages as bactericides in plant protection

Control of plant pathogenic bacteria is a serious problem in production of many agricultural crops. High multiplication rate, adaptability and life inside plant tissue make bacteria unsuitable and inaccessible for most of control measures. Consequently, the list of bactericides available for plant protection is very short. Lately, biological control measures have been intensively studied as a potential solution of the problem. Investigation of bacteriophages, viruses that attack bacteria, is a fast-expanding area of research in plant protection. Several experiments have shown that they can be used as a very efficient tool for control of plant pathogenic bacteria. The fact that they are widespread natural bacterial enemies, simple for cultivation and management, host-specific, suitable for integration with other control practices, human and environment friendly, provide a great advantage for the application of phages over other bactericides.

Benzilaminopurina (BAP) e thidiazuron (TDZ) na propagação in vitro de Pfaffia glomerata (Spreng.) Pedersen

Pfaffia glomerata (Spreng.) Pedersen, conhecida como ginseng brasileiro, é muito utilizada pela medicina popular devido suas propriedades fitoterápicas. Este trabalho teve como objetivo avaliar o efeito de concentrações de BAP e de TDZ na propagação in vitro de dois acessos (BRA e JB-UFSM) desta espécie. Segmentos nodais, provenientes de plantas assépticas, foram cultivados em meio Murashige e Skoog (MS) suplementado com 0, 1 e 5 μM de BAP ou TDZ. Após 30 dias, as plantas foram transferidas para meio MS não suplementado com citocinina. Observou-se que a organogênese in vitro de P. glomerata é genótipo-dependente. O acesso BRA mostrou um maior potencial para a propagação in vitro em relação ao JB-UFSM. O cultivo dos segmentos nodais do acesso BRA em meio com 1 μM de TDZ, seguido pelo subcultivo dos brotos para meio isento de citocininas mostrou ser um método viável para a propagação in vitro devido à alta taxa de multiplicação e o bom desenvolvimento das plantas. No acesso JB-UFSM, o cultivo dos segmentos nodais em meio não acrescido de citocinina mostrou ser o método mais adequado para a produção de um grande número de plantas com alta qualidade.

An In Vivo and In Vitro Model of Plasmodium falciparum Rosetting and Autoagglutination Mediated by varO , a Group A var Gene Encoding a Frequent Serotype

In the Saimiri sciureus monkey, erythrocytes infected with the varO antigenic variant of the Plasmodium falciparum Palo Alto 89F5 clone bind uninfected red blood cells (rosetting), form autoagglutinates, and have a high multiplication rate, three phenotypic characteristics that are associated with severe malaria in human patients. We report here that varO parasites express a var gene having the characteristics of group A var genes, and we show that the varO Duffy binding-like 1alpha(1) (DBL1alpha(1)) domain is implicated in the rosetting of both S. sciureus and human erythrocytes. The soluble varO N-terminal sequence (NTS)-DBL1alpha(1) recombinant domain, produced in a baculovirus-insect cell system, induced high titers of antibodies that reacted with varO-infected red blood cells and disrupted varO rosettes. varO parasites were culture adapted in vitro using human erythrocytes. They formed rosettes and autoagglutinates, and they had the same surface serotype and expressed the same varO gene as the monkey-propagated parasites. To develop an in vitro model with highly homogeneous varO parasites, rosette purification was combined with positive selection by panning with a varO NTS-DBL1alpha(1)-specific mouse monoclonal antibody. The single-variant, clonal parasites were used to analyze seroprevalence for varO at the village level in a setting where malaria is holoendemic (Dielmo, Senegal). We found 93.6% (95% confidence interval, 89.7 to 96.4%) seroprevalence for varO surface-reacting antibodies and 86.7% (95% confidence interval, 82.8 to 91.6%) seroprevalence for the recombinant NTS-DBL1alpha(1) domain, and virtually all permanent residents had seroconverted by the age of 5 years. These data imply that the varO model is a relevant in vivo and in vitro model for rosetting and autoagglutination that can be used for rational development of vaccine candidates and therapeutic strategies aimed at preventing malaria pathology.

Slip band formation and mobile dislocation density generation in high rate deformation of single fcc crystals

The mechanisms for the nucleation, thickening, and growth of crystallographic slip bands from the sub-nanoscale to the microscale are studied using three-dimensional dislocation dynamics. In the simulations, a single fcc crystal is strained along the [111] direction at three different high strain rates: 104, 105, and 106 s− 1. Dislocation inertia and drag are included and the simulations were conducted with and without cross-slip. With cross-slip, slip bands form parallel to active (111) planes as a result of double cross-slip onto fresh glide planes within localized regions of the crystal. In this manner, fine nanoscale slip bands nucleate throughout the crystal, and, with further straining, build up to larger bands by a proposed self-replicating mechanism. It is shown that slip bands are regions of concentrated glide, high dislocation multiplication rates, and high dislocation velocities. Cross-slip increases in activity proportionally with the product of the total dislocation density and the square root of the applied stress. Effects of cross-slip on work hardening are attributed to the role of cross-slip on mobile dislocation generation, rather than slip band formation. A new dislocation density evolution law is presented for high rates, which introduces the mobile density, a state variable that is missing in most constitutive laws.

In vitro propagation of Inula verbascifolia (Willd.) Hausskn. subsp. verbascifolia

A clonal propagation method has been developed for Inula verbascifolia (Willd.) Hausskn. subsp. verbascifolia, a species of horticultural as well as potential medicinal interest. Shoots originating from aseptically germinated seeds were used for culture initiation. The highest multiplication rate of 6.5 shoots per explant was achieved in an 8-week culture period on Murashige and Skoog medium supplemented with 2.2 μM 6-benzylaminopurine and 2.9 μM gibberellic acid. During the first three subcultures of the multiplication phase, two-thirds of explants spontaneously rooted on all tested media. Rooting of excised shoots on MS medium supplemented with 3 μM IAA or 3 μM IBA was 100%. Aside from the fact that all the explants were rooted on this root-inducing media, explants developed a surprisingly high mean number of shoots, 4.6 and 2.9 after 4 weeks, on medium supplemented with IAA or IBA, respectively. Rooted plantlets were transferred to potting soil and acclimatized to outdoor conditions.

Inflorescence proliferation for somatic embryogenesis induction and suspension-derived plant regeneration from banana (Musa AAA, cv. ‘Dwarf Cavendish’) male flowers

Availability of explants with adequate embryogenic competence is one of the most important limitations for the development of regenerable cell suspensions in banana. To increase the number and ease of accessibility to potentially embryogenic explants, a novel methodology is described by which young male flower clusters isolated from adult plants are induced to form new flower buds and proliferate in vitro. Different concentrations of the plant growth regulator thidiazuron (TDZ) induced inflorescence proliferation, which could be maintained over time as a continuous source of young flower buds. Intensity of proliferation was evaluated during successive subcultures. At the third cycle of proliferation, the highest multiplication rate (2.89) was obtained on the medium containing 5 microM TDZ. Newly generated floral tissues were assessed for embryogenic competence, resulting in an average embryogenic frequency of 12.5%. The observed embryogenic capacity, together with the recurrent availability of immature flowers, allowed for the direct initiation of cell suspensions from bulked explant cultures. Regular observation and regeneration tests during the development of suspended cell cultures confirmed their embryogenic condition. Produced embryos successfully matured and germinated to regenerate hundreds of somatic in vitro plants.

In vitro propagation of blue honeysuckle

We have developed a rapid shoot multiplication procedure for <I>in vitro</I> propagation of blue honeysuckle (<I>Lonicera kamtschatica</I> [Sevast.] Pojark). Shoot tips of two genotypes 20/1 and Altaj were successfully established <I>in vitro</I> and micropropagated on the Murashige and Skoog (MS) based media containing different concentrations of 6-benzylaminopurine (BAP). Multiplication rates varied depending on the genotype and concentration of BAP. The highest multiplication rate was obtained for the genotype 20/1 that produced 10.5 ± 0.7 shoots (longer than 10 mm) on the MS medium containing 2 mg/l BAP. The lowest multiplication rate was obtained for Altaj producing only 1.6 ± 0.1 shoots on MS medium containing 4 mg/l BAP. Moreover, <I>in vitro</I> rooting on the modified MS medium supplemented with 2.5 mg/l indole-3-butyric acid (IBA) was reported. Rooted shoots were transferred to the greenhouse for further evaluation.

High frequency in vitro propagation of Holarrhena antidysenterica from nodal buds of mature tree

An in vitro method for propagation of Holarrhena antidysenterica Wall. has been developed using nodal explants from mature trees growing in the field. Irrespective of concentrations and combinations of growth regulators used, the axillary and terminal buds sprouted and elongated when inoculated on Murashige and Skoog (MS) medium. The highest numbers of shoots were formed when sprouted shoots were subcultured from MS basal medium onto MS medium containing 2 mg dm−3 N6-benzyladenine (BA) and 0.5 mg dm−3 α-naphthalene acetic acid (NAA). The shoot number further increased upon subculture on MS medium containing 0.5 mg dm−3 BA. By repeated sub-culturing of shoots derived from nodal axillary buds, a high frequency multiplication rate was established. The elongated shoots were excised and rooted in auxin free MS basal medium. Ex vitro rooting of in vitro formed shoots was achieved upon dipping the microshoots for 2 min in 2 mg dm−3 of indole-3-butyric acid solution. Successful field establishment and high (80–90 %) survival of plants was observed.

Annotated expressed sequence tags and xenobiotic detoxification in the aphid Myzus persicae (Sulzer)

AbstractAphids (Hemiptera: Aphididae) are phytophagous insects that are important agricultural pests. The enormous negative economic impacts caused by aphids worldwide are well known, and are mostly due to their high multiplication rate and the transmission of phytopathogenic viruses. Aphid management strategies mainly involve chemical treatments which are pollutants and are increasingly inefficient, since aphids have developed multiple insecticide‐resistant mechanisms. Among the most economically important species is the green peach aphid Myzus persicae Sulzer (Aphididae: Macrosiphini), which is able to colonize a wide range of host plants belonging to many different families, and transmits numerous plant viruses. Because of its large prevalence, M. persicae has been the target of massive insecticide treatments; consequently, it has evolved several insecticide‐resistant mechanisms. In this work, a collection of expressed genes from M. persicae is presented in order to identify putative genes involved in xenobiotic detoxification. After cDNA cloning and sequencing, 959 expressed sequence tags (EST) were annotated. Most sequences matched known genes corresponded to metabolism proteins (26%), ribosomal proteins (23%) and structural proteins (8%). Among them, several sequences corresponded to proteins putatively involved in sensing, degradation or detoxification of plant xenobiotic products.

An investigation on in vitro propagation of Colchicum luteum and its evaluation of colchicine for the economic benefit of rural people in West Bengal

India is bestowed with a rich wealth of medicinal plants due to its diverse agro climatic and regional topography but indiscriminate collection from the wild has brought much of this biodiversity to the brink of extinction. The present research was aimed to introduce a commercially viable rare medicinal plant, Colchicum luteum from the semi-temperate, high altitude region of our country to the tropical agroclimatic zone of lower Indian Gangetic plains in view of producing the raw material of the species at higher rate than that obtained by natural propagation. Colchicine, the commercially important secondary metabolite of the plant is used in conventional crop breeding, in preparing anti-gout drugs and in anti-cancer research. A high multiplication rate of C. luteum (12 shoots on average/explant) was achieved in vitro by culturing small segments of bulbs in MS medium1 supplemented stepwise with 8.88µm BAP for shooting and IAA (5.71µm) or IBA (4.92µm) for rooting and bulblet formation. The hardened plants survived ex-vitro by 99%. Colchicine of 1 year old bulbs was estimated by TLC and HPLC followed by UV-vis spectral analysis. Genetic fidelity of the in vitro-raised plants was checked using a genetic marker. The finding of our study ensures feasibility of cultivation of this important plant in the proposed agro climatic region and may provide scope to generate a source of income, especially for the underprivileged section of the rural community.

Host resistance and the evolutionary response of plant viruses

Summary Plant virus diseases severely constrain agricultural production world‐wide, especially in less developed countries. The use of resistant cultivars may put a selection pressure on the plant virus to evolve towards more aggressive types. We used a modelling approach to show the impact of resistance, expressed through different mechanisms, on selection for plant virus strains with a higher multiplication rate. Begomoviruses (Geminiviridae: Begomovirus) inducing leaf curl diseases on tomato were used as key examples. A model for the epidemiology of the plant–virus–vector system was combined with a model for the within‐plant dynamics of the virus. Four types of resistance were defined, each expressing resistance through one or more model parameters. The evolutionary stable strategy (ESS) approach was used to study the effect of resistance on the evolution of within‐plant virus multiplication rate. Resistance expressed through reduced virus acquisition by the vector, and resistance expressed through reduced inoculation of the plant, do not put a selection pressure on the virus to evolve towards a higher multiplication rate. Resistance expressed through reducing within‐plant virus titre and symptom reducing resistance do put a selection pressure on the virus to evolve towards a higher multiplication rate. Synthesis and applications. We have shown how to disentangle different types of plant resistance. We have also shown that each type of resistance puts a different type of selection pressure on the virus. Virologists and plant breeders can use these results to develop methods to characterize the combination of resistance mechanisms in the cultivars they breed and, on the basis of this, determine whether the cultivar will put a selection pressure on the virus to evolve more harmful types. This new approach to plant resistance against virus diseases has been made possible by combining ecological insight in virus–vector–plant interactions with ESS calculations.