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Puccinia horiana is the causal agent of chrysanthemum white rust. This microcyclic autoecious rust has a quarantine status and cause major damage in the commercial production of Dendranthema grandiflora. The experiment was carried out to identify genetic resources of chrysanthemum that are resistant/susceptible to white rust disease. A total 20 chrysanthemum genotypes were screened for resistance to P. horiana isolates collected from ICAR-IIHR, Bengaluru. By combing the observation methods without and with optical microscope, we established the identification standards for chrysanthemum white rust. The results showed that out of 20 genotypes screened for white rust, eleven genotypes/lines viz., Sweta Singar, Punjab Gold, Garden Beauty, Red Stone, Punjab Anuradha, Lal Pari, White Dolly, White Andaman, IIHR6-32, IIHR9-3 and IIHR6-41 were determined to be resistant. The use of white rust resistant genotypes will be useful for breeding programs in developing varieties with novel flower quality coupled with resistant to white rust for safe cultivation of chrysanthemum.

The present study was carried out to evaluate the performance of two novel gladiolus hybrid selections IIHRG-7 and IIHRG-11 along with commercial checks, for flower quality traits and Fusarium wilt resistance in completely randomized block design, during 2012-13 to 2014-15. Three years data were pooled and analyzed statistically. The hybrid selections IIHRG-7 and IIHRG-11 had been developed through hybridization by crossing Arka Meera x Picardy and Gold Medal 412 x Arka Poonam, respectively followed by selection. IIHRG-7 has novel flower colour (as per RHS Colour Chart) i.e., Red-Purple (65.B) having Red-Purple (62.A) streaks with Red-Purple (67.B) splash and spike with variegated florets, while, IIHRG-11 has novel floret colour as Red (41.C) having Red (41.A) margin. Blotch Red (46.B) with yellow (13.C) border and resistance to Fusarium wilt disease. These hybrid selections are suitable for cut-flower and flower arrangement purposes. Further, these hybrid selections will be useful for developing new gladiolus hybrid selections with novel traits and resistance to Fusarium wilt disease.

The present study was carried out to evaluate the performance of two gerbera hybrids IIHR15-7 and IIHR16-8 along with their parents and a commercial check, for flower quality traits under polyhouse condition in completely randomized block design, during 2016-17 to 2018-19. The hybrids IIHR15-7 and IIHR16-8 had been developed through the half-sib method of breeding with IIHR9 and Arka Ashwa, respectively, as parents. Data for three years were pooled and analyzed statistically. In both hybrids IIHR15-7 and IIHR16-8, all the quantitative traits were found to be on par with the respective commercial checks. They had novel flower colour (as per RHS Colour Chart) i.e. NN155A, White Group for IIHR 15-7 and 65A Red Purple Group for IIHR16-8, with semi-double and double forms of flowers, respectively. These hybrids are suitable for cut-flower and flower arrangement purposes. Further, these hybrids will be useful for developing new gerbera hybrids with novel traits.

The present study was conducted in the existing germplasm block of gerbera under protected condition at ICAR-IIHR, Bengaluru, India during 2017–2019 to obtain comprehensive information on biomass p...

This study was aimed to examine the genetic diversity and population structure of Indian melon landraces with special reference to disease and insect resistance loci. Thirty-six simple sequence repeat (SSR) markers along with seven markers at disease and insect resistance loci were used for this purpose on a panel of 91 accessions available at Indian Institute of Horticultural Research, Bengaluru, India. Model-based structure analysis revealed the presence of four groups that were consistent with the results of principal coordinate analysis (PCoA). The delineation of populations was mostly based on geography with improved varieties as a separate group. Ten accessions have been identified to possess beneficial alleles at all the selected disease resistance loci and shall be useful for incorporating multiple disease resistance after phenotypic validation. The results obtained in the current study demonstrate the importance of the Indian melon group as a valuable genetic reservoir and the need to plan strategies for its conservation and utilization in breeding programmes.

Molecular fingerprinting exploits the variation between individuals at the genome level. It is generally performed for clear identification of various accessions, verifying ambiguous nomenclature, i.e., if similar cultivars are known by different names and different cultivars are called by similar names; to address Intellectual Property Rights related issues in the case of developed hybrids. The objective of the present study was to genotype and deoxyribonucleic acid (DNA) fingerprint 79 guava (Psidium guajava) accessions. Statistical analysis was performed by CERVUS 3.0 software. DNA fingerprint of the guava genotypes was developed by using 13 microsatellite loci that showed high polymorphic information content (PIC), allelic number per loci, and heterozygosity values. A total of 86 different alleles were amplified; number of alleles per locus ranged from five to nine, with a mean of 6.5. Allelic sizes ranged from 86 to 256 bp and the observed heterozygosity values ranged from 0.00 to 0.364. The expected heterozygosity varied from 0.689 to 0.821. The PIC varied from 0.630 to 0.789. Probability of identity varied from 0.05 to 0.12. The DNA barcode developed is very discriminative. So, it can be used for efficient and unambiguous identification of guava accessions, thereby increasing the accuracy in maintenance of genetic resources. Apart from the DNA fingerprint, interpretation of the results clearly indicated that each accession had a unique allelic combination at the 13 nuclear microsatellite loci, indirectly reflecting the fact that none of accessions were similar.

In the present study genotyping of guava full-sib population with 94 F1 progenies, derived from a two-way pseudo-testcross strategy differing in fruit quality traits such as seed strength (hardness/softness), fruit weight, and TSS, was carried out using simple sequence repeat (SSR) markers and sequence-related amplified polymorphic (SRAP) primer combinations. In the case of SSR's high-throughput genotyping, through a M13-Tailed PCR principle, using a set of 160 SSR primer pairs revealed 64.3% parental polymorphism that generated 321 alleles during the mapping population survey. Twenty percent of parental polymorphism was revealed with SRAPs that generated 126 scorable markers. Two linkage maps were constructed for parents using maternal-specific 143 testcross marker loci and paternal-specific 127 testcross markers along with 60 intercross marker loci. At a minimum logarithm of the odds (LOD) score of 4.0 and a maximum map distance of 40 cM the maternal Kamsari map covered 2551.3 cM with an average marker interval distance of 13.21 cM having a total of 193 framework marker loci being ordered into 11 linkage groups. The paternal Purple Local map covered 2113.0 cM with an average marker interval distance of 12.07 cM having 175 framework marker loci being ordered into 11 linkage groups. The estimated genome coverage was of 87.32% in Kamsari and 83.74% in Purple Local. These genetic maps will play a pivotal role in identification of complex quantitative trait loci (QTLs) related to fruit quality. This is the first report of linkage maps in guava based on the combination of SSR along with SRAP markers.

Bacterial wilt (causal organism-Ralstonia solanacearum) is one of the most important soil-borne diseases of eggplant (Solanum melongena) worldwide. The best way to control it economically is to develop cultivars resistant to this soil-borne pathogen. Resistance gene (R-gene) cloning and sequencing to obtain resistance gene analogs (RGAs) is one of the most recent approaches for obtaining disease resistant cultivars. Three different types of degenerative PCR based primers were used for isolating RGAs from resistant cultivated/wild species through amplification of the target region of nucleotide binding site-leucine rich repeat (NBS-LRR). Genetic diversity was observed in the sequences isolated, and six sequences showing specific conserved motifs were shortlisted as Solanum melongena RGAs (Sm7RGA1, Sm7RGA2, Sm7RGA4, Sm7RGA8 and Sm7RGA10) and Solanum viarum RGA (SvRGA2). The RGAs isolated in this study belong to both toll interleukin-1 receptors (TIR)-NBS-LRR and non-TIR-NBS-LRR type R-genes and show similarity with other plant resistance genes. This study also confirmed the hypothesis that dicots have both TIR and non-TIR resistance genes. The present study on eggplant RGAs will help develop RGA based markers linked to bacterial wilt in eggplant and other plant species. Further, it will provide information and pave the way for elucidation at the molecular level of wild and cultivated species’ mechanism of resistance to bacterial wilt. This is the first report of NBS-LRR class resistance genes/RGA in resistant eggplant and its wild relatives against bacterial wilt (BW).

SummaryA major disease in garden pea (Pisum sativum var. hortense) is powdery mildew caused by Erysiphe pisi. Homozygous recessive alleles of the er1 and er2 genes, and the dominant allele of Er3 have been found to contribute to powdery mildew resistance in pea. Nine parental genotypes used for pea breeding in India were screened using 12 sequence characterised amplified region (SCAR) markers and five simple sequence repeat (SSR) markers. None of the SCAR markers could differentiate between the resistant or susceptible genotypes, although they amplified at the specific loci previously reported. The SSR marker A5 clearly distinguished the homozygous resistant and susceptible parents and three F2 progeny from crosses of ‘Arka Priya’ × 'IP-3’, ‘Arka Pramod’ × ‘IP-3’, and ‘Arka Ajit’ בAzad-Pea’. Chisquare analysis showed a 1:3 phenotypic segregation pattern and a genotypic ratio of 1:2:1 for the SSR marker A5. Since SSR A5 is a co-dominant marker, it distinguished the clear homozygous (Er1Er1/er1er1) and het...

The present study was taken up with a view to ascertain the possibility of introduction of alcohol resistant bacteria in vitro through the aseptically raised watermelon (Citrullus lanatus) seedlings in the backdrop of isolating such organisms from micropropagated watermelon stocks. Watermelon cv. Arka Manik seedlings grown in vitro from surface-sterilized seeds with the intact seed coat on MS medium appeared visibly clean largely, but upon subjecting them to tissue-indexing, the segments from the collar or root tissue showed bacterial colony growth on Nutrient Agar (NA) from 72% of such healthy seedlings and the cotyledon and hypocotyl tissue of 44% seedlings. The pooled colony growth from NA upon challenge with 90% alcohol yielded 10 distinct colony types, identified as B. pumilus (4×), B. subtilis (4×), B. cereus (1×) or B. safensis (1×) based on partial 16S rRNA sequence analysis. The shoot-tip tissue from the healthy index-negative seedlings cultured on watermelon proliferation medium partly turned index-positive within 2 - 4 sub-culture cycles while being apparently clean. On the other hand, those from the previously index-positive cultures tended to show obvious bacterial growth during subsequent in vitro culturing. The observations suggested the possibility of introduction of spore-forming Bacillus spp. through surface-sterilized seeds, their gradual emergence in vitro in visibly clean seedlings, possible transmittal of spores to the alcohol through tissue-culturing tools and the survival therein with the chances of unsuspected lateral spread. Seed coat removal followed by surface sterilization with sodium hypochlorite facilitated the raising of clean seedlings with no detectable bacterial association.

Short Retraction Notice The following article has been retracted due to the investigation of complaints received against it. The Editorial Board found that substantial portions of the text came from other published papers without appropriate attribution to the source. This article has been retracted to straighten the academic record. In making this decision the Editorial Board follows COPE's Retraction Guidelines. The aim is to promote the circulation of scientific research by offering an ideal research publication platform with due consideration of internationally accepted standards on publication ethics. The Editorial Board would like to extend its sincere apologies for any inconvenience this retraction may have caused. Editor guiding this retraction: Prof. Sukumar Saha (EiC of AJPS). Please see the article page for more details. The full retraction notice in PDF is preceding the original paper which is marked "RETRACTED".

The present study was designed to develop an efficient protocol for micro propagation of S. rebaudiana from nodal explants and study the influence of additives on enhancement of shoot proliferation. A two-step protocol has been standardized in which, first step comprising growth hormones concentration is optimized and it was found that MS medium supplemented with 2.0 mg/l BAP + 0.5 mg/l Kin + 0.1 mg/l NAA turned out to be the best treatment for shoot induction. In the second step, the best treatment for shoot induction was fortified with different growth additives for further shoot proliferation. Among the different types of additives used, casein hydrolysate at 0.05% (w/v) was found to be most effective, resulted with maximum of 15.0 shoots. 90% regeneration frequency and shoot length of 6.0 cm were recorded per explant. Thus, the procedure described is a quick and reliable method which could be applied for efficient large scale propagation, genetic transformation assays and secondary metabolite production of Stevia.

Traditionally hybrid purity of F1 hybrids is assessed through grow-out tests, which are time consuming and labor intensive. There is need for a fast and reliable alternative method for hybrid purity testing. The objective of this work was to assess purity of interspecific hybrids of Solanum melongena L. (‘IIHR3’, Arka Keshav (‘AK’), ‘2BMG’) and Solanum macrocarpon L. (‘SM’) using simple sequence repeats (SSR). Genomic DNA from parents and F1 hybrids were subjected to SSR analysis to detect parental polymorphism. Among 119 SSRs screened, 5 SSRs were codominant. There were five unique microsatellite markers, two for ‘IIHR3’ בSM’, emf 01C03 and emh 02E08; one for ‘AK’ בSM’, emi 02 F16; and two for ‘2BMG’ בSM’, emb 01E 03 and emg 11I03, which were useful to detect purity of three interspecific eggplant hybrids. This is the first report demonstrating the utility of SSR markers for assessment of genetic purity of interspecific hybrids in eggplant.

An experiment was conducted in the field of Indian Institute of Hortricultural Research, Hessaraghatta, Bangalore during August 2006 to June 2008. The experiment consisting of eight treatment combinations were laid out in ‘2x4’ factorial RCBD with 5 replications to assess seed set per capsule. The results revealed that highly significant differences were observed for number of well-developed seeds and underdeveloped seeds. Among four cross combinations ‘H.S. 88-10-22 x Shobha’ (27.63 well-developed seeds per capsule) and ‘H.S. 84-7-11 x Shobha’ (27.01 well-developed seeds per capsule) were significantly higher than those of other two cross combinations. The interaction effect of fresh pollen- cum- ‘H.S.88-10-22 x Shobha’ produced significantly higher number of welldeveloped seeds (41.02 per capsule) than those of the other treatment combinations. In contrast, treatment combinations viz., cryopreserved pollen- cum- ‘H.S. 88-10-22 x Shobha’ produced the lowest number of welldeveloped seeds (10.85 per capsule).Inclusion of fresh pollen to genotype ‘Shobha’ and cryopreserved pollen of H.S. 88-10-22' revealed better performances for maximum seed set per capsule. Nepal Journal of Science and Technology Vol. 14, No. 1 (2013) 31-34 DOI: http://dx.doi.org/10.3126/njst.v14i1.8874

SummaryMicrosatellites or simple sequence repeats (SSRs) play an important role in plant genetics and breeding. The development of microsatellites is a time-consuming and expensive process. In silico mining of microsatellites from expressed sequence tags (ESTs), which are available in electronic molecular databases, is a cheaper alternative. In the present study, we used a computational approach for mining SSRs from 20,159 ESTs in Allium cepa. These onion ESTs represented a total length of 13.2 Mb and were downloaded from the dbEST database of the National Center for Biotechnology Information (NCBI) and subjected to various pre-processing steps. The pre-processed ESTs were clustered, resulting in non-redundant unigenes. These unigenes were analysed for their SSR content and distribution. In all, 1,464 SSRs consisting of di-, tri-, tetra-, penta- and hexa-nucleotide repeats were mined from the non-redundant ESTs (contigs and singletons). Tri-nucleotide SSRs were the most abundant, followed by tetra-, di-, ...

The bark-eating caterpillar (Indarbela tetraonis Moore) is one of the two species of insect pests known to infest guava (Psidium guajava). Severe infestation with this pest causes drying up of shoots, which ultimately results in substantial losses in fruit yield and quality. Genetic options are considered most eco-friendly and cost effective to mitigate such losses. DNA marker-assisted breeding of guava for improved resistance to bark-eating caterpillar is expected to increase the efficiency of developing resistant cultivars. As a prelude to this, an investigation was carried out to identify pairs of genotypes contrasting for responses to infestation by bark-eating caterpillar and for a large number of simple sequence repeat (SSR) markers, for use as putative parents to develop mapping populations for chromosomal localization of genomic regions controlling resistance to bark-eating caterpillar in guava. Dendrogram generated by 135 polymorphic SSR markers could separate five morphologically resistant and three morphologically highly susceptible genotypes into two different clusters, barring two exceptions (Bangalore Local and 7–12EC 147036). Four pairs of accessions, viz., Superior Sour Lucidum and Seedless, Portugal and Seedless, Lalit and Seedless, Spear Acid and Seedless, had contrasting response to bark-eating caterpillar and were polymorphic at 111, 103, 101, and 101, SSR loci, respectively. These contrasting pairs of accessions are suggested for use as parents to develop mapping populations to identify DNA markers linked to genomic regions controlling resistance to bark-eating caterpillar, which could help in implementing SSR marker-assisted breeding of guava for resistance to bark-eating caterpillar.

The study was taken up to assess the chances of alcohol and instrument mediated horizontal transmission of bacterial spores and to fix the sterilization needs of tools recurrently used in bacteriological or plant tissue culture work in the backdrop of encountering mixtures in purified microbial cultures and the re-emergence of contaminants in ‘bacteria-sanitized’ plant tissue cultures. The microbial inoculating needle after contaminating the loop portion with Bacillus subtilis or B. pumilus spores was flamed over a sprit-lamp or gas-burner directly for 10–40 s, or after dipping the instrument (10–12 cm) in spore-adulterated 90 % ethanol or rectified spirit (96 %). The loop and rod portions were monitored for any residual inoculum by bringing the loop region in contact with nutrient agar, or swabbing the rod portion with moistened cotton-bud and imprinting on agar medium. Direct flaming of loop region for ≥20 s eliminated the hardy spores therein, whereas alcohol-dip and flaming increased the chances of spore survival on the rod portion that were acquired from the contaminated alcohol. Similar results were observed with the set of forceps used in tissue culturing work after dip in spore-containing ethanol. Alcohol once got adulterated with the hardy spores served as a source of bacterial inoculum causing unsuspected lateral spread of contamination. Direct flaming of inoculating loop nichrome or the forceps-tips, which came in contact with the microbial inoculum, preferably over a gas flame proved satisfactory for instrument sterilization. Alternatively, the use of autoclaved micropipette tips for handling bacterial cultures in the petri-dishes or attaching the tips to a pair of sterilized forceps is suggested for handling the cultures in tubes. Exposing the forceps and scalpel in a glass bead sterilizer set at 260 °C for ≥5 min effectively sterilized the tissue culturing tools.

SummaryPlant micro-RNAs (miRNAs) are conserved and play important roles in abiotic stress responses or in plant responses to pathogen attack. Six miRNAs were identified in Solanum melongena (brinjal, eggplant) using bioinformatic methods from 98,089 EST sequences. Sixty-one potential mRNA targets were identified by homology searches of all six identified miRNAs against the Arabidopsis mRNA dataset using on-line miRU software (http://www.mirbase.org). The newly-identified miRNAs were studied further to compare their level of conservation with respect other family members. Later, the core promoter found in all targeted genes was identified and a highly-conserved GNAA motif with a critical role in the biogenesis of miRNAs was identified. The findings from this study will be useful for further research on the features of miRNAs and their mechanisms of gene regulation in S. melongena.

Guavas (Psidium guajava) are perennial fruit trees cultivated in tropical and subtropical areas of the world. In this study, we have characterized nine guava cultivars using 23 microsatellite markers. The number of alleles ranged from 3 to 12 with a mean of 6.39 alleles per locus. The polymorphic information content of the markers ranged from 0.340 to 0.900 with a mean of 0.749. The expected heterozygosity ranged from 0.392 to 0.961 with a mean of 0.824. The probability of identity ranged from 0.031 to 0.487 with a mean of 0.143. The total probability of identity was 2.73 × 10−22. Additionally, cluster analysis was done using both Wards minimum variance method and Neighbor Joining method. The clustering pattern generated from both the methodologies, distinctly grouped the pink flesh varieties and the white flesh varieties into two groups. Molecular barcodes have been developed for all the cultivars, which will increase the precision for their identification.

Vitamin C (ascorbic acid) is an essential component for collagen biosynthesis and also for the proper functioning of the cardiovascular system in humans. Unlike most of the animals, humans lack the ability to synthesize ascorbic acid on their own due to a mutation in the gene encoding the last enzyme of ascorbate biosynthesis. As a result, vitamin C must be obtained from dietary sources like plants. In this study, we have developed transgenic potato plants (Solanum tuberosum L. cv. Taedong Valley) over- expressing strawberry GalUR gene under the control of CaMV 35S promoter with increased ascorbic acid levels. Integration of the GalUR gene in the plant genome was confirmed by PCR and Southern blotting. Ascorbic acid (AsA) levels in transgenic tubers were determined by high-performance liquid chromatography (HPLC). The over-expression of GalUR resulted in 1.6-2-fold increase in AsA in transgenic potato and the levels of AsA were positively correlated with increased GalUR activity. The transgenic lines with enhanced vitamin C content showed enhanced tolerance to abiotic stresses induced by methyl viologen (MV), NaCl or mannitol as compared to untransformed control plants. The leaf disc senescence assay showed better tolerance in transgenic lines by retaining higher chlorophyll as compared to the untransformed control plants. Present study demonstrated that the over-expression of GalUR gene enhanced the level of AsA in potato tubers and these transgenics performed better under different abiotic stresses as compared to untransformed control.

Transgenic lines of creeping bent grass were generated by Agrobacterium-mediated transformation with the VuNCED1 which was cloned from cow pea has a homology to 9-cis-epoxycarotenoid dioxygenase, which is supposed to be involved in abscisic acid (ABA) biosynthesis. ABA, a cleavage product of carotenoids, is involved in stress responses in plants. The limiting step of ABA biosynthesis in plants is presumably the cleavage of 9-cis-epoxycarotenoids, the first committed step of ABA biosynthesis. Molecular analyses of transgenic lines as performed by Southern hybridization genomic DNA-PCR revealed integration of the VuNCED1. Challenge studies performed with transgenic plants by exposure to salt stress (up to 10 dS m−1) and water stress (up to 75%) for 10 weeks, revealed that more than 50% of the transgenic plants could survive NaCl and drought stress whereas wild-type was not. ABA levels were measured under drought and normal conditions, endogenous ABA was dramatically increased by drought and NaCl stress in transgenic plants. These results indicate that it is possible to manipulate ABA levels in plants by over expressing the key regulatory gene in ABA biosynthesis and that stress tolerance can be improved by increasing ABA levels.

A new selection system for onion transformation that does not require the use of antibiotics or herbicides was developed. The selection system used the Escherichia coli gene that encodes phosphomannose isomerase (pmi). Transgenic plants carrying the manA gene that codes for pmi can detoxify mannose-6-phosphate by conversion to fructose-6-phosphate, an intermediate of glycolysis, via the pmi activity. Six-week-old embryogenic callus initiated from seedling radicle was used for transformation. Transgenic plants were produced efficiently with transformation rates of 27 and 23% using Agrobacterium and biolistic system, respectively. Untransformed shoots were eliminated by a stepwise increase from 10 g l(-1) sucrose with 10 g l(-1) mannose in the first selection to only 10 g l(-1) mannose in the second selection. Integrative transformation was confirmed by PCR, RT-PCR and Southern hybridization.

MADS-box genes encode a family of transcription factors, which control developmental processes in flowering plants ranging from flower to root development. During the last few years increasing evidence point to more general roles of these factors not only in the control of flowering time, but also in other reproductive processes. However, they are also expressed in roots, stems and leaves. These results suggest that their function may be much more diverse than those involved in flowering, and the possibility of uncovering new roles for MADS-box genes in plant development. Here, we specifically explore the role of the STMADS subfamily in development of vegetative structures. This subfamily continues to grow, providing new insight into the vegetative development of other plant species and how it is distinct from the one in Arabidopsis is investigated.

A new MADS-box gene, IbMADS4, had been cloned in Ipomoea batatas (L.) Lam. that is expressed in all vegetative tissues of the plant, mainly in the root tissues, but not in flower organs. Sequence similarity besides the spatial and temporal expression patterns allows defining a novel MADS-box subfamily comprising STMADS16 and the other MADS-box genes expressed specifically in vegetative tissues. Expression of the IbMADS4 sense cDNA under the control of the 35S cauliflower mosaic virus promoter modifies dramatic changes in the phenotype, such as axillary shoot formation in chrysanthemum. Leaf and axillary shoot number of sense transgenic plants showed a three- and four-fold increase in shoot regeneration compared with the wild-type, respectively. The results presented here are aimed at understanding the molecular mechanisms involved in shoot morphogenesis.

Different types of ventilation of the culture vessel with and without the ethylene inhibitor KMnO 4 in the culture media were investigated in terms of their effect on hyperhydricity of in vitro cultured potato shoots. The shoots grown in a completely sealed vessel (CSV) were severely vitrified, but the shoots cultured in a gas permeable vessel (GPV) showed normal shoot proliferation. Dry weight percentage and chlorophyll content were lower in the vitrified shoots than in the normal shoots. The levels of ethylene and CO 2 were significantly higher in the CSV, but little ethylene was detected in the GPV system. When an ethylene scrubber (perlite treated with KMnO 4 ) was applied to the CSV, the shoots exhibited normal growth without any sign of vitrification. In addition, no ethylene was found in CSV with the ethylene scrubber (CSVE). These results indicate that hyperhydricity is related to the ethylene accumulated in the culture vessel during the in vitro culture of potato shoots. It is suggested to use CSVE to reduce the ethylene level and overcome hyperhydricity.

The basic factor underlying the success of the tissue culture, large-scale micropropagation and genetic transformation of any plant species is regeneration. This has been achieved over the years through the use of various-sized explants ranging from protoplasts (small scale) to entire organs (large scale). Inherent problems underlie the use of either extreme, leading to both nonspecific morphogenic reactions in the latter, or to undesired necrosis in the former. This review investigates the importance of different aspects of a thin cell layer (TCL) explant, from its source to its size. TCLs, as a results of their size and origin, in combination with other controllable factors such as media and environmental conditions, have shown this system to be superior to the use of conventional explants. Numerous species that were previously unsuccessfully tissue-cultured have, with the use of TCL technology, resulted in their successful micropropagation and regeneration. These successes, based on the inherent qualities of the TCL explant—specific for a given species—are also examined.

French bean ( Phaseolus vulgaris L.) 2n=14 is an important legume vegetable grown for its tender green pods which are rich in proteins, minerals and dietary fibre. Though it is a short duration crop, it is prone to several biotic and abiotic stresses. Among the biotic stresses, rust caused by Uromyces phaseoli (Reben Wint) has become epidemic in bean growing areas and the yield loss to the tune of 80% is reported. Rust fungi have wide variability in pathogenicity and also demonstrate frequent sexual recombination and more than 150 physiological races of the pathogen are reported. Hence, the induction of genetic resistance is always preferred because it is least expensive and has no adverse environmental effects. Inheritance of rust resistance was studied in F 2 generation by using molecular markers. Resistance was confirmed in parent genotype IC525236 by using SK 14. In IC525236 resistance to rust is controlled by single dominant gene.

Lilies are one of the most valuable bulbous ornamental cut flower crops and are commercially propagated by conventional scaling, which results in varied bulb quality. This article demonstrates the effectiveness of using specific organ sources in conjunction with the thin cell layer (TCL) system to establish successful organogenic and somatic embryogenic pathways in Lilium longiflorum. TCLs derived from different explant sources, such as receptacle, leaf, young stem, stem node, bulblets, pseudo-bulblets, shoot and somatic embryos, respectively, can be manipulated to form different organs. Furthermore, the choice of plant growth regulator and medium additives such as activated charcoal and sucrose strongly affect the success of the process. This article further highlights that transient transgene expression derived from either particle bombardment or Agro-infection is both strong and repeatable, as a result of the direct exposure of competent cells to the gene introduction method, resulting in a reduction of escapes. The ability to manipulate and control organogenesis through a TCL system, coupled with repeatable, efficient transformation opens up the possibility of micropropagating members of this genus with new and available characteristics, producing superior plants of high quality.

Micropropagation of Phalaenopsis through flower stalk culture was investigated. Bracts of flower stalks were removed before or after sterilization. Decontamination rate of nodal sections was higher when they were sterilized with bract. Subsequent growth of lateral buds was affected by the timing of bract removal. Much lateral bud developed flower stalk secondary when bracts were removed after sterilization, but much of them developed vegetative shoots when bract was removed before sterilization. Propagation from a plantlet was investigated using in vitro clone plantlets. Base part of a plantlet, 1.5 cm was cut into 2.5 mm or 5 mm slice segments, and they were cultured on NP medium with or without coconut water (CW) and/or 6-benzylaminopurine (BA). Regeneration of shoot(s) and callus like body (CLB) was dominant in the slice segments derived from 5-10 mm part from the base of the shoot and was promoted by addition of CW and/or BA.

Potato microtubers produced in vitro of the cultivar ‘Superior’ were assessed to decide up to what size it can be used for the seed potato with respect to storability, dormancy period, and sprouting vigor. The larger microtubers lost moisture content more slowly and retained firmness longer when stored at 4 °C. In the sprouting test, the larger ones had less period of dormancy and showed more vigorous sprouting ability. The starch increased with increasing size of the microtuber and showed the distribution of about 70–80% of dry matter content. The amounts of sugars were positively co-related with the size of the potato. The internal factors such as dry matter and carbohydrate content reveal that potato microtuber follows the field-grown potatoes in all aspects. The results suggest that the size of microtubers can be used as an index for grading their quality as seed potatoes, and the size of the microtuber should be at least 0.5 g to be used as seed potato.

To gain a better understanding of the cellular factors that are involved in the competence of cells for regeneration and transformation, research should be carried out in a well-defined tissue culture system. Important prerequisites of such a system are that the morphogenic response can be directed very precisely and that the explants are accessible for microscopic examination. The thin cell layer (TCL) system as originally developed by Tran Thanh Van for tobacco (Tran Thanh Van et al 1974) has such properties. The advantages of TCLs for the study of transformation have already been outlined by Tran Thanh Van et al (1990).

Plant differentiation, including morphogenesis, growth, development and plant senescence result from a complex interaction between different cells, tissues and organs. Analysis at the molecular level of the mechanism of differentiation is still difficult due to the lack of knowledge on i) the nature of the morphogenic signal, ii) the perception and transduction mechanisms and iii) the localization of target and responsive cells. In order to answer the question of how plant cells sense and process signals for differentiation, our strategy is to select for signals that induce a specific response in defined target cells that are also the responsive cells. In thin cell layer (TCL) systems, the responsive cells are well defined and are not scattered as observed in heterogenous organisms, organs or callus. Chemical signals such as kinetin, zeatin and oligosaccharides induce specific differentiation patterns, which is referred to as the specific program of differentiation.

As the world population continues to show an explosive increase, so the demand for crops and vegetables increases. To satisfy this demand, increased productivity comes about through advanced plant breeding and selection techniques. Modern plant breeding addresses this demand by production of desired end products (cultivar, variety or hybrid) with desired/useful characteristics or traits, which may be controlled by one or a few genes (qualitative traits) or may be under the control of many interacting genes with small individual effects (quantitative traits). To better allow the breeder to reliably select for genes controlling desirable traits, genetic markers can be used to create linkage or plant genome maps.

Fresh pollen of 16 promising genotypes of gladiolus was tested for their pollen viability. Modified cellophane method was employed to assess the pollen viability. Pollen germination media consisted of 15% sucrose supplemented with 300 ppm calcium nitrate, 200 ppm magnesium sulphate, 100 ppm potassium nitrate and 100 ppm boric acid. Highly significant variations were observed for percentage of pollen germination, non-germinated pollen and sterile pollen. The highest pollen germination (76.41%) was in genotype Hybrid selection 88-10-22, and did not differ significantly from Gladiolus callianthus (75.41%), Sapna (75.10 %), Hybrid selection 86-32-11, (73.28 %), Kum Kum (69.41%), Poonam (69.22 %), Hybrid selection 87-22-1 (67.87 %), Hybrid selection 87-1-1 (67.61 %), Psittacinus hybrid (64.64%) and Darshan (63.97%). The lowest non- germinated pollen (10.47%) was in genotype Gladiolus callianthus, and insignificantly followed by Hybrid selection 88-10-22 with 18.77 % and Hybrid selection 87-22-1 with 18.95 %. The lowest percentage of sterile pollen was noticed in genotype Sapna (2.82%) followed by Poonam with 4.00 % Hybrid selection 88-10-22 with 4.82% and Hybrid selection 82-11-27 with 5.22%. Key words: Gladiolus; germination; pollen DOI: 10.3126/njst.v11i0.4089Nepal Journal of Science and Technology 11 (2010) 47-50