Transformation of <Emphasis Type="Italic">Campanula</Emphasis> by wild type <Emphasis Type="Italic">Agrobacterium rhizogenes</Emphasis>

Compact growth is an important quality criterion in horticulture. Many Campanula species and cultivars exhibit elongated growth which is suppressed by chemical retardation and cultural practice during production to accommodate to the consumer’s desire. The production of compact plants via transformation with wild type Agrobacterium rhizogenes is an approach with great potential to produce plants that are non-GMO. Efficient transformation and regeneration procedures vary widely among both plant genera and species. Here we present a transformation protocol for Campanula. Hairy roots were produced on 26–90% of the petioles that were used for transformation of C. portenschlagiana (Cp), a C. takesimana × C. punctata hybrid (Chybr) and C. glomerata (Cg). Isolated hairy roots grew autonomously and vigorously without added hormones. The Cg hairy roots produced chlorophyll and generated plantlets in response to treatments with cytokinin (42 µM 2iP) and auxin (0.67 µM NAA). In contrast, regeneration attempts of transformed Cp and Chybr roots lead neither to the production of chlorophyll nor to the regeneration of shoots. Agropine A. rhizogenes strains integrate split T-DNA in T_L- and T_R-DNA fragments into the plant genome. In this study, regenerated plants of Cg did not contain T_R-DNA, indicating that a selective pressure against this T-DNA fragment may exist in Campanula.     

High frequency shoot proliferation from cotyledonary node of <Emphasis Type="Italic">Lawsonia inermis</Emphasis> L. and validation of their molecular finger printing

An efficient and reproducible protocol for in vitro plant regeneration was developed for Lawsonia inermis L. using cotyledonary node explant derived from axenic seedlings. Highest shoot proliferation frequency (ca 96.6%) was achieved on Murashige and Skoog’s, 1962 (MS) basal medium supplemented with 8.88 μM 6-Benzyladenine (BA) + 2.68 μM Napthalene acetic acid (NAA). Up-scaling of shoots was carried out using in vitro nodes on MS medium supplemented with 4.44 μM BA. So overall, an average of 238 shoots was produced at 75 days. Of the four different forms of cotyledonary node explants evaluated, highest shoot multiplication was observed in cotyledonary node explant with two whole cotyledons. In vitro regenerated shoots were best rooted (ca 34.3 roots / shoot) on ½ MS medium devoid of any growth regulator. The plantlets were successfully acclimated in sand:soil:: 1:1and established in the garden soil. Random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) analysis revealed a homogeneous amplification profile for all micropropagated plants validating the genetic fidelity of the in vitro-regenerated plants and supporting the regeneration protocol for economic commercial exploitation.     

<Emphasis Type="Italic">In vitro</Emphasis> plant regeneration,flowering and fruiting from nodal explants of <Emphasis Type="Italic">Andrographis lineata</Emphasis> nees (Acanthaceae)

In the present study, in vitro propagation of tribal endemic medicinal plant, Andrographis lineata has been established using mature nodal explants. High frequency of regeneration (91.4%) was achieved on MS medium containing BA (3.0 mg L^–1) along with IAA (0.2 mg L^–1). Strikingly, irrespective of the season and collection period, we observed axillary flower induction and fruit formation from the above in vitro cultures supplemented with BA and NAA. Transition from the vegetative to the reproductive phase occurred within 2 months of culture, and importantly was influenced by factors such as sucrose and cytokinins. In vitro-regenerated flowers were morphologically identical to in vivo flowers. Furthermore, our scanning electron microscopic studies revealed that pollen external morphology of both in vitro and in vivo flowers were similar. The flowers self-fertilized and produced fruits in vitro. Elongated shoots rooted well on half-strength MS basal medium, and were successfully acclimatized to the garden conditions. Altogether, our established protocol can be utilized in plant breeding for the purpose of ex situ conservation, quick flowering, and fruit set.     

Resistance to <Emphasis Type="Italic">Cucumber green mottle mosaic virus</Emphasis> in <Emphasis Type="Italic">Cucumis sativus</Emphasis>

Cucumber green mottle mosaic virus (CGMMV) is a severe threat for cucumber production worldwide. At present, there are no cultivars available in the market which show an effective resistance or tolerance to CGMMV infection, only wild Cucumis species were reported as resistant. Germplasm accessions of Cucumis sativus, as well as C. anguria and C. metuliferus, were mechanically infected with the European and Asian strains of CGMMV and screened for resistance, by scoring symptom severity, and conventional RT-PCR. The viral loads of both CGMMV strains were determined in a selected number of genotypes using quantitative RT-PCR. Severe symptoms were found following inoculation in C. metuliferus and in 44 C. sativus accessions, including C. sativus var. hardwickii. Ten C. sativus accessions, including C. sativus var. sikkimensis, showed intermediate symptoms and only 2 C. sativus accessions showed mild symptoms. C. anguria was resistant to both strains of CGMMV because no symptoms were expressed and the virus was not detected in systemic leaves. High amounts of virus were found in plants showing severe symptoms, whereas low viral amounts found in those with mild symptoms. In addition, the viral amounts detected in plants which showed intermediate symptoms at 23 and 33 dpi, were significantly higher in plants inoculated with the Asian CGMMV strain than those with the European strain. This difference was statistically significant. Also, the amounts of virus detected over time in plants did not change significantly. Finally, the two newly identified partially resistant C. sativus accessions may well be candidates for breeding programs and reduce the losses produced by CGMMV with resistant commercial cultivars.     

Micropropagation of <Emphasis Type="Italic">Kaempferia angustifolia</Emphasis> Roscoe - An Aromatic,Essential Oil Yielding,Underutilized Medicinal Plant of Zingiberaceae Family

Kaempferia angustifolia is an aromatic, essential oil-yielding plant of the Zingiberaceae family with an ethno-medicinal repute. We standardized an effective system for micropropagation of K. angustifolia, and this is probably the very first report of in vitro culture of this species. Axillary buds were cultured on a Murashige and Skoog (MS) medium supplemented with various concentrations and combinations of plant growth regulators (PGRs) and spermidine. Highest multiplication occurred when the MS medium was supplemented with a combination of 2.0 mg L^?1 6-benzylaminopurine (BAP), 2.0 mg L^?1 kinetin (KIN) and 1.0 mg L^?1 α-naphthalene acetic acid (NAA). Addition of spermidine (2.0 mM) along with optimum PGRs had further improved the multiplication rate with a maximum of 6.6 ± 0.36 shoots per explant within 60 days of implantation. The number of multiplied shoots per explant increased with each subsequent regeneration cycle; and the shoots per explant increased from 6.6 ± 0.36 on the 1^st regeneration cycle to 10.3 ± 0.42 on the 2^nd regeneration cycle and further increased to 13.7 ± 0.37 on the 3^rd regeneration cycle on the same medium composition. The best result for in vitro root induction of multiplied shoot was achieved on a half-strength MS medium fortified with 2.0 mg L^?1 IBA, with a maximum of 18.5 ± 0.28 roots per shoot. Regenerated plantlets were acclimatized with 88.9 % survival rate. After 9 months of field-transfer, all these plants were harvested and rhizomes were collected. However, the present protocol can definitely be applied for large-scale propagation and commercial cultivation of K. angustifolia.     

Direct shoot organogenesis from rhizomes of medicinal zingiber <Emphasis Type="Italic">Alpinia calcarata</Emphasis> Rosc. and evaluation of genetic stability by RAPD and ISSR markers

A simple and efficient protocol for direct in vitro shoot multiplication and plant regeneration was established for an important aromatic medicinal plant, Alpinia calcarata. Preinduction of rhizome segments in medium containing 8.8 μM 6-benzylamino purine (BAP) rescued the buds from dormancy in 60% of the cultures. An average of 6.2 shoots were produced from rhizomatous bud explants on Murashige and Skoog (MS) medium supplemented with 5 μM BAP, 10 μM kinetin, and 2.5 μM α-Naphthalene acetic acid (NAA). The mother cultures retained their morphogenetic potential upto four subcultures and a maximum of 1.77-fold increase in shoot multiplication was recorded after the 3^rd subculture. Rooting was simultaneously induced during subculture on shoot multiplication medium eliminating an additional step for rooting induction. Rooted plantlets were successfully acclimatized in pots in the greenhouse and subsequently established in the experimental garden without any visible symptoms of wilting and necrosis. The genetic fidelity of regenerated plants was evaluated by adapting to two PCR-based DNA marker techniques, Random Amplified Polymorphic DNA (RAPD) and Inter Simple Sequence Repeats (ISSR) which detected no variability in the in vitro multiplied plantlets of A. calcarata. This efficient method of clonal multiplication may be useful for commercial scale multiplication, and in situ and ex situ conservation of elite germplasm of A. calcarata.     

Resistance screening of breeding lines and commercial tomato cultivars for <Emphasis Type="Italic">Meloidogyne incognita</Emphasis> and <Emphasis Type="Italic">M. javanica</Emphasis> populations (Nematoda) from Ethiopia

Soil and root samples were collected from major tomato growing areas of Ethiopia during the 2012/2013 growing season to identify root-knot nematode problems. DNA-based and isozyme techniques revealed that Meloidogyne incognita and M. javanica were the predominant Meloidogyne species across the sampled areas. The aggressiveness of different populations of these species was assessed on tomato cultivars Marmande and Moneymaker. The two most aggressive populations of each species were selected and further tested on 33 tomato genotypes. The resistance screening and mechanism of resistance was performed after inoculation with 100 freshly hatched (<24 h) second-stage juveniles (J2). Eight weeks after inoculation the number of egg masses produced on each cultivar was assessed. For the resistance mechanism study, J2 penetration and their subsequent development inside the tomato roots were examined at 1, 2, 4 and 6 weeks after inoculation. On both cultivars Marmande and Moneymaker all M. incognita and M. javanica populations formed a high number of egg masses indicating highly aggressive behaviour. Populations from ‘Jittu’ and ‘Babile’ for M. incognita and ‘Jittu’ and ‘Koka’ for M. javanica were selected as most aggressive. None of the 33 tomato genotypes were immune for these M. incognita and M. javanica populations. However, several tomato genotypes were found to have a significant effect on the number of egg masses produced indicating possible resistance. For M. javanica populations there were more plants from cultivars or breeding lines on which no egg masses were found compared to M. incognita populations. The lowest number of egg masses for both populations of M. incognita was produced on cultivars Bridget40, Galilea, and Irma while for M. javanica it was on Assila, Eden, Galilea, Tisey, CLN-2366A, CLN-2366B and CLN-2366C. Tomato genotypes, time (weeks after inoculation) and their interaction were significant sources of variation for J2 penetration and their subsequent development inside the tomato roots. Differential penetration was found in breeding lines such as CLN-2366A, CLN-2366B and CLN-2366C, but many of the selected tomato genotypes resistance for the tested M. incognita and M. javanica populations were expressed by delayed nematode development. Therefore, developing a simple screening technique to be used by local farmers or extension workers is crucial to facilitate selection of a suitable cultivar.     

Induced expression of selected plant defence related genes in pot azalea, <Emphasis Type="Italic">Rhododendron simsii</Emphasis> hybrid

A set of putative marker genes to study plant defense responses against Polyphagotarsonemus latus, a key pest in the production of Rhododendron simsii hybrids, was selected and validated. Genes belonged to the biosynthetic pathway of phytohormones jasmonic acid (JA) (RsLOX, RsAOS, RsAOC, RsOPR3 and RsJMT) and salicylic acid (SA) (RsPAL and RsICS). Furthermore, RsPPO, a putative marker gene for oxidative stress response was successfully cloned from R. simsii. A CTAB-based extraction protocol was optimized to assure excellent RNA quality for subsequent RT-qPCR analysis. The RT-qPCR protocol was extensively tested and RsRG7 and RsRG14 were selected as reference genes from a geNorm pilot study. Validation of the marker genes was done after application with elicitors [methyl jasmonate (MeJA), coronatine, β-aminobutyric acid and acibenzolar-Smethyl] or wounding. Both 100 μM MeJA and 0.1 μM coronatine had a significant effect on the expression of all marker genes. Foliar application of MeJA on the shoots resulted in a significantly earlier response when compared to root application and subsequent sampling of the shoots. Expression patterns after MeJA treatment were generally the same in six R. simsii genotypes: ‘Nordlicht’, ‘Elien’, ‘Aiko Pink’, ‘Michelle Marie’, ‘Mevrouw Gerard Kint’ and ‘Sachsenstern’. Wounding resulted in the same expression patterns as MeJA treatment except for RsJMT. None of the genotypes showed a significant induction of the latter gene 6 h upon wounding. Findings of these experiments indicated that the tolerant genotype ‘Elien’ has low basal expression levels of RsPPO. This might be the first step towards the breeding of mite-tolerant genotypes.     

Tissue culture and <Emphasis Type="Italic">Agrobacterium</Emphasis>-mediated genetic transformation studies in four commercially important indica rice cultivars

This research was undertaken to find an efficient tissue culture system and Agrobacterium-mediated genetic transformation method for recalcitrant indica rice cultivars. For this, mature seeds of commercially important indica rice varieties, ASD16, ADT43, IR 64, and Pusa Basmati were cultured on MS and N6 medium supplemented with 2 mg l^-1 2, 4-D + 30 g l^-1 sucrose. The calli grown in N6 medium showed better friability and embryogenic response. Out of the four varieties tested, ASD16 and IR64 showed better callusing and embryogenic capacity as compared to ADT43 and Pusa Basmati. For genetic transformation studies, embryogenic calli of all the cultivars were co-cultivated with the Agrobacterium tumefaciens strain LBA 4404 harboring the binary vector pCambia 1305.1 with GUS gene. GUS assay was performed for the putative transformed calli and its activity was found to be qualitatively higher in ASD16 and IR64 than the other two varieties. The best responsive ASD16 transformed calli was regenerated and the putative transgenic lines were regenerated. ASD16 transformed calli were confirmed by GUS assay. PCR analysis confirmed the presence of both GUS and HPT genes in ASD16 transgenic lines.     

The drivers and methodologies for exploiting wild <Emphasis Type="Italic">Cajanus</Emphasis> genome in pigeonpea breeding

With the exception of Cajanus cajan (L.) Millspaugh (pigeonpea), the remaining species of genus Cajanus have not been domesticated. For millennia these taxa have persisted in natural habitats through self-sown seeds. These wild species are an asset for sustaining future pigeonpea breeding programmes since they contain certain traits (genes) that are necessary for encountering various breeding challenges related to crop improvement and adaptation. In this review we identify the key traits from wild Cajanus species, and discuss various physical and genetic constraints encountered in their utilization in introgression breeding. Some noteworthy achievements recorded from inter-specific breeding programmes in pigeonpea are also discussed. These include the development of (1) high protein (>?28%) genotypes (2) cytoplasmic nuclear male sterility systems (3) highly (>?95%) self-pollinating genotypes, and (4) resistance sources to sterility mosaic disease, nematodes, salinity, photo-insensitivity, pod borers, podfly, bruchids, and Phytophthora blight. To help pigeonpea breeders engaged in inter-specific breeding programmes, we suggest the division of the secondary gene pool germplasm into two sub-group/tiers on the basis of ease in hybridization.     

Complementary DNA (cDNA) cloning and functional verification of resistance to head smut disease (<Emphasis Type="Italic">Sphacelotheca reiliana</Emphasis>) of an NBS–LRR gene <Emphasis Type="Italic">ZmNL</Emphasis> in maize (<Emphasis Type="Italic">Zea mays</Emphasis>)

The nucleotide-binding site (NBS)-leucine-rich repeat (LRR) gene family comprises the largest number of known disease resistance (R) genes and is one of the largest gene families in plants. In the present study, the full-length cDNA of ZmNL (GenBank Accession Number KF765443) was isolated using Rapid Amplification of cDNA Ends. The nucleotide sequence of ZmNL contains an open reading frame of 3156 bp that encodes the ZmNL protein, which is comprised of 1051 amino acid residues. This putative protein has high homology to other known resistance proteins (84% to Triticum aestivum LR10) and belongs to the CC–NBS–LRR type R gene family. The ZmNL gene was introduced into the maize inbred line of Huangzao4 which was highly susceptible to head smut under the control of the maize ubiquitin promoter by Agrobacterium-mediated transformation. The head smut disease incidence of 3 T₂ transgenic lines was significantly reduced (by 18.38–29.40%) compared with the wild type, which indicated that the overexpression of ZmNL gene in maize enhanced the resistance to the fungus Sporisorium reilianum (Kühn) Clint of these plants.     

Effects of introgressions from <Emphasis Type="Italic">Festuca pratensis</Emphasis> on winter hardiness of <Emphasis Type="Italic">Lolium perenne</Emphasis>

Previous studies reported that some genotypes with introgressed Festuca chromosome segment(s) in Lolium genome showed enhanced winter hardiness compared to Lolium. The aim of this study was to search comprehensively for the Festuca pratensis chromosome regions affecting winter hardiness-related traits when introgressed into the Lolium perenne genome. Association between F. pratensis introgression and winter hardiness-related traits (fall and winter hardiness indexes, early-spring dry matter yield, and freezing tolerance) were screened in the diploid introgression populations (n = 203) that had some F. pratensis chromosome segments introgressed. Eighty-four intron markers corresponding to unique rice genes randomly distributed across the genome were used for genotyping. Winter hardiness of almost all plants in the introgression populations was lower than that of the F. pratensis and triploid hybrid parents, but the average was higher than that of L. perenne. A significant positive effect of F. pratensis introgression on early-spring dry matter yield was detected on chromosome 7. This quantitative trait locus (QTL) was confirmed by linkage analysis using a backcross population with F. pratensis introgression in the target region of chromosome 7. However, the contribution of the newly identified QTL was rather small (6.7–9.6%), suggesting that superior winter hardiness of F. pratensis compared to L. perenne is conferred by multiple small-effect QTLs. We also detected a previously unreported negative effect of Festuca introgression on winter hardiness. Newly obtained QTL information in this study would contribute to the design of Festuca/Lolium hybrid breeding.     

Resistance to the cabbage root fly, <Emphasis Type="Italic">Delia radicum</Emphasis> (Diptera,Anthomyiidae), of turnip varieties (<Emphasis Type="Italic">Brassica rapa</Emphasis> subsp. <Emphasis Type="Italic">rapa</Emphasis>)

The cabbage root fly Delia radicum L. (Diptera: Anthomyiidae) is one of the major pests of many Brassica crops in the temperate areas of Europe and North America. At present, turnip (B. rapa ssp. rapa L.) varieties resistant to the pest does not exist. With the aim to fill this gap, a no-choice tolerance test of 56 accessions among turnips, turnip tops and turnip greens was performed under controlled conditions by introducing D. radicum eggs. Plant survival, leaf and root conditions, pupae number and weight significantly varied among plant accessions. Ten putatively resistant and ten susceptible accessions (control group) were selected from this first screening, transplanted in the field and exposed to natural infestation to detect antibiosis and antixenosis mechanisms. Both in the laboratory and in the field, pupae number significantly varied within accessions and between resistant and susceptible group, although pupal weight did not, indicating the absence of antibiosis effect on this early stage. In the field, the number of galleries was significantly lower in the resistant group in comparison with the control. Resistant accessions had smaller size, and a smaller, white and mostly buried root. Within the resistant and susceptible accessions, larger plants harboured more pupae, however purple roots were those most preferred, and the hosted pupae weighed most. Three accessions from the resistant group (MBGBR0178, MBGBR0570 and MBGBR0371) stand out for resistance to D. radicum possibly through antixenosis mechanisms.     

Screening <Emphasis Type="Italic">A. ventricosa</Emphasis> populations for 2n gametes

Sexual polyploidization via the formation of 2n gametes has been acknowledged as the most significant evolutionary mode of polyploidization among plant species. The present study was conducted in order to determine whether 2n gametes are present in the C-genome diploid Avena ventricosa Bal. ex Coss., a species that contributed to the evolution of the cultivated hexaploid species (Avena sativa L). Individual plants belonging to four different Cypriot populations, were screened for pollen grain size variation with the aim to distinguish 2n gametes. Avena ventricosa ARI00-845 was identified to produce large pollen grains at a low percentage (1.21%). Subsequent analysis using flow cytometry confirmed the presence of 2n gametes in the pollen. Cytogenetic analyses of pollen mother cells revealed cells with twice the typical chromosome number at metaphase I (i.e., 28 chromosomes). We postulate that irregularities in cell wall formation preceding meiosis could have contributed to the mode of chromosome doubling.     

Development and application of a molecular marker for TMV resistance based on <Emphasis Type="Italic">N</Emphasis> gene in tobacco (<Emphasis Type="Italic">Nicotiana tabacum</Emphasis>)

Tobacco mosaic virus (TMV) caused serious loss in yield and quality of tobacco every year. It is a long-term goal to improve the tobacco resistance against TMV by tobacco breeding. N gene was the firstly reported TMV-resistant gene, which showed resistance against all Tobamoviruses except the Ob stain and belonged to the toll-interleukin-1 receptor/nucleotide-binding site/leucine-rich repeat class of plant resistance (R) genes. At present, N gene had already been widely used in tobacco conventional breeding, but there is rare available molecular maker used in marker-assisted selection of TMV resistance. In this study, we designed a pair of primers that specific amplify N gene fragment based on the sequence of N gene intron III, named N-marker. Then, we identified TMV resistance by two selecting methods, PCR with N-marker and inoculated with the TMV-C strain. Results from the two method showed that (1) 13 varieties among 67 tobacco varieties displayed hypersensitive reaction when inoculated with the TMV-C strain, also contained N gene fragments screened by PCR with N-marker; (2) 105 strains of 200 BC1 strains showed resistance against TMV when inoculated with TMV-C strain, meanwhile, 103 of the 105 strains contained N gene fragment verified by PCR with N-marker. Therefore, the N-marker is reliable for high throughput screening of germplasm resources and tobacco breeding materials in selection of N-mediated TMV resistance. Our study not only developed a molecular marker for tobacco breeding, but also identified new germplasm resources that are resistant to TMV.     

Sources of resistance to <Emphasis Type="Italic">Phytophthora</Emphasis> root rot within the genus <Emphasis Type="Italic">Beta</Emphasis>

Phytophthora root rot caused by Phytophthora drechsleri Tucker is one of the most devastating sugar beet diseases in tropical areas. To identify genetic resources resistant to this disease, an aggressive isolate of P. drechsleri was selected. Then, a screening method was optimized based on the standard scoring scales of 1–9 (1: no symptoms, 9: complete plant death). Finally, 19 sugar beet lines, three cultivars, and 14 accessions of the wild species Beta vulgaris subsp. maritima, B. macrocarpa, B. procumbens, and B. webbiana were evaluated for resistance to the most aggressive isolate of P. drechsleri by using the optimized method (inoculum included 20 g of rice seed together with superficial wound creation). The isolates of P. drechsleri had significant variation in aggressiveness, and Kv10 was the most aggressive isolate on the susceptible variety Rasoul. The lines O.T.201-15, SP85303-0 (resistant check), and S2-24.P.107 had the lowest disease index with scores of 3.09, 3.13, and 3.27 respectively; they were categorized into the resistant group. The interaction between isolates and genotypes was not significant, which indicated the same response of each genotype to different isolates. Investigating the resistance of different generations of sugar beet revealed that progeny selection would be an effective method for increasing the resistance level of breeding materials to P. drechsleri. Among the wild species, the accession 9402 belonging to B. macrocarpa and the accession 7234 of B. vulgaris subsp. maritima had the lowest disease index (2.29 and 2.60, respectively) and were categorized into the resistant group.     

Phenotypic variation in root architecture traits and their relationship with eco-geographical and agronomic features in a core collection of tetraploid wheat landraces (<Emphasis Type="Italic">Triticum turgidum</Emphasis> L.)

To obtain varieties with root systems adapted to marginal environments it is necessary to search for new genotypes in genetically diverse materials, such as landraces that are more likely to carry novel alleles for different root features. A core collection of ‘durum’ wheat, including three subspecies (dicoccon, turgidum and durum) from contrasting eco-geographical zones, was evaluated for root traits and shoot weight at the seminal root stage. Distinctive rooting phenotypes were characterized within each subspecies, mainly in subsp. durum. Contrasting rooting types, including large roots with shallow distributions, and others with high root numbers were identified. Correlations with climatic traits showed that root shape is more relevant in adaptation to eco-geographical zones in subsp. dicoccon, whereas in subsp. turgidum and durum, which come from warmer and drier areas, both size and shape of roots could have adaptive roles. Root traits with the largest positive effects on certain yield components under limited water conditions included root diameter in subsp. dicoccon, root size in turgidum, and root number in durum. Additionally, shoot weight at the seedling stage had important effects in subsp. turgidum and durum. Twenty-eight marker–trait associations (MTAs) previously identified in this collection for agronomic or quality traits were associated with seminal root traits. Some markers were associated with only one root trait, but others were associated with up to six traits. These MTAs and the genetic variability characterized for root traits in this collection can be exploited in further work to improve drought tolerance and resource capture in wheat.     

Identification and validation of root length QTLs for water stress resistance in hexaploid wheat (<Emphasis Type="Italic">Titicum aestivum</Emphasis> L.)

Thorough understanding of the genetic mechanisms governing drought adaptive traits can facilitate drought resistance improvement. This study was conducted to identify chromosome regions harbouring QTLs contributing for water stress resistance in wheat. A RIL mapping population derived from a cross between W7984 (Synthetic) and Opata 85 was phenotyped for root length and root dry weight under water stress and non-stress growing conditions. ANOVA showed highly significant (p ≤ 0.01) variation among the RILs for both traits. Root length and root dry weight showed positive and significant (p ≤ 0.01) phenotypic correlation. Broad sense heritability was 86% for root length under stress and 65% for root dry weight under non-stress conditions. A total of eight root length and five root dry weight QTLs were identified under both water conditions. Root length QTLs Qrln.uwa.1BL, Qrln.uwa.2DS, Qrln.uwa.5AL and Qrln.uwa.6AL combined explained 43% of phenotypic variation under non-stress condition. Opata was the source of favourable alleles for root length QTLs under non-stress condition except for Qrln.uwa.6AL. Four stress specific root length QTLs, Qrls.uwa.1AS, Qrls.uwa.3AL, Qrls.uwa.7BL.1 and Qrls.uwa.7BL.2 jointly explained 47% of phenotypic variation. Synthetic wheat contributed favourable alleles for Qrls.uwa.1AS and Qrls.uwa.3AL. Two stable root dry weight QTLs on chromosomes 4AL and 5AL were consistently found in both water conditions. Three validation populations were developed by crossing cultivars Lang, Yitpi, and Chara with Synthetic W7984 to transfer two of the QTLs identified under stress condition. The F_2.3 and F_3.4 validation lines were phenotyped under the same level of water stress as RILs to examine the effect of these QTLs. There were 13.5 and 14.5% increases in average root length due to the inheritance of Qrls.uwa.1AS and Qrls.uwa.3AL, respectively. The result indicated that closely linked SSR markers Xbarc148 (Qrls.uwa.1AS) and Xgwm391 (Qrls.uwa.3AL) can be incorporated into MAS for water stress improvement in wheat.     

Expression of the <Emphasis Type="Italic">Ga1-s</Emphasis> gametophyte factor in <Emphasis Type="Italic">shrunken2</Emphasis> sweet corn

Outcrossing is an important problem in specialty maize (Zea mays L.) that can be prevented by using gametophyte factors, such as Ga1-s, which preserve maize plants from pollen contamination. Our objective was to check if the gametophyte factor Ga1-s can protect sweet corn homozygous for sh2 in an efficient and stable way. We combined Ga1-s and sh2 by crossing two popcorn and three sweet corn inbred lines, respectively, in a North Carolina Design II, followed by an ear-to-row breeding program with selection for sh2 phenotype and absence of outcrossing. The released inbred lines homozygous for Ga1-s and sh2 were used for obtaining five hybrids that were evaluated for outcrossing and agronomic performance. Our results show that the gametophyte factor Ga1-s effectively protects the sh2 plants and that this effect was stable across environments. However, the agronomic performance of these inbred lines must be improved. Popcorn donors and sweet corn receptors of Ga1-s were unevenly represented in the released Ga1-s / sh2 inbred lines, suggesting that the viability of sh2 is affected by the genotypes involved. Therefore, breeders should pay attention to the choice of donors of Ga1-s that favors the viability of sh2.     

<Emphasis Type="Italic">In vivo</Emphasis> Acclimatization Responses of <Emphasis Type="Italic">Platycodon grandiflorum</Emphasis> For. Duplex to Different Soil Types and Environmental Factors

This study aimed to evaluate the effects of soil types and environmental factors for optimum conditions of seedlings growth of the Platycodon grandiflorum for establishing the in vivo acclimatization system of regenerated plants derived from the in vitro culture. P. grandflorum seedlings were transferred to the in vivo condition and acclimatized under different soil types, light intensities, and various temperatures. Changes caused by environmental factors and soil types in plant growth viz. plant height, leaf width, leaf length, stem diameter, number of leaves, branches and nodes were recorded in this study. Among the nine types of soil, the best growth performances were obtained from the soil type SVP (Soil mixed with horticultural bed soil, vermiculite, and perlite @ 2:1:1). Seedlings of P. grandiflorum showed the best growth at higher levels of light intensity (60 μmol·m^-2·s^-1). In contrast, P. grandiflorum seedlings showed the best growth response at a moderate level of temperature (25°C). Collectively, the present study provides a better understanding of the responses of growth characteristics in P. grandiflorum seedlings exposed to various soil types, light intensities, and temperatures.