Reeta Bhatia

In vitro maintenance of CMS lines of Indian cauliflower: an alternative for conventional CMS-based hybrid seed production

Summary Three Ogura cytoplasmic male-sterile (CMS lines) of Indian cauliflower (Brassica oleracea var. botrytis L.; Ogu1A, Ogu2A and Ogu3A) were compared for their in vitro regeneration ability using two types of explant, hypocotyls and curds (i.e., pre-floral fleshy apical meristems). The highest rate of in vitro establishment and the highest multiplication index were recorded in Ogu3A. Ogu2A showed poor in vitro establishment. The choice of explant had a significant impact on the morphogenetic potential of all three lines. Among the two types of explant, curds proved to be more efficient for the initial establishment of cultures.The highest rate of in vitro establishment and multiplication index were recorded for Ogu3A on Murashige and Skoog (MS) medium supplemented with 2.5 mg l-1 kinetin, 0.2 mg l-1 _- naphthaleneacetic acid and 0.2 mg l-1 gibberellic acid. The three CMS lines also showed significant variations in the numbers of roots induced per shoot.The maximum number of primary roots per shoot was recorded in Ogu3A on 0.5_ MS medium supplemented with 1.0 mg l-1 indole-3-butyric acid. In vitro-raised plants were hardened and used successfully for F1 hybrid development.When the F1 hybrids developed using in vitro-maintained or conventionally maintained CMS lines were compared, it was observed that variations in plant height, days to 50% curd maturity (DCM), and net curd fresh weight (FW) were lower in those F1 hybrids developed through in vitro-maintained CMS lines. In F1 hybrids developed from in vitro-raised CMS lines, the range of standard deviation (SD) values as percentages of the mean value for DCM and net curd FW were 2.5 - 3.7% and 6.6 - 10.7%, respectively. In contrast, the corresponding SD values ranged from 5.8 - 7.9% and from 13.6 - 19.9% for F1 hybrids developed from conventionally maintained CMS lines.This in vitro protocol, using curd explants, will be useful for the rapid multiplication of breeding lines of cauliflower without inbreeding depression, and for high-quality hybrid seed production.

Molecular breeding for resistance to black rot [Xanthomonas campestris pv. campestris (Pammel) Dowson] in Brassicas: recent advances

The Brassicas are affected by several diseases, of which black rot, Xanthomonas campestris pv. campestris (Pam.) Dowson (Xcc), is one of the most widespread and devastating worldwide. The black rot bacteria causes systemic infection in the susceptible plants and penetrate the plants through the hydathodes or wounds. Typical disease symptoms are ‘V’ shaped necrotic lesions appearing from the leaf margins with blackened veins. Periodic outbreaks of the black rot pathogen have occurred worldwide, especially in the continental regions, where high temperatures and humidity favor the incidence of disease occurrence causing huge yield loss. The challenge to control the losses in vegetable brassicas production is made more difficult by the adverse climatic changes and evolution of new pathogenic races. The development of black rot resistant hybrids/varieties is the most reliable long term practical solution for effective disease control. Identification of new resistant genetic resources, tightly linked markers with resistance loci and QTL mapping would facilitate the breeding programme for black rot resistance. Information regarding genetics of resistance and mapping of resistance genes/QTLs will accelerate the marker assisted resistance breeding in brassica crops against Xcc. In future we need to identify the race specific candidate genes for and their validation through transgenics and gene expression. Moreover, it is imperative to identify functional markers for resistance genes through identification of R gene families and their relationship with resistance expression. This comprehensive review will help the researchers working in this area to understand the dynamics of black resistance breeding and to formulate future breeding strategies.

Genetic analysis of important antioxidant compounds in cabbage (Brassiaca oleracea var. capitata L.)

ABSTRACT The paucity of research on development of antioxidant-rich hybrids in cabbage by utilizing combining ability estimates, gene action, and heterosis motivated us to undertake this study. We made 60 crosses between 5 cytoplasmic male-sterile lines and 12 male-fertile testers during the summer of 2015, as per the line × tester design. The seedlings of all the parents and 60 F1 crosses, along with three checks, were transplanted during the Rabi (winter) season of 2015–2016 and evaluated using a randomized complete-block design. Combining ability, gene action, and heterosis were determined for different antioxidant compounds. Experimental results revealed that the range of cupric ion reducing antioxidant capacity (CUPRAC) [parents = 1.26–7.33 and hybrids = 0.04–6.54 μmol trolox/g], ferric reducing ability of plasma (FRAP) [parents = 1.65–4.76 and hybrids = 0.16–4.67 μmol trolox/g], β-carotene (parents = 0.44–2.29 and hybrids = 0.04–1.89 μg/100 g), and chlorophyll-a (parents = 0.71–4.08 and hybrids = 0.19–3.08 mg/g f.w.) for hybrids was lower than that of the parents because of outbreeding depression. The parental lines 6A, 208A, 83-5-8, and Sel-5-83-6 were found to be good general combiners for most of the antioxidant compounds studied. Based on the mean performance, specific combining ability effects and heterosis, five hybrid combinations viz., 9A × KIRC-8 for CUPRAC and FRAP; 208A × C-122 for ascorbic acid; 6A × Chhaki-2 for total carotenoids and β-carotene; 831A × Chhaki-2 for chlorophyll-a; and 6A × 83-5-8 for chlorophyll-b and total chlorophyll content, were most promising. The ratio of general combining ability (GCA) and specific combining ability (SCA) variances, i.e., [2 σ2g/(2σ2g + σ2s)], which reflects the relative importance of GCA versus SCA, was less than unity for different antioxidant compounds, which implied that for these traits, nonadditive gene effects were more important than additive effects. The numerical values of range for contribution of lines × testers interaction for different traits (41.47–70.18%) were found to be higher than the individual contribution of lines (11.24–47.22%) and testers (8.31–21.76%). Hence, heterosis could be exploited for developing antioxidant-rich hybrid cabbage.

Circumventing phenolic exudation and poor survival in micropropagation of marigold

Marigold is one of the popular ornamental crops grown mostly for loose flower production and garden display. It is usually propagated through seeds, but some germplasm including male sterile lines (petaloid and gynomonoecious forms) can only be maintained through vegetative means of propagation. Year round production and maintenance of true-breeding lines can be possible by employing efficient tissue culture techniques. However, exudation of phenols from explants and poor ex vitro survival of marigold plants are the major hindrances. Therefore, the present investigation was carried out with an objective to standardize the protocol for controlling phenolic exudation from nodal explants and also enhancing the ex vitro survival of four marigold genotypes viz., Pusa Arpita, Pusa Basanti Gainda, Siracole Orange and Siracole Yellow. The exudation of phenolic compounds from nodal explants was significantly controlled by incorporating 125 mgl−1 ascorbic acid into the culture induction medium supplemented with BAP (2.0 mgl−1) + NAA (0.1 mgl−1) in all the genotypes. Marigold micro-shoots cultured on ½ MS liquid rooting medium supplemented with 0.5 mgl−1 IBA showed highest rooting percentage (99.00%) which was followed by ½ MS + 0.5 mgl−1 NAA (98.75%). Early root induction (5.88 days), longest roots (2.78 cm), moderately high number of roots (47.56) per shoot and highest ex vitro survival (98.75%) were observed with ½ MS + 0.5 mgl−1 NAA. Among the different hardening strategies employed, lowest mortality (11.55%), maximum plant height (15.15 cm) and leaf number (20.95) were noted in plants that were hardened in disposable polypropylene glasses.

Cytoplasmic male sterile and doubled haploid lines with desirable combining ability enhances the concentration of important antioxidant attributes in Brassica oleracea

The Brassica vegetable crops are rich source of important antioxidant compounds having anticancer and health promoting properties. Development of F1 hybrids with better nutritional traits is one of the main breeding objectives in different vegetable crops. Our study is the first report of determining heterotic combinations utilizing cytoplasmic male sterile (CMS) and doubled haploid (DH) inbred lines for antioxidant compounds in snowball cauliflower. Twenty genetically diverse Ogura CMS lines of cauliflower and six DH male fertile inbred lines were crossed to develop 120 F1 hybrids in line × tester mating design. The resulting 120 test cross progenies along with 26 parents and 4 standard checks were evaluated in 10 × 15 alpha lattice design with three replications during next cropping season. The CMS lines Ogu33-1A, Ogu122-5A and Ogu119-1A were good general combiner and CMS line Ogu118-6A was poor general combiner for majority of traits. Most of the heterotic hybrids were associated with high positive SCA effects. The proportions of σ2A/D and

Genetic divergence studies in tulip (Tulipa gesneriana L.)

\upsigma^{2}_{\text{gca}} /\upsigma^{2}_{\text{sca}}

Genetic combining ability and heterosis for important vitamins and antioxidant pigments in cauliflower (Brassica oleracea var. botrytis L.)

σgca2/σsca2 ratios were less than unity in all the cases indicating preponderance of non-additive gene action in the genetic control of all the traits. Highest number of heterotic hybrids with SCA effects in desired positive direction was recorded for ascorbic acid content and phenolic content followed by total carotenoid content. The F1 hybrids with better combining ability and better per se performance could be useful in accumulation of favourable allele for higher concentration of important anti-oxidant compounds.

Superior CMS (Ogura) lines with better combining ability improve yield and maturity in cauliflower (Brassica oleracea var. botrytis)

A comprehensive study on characterization and genetic diversity analysis was carried out in 16 ‘Ogura’-based ‘CMS’ lines of cabbage using 14 agro-morphological traits and 29 SSR markers. Agro-morphological characterization depicted considerable variations for different horticultural traits studied. The genotype, ZHA-2, performed better for most of the economically important quantitative traits. Further, gross head weight (0.76), head length (0.60) and head width (0.83) revealed significant positive correlation with net head weight. Dendrogram based on 10 quantitative traits exhibited considerable diversity among different CMS lines and principle component analysis (PCA) indicated that net and gross head weight, and head length and width are the main components of divergence between 16 CMS lines of cabbage. In molecular study, a total of 58 alleles were amplified by 29 SSR primers, averaging to 2.0 alleles in each locus. High mean values of Shannon’s Information index (0.62), expected (0.45) and observed (0.32) heterozygosity and polymorphic information content (0.35) depicted substantial polymorphism. Dendrogram based on Jaccard’s similarity coefficient constructed two major groups and eight sub-groups, which revealed substantial diversity among different CMS lines. In overall, based on agro-morphological and molecular studies genotype RRMA, ZHA-2 and RCA were found most divergent. Hence, they have immense potential in future breeding programs for the high-yielding hybrid development in cabbage.