Dhurendra Singh

Somaclonal variations and their applications in horticultural crops improvement

The advancements made in tissue culture techniques has made it possible to regenerate various horticultural species in vitro as micropropagation protocols for commercial scale multiplication are available for a wide range of crops. Clonal propagation and preservation of elite genotypes, selected for their superior characteristics, require high degree of genetic uniformity amongst the regenerated plants. However, plant tissue culture may generate genetic variability, i.e., somaclonal variations as a result of gene mutation or changes in epigenetic marks. The occurrence of subtle somaclonal variation is a drawback for both in vitro cloning as well as germplasm preservation. Therefore, it is of immense significance to assure the genetic uniformity of in vitro raised plants at an early stage. Several strategies have been followed to ascertain the genetic fidelity of the in vitro raised progenies comprising morpho-physiological, biochemical, cytological and DNA-based molecular markers approaches. Somaclonal variation can pose a serious problem in any micropropagation program, where it is highly desirable to produce true-to-type plant material. On the other hand, somaclonal variation has provided a new and alternative tool to the breeders for obtaining genetic variability relatively rapidly and without sophisticated technology in horticultural crops, which are either difficult to breed or have narrow genetic base. In the present paper, sources of variations induced during tissue culture cycle and strategies to ascertain and confirm genetic fidelity in a variety of in vitro raised plantlets and potential application of variants in horticultural crop improvement are reviewed.

Molecular markers to distinguish ‘Thar Shoba’, a variety of khejri [Prosopis cineraria (L.) Druce], from trees in natural populations

ABSTRACT Prosopis cineraria (L.) Druce, commonly called khejri, is an important multipurpose, leguminous tree of the Thar Desert. ‘Thar Shoba’ is a variety of khejri without thorns which was developed as a vegetable. In order to develop markers for varietal identification, 80 RAPD primers were tested, of which nine were polymorphic between ‘Thar Shoba’ and trees in a natural population of khejri. Phenetic analysis revealed that ‘Thar Shoba’ formed a separate cluster from the natural population with similarity coefficients of 0.57–0.78. The 10-mer primers OPBE05, OPBA13, OPA12, and OPA14 were each found to differentiate ‘Thar Shoba’ from the natural population by one amplicon. These differential amplicons were sequenced and SCAR markers were developed based on the sequences that differentiated ‘Thar Shoba’ from the natural population. Natural populations of khejri from different regions of the Thar Desert, and clonally multiplied ‘Thar Shoba’ plants in the ICAR-CIAH bud-wood genebank, were used to validate these primers. These markers will be useful in further developing the bud-wood genebank, and for certification, identification, and protection of the khejri variety ‘Thar Shoba’.

Characterization of Prosopis cineraria (L.) Druce germplasm with suitable horticultural traits from the hot arid region of Rajasthan, India

Sixteen germplasm accessions of Prosopis cineraria with suitable horticultural traits were identified from north-western Rajasthan, India, propagated clonally by budding on seedling rootstock and maintained in the field gene bank. Morphological characterization of seven-year-old trees of these accessions by 21 traits indicated a lot of variation among the accessions tested. Higher number of flowers per raceme was found in accession CIAH/K2, higher width of ripened pod in CIAH/K5, higher number of seeds per pod in CIAH/K12 and a higher weight of seed per pod in CIAH/K6. Overall, CIAH/K16 was found to be a superior genotype for most of the useful traits. High significant positive correlation was obtained with traits useful for horticultural values. Out of 62 random decamer primers for random amplification (RAPD) reaction, and four minisatellite core sequence for direct amplification of minisatellite DNA (DAMD) screened with these accessions, 12 RAPD and 2 DAMD primers were found polymorphic. Average polymorphism resolved by these markers among the accessions was 93.2%. Genetic diversity revealed by Jaccard’s co-efficient was between 0.11 and 0.77, and four major clusters were identified among these accessions by phylogenetic analysis using NTSYSpc-2.02e software. This study shows the existence of high genetic diversity within these accessions.

Phenological growth stages of Indian jujube (Ziziphus mauritiana Lamk.) according to the BBCH scale

Division of Crop Improvement, ICAR-Central Institute for Arid Horticulture, Beechwal, Bikaner-334 006, Rajasthan, India Correspondence Dr Hare Krishna, ICAR-Central Institute for Arid Horticulture, Bikaner, Rajasthan, India. Email: kishun@rediffmail.com Indian jujube (Ziziphus mauritiana Lamk.) has been recognised as an underutilised plant worthy of further research and development by the Indian National Genetic Resources Programme and the International Centre for Underutilised Crops, UK. It is an important fruit crop of the hot arid regions in India as it forms an integral part of the life of the locals as a source of nutrition, fodder (leaves), fuel (pruned wood) and it has several ethnobotanical uses. In this study, 8 of the 10 principal growth stages based on the existing Biologische Bundesantalt, Bundessortenamt und Chemische Industrie (BBCH) scale were used to describe Indian jujube. These growth stages were vegetative bud development (Stage 0), leaf development (Stage 1), shoot development (Stage 3), inflorescence development (Stage 5), flower development (Stage 6), fruit development (Stage 7), fruit maturity (Stage 8) and senescence or beginning of dormancy (Stage 9). The phenological BBCH scale for Indian jujube can be used to guide the growers as to when to carry out orchard management practices such as canopy training and pruning, nutrient and water application, pest and disease control and post-harvest processing.

Genetic variability studies for improvement in brinjal under hot arid agro-climate

Variability studies in brinjal indicated good amount of genetic variation is the evaluated germplasm. PCV was in general higher than the GCV. PCV and GCV of higher order for average fruit yield of plant, fruit weight, number of fruits per plant, fruit length, and fruit width were desired. High heritability and high genetic advance was observed in traits like average fruit yield per plant and fruit weight, which indicates participation of additive genetic variance. Correlation studies among morphological and yield related traits revealed that average fruit yield had positive and significant correlation with fruit width, number of fruits per plant and average fruit yield per plant at phenotypic as well as genotypic levels. The path coefficient revealed that the total fruit yield per plant was positively dependent on traits like fruit weight, number of fruits per plant, leaf width and plant height. Multivariate analysis grouped the genotypes under five clusters, the highest being eight in clusters I. Intra-clusters distances was high in cluster IV, while the inter-cluster distances was highest between cluster III and cluster V, thus signifying their role in exploitation of heterosis.