Satyabrata Maiti

Identification of RAPD markers linked to sex determination in guggal [Commiphora wightii (Arnott.)] Bhandari

Decamer RAPD primers were tested on dioeceious and hermaphrodite plants of Commiphora wightii to identify sex-specific molecular markers. Sixty different random decamer primers were screened out of which only three primers were found to be associated with sex expression. A ~1,280-bp fragment from the primer OPN06 was found to be present in all the female individuals. Another primer OPN 16 produced a unique ~400-bp amplification product in only hermaphrodite individuals. The third marker, OPA20 amplified a ~1,140-bp fragment from female and hermaphrodite DNAs, but failed to do so from the male plant DNAs.

A novel pathovar of Xanthomonas axonopodis causes gumming of Guggal (Commiphora wightii)

Guggal (Commiphora wightii (Arnott) Bhandari comb. nov.) is a small tree which is tapped for medicinally important oleo–gum–resin. Naturally infected plant oozes oleo–gum–resin from its trunk and primary branches. However, in either case, the plant dies slowly after oozing. A bacterium was established to be responsible for these phenomena. Four isolates of this bacterium were characterised by biochemical tests, Biolog GN2 microplate reaction, rDNA sequencing, which suggested that the pathogen belonged to the genus Xanthomonas. However, phylogenetic analysis based on chaperone protein (dnaK) gene, TonB–dependent receptor (fyuA) gene, DNA gyrase B (gyrB) gene and RNA polymerase sigma factor (rpoD) gene sequences placed it as a member of X. axonopodis 9.2 rep–PCR/DNA–DNA homology cluster close to X. perforans, X. alfalfae and X. euvesicatoria. Further elucidation of phylogenetic position of the test strains was achieved from a gyrB based tree considering sequences from 71 representative strains. Test strains were confirmed to be members of X. axonopodis. These had very narrow infectivity limited to Commiphora spp. Hence, we propose a novel pathovar, X. axonopodis pv. commiphoreae pv. nov. as the cause of gum oozing in guggal. Pathotype is DXA 01 = CFBP 7580 = LMG 26789.

Direct shoot regeneration from immature inflorescence cultures of Chlorophytum arundinaceum and Chlorophytum borivilianum

Direct shoot regeneration was achieved from immature inflorescence explants of Chlorophytum arundinaceum and C. borivilianum on half-strength Murashige & Skoog (MS) medium supplemented with 3.0 mg L−1 BA, 150 mg L−1 Ads, 0.1 mg L−1 NAA and 3% (w/v) sucrose under a 16-h photoperiod. The shoot buds developed within 2–3 weeks of culture. High frequency of shoot bud regeneration was achieved when cultured on similar medium in subsequent subcultures. The apex portion (Type I) of the inflorescence produced more shoot buds as compared to the middle ones (type II). More than 75% of the terminal segment explants produced shoot buds within 4-week of culture. Response of basal portion (Type III) was negative for shoot bud initiation. Shoots rooted on half-strength basal MS medium supplemented with half-strength MS medium, 0.1 mg L−1 IAA and 2% (w/v) sucrose. Micropropagated plantlets were hardened in the green house and successfully established in the soil where 90% of the plants survived. This protocol would be useful for commercial micropropagation and genetic improvement prograrmme.

Rapid plant regeneration and assessment of genetic fidelity of in vitro raised plants in Aloe barbadensis Mill. using RAPD markers

Abstract Rapid micropropagation was achieved in Aloe barbadensis Mill. using shoot meristems as explants. Random Amplified Polymorphic DNA (RAPD) markers were used to determine the genetic fidelity of in vitro raised plants. Forty decamers were used to amplify DNA from in vitro and in vivo donor plants to assess the genetic integrity. All RAPD profiles from in vitro raised plants were monomorphic and similar to that of field grown donor plants. No variation was detected within the in vitro raised plants. High multiplication frequency and molecular stability ensure the efficacy of the protocol developed for the production and conservation of this important medicinal plant.

Identification and assessment of genetic relationships in three Chlorophytum species and two high yielding genotypes of C. borivilianum through RAPD markers

Conservation of identified germplasm is an important component for efficient and effective management of plant genetic resources. Since Chlorophytum species are important medicinal plants, studies were carried out for identification and establish genetic relationships in three species of Chlorophytum and two high yielding genotypes of Chlorophtum borivilianum using RAPD markers. Out of one hundred primers tested, 47 decamers amplified a total of 454 distinct bands ranging from 0.25–3.0 kbp to identify and to evaluate genetic relationships between and among three species of Chlorophytum and two genotypes of Chlorophtum borivilianum. The cluster analysis indicated that three species of Chlorophytum and two genotypes (NRCCB-1 and NRCCB-2) of C. borivilianum formed two major clusters. The first major cluster constituted C. arundinaceum and C. tuberosum, and the second major cluster composed of two subclusters; the first subcluster represented NRCB-1 and NRCB-2 where as the second subcluster represented C. borivilianum. Thus, the RAPD markers have the potential for identification and characterization of genetic relatedness among the species and genotypes. C. borivilianum along with two genotypes also showed similar banding patterns which could be chosen as candidate markers for differentiating the other two species such as C. arundinaceum and C. tuberosum. This would helpful for breeding programmes and provides an important input in conservation biology.

First report of downy mildew on Lepidium sativum in India

Downy mildew caused by Hyaloperonospora parasitica on different members of Brassicaceae has been reported from different parts of the world. In India, the pathogen is recorded for the first time on Lepidium sativum. Proper management strategies need to be formulated against this disease as incidence is increasing.

Induction of male and female sterility in isabgol (Plantago ovata) due to floral infection of downy mildew (Pernospora plantaginis)

Downy mildew (Peronospora plantaginis) caused two different types of infection in the floral parts of isabgol (Plantago ovata). Systemic infection resulted in long spikes bearing weak and sterile florets, which later turned black due to saprophytic growth. Localised infection produced various symptoms ranging between normal flower opening and failure to bloom. Different parts of infected flowers such as sepal, petal, filament and anther were reduced in size compared to healthy flowers. However, gynoecium was elongated in localised infection. P. plantaginis induced gradual sterility of isabgol flowers. Androecium was affected more than the gynoecium was. Pollen number, pollen viability and germination reduced drastically due to localised infection. On the contrary, there were no significant differences between healthy and locally infected flowers in terms of stigma receptivity. In systemically infected spikes, bud development was arrested leading to sterility. When localised disease severity was high, secondary systemic infection caused similar symptoms. Microscopic observations showed presence of the pathogen in different parts of the flowers. Downy mildew adversely affected seed yield and quality; producing seeds, which were smaller and lighter than the healthy ones and later, became black. Seed yield was reduced by as much as 73.45 percent. Husk content per unit seed mass increased relatively as the total surface area of infected seeds increased.

First report of downy mildew onLepidium sativum in India

Downy mildew caused byHyaloperonospora parasitica on different members of Brassicaceae has been reported from different parts of the world. In India, the pathogen is recorded for the first time onLepidium sativum. Proper management strategies need to be formulated against this disease as incidence is increasing.