Browsing by Author "Aparna, S V."

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    Induction of early floral meristem in saffron (Crocus sativus L.)
    (Department of Molecular Biology and Biotechnology, College of Agriculture,Vellayani, 2024-02-05) Aparna, S V.; Smitha Bhasi
    The study entitled "Induction of early floral meristem in saffron (Crocus sativus L.)" was conducted at the Department of Molecular Biology and Biotechnology, College of Agriculture, Vellayani during 2023-2024. The objective of the study was to assess the effect of various inducers in inducing early floral meristem transition, morphological analysis of different stages of bud development and differential expression of key genes involved in floral meristem transition in saffron. The experimental design followed was CRD with twenty treatments and three replications each. The explants (corms) were collected from farmer's fields in Pampore, Kashmir and subjected to a rigorous three-step surface sterilization process using 0.02% bavistin (20min), 0.04% mancozeb (20min), 1% sodium hypochlorite bleach (30min) and a final dip in 1.5% mercuric chloride solution. Surface sterilised corms were placed on Murashige and Skoog medium supplemented with various concentration of different inducers viz., GA3 (T1-T3), IAA (T4-T6), Zeatin (T7-T9), Glucose (T10-T11), Fructose (T12-T13), Sucrose (T14-T15), KNO3 (T16-T17) and Paclobutrazol (T18-T19) along with control (T20-Basal MS medium). The cultures were maintained under 24ºC temperature, 16/8hrs photoperiod with 60% humidity. 100% sprouting was noticed within 14 days of treatment using 40 mg L-1 GA3 followed by 30 mg L-1 GA3 (19 days), 10% sucrose (35 days), 5% sucrose (38 days), 10% glucose (37 days) and 5% glucose (37 days) whereas the control plants took around 45-50 days for sprouting. The bud transition from stage 1 to stage 3 was prominent in treatment using 40 mg L-1 GA3 followed by 30 mg L-1 GA3 compared to other treatments. The present study showed 40 mg L-1 GA3 as the best treatment for inducing early floral meristem in saffron. Morphological analysis focussed on the three development stages of bud based on its length viz, stage 1 (length of bud ≤ 1mm), stage 2 (length of bud between 1.5-2.0 mm) and stage 3 (length of bud ≥ 3mm) was carried out. Stage 1 was further divided into stage 1 (a) and stage 1 (b) based on morphological differences noticed around the basal region of the bud. Histological sections revealed undifferentiated floral primordium in stage 1(a) representing the vegetative phase, whereas stage 1(b) showed floral primordia initiation, representing the transition to the floral bud stage. Histological sections of stage 2 revealed prominent floral bud differentiation and initiation of perianth primordia which expanded and elongated in stage 3 accompanied by pistil primordia initiation. Molecular analysis investigated the differential expression of key genes involved in floral meristem transition, such as SUPPRESSOR OF OVEREXPRESSION OF CO1 (SOC1), FLOWERING LOCUS T (FT), SEPALLATA 3 (SEP3) and CHROMATIN REMODELING 4 (CHR4). SEP3 is reported to form complexes with other floral homeotic genes to initiate differentiation of all floral organs viz sepals, petals, stamen and carpel. The differential expression analysis revealed a significant (10-fold) upregulation of SEP3 during stage 2, which correlates with the prominent floral meristem differentiation observed in stage 3, where perianth and pistil primordia became more prominent. CHROMATIN REMODELING 4 (CHR4) is a positive regulator of floral meristem transition and is also associated with the epigenetic silencing of FLC (FLOWERING LOCUS C), a crucial MADS-box transcription factor (TF) that negatively regulates floral transition. A 1.5-fold upregulation of CHR4 during the transition from stage 2 to stage 3 could be correlated with the active floral differentiation. The present investigation reveals that GA3 and sugars can be used for inducing early floral meristem in saffron. Morphological analysis confirmed that stage 1(b) marks the initiation of floral transition. Additionally, upregulation of floral meristem identity genes was observed during the floral meristem transition phase.