MSc

The study entitled “Molecular analysis of spike branching observed in black pepper (Piper nigrum L.) type from Idukki” was conducted at the Department of Plant Biotechnology, College of Agriculture, Vellayani, Thiruvananthapuram during 2006-2008. The objective of the study was to analyse the sequence homology for the inflorescence architecture gene (TFL1) and flowering gene (FT) in spike branching black pepper type from Idukki, using polymerase chain reaction technique.

Spike branching in black pepper is very rare phenomenon. Profuse spike branching was observed in an uncharacterized black pepper type from Idukki. Single spike had three to four times more berry yield, compared to improved varieties. This type needed to be characterized at morphological and molecular levels to know its parental descendent and possible involvement of gene regulation responsible for spike branching. As an initial approach, molecular analysis was done to find out the presence of TFL1 and FT genes, which have been reported to be involved in inflorescence branching in modal plants.

TFL1 primer pair (TFL-F1 and TFL-R1), designed for the fourth exonic sequence of TFL1 gene in Arabidopsis thaliana, could amplify a 700 bp DNA sequence in the spike branching type, as well as in Karimunda and Vellamundi, indicating homology for the gene sequence and possible conserved exonic sequence in black pepper. Presence of sequence homology for the gene TFL1 indicated the possible involvement of TFL1 gene, which had been reported to be associated with inflorescence branching in Arabidopsis thaliana, in the spike branching trait of the black pepper type. This result is significant, as five out of the eight cultivars tested did not give any positive response for the primer pair designed based on TFL1 gene. However, two non-spike branching varieties including Karimunda and Vellamundi have also shown amplification for the TFL1 primer pair.

As an initial step towards characterisation of the spike branching type, RAPD analysis of it along with seven other cultivars/varieties was done. This analysis revealed variability, accounting for 83 per cent polymorphism. In the dendrogram, at a similarity index of 0.43 the plants grouped into two big clusters, indicating 67 per cent dissimilarity. All the eight plants under study formed individual clusters at similarity index 0.74, except the spike branching type and Vellamundi.

Results of gene specific PCR which yielded single amplicon can be hypothecated for the presence of sequence homology for the gene TFL1 and has conserved fourth exon in black pepper cultivars and varieties. Further transcript level and expression level studies are essential to find the specific role of the TFL1 gene in spike branching black pepper.