Essential amino acid profiling of the four lac hosts belonging to genus Flemingia: its implications on lac productivity

The Indian lac insect (Kerria lacca), a hemipteran, phloem sap sucking sedentary insect is an important bioresource which thrives on tender twigs of more than 400 plant species belonging to various genera and families. The most common commercial host plants for lac cultivation are big trees hence cultivation was concentrated mainly to dense forests across the country till last decade. Recently, a new bushy host plant belonging to the genus Flemingia has been introduced so that lac can be cultivated on farmlands like other cash crops. The insect is sedentary and feeds on the phloem sap of the host plants, the only source of its nutrition. Interestingly, the biological attributes of the insect as well as the qualitative and quantitative production of lac is influenced by the host plant on which the insect feeds upon. The present study was thus aimed at deciphering the effect of phloem sap constituents obtained from four plant host taxa belonging to the same genus Flemingia viz. F. semialata, F. macrophylla, F. bracteata and F. chapar (essential amino acids only-EAAs) on lac productivity. Moreover, a newer method for phloem sap collection i.e. Dot-blot in addition to the facilitated exudation using EDTA was also investigated. Dot-blot method for phloem sap collection also came out to be a promising method for field studies; although slightly higher concentration of EAAs were obtained from EDTA method, thus the later was used for further analysis. Phloem sap of four plant host taxa belonging to the same genus Flemingia were qualitatively and quantitatively analysed for seven EAAs (Arginine, Glycine, Leucine, Methionine, Phenylalanine Tyrosine and Valine). Amino acid concentration regime and further analysis done using statistical tools (ANOVA and PCA) points out the EAA concentration in the phloem sap is in congruency with the lac production data obtained through previous studies as F. semialata > F. macrophylla > F. chapar > F. bracteata. The present study thus scientifically points out that F. semialata can be a promising plant for lac cultivation on the basis of higher EAA content as compared to the rest three.

Keywords: Essential amino acids; Flemingia spp.; Indian lac insect; Kerria lacca; Lac productivity; Phloem sap.