Anatomical biochemical Investigations on Phytophthora foot rot disease reaction in piper spp.

Abstract

Anatomical and biochemical investigations on Phytophthora foot rot disease reaction in Piper spp. were carried out in the Department of Plantation Crops and Spices and Biochemistry Laboratory of the College of Horticulture, Vellanikkara during 1996 to 1998. The study revealed that the two species viz., Piper colubrinum L. and P. nigrum L. and two genotypes of P. nigrum viz., Panniyur I and Kalluvally differed significantly in the various anatomical and biochemical parameters studied. The immune genotype was characterised by compact arrangement of cells, small epidermal, mesophyll and spongy parenchyma cells, thick palisade and collenchyma tissues, large vascular bundles and mucilage canals, thick lower epiderm with large cells and less number of stomata per unit area in the leaves. The stem was characterised by thin cuticle, epiderm and hypoderm, small sized epidermal cells, thick cortex, large cortical cells with more inter- cellular spaces, thick chlorenchyrna and sclerenchyma, more number of large peripheral and medullary vascular bundles, large mucilage canals and small indistinct pith. It had thick root epiderm,less number of root hairs, small cortical cells, thick endoderm, big stele, pericycle cells and vascular bundles. In contrast, the susceptible genotype was characterised by thin palisade and collenchyma tissues, small vascular bundles and mucilage canals, thin lower epiderm with small ceIls and more number of stomata per unit area. The stems of the susceptible genotype exhibited thicker cuticle with large epidermal cells, more epidermal appendages, thick hypoderm with small cells, thin cortex with small cortical cells arranged with less interceIlular spaces and thin sclerenchymatic tissues. It had thin root epiderm, more number of epidermal appendages, small cortical cells with large stele, thin pericycle with small cells and distantly placed small vascular bundles.

The tolerant genotype Kalluvally exhibited somewhat intermediate values to P. colubrinum and Panniyur 1 in all the anatomical characters tested. In the biochemical parameters studied, I). colubrinum registered high content or total phenol, reducing sugar, total free amino acid and higher activities of peroxidase and polyphenol oxidase enzymes. The susceptible genotype: Panniyur I was marked by low of total and OD phenols, reducing sugars, total free amino acids, peroxidase and polyphenol oxidase activities and 'high glucanase and IAA oxidase activities. The tolerant genotype Kalluvally registered medium values for total phenols, reducing and non reducing sugars, total free amino acid" and enzymes like peroxidase, glucanase and polyphenol oxidase. However, the content of OD phenol was high and IAA oxidase activity was low in Kalluvally. On inoculation with Phytophthora capsici, the content of total phenol, reducing sugar, total free amino acid and enzyme activities like glucanase and peroxidase increased in Panniyur 1 whereas the contents of OD phenol, non reducing sugar and activities of IAA oxidase and polyphenol oxidase decreased. In P. colubrinum the contents of total free amino acids and peroxidase enzyme activity increased at a higher rate than in the other genotypes while the content of OD phenol, reducing and non reducing sugars decreased drastically on inoculation. Kalluvally exhibited similar trend as that of P. eolubrinum and registered somewhat intermediate values between P. colubrinum and Panniyur 1 in almost all the biochemical parameters tested. However, decrease in glucanase activity and a greater reduction in polyphenol oxidase activity were observed in Kalluvally on inoculation. The anatomical and biochemical differences observed in Piper spp. can effectively be used for screening the genotypes for tolerance I resistance to Phytophthora capsici and for the management of the disease.