BIOCHEMICAL AND BIOLOGICAL BASES OF RESISTANCE IN SOLANACEOUS VEGETABLES AGAINST. BACTERIAL WILT INCITED BY. RAlSTONIASOlANACEARUM(SMITH) VABUUCHI 1 Ai. By T. SHEELA PAUL THESIS Submitted in partial fulfilment of the requirement for the degree Joctorof PhiloSDpky in Jlgriculturt Faculty of Agriculture Kerala Agricultural University ~tpartmtnt of 'Iant JatlyoloBU COLLEGE OF HORTICULTURE VELLANIKKARA,THRISSUR 680654 KERALA, INDIA 1998
C E R T I PI CAT B Certified that this thesis entitled "Biochemical and biological bases of resistance in solanaceous vegetables against bacterial wilt incited by Ralst:onia solanacearujll (Smith) Yabuuchi et: al. " is a record of research work done independently by Smt~ T. Sheela Paul under my guidance and supervision and that it has not previously formed the basis for the award of any degree, diploma, fellowship or associateship to her. ~ L ~~ --" Vellanikkara, 10.3.98. Dr. James Mathew, Chairman, Advisory Committee, Professor & Head, Dept. of plant pathology, College of Horticulture.
ABSTRACT An investigation on biochemical, biological and nutritional bases of resistance in solanaceous vegetables against bacter'ial wilt incited by Ralstonia solanacearum (Smith) Yabuuchi et al., has been attempted. The pathogen R. solanacearumwas isolated from respecti ve hosts and characterised by various morphological, cultural, biochemical and physiological tests upto biovar level. The three isolates were cross inoculable, and were sensitive to AmbistrYn and Streptocycline. Based on these studies the tomato and chilli isolates were identified as Ralstonia solanacearum race I biovar III and that from brinjal as R. solanacearum race I biovar V. The study on toxigenic property of the bacterial isolates revealed that the toxic metabolites were not host specific. Out of the 43 varieties / lines screened, 12 varieties / lines were sele~ted, one each from resistant, moderately resistant, moderately susceptible and susceptible
categories. The varieties / lines selected were LE 79-5, BT-lO, LE 470 and Pusa Ruby for tomato; Swetha, Composite-2, BB-7 and Pus a Purple Long for brinjal and Ujwala, Manjari, Jwalasakhi and Pusa Jwala for chilli. The studies on biochemical, biological and nutritional factors in tomato, brinjal and chilli showed considerable variation between crops, between varieties/ lines, and between plant parts. However the root being the - primary foci of infection by R. solanacearum the biochemical reactions in root is considered more important than other plant parts. Among the biochemical factors, the OD phenol and specific activity increased due to infection and the content was higher in the resistant genotype (LE 79-5) both under healthy and diseased condition in tomato. In brinjal, the polyphenol oxidase acti vi ty, specific activity and peroxidase activity increased due to infection and were higher in resistant genotype (Swetha) both under healthy and diseased condition. In chilli, total phenol and OD phenol, increased due to infection and were higher in r~sistant plants (Ujwala) under healthy and diseased conditions. The soluble sugar content and specific activity were also higher in resistant plants both under healthy and diseased condition even though a decrease was observed due to infection.
In tomato, the resistant genotype showed a higher content of OD phenol, polyphenol oxidase activity, specific activity and alkaloids under healthy condition; and total phenol, OD phenol, soluble protein, specific activity ~d peroxidase activity under diseased condition. In brinjal, the resist~t genotype recorded higher content of total phenol, OD phenol, soluble sugars, amino acids, soluble protein, polyphenol oxidase activity, specific activity and peroxidase activity under healthy condition; and polyphenol oxidase activity, specific activity and peroxidase activity under diseased condition. In chi 11 i, the resist~t genotype recorded higher total phenol, OD phenol, solubl~ sugars ~d specific acti vi ty under heal thy condition; and total phenol, OD phenol, soluble sugars, specific activity and peroxidase activity under diseased condition. Among the biological factors, the total microflora (fungi and actinomycetes), Pseudomonads and parasitic nematodes increased due to infection in resistant genotype whereas beneficial microbes recorded a decrease in population in resistant genotype by infection. In tomato the resistant genotype recorded higher nematode population under heal thy condi tion and higher total microflora, virulent Ralstonia and avirulent Pseudomonas under diseased condition. In brinj al the
resistant genotype recorded higher population of fungi, avirulent Pseudomonas, mycorrhiza and saprophytic nematodes under heal thy condition, and fungi, virulent Ralstonia, avirulent Pseudomonas and nematodes under diseased condition. In chilli, the resistant genotype recorded higher populations of avirulent Pseudomonas, mycorrhiza and nematodes under heal thy condition and fungi, avirulent Pseudomonas and mycorrhiza under diseased condition. Among the nutritional factors, in tomato the resistant genotype recorded higher 'content of potassium and calcium under healthy condition and iron, zinc and manganese under diseased condition. In brinj al the resistant genotype recorded higher content of nitrogen, calcium, magnesium and zinc under heal thy condi tion; and potassium, magnesium, iron and zinc under diseased condition. In chilli, the resistant genotype recorded higher content of phosphorus, calcium and iron under healthy condition; and nitrogen, potassium magnesium and zinc under diseased condition. Thus the study revealed that it was not possible to arrive at common bases for resistance to bacterial wil t in tomato, brinj al and chilli taken together. However it was possible to o~tline the important parameters that conditions resistance in individual crops.