MANAGEMENTOF FOOT ROT OF BLACKPEPPER

Transcription

1 MANAGEMENTOF FOOT ROT OF BLACKPEPPER (Piper nigrum L.) WITH VA MYCORRHIZA AND ANTAGONISTS By CHRISTIN P. ROBERT THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENT FOR THE DEGREE DOCTOR OF PHILOSOPHY FACULTY OF AGRICULTURE KERALA AGRICULTURAL UNIVERSITY DEPARTMENT OF PLANT PATHOLOGY COLLEGE OF AGRICULTURE, VELLAYANI THIRUVANANTHAPURAM KERALA

2 CERTIFICA TE Certified that this thesis entitled" M.snagement oe foot rot of iji.u:k pepper (Piper nigrum L.J witl1 VA mycorrl1iza.lo anj t " anr;agonls S İS A record of research work done independently by Mr..Christin P. Robert ( ) under my guidance and supervision and that it has not previously formed the basis for the award of any degree, fellowship or associateship to hin~. Vellayani -fr- t.998 Lf-1- (Q<?,,! Dr. Po Sivaprasad Associate Professor (Ag. Micro biology) Department of Plant Pathology, College of Agriculture, Vellayani,

3 ABSTRACT Extensive investigation was carried out to develop a native microbial inoculant based technology involving Arbuscular Mycorrhizal Fungi (AMF) and fungal anta~onists for the foot rot Qise~se management and..growth improvement of black pepper in the nursery and field. Phytophthora capsici Leonian emend A. Al i zadeh and P.B. Tsao, the foot rot pathogen isolated from Perin~ammala. / Thiruvananthapuram district was found most virulent isolate. Seven native ~F cultures and fifty fun~al antagonists were isolated from Kerala soils. AMF isolat~s were screened in the green house for plant growth improvement and disease tolerance in comparison with identified species-glomus fasciculatum, G. clarud and Gigaspora Dargarita. Of the ten AMF tested isolates Is-6, Pi-ll, Pi-9, G. fasciculatud and Gigaspora margarita were very effective in stimulating growth and nutrient (P, K, Ca, Mg, Cu, Fe, Mn and Zn) uptake of black pepper. Regarding the ability of AMF in reducing the foot rot incidence, Glomus fasciculatud recorded the lowest plant mortality and root rot index (53.35% and 62.50%) followed by 1s-6(60.00% and 64.77%) and Pi-ll (60.64% and 68.18%) as against 100 per cent mortality and per cent root rot index noticed in control. The above five, cultures were subjected for further studies.

4 Characterisation of AMF associated with different genotypes of black pepper grown in various soil types indicated the definite influence of soil type on AMF colonization. Sandy soil (oxyaquic quartpsamment) harboured maximum root colonization while forest soil (haplic argiustoll) had the lowest. Species of GloBUS particularly G. ~asciculatub was the predominant AMF associated with black pepper irrespective of soil type. As an exception Acaulospora and Gigaspora species were frequently noticed in sandy soils. Based on the ability of the fungal antagonists to suppress P. capsici in vitro either through mycoparasitism, antibiosis or soil fungistasis, 24 isolates were selected for green house studies. In the further testing isolates Al' Al3' A2l' A22 and A35 significantly reduced the foot rot infection and increased the plant growth. They showed better population build up in the soil and suppressed the P. capsici population considerably. These native antagonists were further tested in combination with selected AMF in the green house and field. G. TasciculatuB Under green house condition, combination of x Al or A2l showed significant influence on growth stimulation, while Is-6 x A22 recorded lowest mortality of per cent due to foot rot incidence as against 97 per cent in control. The dual inoculation of Is-6 x Ail and Pi-I! x Al was ) highly effective in plant g~owth stimulation and disease suppression. Both the combination recorded less than

5 60 per cent infection and mortality due to the disease. while control showed per cent infection and plant mortality. Bordeaux mixture and copper oxychloride recorded and per cent mortality respectively. AMF colonization and multiplication of antagonists were also favoured by dual inoculation. The potential AMF isolates Is-6 and Pi-11 were identified as species of Glo.us while, the antagonistic isolates A l' A 13' A21'. A22' and A35 were confirmed as Aspergillus ~umigatus Fres., Fusariu8 oxysporum Schlecht. ex Fr. Aspergillus sydolalii (Bain. & Sart. ) Thom. & Church, Trichoderlla viride Pers. ex Gray. and Glioaastix 8urorua (Corda) Hughes respectively. A technique for AMF inoculation to established pepper vines was developed using 'carrier plants'. Raisinli{ sorli{hum with AMF inoculation around the pepper vines was found effective to achieve intense colonization in pepper roots by the introduced AMF in the field. This technique developed for the pepper vines may be tried for extendinli{to other perennial crops for AMF inoculation. Promising AMF cultures Pi-11, 15-6, G. ~asciculatum and antagonists Aspergillus ~u.igatus, A. sydolalii. Trichoderma viride were further tested on eight year old established pepper, vines following 'carrier plant' based AMF inoculation and cowdung-neem cake based antagonist inoculation. The treatment

6 Pi-!! x A. syd(.),.,ii was most effective with no symptom development. followed by Is-6 x T. viride or A. syd(.),.,ii with disease score of 2.0 as against 7.0 recorded for control. The disease score for bordeaux mixture and copper oxychloride application was 3.5 and 3 respectively. Neem cake-cowdung food base was highly favourable for multiplication and activity of fungal antagonists. The amino acids. total sugar and reducing sugar and total phenols and orthodihydroxy phenol content and activity of cellulase and chitinase were influenced by AMF colonization particularly by Is-6 and Pi-!!. The positive change could be related with the relative disease tolerance recorded for various AMF isolates. The development of native AMF and antagonists through extensive testing in the green house and field and also the technology of AMF inoculation for established pepper vines are the first record of work. \l \6;(\,