PhD

Nursery diseases are the major limiting factor in the production of quality
planting materials of black pepper. Investigations were carried out to study the various
diseases occurring in black pepper nurseries of northern districts of Kerala, the effect
of nursery practices on the incidence of diseases and to evolve an integrated
management strategy against Phytophthora rot in black pepper nursery.
Four nursery diseases viz., Phytophthora rot, Colletotrichum rot,
Rhizoctonia rot and Sclerotium rot were recorded from different nurseries surveyed.
The pathogens causing the diseases were isolated and identified as Phytophthora
capsici Leonian emend A. Alizadeh and P.H.Tsao, Colletotrichum gloeosporioides
(Penz.) Penz. Sacc., Rhizoctonia solani Kuhn and Sclerotium rolfsii Sacc.
Symptomatology of these diseases were studied. The pathogen P. capsid
produced symptoms on all parts of the plant, while C. gloeosporioides infected mainly
on leaves. R. solani and S. rolfsii infected both leaves and collar regions. The infected
plants produced typical symptoms depending upon the pathogen and plant parts
affected.
Incidence of nursery diseases varied with locations and nursery seasons.
Among the nursery diseases noticed during the survey, Phytophthora rot was the most
predominant one. Incidence of other three diseases was comparatively less than that of
Phytophthora rot.
Various nursery practices followed for raising pepper nursenes viz.,
nursery structures, potting mixture, place of collection of planting materials, variety /
cultivar planted, processing of runner vines, treatment of potting mixture, time of
planting, frequency of irrigation and application of fungicides had an effect on the
incidence of nursery diseases especially Phytophthora rot. However, cuttings raised
under high density polyethylene sheet did not show any incidence of diseases.
Screening for host resistance indicated tolerant and moderately susceptible
reactions of Kalluvally-II and Panniyur-5 respectively against nursery diseases. The

biochemical parameters of these genotypes, which impart this type of reactions, were
studied in comparison with susceptible Panniyur-l.
Total phenols, OD phenol and total free amino acid contents and
peroxidase, catalase and esterase activities were more in tolerant Kalluvally-II, while
total carbohydrates, starch and acid phosphatase activity were maximum in susceptible
Panniyur-l. Reducing sugar content was high in moderately susceptible Panniyur-5.
Quantitative estimation of rhizosphere microflora from different pepper
nurseries yielded bacteria, actinomycetes and fungi. Fungal antagonists exerted more
antagonistic activity against P. capsid both under in vitro and in vivo conditions.
Among these two isolates F 14 and F 48 were selected based on their better antagonistic
efficiency against P. capsid and they were identified as Trichoderma harzianum Rifai
and Trichoderma viride Pers. ex S.F. Gray aggr. The established antagonists
T. harzianum and T. viride also exerted good antagonistic efficiency against
P. capsid.
The native and established antagonists were compatible with Akomin-40
and Ridomil MZ, while Bordeaux mixture and Fytolan were not compatible with any
ofthe four fungal antagonists.
Better growth and minimum disease incidence in pepper cuttings were
recorded when nurseries were raised during February-March.
Pepper cuttings raised in solarized potting mixture for 30 days showed
more sprouting, better plant growth and less incidence of disease.
Integrated management of Phytophthora rot in black pepper nursery was
carried out using tolerant Kalluvally-II, moderately susceptible Panniyur-5 and
susceptible Panniyur-l. In all the three black pepper genotypes, all the treatments had
a significant effect in reducing the incidence of Phytophthora rot when compared with
control. The minimum disease incidence in Panniyur-l and Panniyur-5 was recorded
in cuttings in treatment T14 (Solarization of potting mixture for 30 days + T. viride +

Akomin-40), while in Kalluvally-II it was T20 (Solarization of potting mixture for 30
days + T. harzianum - F14 + Akomin-40). In general, solarization of potting mixture,
application of Trichoderma spp. and fungicides like Akomin 40 and / or Ridomil MZ
can be used for managing the incidence of Phytophthora rot in black pepper nursery.