evaluate the potential antagonistic efficacy of fungal endophytes harbored in
C. sativa against two major phytopathogens namely, Botrytis cinerea and
Trichothecium roseum(Kusari et al. 2013 ,2014a,b), which are reported to be
potent greenhouse threats ofCannabis. These phytopathogens are known to cause
gray mold, damping off and pink rot disease that weaken and eventually kill the
plant. It is therefore desirable to address such infections that would drastically
reduce the cultivation of medicinally important plants. Endophytes could ideally
protect the host plants from inside. As an attempt to address such problems, we
evaluated the fungal endophytic microorganisms of this plant with biocontrol
efficacies. The isolated endophytes were challenged, using suitable in vitro assays,
against the two host specific phytopathogens underfive different media conditions
(OSMAC approach;OneStrainManyCompounds; Bode et al. 2002 ; Kusari et al.
2012 ) to evaluate the various types of interactions and growth inhibitions that could
exist between them. The endophyte-pathogen interactions were performed in
Nutrient agar (NA), Malt extract agar (MEA), Potato dextrose agar (PDA),
Sabouraud agar (SA) and water agar (WA). Antagonism was defined microbio-
logically as the varying extent of inhibitory capability of endophytic isolates under
different media conditions against either one or both the phytopathogens
(Fig.20.2). Interestingly, 11 different types of dual-culture interactions were
observed accompanied with varying degrees of growth inhibitions. The
attack-defense interactions were a result of either physical or chemical mediated
defense responses like release of exudates, formation of inhibition zones, profuse
sporulation, change of mycelia color, and change of mycelia pattern, among others.
Interestingly, three endophytic fungal isolates namely Paecilomyces lilacinus,
Penicilliumsp., andPenicillium copticolaproved to be dominant antagonists in
inhibiting both pathogens on one or more media conditions.
In line with our study, Qadri et al. ( 2013 ) employed a similar dual culture
antagonistic strategy to assess antifungal potential of endophytic isolates against
seven plant pathogens, namely Fusarium oxysporum, Aspergillus flavus,
Geotrichum candidum,Verticillium dahlia,Fusarium solani,Ceratocystisfimbriata
andRhizoctonia solani. The pathogens of genusFusariumhave been reported to
cause damping off and stem cankers inCannabisplants (Bush Doctor 1985 ;
McPartland 1991 , 1994 , 1995 ), killing the seeds and seedlings immediately after
they emerge from soil and infesting the stems of mature plants. Damping off has
been one of the major threats toCannabiscultivars. Apart from causing damping
off,F. oxysporiumis also responsible for causing severe wilt diseases or root rots.
Further, reports of serious damage to roots byR. solani, destroying almost 90% of
Cannabisplants in northern India (Pandotra and Sastry 1967 ), also highlights the
necessity of effectively addressing such threats relevant to this plant. In this study
by Qadri et al. ( 2013 ), six endophytic isolates were found effective againstfive
plant pathogens and exhibited highest degree of growth inhibition, whereas 24 other
isolates were slightly effective (more than 50%) against three or more pathogens.
Such growth inhibition further pointed towards the fact that fungal endophytes of
Cannabisare also effective against a broad range of phytopathogens, either specific
or non-specific to this plant.
424 P. Kusari et al.