000			07780nam a22002057a 4500
999			_c291824 _d291824
082			_a632.3 _bWON/EV Ph.D
100			_aWongamthing, R
245			_aEvaluation of phylloplane microorganisms for the management of early blight of Tomato (Solanum lycopersicum L.)
260			_aVellanikkara _bDepartment of Plant Pathology, College of Agriculture _c2024
300			_a227,LXII,IIIp.
502			_aPh.D
520	3		_aTomato (Solanum lycopersicum L.) is a widely grown vegetable and the most remunerative solanaceous crop in both tropics and sub tropics of the world. It is vulnerable to various biotic diseases among which, early blight caused by Alternaria solani is a destructive one. Management of diseases using biocontrol agents is a safe alternative in the integrated disease management system. However, success of a bioagent is dependent on its comparative survivability in the new niche. Therefore, the present investigation was undertaken to identify strains of beneficial microorganisms adept on the phylloplane of tomato for use against early blight as it is a disease affecting mainly the foliage. As part of the investigation, purposive sampling survey was conducted in Thrissur and Palakkad districts of Kerala. It was found that early blight is prevalent in all the areas surveyed and the disease severity on foliage varied from 23 to 78 per cent at various locations. Though several fungi were found to be associated with the disease, only six isolates collected from Pudukkad, Valapad, Mundathikode, Vadakarapathy, Nenmara and Parrisakal were identified as Alternaria sp.(PDK), A. alternata (VAL), Fusarium oxysporum (MUN), A. solani (VAD and NEM) and Corynespora cassiicola (PAR) which could be proved as pathogens on tomato. Phylloplane microorganisms were isolated from both the healthy and diseased leaves collected from plants at various locations and a total of 132 isolates were then subjected to preliminary in vitro screening for their ability to suppress A. solani and 59 were selected as they could antagonize the pathogen in various degrees. The antagonists thus selected were further screened by dual culture technique and 36 showed more than 60 per cent inhibition. The antagonism exerted by phylloplane isolates was clearly discerned by limited growth, or the complete absence of fungal mycelium in the inhibition zone between the pathogen and the test isolate. Out of the 36, five were selected as promising potential antagonists as they could give more than 80 per cent inhibition of the pathogen. The selected five are identified as Trichoderma spp. (PF2 and PRF1), Bacillus subtilis (MNB2), Bacillus mojavensis ii (TB1) and Ochrobactrum sp. (EB1) which showed per cent inhibition of 91.2, 90, 89.4, 88 and 85 respectively. Furthermore, when these isolates were tested for growth promotion on tomato, the vigour index of tomato seedlings varied from 2110 (Trichoderma sp., PF2) to 1676 (Bacillus mojavensis, TB1). As next step, selected antagonists were tested for induction of systemic resistance (ISR) on tomato by conducting a pot culture experiment. Increased accumulation of peroxidase (PO), polyphenol oxidase (PPO) and, phenylalanine ammonia-lyase (PAL) was observed in plants treated with phylloplane antagonists. Higher activity of PO and PPO was induced by Trichoderma sp. (PF2) and B. subtilis (MNB2) at fifth day after inoculation (DAI) of pathogen. The phylloplane antagonists Trichoderma sp. (PF2) and B. subtilis (MNB2) recorded 169.54 min-1 g -1 and 152.56 min-1 g -1 respectively for PO and 199.19 min-1 g -1 and 172.24 min-1 g -1 respectively for PPO. Higher activity of PAL at fifth DAI was obtained by Pseudomonas fluorescens (KAU) followed by Trichoderma sp. (PF2) and B. subtilis (MNB2) recording 209.86 min-1 g -1 , 198.59 min-1 g -1 and 180.85 min-1 g -1 respectively. However, the highest per cent reduction of early blight after the first spray (68.58) was effected by Trichoderma sp. (PF2) followed by (64.92 and 60.22) B. subtilis (MNB2) and Ochrobactrum sp. (EB1), respectively. The disease reduction at early stage was reflected on yield of tomato and the same treatments; Trichoderma sp. (PF2), B. subtilis (MNB2) and Ochrobactrum sp. (EB1) gave 410 g, 389.33 g and 340 g fresh tomatoes per plot respectively. Hence these three phylloplane antagonists were selected for further evaluation. An experiment was carried out under rain shelter to evaluate the efficacy of the selected antagonists, conventional biocontrol agents such as Trichoderma sp. (KAU) and P. fluorescens (KAU) and a chemical check, propineb (0.2 %). The results showed that the phylloplane antagonists Trichoderma sp. (PF2) and B. subtilis (MNB2) offered significant effect against the disease recording 40.74 and 37.04 reduction in per cent disease severity (PDS) which in turn resulted in per cent yield increase of 32.63 and 28.10 respectively. Enumeration of phyllopane microflora proved that, there is drastic reduction in microbial population on leaf surface after iii spraying with propineb whereas the population increased after application of bioagents. Further, it was found that Trichoderma sp. (PF2) and B. subtilis (MNB2) are compatible with P. fluorescens (KAU) but B. subtilis (MNB2) is not compatible with Trichoderma sp. (KAU). Trichoderma sp. (PF2) is weakly inhibited by propineb (0.2 %), but azoxystrobin (0.1 %) could reduce its growth by 58 per cent. However, B. subtilis (MNB2) could not be affected by any of the two fungicides used against leaf blight. Hence, based on the results of various experiments in this study, phylloplane antagonists, especially, B. subtilis (MNB2) seems to be suitable for inclusion in IDM for early blight of tomato. Enumeration of culturable microflora on tomato leaves revealed that, bacteria are more on healthy leaves while fungi are more on the infected leaves. However, metagenomic analysis of the phylloplane revealed great difference in density and diversity of microbial taxa between healthy and infected leaves. This indicates that, specific functions of the phylloplane microbes and their antagonistic potential are also important in determining their efficacy as biocontrol agents. The study also revealed the presence of plant pathogenic fungal genera like Cladosporium, Corynespora, Pseudocercospora, Conidiosporomyces and Ustilago on tomato leaves. Both healthy and diseased tomato leaves harbour great microbial diversity and the phylloplane dwellers include well-known antagonists like species of Bacillus, Pseudomonas, Trichoderma and Penicillium. Presence of members of genera like Klebsiella and Enterobacter which are human pathogens was also revealed by metagenomic analysis. However, they are beneficial to plants as N fixers, P and K solubilizers and siderophore and IAA producers. Phylloplane dwellers also include species of Methylobacterium, Sphingomonas and Massilia and they are reported to produce different pigments and antibiotics besides being plant growth promoters, and antagonists to plant pathogens. Furthermore, species of Staphylococcus, Cladosporium, Coprinellus and Moesziomyces are also detected from tomato phylloplane and are reported to have antifungal properties with good plant growth attributes, while species of Meira are reported as potential biological control agents against phytophagous mites
650			_aPlant Pathology
650			_aphylloplane microorganisms
650			_aTomato
650			_aSolanum lycopersicum L.
700			_aSainamole Kurian, P(Guide)
856			_uhttps://krishikosh.egranth.ac.in/handle/1/5810220710
942			_2ddc _cTH