Ganoderma Boninense Disease Detection by Near-Infrared Spectroscopy Classification
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sensors Review Ganoderma boninense Disease Detection by Near-Infrared Spectroscopy Classification: A Review Mas Ira Syafila Mohd Hilmi Tan 1, Mohd Faizal Jamlos 1,*, Ahmad Fairuz Omar 2 , Fatimah Dzaharudin 3, Suramate Chalermwisutkul 4 and Prayoot Akkaraekthalin 5 1 College of Engineering, Universiti Malaysia Pahang, Gambang 26300, Malaysia; [email protected] 2 School of Physics, Universiti Sains Malaysia, Gelugor 11800, Malaysia; [email protected] 3 Department of Mechanical, Kuliyyah of Engineering, International Islamic University Malaysia, Jalan Gombak 53100, Malaysia; [email protected] 4 The Sirindhorn International Thai-German Graduate School of Engineering (TGGS), King Mongkut’s University of Technology North Bangkok, Bangkok 10800, Thailand; [email protected] 5 Faculty of Engineering, King Mongkut’s University of Technology North Bangkok, Bangkok 10800, Thailand; [email protected] * Correspondence: [email protected]; Tel.: +60-1-2700-1248 Abstract: Ganoderma boninense (G. boninense) infection reduces the productivity of oil palms and causes a serious threat to the palm oil industry. This catastrophic disease ultimately destroys the basal tissues of oil palm, causing the eventual death of the palm. Early detection of G. boninense is vital since there is no effective treatment to stop the continuing spread of the disease. This review describes past and future prospects of integrated research of near-infrared spectroscopy (NIRS), machine learning classification for predictive analytics and signal processing towards an early Citation: Mohd Hilmi Tan, M.I.S.; G. boninense detection system. This effort could reduce the cost of plantation management and Jamlos, M.F.; Omar, A.F.; Dzaharudin, avoid production losses. Remarkably, (i) spectroscopy techniques are more reliable than other F.; Chalermwisutkul, S.; detection techniques such as serological, molecular, biomarker-based sensor and imaging techniques Akkaraekthalin, P. Ganoderma in reactions with organic tissues, (ii) the NIR spectrum is more precise and sensitive to particular boninense Disease Detection by diseases, including G. boninense, compared to visible light and (iii) hand-held NIRS for in situ Near-Infrared Spectroscopy measurement is used to explore the efficacy of an early detection system in real time using ML Classification: A Review. Sensors 2021, classifier algorithms and a predictive analytics model. The non-destructive, environmentally friendly 21, 3052. https://doi.org/10.3390/ s21093052 (no chemicals involved), mobile and sensitive leads the NIRS with ML and predictive analytics as a significant platform towards early detection of G. boninense in the future. Academic Editor: Simone Borri Keywords: oil palms; near-infrared spectroscopy; NIR spectrum ML classifier algorithms Received: 5 March 2021 Accepted: 20 April 2021 Published: 27 April 2021 1. Introduction Publisher’s Note: MDPI stays neutral The oil palm industry gives a major contribution to Malaysia’s economy and generates with regard to jurisdictional claims in profitable export earnings for the country. In 2018, oil palm contributed 37.9% to the gross published maps and institutional affil- domestic product (GDP) of the agricultural sector [1]. The Malaysian Palm Oil Board iations. (MPOB) reported that in 2019, Malaysia produced 17.18 tonnes per hectare of fresh oil palm fruit over 5.9 million hectares of the total planted area. Malaysia contributed 20.5% of world palm oil supplies, making Malaysia the world’s second-biggest palm oil manufacturer and exporter. Total export revenue was approximately RM 67.52 billion [2]. After 30 months Copyright: © 2021 by the authors. of planting, oil palm trees begin to produce fruit and can bear fruits for 20 to 30 years. Licensee MDPI, Basel, Switzerland. Oil palm is the world’s most efficient oil-bearing crop, which produces one tonne of oil in This article is an open access article just 0.26 hectares of land (www.mpob.gov.my) (accessed on 30 January 2020). distributed under the terms and Unfortunately, infection with G. boninense, a type of fungus, has caused great losses conditions of the Creative Commons in the production of oil palm, which is of significant concern to the palm oil industry. Attribution (CC BY) license (https:// Basal stem rot (BSR) disease caused by G. boninense can reduce the yield of oil palm creativecommons.org/licenses/by/ production by 80% (estimated USD 28.4 billion/RM 117.6 billion). This disease is the main 4.0/). Sensors 2021, 21, 3052. https://doi.org/10.3390/s21093052 https://www.mdpi.com/journal/sensors Sensors 2021, 21, x FOR PEER REVIEW 2 of 24 Sensors 2021, 21, 3052 2 of 21 Basal stem rot (BSR) disease caused by G. boninense can reduce the yield of oil palm pro- duction by 80% (estimated USD 28.4 billion/RM 117.6 billion). This disease is the main concernconcern whichwhich badlybadly affectsaffects SoutheastSoutheast Asia’sAsia’s oiloil palmpalm plantations,plantations, particularlyparticularly inin NorthNorth SumatraSumatra andand Malaysia Malaysia [ 3[3]]. G.. G. boninense boninensecan can infect infect oil palmoil palm trees trees at all at stages, all stages, from from seedlings seed- tolings mature to mature plants plants [4]. This [4] fungus. This fungus is found is tofound infect to seedlings infect seedlings and trees and less trees than less a year than old a inyear the old nursery in the [ 5nursery,6] and spreads[5,6] and in spreads the soil in through the soil roots through and roots the air and [7]. the air [7]. G.G. boninenseboninenseis anis an unnoticeable unnoticeable necrotrophic necrotrophic fungus fungus in the in earlythe early stages stages of infection of infection and formsand forms uniform uniform hyphae hyphae of infection of infection within within the host the [ 8host]. The [8] fungus. The fungus absorbs absorbs nutrients nutrients while producingwhile producing enzymes enzymes and mycelia and mycelia which which degrade degrade cell walls, cell walls, thus generatingthus generating the defense the de- mechanismfense mecha innism the in host the plantshost plants [9]. [9] The. The host host cell cell dies dies in in the the final final stage stage even even before before the the GanodermaGanoderma fruiting bod bodies,ies, b basidiomata,asidiomata, are are formed formed [10] [10.]. Secondary Secondary metabolites metabolites such such as asquinoline quinoline [11] [11 are] are released released in inthe the tree tree within within 24 24 h hof of a aG.G. boninense boninense infectioninfection toto combatcombat fungalfungal incursionincursion [[12,12,1313]].. QuinolineQuinoline belongsbelongs toto thethe secondarysecondary metabolitemetabolite alkaloidalkaloid groupgroup andand isis derivedderived fromfrom tryptophan,tryptophan, aa precursorprecursor basedbased onon aminoamino acidsacids [14[14,,1515]].. VariousVarious studiesstudies andand approachesapproaches havehave beenbeen carriedcarried outout toto controlcontrol BSRBSR diseasedisease inin oiloil palmpalm treestrees butbut asas yetyet therethere isis nono effectiveeffective detection method for G. boninense. boninense. ThisThis failurefailure hashas resultedresulted in the death death of of oil oil palm palmss due due to to the the late late detection detection of ofinfection. infection. When When the thedis- diseaseease symptoms symptoms begin begin to appear, to appear, more more than than half halfof the of internal the internal tissues tissues are already are already rotten rotten[16]. It [ 16takes]. It 1 takes to 2 years 1 to 2 for years young for young palms palmsto die from to die the from onset the of onset disease of disease symptoms, symptoms, while whilemature mature trees can trees live can only live up only to 3 up years to 3 [17] years. The [17 ].infection The infection causes causesrotten internal rotten internal tissues, tissues,which leads which to leads stem to fracture stem fracture and the and tree the might tree might collapse collapse at any at stage any stage of the of infection. the infection. The Theearliest earliest visible visible external external symptoms symptoms of BSR of BSR occur occur in the in the leafage leafage,, which which are are almost almost similar similar to tothe the physical physical condition condition of ofwater water stress, stress, malnutrition, malnutrition, hyperacid hyperacid soil soil or orhigh high soil soil water water sa- salinity,linity, as as shown shown in inFigure Figure 1 [18,1[ 19]18,.19 It]. is Ittherefore is therefore a physical a physical diagnosis diagnosis including including a hyper- a hyperspectralspectral imaging imaging method method,, but it butis not itis effective. not effective. FigureFigure 1.1. (a–d) Oil palm palm infected infected with with G.G. boninense boninense with ( a) rotten rotten bole bole tissue tissue,, ( (bb)) b basidiomataasidiomata of of G. boninense, (c) foliar symptoms, (d) decaying oil palm bole tissues [20]. G. boninense,(c) foliar symptoms, (d) decaying oil palm bole tissues [20]. EarlyEarly detectiondetection and and control control strategies strategies for G.for boninense G. boninenseare still are undeveloped, still undeveloped, although alt- it ishough identified it is identified as the major as the cause major of cause death of of death oil palms. of oil palms. To date, To removing date, removing the tree the is tree an effective method for preventing BSR disease from spreading to others [21]. This is done through isolation processes of trenching, ploughing, harrowing, clearing, burning and Sensors