Table 2.
Potential and actual impacts of climate change on some Pacific food crops and associated crop improvement interventions
| Scientific name | Local names | Climatic factor and observed and/or anticipated impacts in the Pacific Islands | Crop improvement interventions | ||||
|---|---|---|---|---|---|---|---|
| Cyclones | High rainfall and flooding | Low rainfall and dry spells | Saltwater intrusion | Increased temperature | |||
| Root and tuber crops | |||||||
| Colocasia esculenta |
Taro (English), dalo (Fiji), talo (Samoa, Tonga), taro tru (PNG) |
Outbreaks of taro cluster caterpillar or armyworm (Liyanage and Misipati 1993; Carmichael et al. 2008) |
Increased incidences of TLB (Bourke and Allen 2009; Carmichael et al. 2008; Onwueme 1999; Singh et al. 2012) Corm rot (Pythium spp.) (Carmichael et al. 2008; Liyanage and Misipati 1993) |
Low stomatal conductance, reduced tuberization and yield (Daryanto et al. 2016; Gouveia et al. 2020; Sahoo et al. 2018) Increased breeding of taro beetle (Freeman et al. 2012) |
Yellowing and dieback of leaf margins and death of plant (Miyasaka et al. 2002) | Increased incidences of TLB (Bourke and Allen 2009; Onwueme 1999; Singh et al. 2012) |
Broadening of the genetic base to target specific needs such as biotic (especially for TLB resistance) and abiotic stress Marker aided selection and back cross breeding for armyworm and taro beetle Breeding for highly nutritionally rich, consumer-preferred varieties coupled with climate-resilient traits |
| Cyrtosperma merkusii |
Giant swamp taro (English), paluku, puraka (Cook Islands), babai, te babai (Kiribati), pula’a (Samoa), via kana (Fiji), pulaka (Tuvalu), navia (Vanuatu) |
Limited wind damage (Pobar et al. 2014; Taylor et al. 2019) | Flood tolerant (Plucknett 1977; Thomas 2019) |
Drying out of taro pits and death of plants (Freeman et al. 2012), Prolonged droughts increase soil salinity, reduce growth and cause rotting of corms (Tekinene 2014) |
Wilting, leaf chlorosis and yield reduction (Rao 2014) | Increased incidences of corm rot (Murukesan et al. 2005; Jeger et al. 2017) |
In vitro screening of giant swamp taro for salinity and waterlogging conditions Identification of saline-resistant germplasm accessions (possibly from Micronesia) Breeding early maturing cultivars and in vitro screening for drought tolerance |
| Ipomea batatus | Sweet potato (English), kumala (Tonga), umala (Samoa) | Tolerant to cyclones (Taylor et al. 2016) |
Reduced root growth due to waterlogging (Iese et al. 2018) Wetter weather also increases scab incidence (Taraken and Ratsch 2009) |
Increased population of sweet potato weevil and yield loss (Iese et al. 2018) Drying up of stem and vines, and stunted growth (Mael 2013) |
Reduced root growth and relative growth rate (Richardson and Caligari 2014) | Reduced tuber formation (Bourke and Allen 2009) |
In vitro conservation and screening of saline-tolerant genetic resources Primary and secondary introduction of pest and diseaseresistant varieties Broadening of genetic diversity for waterlogging conditions through participatory plant breeding approach |
| Dioscorea spp. | Yam (English), uvi (Fiji), u'i (Cook Islands), ufi (Samoa), mami (PNG) |
Highly susceptible to cyclone damage (Taylor et al. 2016) Anthracnose incidence increases (Wright and Peters 2002; O’Sullivan 2010) |
Anthracnose incidence increases (Wright and Peters 2002; O’Sullivan 2010) Rotting and death of plant (Onwueme et al. 1994) |
Tuberization is delayed and yield reduced. (Onwueme et al. 1994; Daryanto et al. 2016) | Salt intolerant, necrosis and poor root development (O’Sullivan 2010) | Reduced tuberization (Bell and Taylor 2015; Onwueme et al. 1994) |
Wild relatives could be utilized for enhancing pest and disease resistance and increasing tuber yield Ex-situ and In-situ conservation of traditional farmer varieties for mining desirable genes |
| Manihot esculenta | Cassava (English), tavioka (Fiji), manioka (Samoa), manioc (Vanuatu), maniota (Cook Islands) | Strong winds can cause lodging of plants resulting in severe root damage (McGregor and Sheehy 2019) |
Root rot (Akrofi et al. 2018; Lebot 2009) Higher incidences of Cassava Bacterial Blight (CBB), anthracnose and superelongation disease of cassava (Frison and Feliu 1991) |
Tolerant to droughts (FAO 2010) Reduced biomass, growth and yield, and increase in the concentration of cyanogens (Vandegeer et al. 2012; Burns et al. 2010, Wasonga et al. 2020) |
Reduced biomass, leaf area and rate of photosynthesis, and low concentration of macro and micronutrients in tubers (Gleadow et al. 2016) | Increased infestation of whitefly, vector of cassava mosaic and cassava brown streak diseases (Macfadyen et al. 2018) |
Genomics, transcriptomics and metabolomics approach for cyanogen accumulation in varied temperatures Improving the existing genetic material present in PICs through recombinant DNA techniques and next-generation sequencing technique Broadening the genetic base of cassava varieties in PICs |
| Plantation and horticultural crops | |||||||
| Artocarpus altilis | Breadfruit (English), uto, buco (Fiji), beta (Vanuatu), bia, bulo (Solomo Islands), kapiak (PNG) |
Reduction in fruit size and number of fruiting trees (Campell 1951; Iese et. 2015) Wilting, leaf damage, stunted growth, branch breakage (Roberts-Nkrumah 2015) |
Flower mortality and increased incidences of fruit rot (Roberts-Nkrumah 2015; Taylor et al. 2016) |
Fruit drop, smaller fruit size, increased tree mortality (Freeman et al. 2012; Taylor et al. 2016) No new flowering in late-season drought (Roberts-Nkrumah 2015) |
Increased incidences of infestation by the trunk rot disease (Phellinus noxious) (PestNet 2020) Stunted trees (Freeman et al. 2012) |
Fruit drop, smaller fruit size (McGregor et al. 2016) Increased incidences of fruit rot (Roberts-Nkrumah 2015; Taylor et al. 2016) |
Elucidating the regulatory genes that modify primary sex ratios and flower, fruit development under temperature variations Utilization of Crop Wild Relatives (CWRs) i.e. A. camansi, A. mariannensis for climate resilience Seedless and high pulp varieties to be evolved through ploidy breeding In vitro techniques for micropropagation, conservation, and disease-free planting materials In vitro mutagenesis to develop dwarf varieties Participatory plant breeding for developing climate-resilient varieties Community clonal seed bank for in-situ conservation |
| Cocus nucifera | Coconut (English), nu (Cook Islands), niu (Fiji, PNG), ni (Marshall Islands) | Uprooting, stripping of fronds, premature nut fall, damage to young inflorescence, delayed nut production, increased chances of infestation by coconut rhinoceros beetles (Taylor et al. 2016; Fiji Times Online 2017) | – |
High incidences of Coconut Foliar Decay Virus (CFDV) (Taylor et al. 2016) Decline in the quality and yield of coconut, premature falling of nuts and increased tree senility (Freeman et al. 2012) |
Stunted growth and yellowing of coconut trees (Freeman et al. 2012) |
Increasing incidences of infestation by CFDV and the burrowing nematode R. similis (Taylor et al. 2016; Jeger et al. 2017) Reduced fruit sets, and flower and fruit abortions (Ranasinghe et al. 2015) |
Breeding coconut hybrids (Vanuatu tall x Semi dwarf) for tolerance to Coconut foliar decay disease In-situ conservation of landraces for desirable genes Embryo culture to develop suitable high yielding semi-dwarf varieties Exploiting male sterility and self-incompatibility for hybrid development In vitro screening of coconut varieties for drought tolerance Association mapping studies can be perpetrated in natural populations |
| Musa spp. | Banana and plantain (English), leka, jaina (Fiji), fa’i (Samoa), sou (Solomon Islands), hopa (Tonga) | Leaf shredding and drying, distortion of the crown, uprooting due to strong winds, and Black Leaf Streak Disease (BLSD) increases in the post-cyclone phase (Taylor et al. 2016) | Increased rotting, and incidences of BLSD, Banana Bunchy Top Virus (BBTV) and Panama wilt (FAO, 2012; Bebber 2019; de Jesus Júnior 2008; Ghini et al. 2011; Niyongere et al. 2013) | Slow rate of leaf emergence, delay in fruit maturity, smaller fruit size and low yield (Thornton and Cramer 2012; Iese et al. 2015) | – |
Heatwaves slow down development and ripening of bunches, plants stop bearing fruits (FAO 2008a, b; Taylor et al. 2016; Thornton and Cramer 2012) Increased incidences of infestation by Panama wilt, BBTV, BLSD and root-burrowing nematodes (Masters and Norgrove 2010; Ghini et al, 2011; Freeman et al. 2012; Calberto et al. 2015; Thornton and Cramer 2012; Niyongere et al. 2013) |
Maintaining a wide range of species diversity Exploiting the wild Musa species (Musa ingens) to increase the allelic diversity In vitro conservation of drought-tolerant ABBB tetraploid genome Mutagenesis and irradiation studies to develop salt-tolerant varieties Wide hybridization and embryo rescue techniques to transfer resistant genes from CWRs Evolution of dwarf and early varieties to evade wind damage through mutation breeding and reverse genetics Precision breeding for climate change Primary introduction of high yielding, leaf streak-resistant varieties to the PICs Establishment of clonal banks for the conservation of genetic resources |
| Carica papaya | Papaya (English), pawpaw, weleti, wi, maoli (Fiji), lesi (Tonga), esi (Samoa), popo (Vanuatu) | Strong winds cause deformed and crinkled leaves, reduced growth, fruit set, fruit quality, and yield, uprooting (Nishina et al. 2000; Paull and Duarte 2011) |
Increased incidences of fungal diseases (Nishina et al. 2000; Paull and Duarte 2011) and Bacterial Crown Rot (Fullerton et al. 2011; Jackson 2017) Chlorosis, loss of leaf turgidity (Chan 2009), leaf abscission and root rots (Paull and Duarte 2011) |
Hermaphrodite flowers become pistillate, flower drop and reduced fruit sets (Teves, 2016; Chan 2009; Paull and Duarte 2011) |
Salt sprays desiccate leaves and kill plants (Nishina et al., 2000) Reduction in leaf area and phytomass (Lima Neto et al. 2016; Sousa et al. 2019) |
Hermaphrodite flowers become pistillate, flower drop and reduced fruit sets (Teves 2016, Chan 2009; Paull and Duarte 2011) Increased incidences of Papaya Ringspot Virus (PRV) (Kalleshwaraswamy et al. 2007) Female sterility, low fruit set and yield (Nishina et al. 2000) |
Germplasm exchange of transgenic ringspot-resistant varieties Backcross breeding for ringspot tolerance Hybridization for drought-tolerant varieties with superior yield Embryogenic culture for developing anthracnose-resistant varieties |
| Mangifera indica | Mango (English), manggo, am (Fiji), kangit (Pohnpei), mago (Samoa), idele (Palau) | Branch breakage and uprooting (Janick and Paull 2008; Crane et al. 2009) | Increased incidences of Mango Anthracnose and reduced yield (Bally 2006; Nelson 2008; Tsatsia and Jackson 2017) | Fruit drop and low fruit mass (Bally 2006; Wei et al. 2017; Janick and Paull 2008) | Necrosis, defoliation and leaf abscission, stem dieback, reduced growth and tree death (Janick and Paull 2008; Vieccelli 2017; Deivasigamani et al. 2019) |
Short growth period of panicles and flowers, reduced flowering duration, flower life span, and days for effective pollination, low productivity (Shu 1999; Nath et al. 2018) Reduced inflorescence size and increased leaf size (Dambreville et al. 2013; Whiley 1989) |
Popular rootstock introduction for abiotic stress tolerance In vitro mutagenesis may be emphasized to develop dwarf trees for vulnerable areas Embryogenic culture for developing anthracnose-resistant varieties Interspecific crosses (M. laurina x M. indica) for anthracnose resistance |
| Areca catechu | Betel nut, areca nut (English), angiro (Solomon Islands), bua (Palau), bu (Yap), pugua (Guam), poc (Pohnpei) | Low wind tolerance (Staples and Bevacqua 2006) | Higher incidence of fruit rot, reduced pollination and nut development (Sujatha et al. 2018) |
Flower abortion and reduced yield |
Wilting and death of trees (Caritas 2018) | – |
Development of disease-resistant varieties Development of interspecific hybrids to tolerate temperature stress |
| Underutilized/orphan crops | |||||||
| Pandanus tectorius | Pandanus, screw pine (English), vadra, voivoi (Fiji), binu (Pohnpei), ongor (Palau), te kaina (Kiribati), choy (Yap) | Bent leaves, fruits, stem and branches, uprooting of the tree (Thomson et al. 2006; Calvert 2011) | – | Drought-tolerant species (Taylor et al. 2016) |
Prolonged exposure to saltwater intrusion causes dieback or death of the tree (Taylor et al., 2016) Stunted trees (Freeman et al. 2012) |
– |
Developing varieties with good pollarding capability, fragrance and rich in carotenoids Germplasm conservation and increasing allelic diversity Mass multiplication of plant propagules through in vitro techniques Exploiting apomictic nature of the plant for climate resilient and improved sex-specific traits Studies to identify GXE interaction for climate change |
| Amaranthus spp. | Amaranth (English), moca (Fiji), te moota (Kiribati), katule (Niue), tupu'a (Tonga) | Seed shattering, lodging, and stem breakage during strong wind conditions (Paredes-Lopez 2017; Hoidal et al. 2019) |
High rainfall and relative humidity enhances the production of white rust zoospores (Albugo bliti) (Wang and Ebert 2012) Lodging under high rainfall (Paredes-Lopez 2017) |
Drought-tolerant crop (Hoidal et al. 2019) | Salt-tolerant plant (Sarker et al. 2018) |
White rust of amaranth is a serious problem during hot summer months (Wang and Ebert 2012) |
Allelic diversity to be maintained In vitro conservation of Amaranths Seed conservation through participatory breeding approach Breeding for non-shattering, lodging resistant, dwarf varieties Mutation breeding |
| Abelmoschus manihot | Slippery Cabbage, Island Cabbage (English), bele (Fiji), aibika (PNG), nuk (Vanuatu), baera (Solomo Islands), pele (Tonga), | Shoot and stem breakage (Taylor et al. 2016) | Increased rainfall favours collar rot, stem and tip rot, fusarium wilt and aibika shoot borer caterpillar (Solomon Islands Government 2014; Preston 1998; Taylor et al. 2016; Rauka and Shigaki 2015) |
Leaf area reduction during prolonged dry spells and drought, leaves turn leathery and fibrous in dry sites, slow growth (FAO 2009; Lyons et al. 2015; Taylor et al. 2016) |
Slow growth rate, reduced number of leaves and yield (Sen 2017) |
– |
In-situ and ex-situ conservation of bele varieties Genetic improvement for drought tolerance Identifying micronutrient rich, climate-resilient varieties through participatory plant breeding approaches Eco-TILLING for heat tolerance and temperature stress Developing Expressed Sequence tags for yield traits Virus indexing for Hibiscus Chlorotic Ringspot Virus |
| Saccharum edule | Duruka (Fiji), navisco (Vanuatu), pitpit (PNG) | Crop damage (ILO 2016) | No flower setting (McLean and Heckler 2017) | – | – | – |
Rescue and establishment of an ex-situ collection of duruka genetic resources in the Pacific Conservation of the crop through tissue culture Increasing genetic enhancement and base broadening through molecular techniques and participatory plant breeding approaches |
| Other crops | |||||||
| Saccharum officinarum | Sugarcane (English), ale, kowu (PNG) | Broken tops, leaf shredding, stalk breakage and lodging (Bedasse 2017) | Reduction in cane height and diameter, tiller number, leaf area, crop yield and nutrient imbalance (Gomathi et al. 2015) |
Increase in the population of the insect vector, Perkinsiella species and increase in Fiji Disease virus (Taylor et al. 2016) Reduced cane height, diameter and weight, and sugar yield (Dinh et al. 2018; Misra et al. 2020) |
Lower juice quality (Lingle and Wiegand 1997) Reduced biomass, cane length and crop yield (Vasanha et al. 2010) |
Reduced sucrose content, length of internodes and increased stalk fibre (Bonnet et al. 2006) Increased incidences of Fiji Leaf Gall Disease (Vercambre 2010) |
Crop improvement techniques for evolving new sugarcane cultivars well adapted to climate change (especially temperature stress) by detecting and introducing gainful genes/QTLs Sugarcane variety divergence for climate change |
| Oryza sativa | Rice (English), raisi (Fiji) | Lodging, stripping, and injury to plants (Blanc and Strobl 2016) | Lodging and death of plants due to prolonged submergence or flooding (Nishiuchi et al. 2012; Oladosu et al. 2020) | Reduced biomass accumulation, leaf area, tiller, and panicle number, delay in flowering and spikelet sterility (Barnabas et al. 2008; Dar et al. 2020; Saikumar et al. 2016) | Nutrient deficiencies and low rice grain yield (Hussain et al. 2017; Razzaq et al. 2019) |
Spikelet sterility and yield reduction (Endo et al. 2009; Korres et al. 2017; Thuy and Saitoh 2017; Yang et al. 2017) Low rice quality (Korres et al. 2017; Lanning et al. 2011; Lyman et al. 2013; Morita et al. 2016; Patindol et al. 2014) |
Eco-TILLING and mutation breeding for developing climate-smart rice Nano biotechnology for developing biofilms to avoid transpiration loss and stomata functioning during submergence conditions Germplasm conservation of Pacific rice varieties |
| Piper methysticum | Yagona (Fiji), seka (Kosrae), ava (Samoa), awa (Hawaii), kava (Marquesas), sakau (Pohnpei), kavainu (Nuie), waka (Tonga) | Breakage of tops, disturbance to roots and death of plants (McGregor and McGregor 1999) | Wilting, root rot and reduced root growth (PHAMA 2017) |
Increased aphid population (vector of CMV and kava dieback) in dry weather (Davis and Brown 1999; Davis 1999) |
Root rot, wilting, desiccation of leaves and death of the plant |
– |
The gene regulation network should be studied for floral development mechanism to break sterility in kava Developing pest and disease-free planting materials through meristem tip culture especially for kava dieback and CMV Broadening the genetic base through crop improvement strategies |