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Since publication of a draft genome of the doubled-haploid 'Pahang' banana (Musa acuminata, DH-Pahang), a new era for banana biology research has begun. With the release of genomic data from some important Musa species and subspecies and the continuous development of molecular biology techniques, significant progress has been made. Here, we summarize the achievements and advances in the banana molecular biology and breeding over the past decade covering origin and domestication, fruit biology, stress biology, and breeding aspects, and highlight their challenges and future perspectives. This review is intended to provide researchers with the latest information on the complex genetic background and evolutionary relationship of bananas, the biology of fruit ripening, and multi-omics-based stress biology research. We especially focus on recent advances in the molecular breeding of bananas, offering an informative research direction and providing valuable technical references for future research in the field. [ABSTRACT FROM AUTHOR]

Abstract Since publication of a draft genome of the doubled-haploid ‘Pahang’ banana (Musa acuminata, DH-Pahang), a new era for banana biology research has begun. With the release of genomic data from some important Musa species and subspecies and the continuous development of molecular biology techniques, significant progress has been made. Here, we summarize the achievements and advances in the banana molecular biology and breeding over the past decade covering origin and domestication, fruit biology, stress biology, and breeding aspects, and highlight their challenges and future perspectives. This review is intended to provide researchers with the latest information on the complex genetic background and evolutionary relationship of bananas, the biology of fruit ripening, and multi-omics-based stress biology research. We especially focus on recent advances in the molecular breeding of bananas, offering an informative research direction and providing valuable technical references for future research in the field.

Banana Xanthomonas wilt (BXW) is a destructive disease caused by Xanthomonas vasicola pv. musacearum (Xvm), a bacterium that indiscriminately infects all banana varieties grown in East and Central Africa (ECA). In this region, BXW was first reported in 2001 in Uganda and was projected to eliminate >90% of Uganda's banana crops (worth USD4 billion) if not controlled in less than 10 years. Lack of basic information led to application of control approaches that were based on similarity of BXW symptoms to those of Moko disease of banana. However, the approaches were unsuccessful and, in 7 to 9 years, BXW had covered six countries and threatened to wipe out the banana industry in ECA. However, BXW has been tamed to date, mainly due to relentless and systematic deployment of carefully crafted and packaged cultural control practices based on epidemiological information generated within target banana cropping ecosystems. In Uganda, the initial “top-down” communication approaches reached >85% of banana farming communities but did not mobilize the communities enough into action; hence, only 30% impact in controlling BXW was registered. In contrast, participatory approaches mobilized farming communities into action and effectively controlled BXW at field and community levels to near eradication. The approaches effectively controlled BXW in Uganda and, consequently, in eastern Kenya, northern Tanzania, Rwanda, Burundi, and the Democratic Republic of Congo. This article reviews step-wise processes leading to success over the 2 decades and identifies critical research gaps. Deployment of resistant genotypes is urgently needed as a significant addition to the BXW management toolbox to create BXW-free banana cropping systems in ECA. [Graphic: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

The semiarid is characterized by extreme heat, which affects agricultural production by limiting the soil's ability to retain water. The objective of this study was to investigate the influence of mulch on soil temperature and soil moisture in a drip irrigated banana plantation in a Brazilian semiarid region. Six thermocouples and three soil moisture probes were used, with coconut coir as mulch. Daytime and nighttime surface temperatures were compared for two mulch densities (4 and 8 t ha-1) and bare soil. Soil temperature and moisture were measured at three depths (0.1, 0.3 and 0.5 m). The study was conducted from November 2014 to March 2015. Mulch had a buffer effect on soil temperature fluctuation. Drip irrigation management associated with mulch provided a uniform moisture profile close to field capacity.

The semiarid is characterized by extreme heat, which affects agricultural production by limiting the soil's ability to retain water. The objective of this study was to investigate the influence of mulch on soil temperature and soil moisture in a drip irrigated banana plantation in a Brazilian semiarid region. Six thermocouples and three soil moisture probes were used, with coconut coir as mulch. Daytime and nighttime surface temperatures were compared for two mulch densities (4 and 8 t ha-1) and bare soil. Soil temperature and moisture were measured at three depths (0.1, 0.3 and 0.5 m). The study was conducted from November 2014 to March 2015. Mulch had a buffer effect on soil temperature fluctuation. Drip irrigation management associated with mulch provided a uniform moisture profile close to field capacity. [ABSTRACT FROM AUTHOR]

[Objectives] To understand the characteristic and the function of Malnc2310,the cis-acting elements on the promoter, the response to Fusarium crude toxin and the potential binding factors were investigated through genetic methods. [Methods]The response of promoter P1(1625 bp) and three complement fragments including P2(400 bp), P3(800 bp) and P4(425 bp), to high salinity and fusarium crude toxin were investigated through the Arabidopsis transformation. The potential binding factors on the promoter P1 and the core binding domain were studied through yeast one-hybrid screening system. [Results]The promoter of Malnc2310 contained many cis-elements, mainly including constitutive regulatory elements, phytohormone response elements, pathogen and salicylic regulatory elements, and light responsive elements through online database analysis. The average activities of GUS in all promoter fragments were higher under the Fusarium crude toxin than high salinity treatment. Moreover, the activities of GUS under P3 were similar with those under P1 during different treatments. One zinc finger protein with two C2H2 domains called ZFP-WIP2 was verified to bind to P1 and P3 through one-hybridization system. [Conclusions]This research verifies the promoter of Malnc2310 is more responsive to Fusarium crude toxin than high salinity, and one zinc finger protein ZFP-WIP2 can bind to the promoter core domain (425-1 225 bp). [ABSTRACT FROM AUTHOR]

Key message: Seventeen classical MaAGPs and 9 MbAGPs were identified and analyzed. MaAGP1/2/6/9/16/17, the antigens of JIM13 and LM2 antibodies are likely to be involved in banana chilling tolerance. Classical arabinogalactan proteins (AGPs) belong to glycosylphosphatidylinositol-anchored proteins, which are proved to be involved in signaling and cell wall metabolism upon stresses. However, rare information is available on the roles of classical AGPs in low temperature (LT) tolerance. Cultivation of banana in tropical and subtropical region is seriously threatened by LT stress. In the present study, 17 classical MaAGPs and nine MbAGPs in banana A and B genome were identified and characterized, respectively. Great diversity was present among different classical MaAGP/MbAGP members while five members (AGP3/6/11/13/14) showed 100% identity between these two gene families. We further investigated different responses of classical AGPs to LT between a chilling sensitive (CS) and tolerant (CT) banana cultivars. In addition, different changes in the temporal and spatial distribution of cell wall AGP components under LTs between these two cultivars were compared using immunofluorescence labeling. Seven classical MbAGPs were upregulated by LT(s) in the CT cultivar. Classical MaAGP4/6 was induced by LT(s) in both cultivars while MaAGP1/2/9/16/17 only in the CT cultivar. Moreover, these genes showed significantly higher transcription abundance in the CT cultivar than the CS one under LT(s) except classical MaAGP4. Similar results were observed with the epitopes of JIM13 and LM2 antibodies. The antigens of these antibodies and classical MaAGP1/2/6/9/16/17 might be related to LT tolerance of banana. These results provide additional information about plant classical AGPs and their involvement in LT tolerance, as well as their potential as candidate genes to be targeted when breeding CT banana. [ABSTRACT FROM AUTHOR]

Hemicellulose is key in determining the fate of plant cell wall in almost all growth and developmental stages. Nevertheless, there is limited knowledge regarding its involvement in the development and ripening of banana fruit. This study investigated changes in the temporal-spatial distribution of various hemicellulose components, hemicellulose content, activities of the main hydrolysis enzymes, and transcription level of the main hemicellulose-related gene families in banana peels. Both hemicellulose and xylan contents were positively correlated to the fruit firmness observed in our previous study. On the contrary, the xylanase activity was negatively correlated to xylan content and the fruit firmness. The vascular bundle cells, phloem, and cortex of bananas are abundant in xyloglucan, xylan, and mannan contents. Interestingly, the changes in the signal intensity of the CCRC-M104 antibody recognizing non-XXXG type xyloglucan are positively correlated to hemicellulose content. According to RNA-Seq analysis, xyloglucan and xylan-related genes were highly active in the early stages of growth, and the expression of MaMANs and MaXYNs increased as the fruit ripened. The abundance of plant hormonal and growth-responsive cis -acting elements was detected in the 2 kb upstream region of hemicellulose-related gene families. Interaction between hemicellulose and cell wall-specific proteins and MaKCBP1/2, MaCKG1, and MaHKL1 was found. The findings shed light on cell wall hemicellulose's role in banana fruit development and ripening, which could improve nutrition, flavor, and reduce postharvest fruit losses. • Hemicellulose and xylan concentration positively linked with banana fruit firmness. • Xyloglucan recognized by CCRC-M104 was positively related to hemicellulose content. • The MaXYNs and MaMANs were increased significantly after fruit ripening. • The hormonal-responsive cis- elements were detected in high numbers. • The hemicellulose-related proteins strongly interacted with some growth-related ones. [ABSTRACT FROM AUTHOR]

Bananas (Musa spp.) are an important fruit crop worldwide. The fungus Fusarium oxysporum f. sp. cubense (Foc), which causes Fusarium wilt, is widely regarded as one of the most damaging plant diseases. Fusarium wilt has previously devastated global banana production and continues to do so today. In addition, due to the current use of high-density banana plantations, desirable banana varieties with ideal plant architecture (IPA) possess high lodging resistance, optimum photosynthesis, and efficient water absorption. These properties may help to increase banana production. Genetic engineering is useful for the development of banana varieties with Foc resistance and ideal plant architecture due to the sterility of most cultivars. However, the sustained immune response brought about by genetic engineering is always accompanied by yield reductions. To resolve this problem, we should perform functional genetic studies of the Musa genome, in conjunction with genome editing experiments, to unravel the molecular mechanisms underlying the immune response and the formation of plant architecture in the banana. Further explorations of the genes associated with Foc resistance and ideal architecture might lead to the development of banana varieties with both ideal architecture and pathogen super-resistance. Such varieties will help the banana to remain a staple food worldwide.

Bananas (Musa spp.) are an important fruit crop worldwide. The fungus Fusarium oxysporum f. sp. cubense (Foc), which causes Fusarium wilt, is widely regarded as one of the most damaging plant diseases. Fusarium wilt has previously devastated global banana production and continues to do so today. In addition, due to the current use of high-density banana plantations, desirable banana varieties with ideal plant architecture (IPA) possess high lodging resistance, optimum photosynthesis, and efficient water absorption. These properties may help to increase banana production. Genetic engineering is useful for the development of banana varieties with Foc resistance and ideal plant architecture due to the sterility of most cultivars. However, the sustained immune response brought about by genetic engineering is always accompanied by yield reductions. To resolve this problem, we should perform functional genetic studies of the Musa genome, in conjunction with genome editing experiments, to unravel the molecular mechanisms underlying the immune response and the formation of plant architecture in the banana. Further explorations of the genes associated with Foc resistance and ideal architecture might lead to the development of banana varieties with both ideal architecture and pathogen super-resistance. Such varieties will help the banana to remain a staple food worldwide. [ABSTRACT FROM AUTHOR]

Key messages: Thirty MaFLAs vary in their molecular features. MaFLA14/18/27/29 are likely to be involved in banana chilling tolerance by facilitating the cold signaling pathway and enhancing the cell wall biosynthesis. Although several studies have identified the molecular functions of individual fasciclin-like arabinogalactan protein (FLA) genes in plant growth and development, little information is available on their involvement in plant tolerance to low-temperature (LT) stress, and the related underlying mechanism is far from clear. In this study, the different expression of FLAs of banana (Musa acuminata) (MaFLAs) in the chilling-sensitive (CS) and chilling-tolerant (CT) banana cultivars under natural LT was investigated. Based on the latest banana genome database, a genome-wide identification of this gene family was done and the molecular features were analyzed. Thirty MaFLAs were distributed in 10 out of 11 chromosomes and these clustered into four major phylogenetic groups based on shared gene structure. Twenty-four MaFLAs contained N-terminal signal, 19 possessed predicted glycosylphosphatidylinositol (GPI), while 16 had both. Most MaFLAs were downregulated by LT stress. However, MaFLA14/18/29 were upregulated by LT in both cultivars with higher expression level recorded in the CT cultivar. Interestingly, MaFLA27 was significantly upregulated in the CT cultivar, but the opposite occurred for the CS cultivar. MaFLA27 possessed only N-terminal signal, MaFLA18 contained only GPI anchor, MaFLA29 possessed both, while MaFLA14 had neither. Thus, it was suggested that the accumulation of these FLAs in banana under LT could improve banana chilling tolerance through facilitating cold signal pathway and thereafter enhancing biosynthesis of plant cell wall components. The results provide background information of MaFLAs, suggest their involvement in plant chilling tolerance and their potential as candidate genes to be targeted when breeding CT banana. [ABSTRACT FROM AUTHOR]

Background: Banana (Musa spp.) is an important staple food, economic crop, and nutritional fruit worldwide. Conventional breeding has been seriously hampered by their long generation time, polyploidy, and sterility of most cultivated varieties. Establishment of an efficient regeneration and transformation system for banana is critical to its genetic improvement and functional genomics. Results: In this study, a vigorous and repeatable transformation system for banana using direct organogenesis was developed. The greatest number of shoots per explant for all five Musa varieties was obtained using Murashige and Skoog medium supplemented with 8.9 μM benzylaminopurine and 9.1 μM thidiazuron. One immature male flower could regenerate 380–456, 310–372, 200–240, 130–156, and 100–130 well-developed shoots in only 240–270 d for Gongjiao, Red banana, Rose banana, Baxi, and Xinglongnaijiao, respectively. Longitudinal sections of buds were transformed through particle bombardment combined with Agrobacterium-mediated transformation using a promoterless β-glucuronidase (GUS) reporter gene; the highest transformation efficiency was 9.81% in regenerated Gongjiao plantlets in an optimized selection medium. Transgenic plants were confirmed by a histochemical assay of GUS, polymerase chain reaction, and Southern blot. Conclusions: Our robust transformation platform successfully generated hundreds of transgenic plants. Such a platform will facilitate molecular breeding and functional genomics of banana.

The cell wall plays an important role in responses to various stresses. The cellulose synthase-like gene (Csl) family has been reported to be involved in the biosynthesis of the hemicellulose backbone. However, little information is available on their involvement in plant tolerance to low-temperature (LT) stress. In this study, a total of 42 Csls were identified in Musa acuminata and clustered into six subfamilies (CslA, CslC, CslD, CslE, CslG, and CslH) according to phylogenetic relationships. The genomic features of MaCsl genes were characterized to identify gene structures, conserved motifs and the distribution among chromosomes. A phylogenetic tree was constructed to show the diversity in these genes. Different changes in hemicellulose content between chilling-tolerant and chilling-sensitive banana cultivars under LT were observed, suggesting that certain types of hemicellulose are involved in LT stress tolerance in banana. Thus, the expression patterns of MaCsl genes in both cultivars after LT treatment were investigated by RNA sequencing (RNA-Seq) technique followed by quantitative real-time PCR (qPCR) validation. The results indicated that MaCslA4/12, MaCslD4 and MaCslE2 are promising candidates determining the chilling tolerance of banana. Our results provide the first genome-wide characterization of the MaCsls in banana, and open the door for further functional studies.

Micro-propagated plants of FHIA-01 (exotic hybrid dessert banana) were grown and their shoot-tip cultures were produced following standard method. Suckers were taken from the same plants as with the shoot-tip culture samples. The design was the randomly complete block. The plant density was 1667 plants/ha. Plants were fertilized at the rate of 40t/ha poultry manure per year split over 3 equal applications. Statistical analysis of data was performed with ANOVA. The field performance of in vitro propagated (tissue culture) tetraploid banana (FHIA-01) plants was compared with that of sucker-derived plants. In vitro-propagated plants established and grew faster, taller (240 cm) and bigger than the conventional sucker-derived plants. The former produced heavier bunches (39.1 t/ha) and could be harvested earlier. They however produced smaller number of fingers than the conventional sucker-derived plants. Significant differences were observed between the plant height and plant girth (48.6 cm) (at one metre above ground) at harvest. No significant difference was observed in bunch weight, number of hands, number of fingers and the number of leaves at harvest. The nutrient used in the Tissue culture medium may have played a significant role in the growth vigour of FHIA-01. It may also be having an influence on the performance of the hybrid. This influence may improve the yield of the crop thus improving the economy of farmers.

Information on the spatial distribution of arabinogalactan proteins (AGPs) in plant organs and tissues during plant reactions to low temperature (LT) stresses is limited. In this study, the extracellular distribution of AGPs in banana leaves and roots, and their changes under LT stresses were investigated in two genotypes differing in chilling tolerance, by immuno-techniques using 17 monoclonal antibodies against different AGP epitopes. Changes in total classical AGPs in banana leaves were also tested. The results showed that AGP epitopes recognized by JIM4, JIM14, JIM16 and CCRC-M32 antibodies were primarily distributed in leaf veins, while those recognized by JIM8, JIM13, JIM15 and PN16.4B4 antibodies exhibited predominant sclerenchymal localization. Epitopes recognized by LM2, LM14 and MAC207 antibodies were distributed in both epidermal and mesophyll cells. Both genotypes accumulated classical AGPs in leaves under LT treatment, and the chilling tolerant genotype contained higher classical AGPs at each temperature treatment. In addition, the abundance of JIM4 and JIM16 epitopes in the chilling-sensitive genotype decreased slightly after LT treatment, and this trend was opposite for the tolerant one. LT induced accumulation of LM2- and LM14-immunoreactive AGPs in the tolerant genotype compared to the sensitive one, especially in phloem and mesophyll cells. These epitopes thus might play important roles in banana LT tolerance. Different AGP components also showed differential distribution patterns in banana roots. In general, banana roots started to accumulate AGPs under LT treatment earlier than leaves. The levels of AGPs recognized by MAC207 and JIM13 antibodies in the control roots of the tolerant genotype were higher than in the chilling sensitive one. Furthermore, the chilling tolerant genotype showed high immuno-reactivity against JIM13 antibody. These results indicate that several AGPs are likely involved in banana tolerance to chilling injury.

The field performance of in vitro-propagated banana (Musa spp.) plants was compared with that of the sucker-derived plants. In vitro-propagated plants established and grew faster, taller and bigger than the conventional sucker-derived plants. The former produced more leaves resulting in a larger total leaf area (8001.5 cm2 per plant) than the latter (6613.1 cm2 per plant) and could be harvested earlier. The former also produced heavier bunches and fruit (15.2 kg for bunch and 200 g per finger of fruit) than the latter (9.0 kg for bunch and 136.4 g per finger of fruit). In this experiment, the in vitro-propagated plants had many intact roots and a bulk of vermiculite around their roots but the sucker-derived plants had many damaged roots at the time of planting. In addition, in vitro-propagated plants started growth earlier and grew faster enabling them to intercept more light for photosynthesis than the sucker-derived plants. This may explain the higher yield in the in vitro-propagated plants. We conclude that in vitro-propagated Shima banana performs better in terms of growth and yield than the sucker-derived plants under field conditions.

This paper describes the effects of auxin added to the culture medium on main and branch root formation of banana (Musa spp.) shoots and growth characters of the plantlet rooted on the medium with and without auxin. Banana shoots cultured in vitro on Murashige and Skoog medium supplemented with 2 μM 1-naphthylacetic acid (NAA), rooted earlier and also had more adventitious roots than those cultured on the medium without NAA. However, the adventitious roots formed on the medium without NAA showed more lateral branching. Plant height and number of leaves per plantlet in in vitro culture were not influenced by the addition of NAA but under nursery conditions, plantlets rooted without NAA showed better growth in terms of days to the appearance of new leaf, plant height and number of leaves per plant. This might be due to the presence of abundant lateral roots. Even though auxins are generally known to promote rooting, NAA inhibited the formation of lateral roots in Banana plants.

Highlights: [•] Relationship for ripening of bananas at 3 temperature and 4 ethylene levels was assessed. [•] The regression predicted scenarios for banana transport in Australia and Costa Rica to Europe. [•] Ambient trucking in Australia may occur in winter and summer at ≤0.90 and ≤0.58μL/L ethylene. [•] Shipping from Costa Rica to Europe may similarly occur at ≤0.04 and ≤0.002μL/L ethylene. [•] Technology available to reduce ethylene suggests refrigerated transport is not necessary. [ABSTRACT FROM AUTHOR]

Recent studies suggest that plant pectin methylesterases (PMEs) are directly involved in plant defence besides their roles in plant development. However, the molecular mechanisms of PME action on pectins are not well understood. In order to understand how PMEs modify pectins during banana (Musa spp.)–Fusarium interaction, the expression and enzyme activities of PMEs in two banana cultivars, highly resistant or susceptible to Fusarium, were compared with each other. Furthermore, the spatial distribution of PMEs and their effect on pectin methylesterification of 10 individual homogalacturonan (HG) epitopes with different degrees of methylesterification (DMs) were also examined. The results showed that, before pathogen treatment, the resistant cultivar displayed higher PME activity than the susceptible cultivar, corresponding well to the lower level of pectin DM. A significant increase in PME expression and activity and a decrease in pectin DM were observed in the susceptible cultivar but not in the resistant cultivar when plants were wounded, which was necessary for successful infection. With the increase of PME in the wounded susceptible cultivar, the JIM5 antigen (low methyestrified HGs) increased. Forty-eight hours after pathogen infection, the PME activity and expression in the susceptible cultivar were higher than those in the resistant cultivar, while the DM was lower. In conclusion, the resistant and the susceptible cultivars differ significantly in their response to wounding. Increased PMEs and thereafter decreased DMs acompanied by increased low methylesterified HGs in the root vascular cylinder appear to play a key role in determination of banana susceptibility to Fusarium. [ABSTRACT FROM AUTHOR]

Highlights: [•] Hormones and cell wall epitopes are compared in embryogenic and non-embryogenic banana calli. [•] Indole-3-acetic acid, abscisic acid and zeatin riboside are more abundant in embryogenic cells. [•] Fucosylated xyloglucans are more abundant in the cell walls of embryogenic cells. [•] The AGP epitopes JIM16, MAC204 and MAC207 are related to embryogenic competence. [Copyright &y& Elsevier]

Micro-propagated plants of FHIA-01 (exotic hybrid dessert banana) were grown and their shoot-tip cultures were produced following standard method. Suckers were taken from the same plants as with the shoot-tip culture samples. The design was the randomly complete block. The plant density was 1667 plants/ha. Plants were fertilized at the rate of 40 t/ha poultry manure per year split over 3 equal applications. Statistical analysis of data was performed with ANOVA. The field performance of in vitro propagated (tissue culture) tetraploid banana (FHIA-01) plants was compared with that of sucker-derived plants. In vitro-propagated plants established and grew faster, taller (240 cm) and bigger than the conventional sucker-derived plants. The former produced heavier bunches (39.1 t/ha) and could be harvested earlier. They however produced smaller number of fingers than the conventional sucker-derived plants. Significant differences were observed between the plant height and plant girth (48.6 cm) (at one meter above ground) at harvest. No significant difference was observed in bunch weight, number of hands, number of fingers and the number of leaves at harvest. The nutrient used in the Tissue culture medium may have played a significant role in the growth vigour of FHIA-01. It may also be having an influence on the performance of the hybrid. This influence may improve the yield of the crop thus improving the economy of farmers. [ABSTRACT FROM AUTHOR]

Banana (Musa spp.) is an important nutrient-rich fruit crop cultivated in the tropics and sub-tropics for local consumption and export. Targets for genetic improvement of banana range from improved fruit quality, yield, disease resistance, tolerance to biotic and abiotic stresses, and the biosynthesis of pharmaceutical compounds. Sterility has limited the success of generating new cultivars by conventional breeding. Tissue culture-based technologies that involve embryo rescue, the generation of somaclonal variation, and gene-transfer procedures are a useful adjunct to sexual hybridization, although considerable effort is required to establish robust protoplast-to-plant systems for somatic hybridization. Transformation involving Agrobacterium and biolistics- mediated gene transfer is feasible, underpinned by shoot regeneration from cultured cells and tissues. Molecular characterization of germplasm will facilitate the selection of material most relevant for incorporation into sexual and somatic genetic-improvement programs. [ABSTRACT FROM PUBLISHER]

Abstract: Recent multidisciplinary investigations document an independent emergence of agriculture at Kuk Swamp in the highlands of Papua New Guinea. In this paper we report preliminary usewear analysis and details of prehistoric use of stone tools for processing starchy food and other plants at Kuk Swamp. Morphological diagnostics for starch granules are reported for two potentially significant economic species, taro (Colocasia esculenta) and yam (Dioscorea sp.), following comparisons between prehistoric and botanical reference specimens. Usewear and residue analyses of starch granules indicate that both these species were processed on the wetland margin during the early and mid Holocene. We argue that processing of taro and yam commences by at least 10,200 calibrated years before present (cal BP), although the taro and yam starch granules do not permit us to distinguish between wild or cultivated forms. From at least 6950 to 6440 cal BP the processing of taro, yam and other plants indicates that they are likely to have been integrated into cultivation practices on the wetland edge. [Copyright &y& Elsevier]

The cell wall plays an important role in responses to various stresses. The cellulose synthase-like gene (Csl) family has been reported to be involved in the biosynthesis of the hemicellulose backbone. However, little information is available on their involvement in plant tolerance to low-temperature (LT) stress. In this study, a total of 42 Csls were identified in Musa acuminata and clustered into six subfamilies (CslA, CslC, CslD, CslE, CslG, and CslH) according to phylogenetic relationships. The genomic features of MaCsl genes were characterized to identify gene structures, conserved motifs and the distribution among chromosomes. A phylogenetic tree was constructed to show the diversity in these genes. Different changes in hemicellulose content between chilling-tolerant and chilling-sensitive banana cultivars under LT were observed, suggesting that certain types of hemicellulose are involved in LT stress tolerance in banana. Thus, the expression patterns of MaCsl genes in both cultivars after LT treatment were investigated by RNA sequencing (RNA-Seq) technique followed by quantitative real-time PCR (qPCR) validation. The results indicated that MaCslA4/12, MaCslD4 and MaCslE2 are promising candidates determining the chilling tolerance of banana. Our results provide the first genome-wide characterization of the MaCsls in banana, and open the door for further functional studies. [ABSTRACT FROM AUTHOR]

Information on the spatial distribution of arabinogalactan proteins (AGPs) in plant organs and tissues during plant reactions to low temperature (LT) is limited. In this study, the extracellular distribution of AGPs in banana leaves and roots, and their changes under LT stress were investigated in two genotypes differing in chilling tolerance, by immuno-techniques using 17 monoclonal antibodies against different AGP epitopes. Changes in total classical AGPs in banana leaves were also tested. The results showed that AGP epitopes recognized by JIM4, JIM14, JIM16, and CCRC-M32 antibodies were primarily distributed in leaf veins, while those recognized by JIM8, JIM13, JIM15, and PN16.4B4 antibodies exhibited predominant sclerenchymal localization. Epitopes recognized by LM2, LM14, and MAC207 antibodies were distributed in both epidermal and mesophyll cells. Both genotypes accumulated classical AGPs in leaves under LT treatment, and the chilling tolerant genotype contained higher classical AGPs at each temperature treatment. The abundance of JIM4 and JIM16 epitopes in the chilling-sensitive genotype decreased slightly after LT treatment, and this trend was opposite for the tolerant one. LT induced accumulation of LM2- and LM14-immunoreactive AGPs in the tolerant genotype compared to the sensitive one, especially in phloem and mesophyll cells. These epitopes thus might play important roles in banana LT tolerance. Different AGP components also showed differential distribution patterns in banana roots. In general, banana roots started to accumulate AGPs under LT treatment earlier than leaves. The levels of AGPs recognized by MAC207 and JIM13 antibodies in the control roots of the tolerant genotype were higher than in the chilling sensitive one. Furthermore, the chilling tolerant genotype showed high immuno-reactivity against JIM13 antibody. These results indicate that several AGPs are likely involved in banana tolerance to chilling injury.