Advances in Tropical Fruit Cultivation and Breeding

A topical collection in Horticulturae (ISSN 2311-7524). This collection belongs to the section "Fruit Production Systems".

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Editors


E-Mail Website
Collection Editor
College of Horticulture, South China Agricultural University, Guangzhou 510642, China
Interests: litchi; longan; grape; calcium; photosynthesis; carbohydrates; water relation; shoot growth cycle; flowering; fruit development

E-Mail Website
Collection Editor
College of Horticulture, South China Agricultural University, Guangzhou 510642, China
Interests: lychee; fruit development; fruit abscission; cultivation; biotechnology and physiology; genetic resources and breeding

E-Mail Website
Collection Editor
Horticulture Division, Agricultural Research Council—Tropical and Subtropical Crops, Mbombela 1200, South Africa
Interests: horticultural science; subtropical fruit tree crops; plant growth regulators; pruning; fruit quality improvement

Topical Collection Information

Dear Colleagues,

Tropical fruits are important to many developing countries in their contribution toward export earnings and income and as a source of nutrition. According to incomplete statistics, there are more than 300 tropical fruit crops, including wild species whose fruits can be eaten. The main tree species include banana, mango, lychee, pineapple, avocado, dragon fruit, longan, sugar apple, guava, rambutan, papaya, passionflower, and so on. The planting area and output of tropical fruits are also increasing worldwide. Therefore, more and more pomologists are focusing on research in and the sustainable production of tropical fruit crops.

The proposed Topical Collection on “Advances in Tropical Fruit Cultivation and Breeding” aims to discuss the major challenges confronting tropical and subtropical fruit-producing countries, including all aspects of tropical fruit production, cultural practices, and breeding. The main themes focus on flowering, fruit set and alternate bearing, pruning, thinning, fertilization, irrigation and water relations, biostimulants and plant growth regulators, biotechnology and physiology, genetic resources and breeding, etc.

We invite horticulturalists to contribute both original research articles and reviews to this Topical Collection and to share your achievements in the field of tropical fruit crops.

Prof. Dr. Xuming Huang
Prof. Dr. Jianguo Li
Dr. Regina Cronje
Collection Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Horticulturae is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2200 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • tropical fruit
  • cultivation
  • flowering
  • fruit set and development
  • biotechnology and physiology
  • genetic resources and breeding

Published Papers (17 papers)

2024

Jump to: 2022, 2021

12 pages, 1200 KiB  
Article
Yellow Pitahaya (Selenicereus megalanthus Haw.) Growth and Ripening as Affected by Preharvest Elicitors (Salicylic Acid, Methyl Salicylate, Methyl Jasmonate, and Oxalic Acid): Enhancement of Yield, and Quality at Harvest
by Alex Estuardo Erazo-Lara, María Emma García-Pastor, Pedro Antonio Padilla-González, María Serrano and Daniel Valero
Horticulturae 2024, 10(5), 493; https://doi.org/10.3390/horticulturae10050493 - 10 May 2024
Viewed by 459
Abstract
Yellow pitahaya (Selenicereus megalanthus Haw.) is an exotic fruit with great potential for exportation in Ecuador. The research was carried out with the objective of evaluating the fruit growth and ripening as affected by four elicitors: salicylic acid (SA), methyl salicylate (MeSa), [...] Read more.
Yellow pitahaya (Selenicereus megalanthus Haw.) is an exotic fruit with great potential for exportation in Ecuador. The research was carried out with the objective of evaluating the fruit growth and ripening as affected by four elicitors: salicylic acid (SA), methyl salicylate (MeSa), methyl jasmonate (MeJa), and oxalic acid (OA), all of them at 1, 5, and 10 mM concentration, compared with untreated plants (control). For each elicitor, nine plants were selected, and on each plant, three fruits were marked to follow up the growth by measuring polar and equatorial diameters. At harvest, yield (kg plant−1 and number of fruits plant−1), fruit weight, percentage of pulp and skin, total soluble solids (TSS), titratable acidity (TA), and firmness were determined. Treated plants enhanced fruit size, crop yield, and fruit weight compared with control fruits, although results depended on the elicitor tested and applied doses. The highest and lowest TSS were found in 10 mM MeSa and 5 mM MeJa-treated fruit, respectively, while the highest TA content was shown in 5 mM SA. Firmness was only enhanced in MeJa-treated fruits. Overall, results suggest that preharvest use of elicitors could modulate the pitahaya ripening and could improve quality attributes at harvest. Full article
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2022

Jump to: 2024, 2021

12 pages, 2845 KiB  
Article
Transcriptome Analysis on the Underlying Physiological Mechanism of Calcium and Magnesium Resolving “Sugar Receding” in ‘Feizixiao’ Litchi Pulp
by Junjie Peng, Jingjia Du, Wuqiang Ma, Tiantian Chen, Xian Shui, Haizhi Liao, Xiaokai Lin and Kaibing Zhou
Horticulturae 2022, 8(12), 1197; https://doi.org/10.3390/horticulturae8121197 - 14 Dec 2022
Cited by 1 | Viewed by 1224
Abstract
The sugar contents of ‘Feizixiao’ litchi (Litchi chinensis Sonn.) decrease at full maturity; calcium (Ca) and magnesium (Mg) foliar fertilizer can resolve this “sugar receding”. To investigate the physiological mechanism of Ca and Mg foliar fertilizer used to resolve the “sugar receding” [...] Read more.
The sugar contents of ‘Feizixiao’ litchi (Litchi chinensis Sonn.) decrease at full maturity; calcium (Ca) and magnesium (Mg) foliar fertilizer can resolve this “sugar receding”. To investigate the physiological mechanism of Ca and Mg foliar fertilizer used to resolve the “sugar receding” phenomenon in ‘Feizixiao’ litchi pulp, 16-year-old litchi trees were treated with 0.3% CaCl2 + 0.3% MgCl2 foliar spraying or water as a control. We determined the pulp sugar content over a two-year period in 2020 and 2021. Pulp total RNA was extracted for transcriptome sequencing in 2020, and the expression pattern of 10 differentially expressed genes (DEGs) was verified by real-time PCR in 2020 and 2021. The results showed that the fertilizer treatment significantly increased pulp fructose and total soluble sugar contents at maturity in both years. According to Gene Ontology (GO) functional enrichment analysis, there were 155 DEGs divided into 35 GO categories, among which 49 DEGs were divided into 49 pathways according to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. We isolated sugar-metabolism-related enzyme genes, including sucrose synthase (SS), acid invertase (AI), neutral invertase (NI), sucrose phosphate synthase (SPS), and hexokinase (HK). All sucrose-metabolism-related enzyme (NI, AI, SS, SPS) genes were downregulated, and six of the seven HK genes were downregulated. The expression patterns of the 10 DEGs were verified by real-time PCR, which showed significant linear relationships (r2020 = 0.9127, r2021 = 0.8705). In conclusion, the fertilizer treatment inhibited the synthesis of sucrose and phosphorylation of hexose by downregulating the expression of the SS, SPS, and HK genes, thus increasing the fructose and total soluble sugar contents in ‘Feizixiao’ litchi. Full article
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11 pages, 651 KiB  
Review
Aroma Volatiles in Litchi Fruit: A Mini-Review
by Zhuoyi Liu, Minglei Zhao and Jianguo Li
Horticulturae 2022, 8(12), 1166; https://doi.org/10.3390/horticulturae8121166 - 8 Dec 2022
Cited by 2 | Viewed by 1862
Abstract
Aroma is considered a fundamental component of fruit flavor. Variations in the composition and content of volatile organic compounds (VOCs) contribute to noticeable differences in fruit aromas. Litchi is a delicious tropical and subtropical fruit, and a large number of germplasm resources with [...] Read more.
Aroma is considered a fundamental component of fruit flavor. Variations in the composition and content of volatile organic compounds (VOCs) contribute to noticeable differences in fruit aromas. Litchi is a delicious tropical and subtropical fruit, and a large number of germplasm resources with unique aromas have emerged during the past 2000 years of cultivation. In this review, our aim is to collect, compare, integrate, and summarize the available literature on the profiles of VOCs of 25 litchi cultivars. We showed that a total of 556 VOCs were reported from litchi fruit, and the aroma of litchi is mainly determined from the content and composition of monoterpenoids and alcohols, including linalool, geraniol, limonene, terpinolene, β-citronellol, p-cymene, nerol, α-terpineol, cis-rose oxide, β-myrcene, 4-terpineol, citral, and neral (cis-citral), which might contribute to the rose-like or citrus-like aroma of litchi fruit. Moreover, sulfur-containing volatile compounds (VSCs) possibly impart a special flavor to litchi fruit. This review would be a valuable resource for researchers aiming to improve litchi aroma quality by elucidating the possible mechanisms underlying VOC biosynthesis and their metabolism in litchi fruit. Full article
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11 pages, 2003 KiB  
Article
Post-Bloom CPPU Application Is Effective at Improving Fruit Set and Suppressing Coloration but Ineffective at Increasing Fruit Size in Litchi
by Xinsheng Liu, Yecheng Luo, Huicong Wang and Xuming Huang
Horticulturae 2022, 8(12), 1096; https://doi.org/10.3390/horticulturae8121096 - 22 Nov 2022
Cited by 1 | Viewed by 1772
Abstract
This study aimed to provide a reference for the practical use of forchlorfenuron (CPPU) in the improvement of fruit set and quality (especially size) in litchi (Litchi chinensis Sonn.). CPPU at 5 mg/L was sprayed to fruit clusters of ‘Feizixiao’ at 2, [...] Read more.
This study aimed to provide a reference for the practical use of forchlorfenuron (CPPU) in the improvement of fruit set and quality (especially size) in litchi (Litchi chinensis Sonn.). CPPU at 5 mg/L was sprayed to fruit clusters of ‘Feizixiao’ at 2, 4, 6 and 8 weeks after female bloom (WAFB) in 2017 and at 2, 4, 6, 8, 9 or 10 WAFB in 2018, with spraying water as the control. The treatments were all effective at suppressing fruit abscission, resulting in higher fruit retention at harvest. Except for treatment at 2 WAFB, which caused stunted fruit and significantly reduced fruit weight, all the treatments had no significant influence on fruit weight and flesh (aril) weight, although CPPU tended to increase pericarp weight and strongly suppressed fruit coloration, and such effects were most significant in treatments at 4, 6 and 8 WAFB. Content of total soluble solids (TSS) in commercially ripe fruit (11WAFB) was not significantly influenced by CPPU applied at any of the stages. Ripe fruit continued to gain redness but lost TSS as it became overripe. CPPU suppressed redness gaining, the effect being stronger in later application. The treatments did not influence TSS loss, but treatments at 4, 6 and 8 WAFB significantly reduced the increase in fruit membrane leakage. In treatment at 6 WAFB, CPPU residue in the pericarp decreased sharply with time but relatively constant in the aril, where it maintained lower than 10 μg/kg, the maximal residue limitation in Australia and the United States. The results suggest that 5 mg/L CPPU is effective at improving fruit set and suppressing fruit pigmentation but has no significant effect on fruit size and TSS accumulation or maintenance in litchi. Full article
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8 pages, 500 KiB  
Article
Inheritance of Fruit Weight, Size and Organic Acid Content in a Distant Hybrid Population of Longan ‘Huanongzao’ and Lychee ‘Ziniangxi’
by Jiahui Wang, Liqin Liu, Jiahui Dong, Lifei Zhu, Yicheng Wang, Guibing Hu and Shengyou Shi
Horticulturae 2022, 8(11), 999; https://doi.org/10.3390/horticulturae8110999 - 26 Oct 2022
Cited by 3 | Viewed by 1948
Abstract
The type and content of organic acids in fruits are important factors that determine the traits, such as the nutrition and flavor of fruits. Fruit weight and size are also very important economic characters in fruit breeding research. To investigate the inheritance patterns [...] Read more.
The type and content of organic acids in fruits are important factors that determine the traits, such as the nutrition and flavor of fruits. Fruit weight and size are also very important economic characters in fruit breeding research. To investigate the inheritance patterns in longan, fruit organic acid contents, weight, and size were measured in the distant hybridization progenies of longan ‘Huanongzao’ and lychee ‘Ziniangxi’. The results revealed that the malic acid accumulation exhibited mid-parent heterosis, citric acid content showed a tendency towards depression, and oxalic acid, ketoglutaric acid, fumaric acid, gallic acid, and total acid contents exhibited transgressive inheritance. The inheritance patterns in fruit weight, length and diameter tended towards smaller and degraded. The coefficient of variation (CV) for the organic acids ranged from 35.77–90.20%, and the heritability (H2) was 72.35–97.44%. High CV (55.44%) coupled with medium H2 (28.72%) were observed in fruit weight, however, low CV (12.29% and 12.50%) coupled with high H2 (68.95% and 69.25%) were shown in fruit length and diameter. In this study, the genetic variation of acid contents, fruit weight and size in the F1 population of longan and lychee were analyzed for the first time, providing an informative and theoretical basis for the selection and breeding of longan cultivars. Full article
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12 pages, 279 KiB  
Article
Effects of Time of Pruning and Plant Bio-Regulators on the Growth, Yield, Fruit Quality, and Post-Harvest Losses of Ber (Ziziphus mauritiana)
by Shashi, Om Prakash Garhwal, Mali Ram Choudhary, Laxmi Narayan Bairwa, Kishan Lal Kumawat, Pradeep Kumar, Boris Basile, Giandomenico Corrado, Youssef Rouphael and Jagan Singh Gora
Horticulturae 2022, 8(9), 809; https://doi.org/10.3390/horticulturae8090809 - 3 Sep 2022
Cited by 10 | Viewed by 2555
Abstract
Indian jujube or ber (Ziziphus mauritiana Lam.) is a deciduous fruit tree typically cultivated in several semi-arid areas of Asia because of its adaptability to yield-limiting conditions. The present study aimed to assess the effect of four pruning times (i.e., the fourth [...] Read more.
Indian jujube or ber (Ziziphus mauritiana Lam.) is a deciduous fruit tree typically cultivated in several semi-arid areas of Asia because of its adaptability to yield-limiting conditions. The present study aimed to assess the effect of four pruning times (i.e., the fourth week of March, second week of April, fourth week of April, and second week of May) and four treatments using stress-mitigating plant bio-regulators (thiourea at 500 ppm and 1000 ppm; salicylic acid at 100 ppm and 150 ppm) as a means to improve both fruit yield and quality post-harvest. To this end, a full factorial experiment lasting two growing seasons was carried out under field conditions in the representative semi-arid region of Rajasthan, the state with the largest production in India. We assessed the vegetative growth of the trees, the fruit size and yield, and some quality parameters (soluble content, acidity, ascorbic acid, and total sugars) as well as the main post-harvest traits (fruit weight loss and spoilage). Overall, pruning during the second week of April had the greatest positive influence on most of the variables studied. For instance, it induced the highest vegetative vigor, allowing the maintenance of relatively higher chlorophyll and relative water content in the leaves. The fruit parameters also responded most positively to the second week of April pruning, a treatment that, compared to the others, induced a higher diameter; a higher amount of TSS (19.6 °Brix), ascorbic acid (86.5 mg/100 g), and total sugar (10.4%); and a better post-harvest shelf-life. Among the plant bio-regulators, the application of thiourea at 1000 ppm had the highest positive influence on the growth parameters, yield, quality, and reduction in spoilage post-harvest. The differences between the doses of PBRs were limited. Full article
10 pages, 2134 KiB  
Article
Amplification of Cherimoya (Annona cherimola Mill.) with Chloroplast-Specific Markers: Geographical Implications on Diversity and Dispersion Studies
by Nerea Larranaga, Gustavo Fontecha, Federico J. Albertazzi, Margarita Palmieri and Jose I. Hormaza
Horticulturae 2022, 8(9), 807; https://doi.org/10.3390/horticulturae8090807 - 2 Sep 2022
Cited by 1 | Viewed by 1735
Abstract
Previously developed Annona cherimola specific primers based on the plant barcode gene matK were tested in 546 cherimoya accessions. Of those, 296 belong to an ex situ world reference germplasm collection maintained at the IHSM La Mayora-CSIC-UMA in Málaga (Spain) and 250 [...] Read more.
Previously developed Annona cherimola specific primers based on the plant barcode gene matK were tested in 546 cherimoya accessions. Of those, 296 belong to an ex situ world reference germplasm collection maintained at the IHSM La Mayora-CSIC-UMA in Málaga (Spain) and 250 to cherimoya samples collected in situ in three Central American countries (Honduras, Guatemala and Costa Rica). Results showed the existence of two different haplotypes in the samples analyzed with geographical association. A new marker that amplified all the samples was designed based on the trnL-F locus using DNA information from seven species of the Annona genus. The information generated will be useful to analyze and conserve the extant genetic diversity present in situ and ex situ and to understand de dispersion of the crop from its center of origin in Central America. Full article
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9 pages, 2013 KiB  
Article
Determination of the Best Planting Season for the Protected Cultivation of Papaya
by Irene Salinas, Juan José Hueso and Julián Cuevas
Horticulturae 2022, 8(8), 738; https://doi.org/10.3390/horticulturae8080738 - 17 Aug 2022
Cited by 3 | Viewed by 1711
Abstract
Papaya is a tropical crop increasingly cultivated in the greenhouses of subtropical regions such as South East Spain, where the determination of the best planting season is important to ensure a stable fruit production and quality during the year. In this work, we [...] Read more.
Papaya is a tropical crop increasingly cultivated in the greenhouses of subtropical regions such as South East Spain, where the determination of the best planting season is important to ensure a stable fruit production and quality during the year. In this work, we studied plant growth, yield, and fruit quality, comparing spring and autumn planting seasons in ‘Intenzza’ cultivar. The results showed that planting in spring favors plant growth, leading to an earlier entry into production. Total yield and fruit quality were similar in both planting seasons, although the spring cycle provided higher profits due to greater commercial yield and lower discards. Our results confirm that adverse environmental conditions affect the crop in a similar way regardless of the planting season, so different growing cycles are not very useful for filling the production gaps and fighting against seasonality in our region, unless unfavorable climate conditions are avoided inside the greenhouse. Full article
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12 pages, 2486 KiB  
Article
Comparing Different Methods for Pruning Pitaya (Hylocereus undatus)
by Emilio Arredondo, Fernando M. Chiamolera, Marina Casas and Julián Cuevas
Horticulturae 2022, 8(7), 661; https://doi.org/10.3390/horticulturae8070661 - 20 Jul 2022
Cited by 3 | Viewed by 3480
Abstract
Recently there have been new trends in global consumption toward fresh foods that are sources of healthy bioactive compounds, as is the case with pitaya. However, pitaya cultivation is a relatively recent phenomenon and little is known about its management. The objective of [...] Read more.
Recently there have been new trends in global consumption toward fresh foods that are sources of healthy bioactive compounds, as is the case with pitaya. However, pitaya cultivation is a relatively recent phenomenon and little is known about its management. The objective of this work is to determine the most appropriate annual fruiting pruning method for pitaya in order to obtain a regular annual yield of quality fruit and an intense shoot renewal that guarantee future production. This study compared the response of Hylocereus undatus to spur, cane, and combined pruning. As control plants, we left some plants where only sanitary pruning was performed. The results indicate that spur pruning greatly reduced flowering (seven times less than controls) and did not promote intense vegetative growth. Cane pruning, on the contrary, allowed greater flowering which is compatible with a higher number of new shoots (8% more than controls). The vigor of the new shoots was equal in all treatments. Fruit size and quality did not differ either among treatments. Spur pruning only seems applicable as a rejuvenation pruning. Combined pruning gave an intermediate response and seems of no interest given the good shoot renewal provided by cane pruning. Performing sanitary pruning alone may be an interesting option, but only in the first years of cultivation. Full article
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10 pages, 1161 KiB  
Article
Less Is More? Field Evaluation of Short-Stature Banana Cultivars in a Mediterranean Environment
by Idan Elingold, Avishi Londener, Amit Rimmer, Avi Tsarfaty, Gilad Hadar and Navot ‘Galpaz
Horticulturae 2022, 8(7), 619; https://doi.org/10.3390/horticulturae8070619 - 8 Jul 2022
Viewed by 1193
Abstract
The shift to cultivation of banana (‘Musa (AAA) Cavendish subgroup’) in screenhouses in Israel has resulted in a significant increase in plant height and, consequently, increased maintenance costs. Here, we evaluated the genetic approach to reducing plantation height. Advanced selections of the local [...] Read more.
The shift to cultivation of banana (‘Musa (AAA) Cavendish subgroup’) in screenhouses in Israel has resulted in a significant increase in plant height and, consequently, increased maintenance costs. Here, we evaluated the genetic approach to reducing plantation height. Advanced selections of the local cultivars ‘Adi’, ‘Zelig’, and ‘Gal’, selected for reduced height, were evaluated in the field. Growth and yield parameters were recorded and compared with the industry standard cv. ‘Grand Naine’ for four crop cycles. ‘Adi’ and ‘Zelig’ were shorter than ‘Grand Naine’, by 20% and 10%, respectively, whereas ‘Gal’ lost its short stature over the years. In addition, leaf area was reduced in the low-stature cultivars. Cumulative yield of ‘Adi’ and ‘Zelig’ was higher than that of ‘Grand Naine’, by 8.8% for ‘Adi’ and 5.0% for ‘Zelig’, due to higher plant density and number of harvested bunches. This multiyear study highlights ‘Adi’ and ‘Zelig’ as short-stature, highly productive cultivars with the potential for improved water-use efficiency. Full article
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14 pages, 5439 KiB  
Article
The Link between Mineral Elements Variation and Internal Flesh Breakdown of ‘Keitt’ Mango in a Steep Slope Mountain Area, Southwest China
by Xiaowei Ma, Jianfang Wang, Muqing Su, Bin Liu, Bang Du, Yuehua Zhang, Liping He, Songbiao Wang and Hongxia Wu
Horticulturae 2022, 8(6), 533; https://doi.org/10.3390/horticulturae8060533 - 16 Jun 2022
Cited by 4 | Viewed by 1841
Abstract
Internal flesh breakdown (IFB), a serious physiological disorder of mango fruit, causes significant economic losses in Southwest China. We investigated the extent of IFB in 100 mango orchards and how changes in the mineral nutrients of fruit flesh, leaves and soil affect IFB. [...] Read more.
Internal flesh breakdown (IFB), a serious physiological disorder of mango fruit, causes significant economic losses in Southwest China. We investigated the extent of IFB in 100 mango orchards and how changes in the mineral nutrients of fruit flesh, leaves and soil affect IFB. We found that 76% of the mango orchards showed IFB symptoms, and the average IFB incidence was 10%. Fruit flesh with IFB showed higher average contents of N, P, K and Mg, lower average Ca content and higher average ratios of N/Ca, K/Ca and Mg/Ca. The leaves from orchards with IFB symptoms exhibited a remarkable increase in the average N and Mg contents. No significant difference was observed in the soil nutrient concentrations between orchards with and without IFB fruit. IFB incidence was significantly positively correlated with the N/Ca, K/Ca and Mg/Ca ratios in the fruit flesh. However, when considering individual orchards with IFB symptoms, fruit flesh that exhibited breakdown symptoms had Ca content higher, lower than or equal to that of the healthy fruit flesh. There was a strong correlation between fruit flesh and leaf in the same mineral elements, but neither of them showed a significant correlation with soil. Considering the mango trees were cultivated on steep slopes, and fertilizer was applied at a fixed position, we hypothesized that long-term fertilization in the partial root zone led to the excess of N, K and Mg in soil, which reduced the total flesh Ca content or resulted in the abnormal cellular distribution of Ca in the flesh, and ultimately triggered IFB development. Full article
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14 pages, 3077 KiB  
Article
Production of Triploid Germplasm by Inducing 2n Pollen in Longan
by Huimin Li, Jichang Gan, Hai Xiong, Xiaodan Mao, Shuwei Li, Huiyun Zhang, Guibing Hu, Chengming Liu and Jiaxin Fu
Horticulturae 2022, 8(5), 437; https://doi.org/10.3390/horticulturae8050437 - 13 May 2022
Cited by 4 | Viewed by 2306
Abstract
Longan (Dimocarpus longan Lour.) is of great economic significance in South China for its unique taste and nutritional properties. However, longan breeding is mainly based on seedling selection, which generally results in small fruits, low flesh recovery, and few seedless germplasm. Triploid [...] Read more.
Longan (Dimocarpus longan Lour.) is of great economic significance in South China for its unique taste and nutritional properties. However, longan breeding is mainly based on seedling selection, which generally results in small fruits, low flesh recovery, and few seedless germplasm. Triploid breeding is a central way to improve these problems. In this study, microspore chromosomes were doubled by colchicine and high-temperature treatment to create triploids in longans. The relationship between the development process of male gametophyte of longans and the morphological changes of male flower buds was established. Cytological observation showed that when the male flower buds were in stage I (when the diameter of the flower bud is 1.4–2.0 mm), most of the microspores were at the pachytene to diakinesis stage of meiosis, and the chromosome doubling induction effect was the best at this stage. The results showed that the 2n pollen rate induced by a high temperature of about 38 °C was higher than that induced by colchicine treatment. The highest 2n pollen rate was 5.7% and 5.5% based on the microscopic measurement method and the abnormal separation in tetrad stage estimation method, respectively. Four triploids were successfully obtained from artificial pollination with 2n pollen, with a triploid induction rate of 0.6%. This study will promote ploidy breeding in longan. Full article
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10 pages, 1060 KiB  
Article
Early Withering of Enlarged Ovules in Pollinated Fruits of Bananas (Musa spp.) Suggest Abortion after Fertilization
by Allan Waniale, Settumba B. Mukasa, Arthur K. Tugume, Jerome Kubiriba, Wilberforce K. Tushemereirwe and Robooni Tumuhimbise
Horticulturae 2022, 8(5), 426; https://doi.org/10.3390/horticulturae8050426 - 10 May 2022
Cited by 1 | Viewed by 2384
Abstract
Sterility in edible bananas is as a result of a long history of anthropogenic-driven selection for sterile genotypes, since seed is not desirable in fruit pulp for human consumption. However, this poses a challenge to conventional genetic improvement by slowing breeding pipelines. In [...] Read more.
Sterility in edible bananas is as a result of a long history of anthropogenic-driven selection for sterile genotypes, since seed is not desirable in fruit pulp for human consumption. However, this poses a challenge to conventional genetic improvement by slowing breeding pipelines. In this study, we investigated whether pollen tubes reach all parts of the ovary, the position of fertilized ovule development in fruits, and potential seed set in selected banana genotypes. We selected four cultivars of East African Highland Cooking bananas (EAHBs), a Matooke hybrid ‘222K-1’, improved diploid ‘2905’, and wild bananas ‘Zebrina (G.F.)’ and ‘Calcutta 4’. There was evidence of pollen tubes in the distal, mid and proximal sections of the fruit, irrespective of hand position and genotype. Fertilization, as indicated by an increase in ovule size, happened along the entire length of the fruit but complete development was biased at the distal end in some genotypes. There were some differences in ovule fertilization rates between hands, with distal hands having more ovules and higher ovule fertilization rates. Ovule fertilization happens in bananas but the vast majority aborts, especially at the proximal end of the ovary. Ovule fertilization rates are generally much lower than available ovules. Full article
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16 pages, 4237 KiB  
Article
Changes of Fruit Abscission and Carbohydrates, Hormones, Related Gene Expression in the Fruit and Pedicel of Macadamia under Starvation Stress
by Weihai Yang and Peijin Xiang
Horticulturae 2022, 8(5), 398; https://doi.org/10.3390/horticulturae8050398 - 1 May 2022
Cited by 2 | Viewed by 1992
Abstract
In order toexplore the regulation mechanism of macadamia fruitlet abscission induced by ‘starvation stress’, a treatment of girdling and defoliation was applied to the bearing shoots of macadamia cultivar ‘H2’ at the early stage of fruit development, simulating the starvation stress induced by [...] Read more.
In order toexplore the regulation mechanism of macadamia fruitlet abscission induced by ‘starvation stress’, a treatment of girdling and defoliation was applied to the bearing shoots of macadamia cultivar ‘H2’ at the early stage of fruit development, simulating the starvation stress induced by interrupting carbon supply to fruit. The levels of carbohydrates, hormones, and related gene expression in the different tissues (husk, seed, and pedicel) were investigated after treatment. The results showed that a severe fruit drop occurred 3~5 d after starvation stress treatment. The contents of glucose, fructose, and sucrose in both the husk and the seed were significantly decreased, as well as the fructose and sucrose in the pedicel; this large reduction occurred prior to the massive fruit shedding. Starvation stress significantly reduced the GA3 and ZR contents and enhanced the ABA level in the pedicel and the seed, whereas it did not obviously change these hormones in the husk. After treatment, IAA content decreased considerably in both the husk and seed but increased remarkably in the pedicel. In the husk, the expression of genes related to sugar metabolism and signaling (NI, HXK2, TPS, and TPP), as well as the biosynthesis of ethylene (ACO2 and ACS) and ABA (NCED1.1 and AAO3), was significantly upregulated by starvation stress, as well as the stress-responsive transcription factors (AP2/ERF, HD-ZIP12, bZIP124, and ABI5), whereas the BG gene associated with ABA accumulation and the early auxin-responsive genes (Aux/IAA22 and GH3.9) were considerably suppressed during the period of massive fruit abscission. Similar changes in the expression of all genes occurred in the pedicel, except for NI and AP2/ERF, the expression of which was significantly upregulated during the early stage of fruit shedding and downregulated during the period of severe fruit drop. These results suggest that complicated crosstalk among the sugar, IAA, and ABA signaling may be related to macadamia fruitlet abscission induced by carbohydrate starvation. Full article
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12 pages, 2483 KiB  
Article
A Study of Shoot Growth, Leaf Photosynthesis, and Nutrients in ‘Lingfengjing’ Litchi Grafted onto Seedlings of Different Cultivars
by Yan Fan, Zhiyuan Li, Binxia Xie, Xiaowen Liang and Xuming Huang
Horticulturae 2022, 8(4), 282; https://doi.org/10.3390/horticulturae8040282 - 28 Mar 2022
Cited by 3 | Viewed by 1887
Abstract
Litchi (Litchi chinensis Sonn.) is one of the important fruit crops in southern China. ‘Lingfengnuo’ (LFN) is a new late-maturing litchi variety which has gained great popularity among consumers and growers due to its high quality and reliable productivity. However, there has [...] Read more.
Litchi (Litchi chinensis Sonn.) is one of the important fruit crops in southern China. ‘Lingfengnuo’ (LFN) is a new late-maturing litchi variety which has gained great popularity among consumers and growers due to its high quality and reliable productivity. However, there has been limited research on the graft compatibility of LFN on different rootstocks, which is important for selecting the optimal rootstocks for propagation, and thus application of this new cultivar. In this study, LFN scions were grafted onto one-year-old seedlings from 13 cultivars including ‘Heiye’ (HY), ‘Shakeng’ (SK), ‘Hehuadahongli’ (HHDHL), ‘Maguili’ (MGL), ‘Xiaojinzhong’ (XJZ), ‘Huaizhi’ (HZ), ‘Chenzi’ (CZ), ‘Shangshuhuai’ (SSH), ‘Baitangying’ (BTY), ‘Shuangjianyuhebao’ (SJYHB), ‘Jingganghongnuo’ (JGHN), ‘Baila’ (BL), and ‘Shuidong’ (SD). Graft success, morphology of the graft joint, shoot growth, leaf photosynthetic rate, and nutrients were compared. Graft success was highest for XJZ, HZ, BL and JGHN. Tree vigor, reflected by flush growth, was highest for HZ, followed by JGHN and BTY, but weakest for HY, SD, SJYHB, and XJZ. The stem significantly swelled above the graft joint in trees with rootstocks of HY, SD, and SJYHB seedlings; however, this did not occur in XJZ. Leaf photosynthesis displayed a similar pattern to tree vigor, and was highest for HZ and lowest for HY, SD, and XJZ. These low vigor trees produced flowers the next year after grafting. The result suggested that HZ, JGHN, and BTY seedlings as rootstock are highly compatible with LFN, while those of HY, SD, and SJYHB are poorly compatible. Rootstocks did not significantly influence the leaf N, P, and Fe, but showed significant differences in other minerals. The leaf Ca, Mg, Zn and B were lowest in the trees graft onto HZ seedlings. Based on these results, HZ seedlings are recommended as the best rootstock for the propagation of LFN; however, a supply of Ca, Mg, B and Zn fertilizers a especially needed for LFN trees on HZ seedling rootstock. Full article
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2021

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13 pages, 3323 KiB  
Article
Dynamics of Energy Metabolism in Carbon Starvation-Induced Fruitlet Abscission in Litchi
by Qian Wu, Xingshuai Ma, Qingxin Chen, Ye Yuan, Huicong Wang, Xinhua He, Minglei Zhao and Jianguo Li
Horticulturae 2021, 7(12), 576; https://doi.org/10.3390/horticulturae7120576 - 14 Dec 2021
Viewed by 2506
Abstract
Fruit abscission is triggered by multiple changes in endogenous components of the fruit, including energy metabolism. However, it is still unknown how the core energy metabolism pathways are modified during fruit abscission. Here, we investigated the relationship between carbon starvation-induced fruitlet abscission and [...] Read more.
Fruit abscission is triggered by multiple changes in endogenous components of the fruit, including energy metabolism. However, it is still unknown how the core energy metabolism pathways are modified during fruit abscission. Here, we investigated the relationship between carbon starvation-induced fruitlet abscission and energy metabolism changes in litchi. The fruitlet abscission of litchi ‘Feizixiao’ was induced sharply by girdling plus defoliation (GPD), a carbon stress treatment. Using liquid chromatography tandem mass spectrometry (LC-MS/MS) targeted metabolomics analysis, we identified a total of 21 metabolites involved in glycolysis, TCA cycle and oxidative phosphorylation pathways. Among them, the content of most metabolites in glycolysis pathways and TCA cycles was reduced, and the activity of corresponding metabolic enzymes such as ATP-dependent phosphofructokinase (ATP-PFK), pyruvate kinase (PK), citrate synthase (CS), succinate thiokinase (SAT), and NAD-dependent malate dehydrogenase (NAD-MDH) was decreased. Consistently, we further showed that the expression of the relative genes (LcPFK2, LcPK2, LcPK4, LcCS1, LcCS2, LcSAT, LcMDH1 and LcMDH2) was also significantly down-regulated. In contrast, the level of ATP, an important metabolite in the oxidative phosphorylation pathway, was elevated in parallel with both higher activity of H+-ATPase and the increased expression level of LcH+-ATPase1. In conclusion, our findings suggest that carbon starvation can induce fruitlet abscission in litchi probably by energy depletion that mediated through both the suppression of the glycolysis pathway and TCA cycle and the enhancement of the oxidative phosphorylation pathway. Full article
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10 pages, 1754 KiB  
Article
Characteristics of Mango Leaf Photosynthetic Inhibition by Enhanced UV-B Radiation
by Hong Wang, Yujian Guo, Jianjun Zhu, Kun Yue and Kaibing Zhou
Horticulturae 2021, 7(12), 557; https://doi.org/10.3390/horticulturae7120557 - 7 Dec 2021
Cited by 10 | Viewed by 4369
Abstract
To investigate the photosynthetic change characteristics of mango leaves under enhanced UV-B radiation, adult ‘Tainong No. 1′ mango (Mangifera indica) trees were treated (N = nine individuals) with simulated enhanced UV-B radiation [24 and 96 kJ/(m2·d)] in the field, [...] Read more.
To investigate the photosynthetic change characteristics of mango leaves under enhanced UV-B radiation, adult ‘Tainong No. 1′ mango (Mangifera indica) trees were treated (N = nine individuals) with simulated enhanced UV-B radiation [24 and 96 kJ/(m2·d)] in the field, and the photochemical reactions, activities of key enzymes in carbon assimilation, and the expression of genes were observed. The results showed that compared with the control, there was a decrease in tree yield, soluble sugar, sugar–acid ratio, and vitamin C of the fruits under the 96 kJ/(m2·d) treatment, while no significant changes were observed under 24 kJ/(m2·d). After 20 or 40 days, the leaves’ net photosynthetic rate (Pn), stomatal conductance (Sc), transpiration rate (Tr), intercellular CO2 concentration (Ci), and chlorophyll a/b under exposure to 96 kJ/(m2·d) of UV-B were significantly lower than in the control, whereas chlorophyll a, chlorophyll b, carotenoids, Hill reaction activity, photochemical quenching coefficient (qP), and Rubisco activities were significantly higher. In contrast, the Hill activity and Rubisco activity under 24 kJ/(m2·d) were significantly higher than the control, and increased by 350% and 30.8%, respectively, while Pn, Sc, Tr, Ci, and the content of photosynthetic pigments were similar to the control. The expression of gene coding the Rubisco big subunit (rbcL) was inhibited by the 96 kJ/(m2·d) treatment. We conclude that stomatal limitation was directly induced by 96 kJ/(m2·d), resulting in the inhibition of photosynthesis and the reduction in yield and deterioration of the quality of mango. Full article
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