Improvement Of Fruit Trees Research Articles

Insights on the potential of RNA-Seq on improving pomological traits of African indigenous fruit trees: a mini review

Fruit tree improvement has taken great strides by roping in improved and efficient biotechnological tools to increase fruit yield and quality to meet local and export demands. For the past decade, the RNA-Seq tool has successfully been used in fruit tree improvement programs to identify genes, dissect complex traits, and understand different molecular pathways and differential expression of genes. However, despite their growing importance in food and nutrition security, medicinal uses, and climate change mitigation strategies, very little has been done to improve the pomological traits of African indigenous fruits, especially at the molecular level. African indigenous fruit trees exhibit unexplained variation in flowering, fruit load, fruit size, fruit ripening, fruit taste, fruit nutritional composition and shelf-life. The booming local commercial companies and export markets are demanding consistent quality indigenous fruits. This has necessitated the need for fast and effective tools that will hasten the understanding and improvement of fruiting qualities. The improvement of fruiting and fruit qualities will go a long way in accelerating the domestication and commercialization of African indigenous fruit trees. This review paper gives molecular biology insights on how RNA-Seq has been successfully used in fruit improvement of exotic fruits through gene identification, comparative transcriptome analysis under different conditions, and understanding molecular pathways that influence important pomological traits. The review article also unearths opportunities where RNA-Seq can improve our knowledge and improvement of undesirable traits common in African indigenous fruits

Prediction and optimization of fruit quality of peach based on artificial neural network

Mineral nutrition is the material basis for growth and quality improvement of fruit trees. In this study, artificial neural networks (ANNs) and Multiple linear regression (MLR) models were used to study the influence of mineral nutrient elements in fruits on the peach fruit quality. The results showed that four established ANN models of the fruit quality with the Log-sigmoid transfer function and the Levenberg-Marquardt back-propagation training function can obtain the highest accuracy (R2 =0.9243, 0.9260, 0.9536, and 0.9644 respectively). The results of the sensitivity and redundancy analysis indicated that the nitrogen, phosphorus, potassium, magnesium, and iron content in fruits had the greatest contribution to these fruit quality indicators of the peach, which was of great significance to the fertilization of peach orchards and the improvement of peach fruit quality.

Screening of Mango Rootstock For Saline Tolerance

An experiment was conducted at Fruit Tree Improvement Project, Fruit Tree Improvement Programme, Bangladesh Agricultural University-Germplasm Center (FTIP, BAU-GPC), Bangladesh Agricultural University (BAU), Mymensingh during the period of April 2020 to June 2020 to study the performance of selected mango rootstocks for the saline area. The two-factor experiment consisted of four mango rootstock varieties such as V1 = BAU Aam-9, V2 = BAU Aam-6, V3 = BAU Aam-4 and V4 = Amropali and six salinity treatments namely control S1 = 0 dSm-1, S2 = 4 dSm-1, S3 = 8 dSm-1, S4 = 10 dSm-1, S5 = 12 dSm-1 and S6 = 14 dSm-1. The experiment was conducted following randomized complete block design with three replications. Results revealed that rootstock line and salinity levels had significant influences on various rootstock characters viz. length of rootstocks, number of leaves and percent rootstocks success and survivability. In case of varietal effect, the highest number of leaves (32.44) found in BAU Aam-6 and the lowest number of leaves was recorded in Amropali (22.55) at 90 days after transplanting. The longest rootstock length observed in 90 DAT which (54.83 cm) found in BAU Aam-9and shortest rootstock recorded in Amropali (47.94 cm). The highest survivability (51.44%) was recorded in BAU Aam-9 and the lowest survivability recorded in Amropali (33.88%). In case of salinity treatments, the highest survivability (95.83%) was recorded in control and the lowest survivability (0.00%) recorded in 14 dsm-1 at 90 DAT. Interaction of rootstock varieties and different salinity treatments showed significant variation on the length leave and survivability of rootstocks at 90 DAT. The maximum number of rootstock leaves recorded in V2S2 (46.33) and lowest number of leave recorded in V4S6 (7.66). The highest rootstock length was found in V1S3 (78.00 cm) and lowest in V1S2 (21.66 cm). The highest Survivability (100 %) observed in V1S1, V1S2, V2S1, V2S2 and V4S1. From the above mentioned it can be said BAU Aam - 9 and BAU Aam – 6 rootstock varieties performed best from 0-8 dSm-1 salinity. The overall salinity tolerance was graded as follows: BAU Aam - 9>BAU Aam – 6> BAU Aam-4>Amropali rootstock line. SAARC J. Agric., 19(1): 93-102 (2021)

Effect of scion defoliation and stock leaf retention on growth of grafted lime (cv. Bau lime-1)

The present experiment was conducted at the Germplasm Centre (GPC) of the Fruit Tree Improvement Program (FTIP), Bangladesh Agricultural University, Mymensingh, during the period from June to October, 2013 to investigate the effects of scion defoliation and stock leaf retention on growth of grafted Lime (cv. BAU lime-1). The experiment consisted of two factors such as Factor A: four scion defoliation periods viz., defoliation before 9 days of grafting, defoliation before 6 days of grafting, defoliation before 3 days of grafting and defoliation on the day of grafting and Factor B: retention of leaf on rootstock below graft union viz., rootstock with leaf and rootstock without leaf. The study was laid out following Randomized Complete Block Design (RCBD) with three replications. The grafts were kept under observation in poly tunnel condition. Results revealed that highest graft height, (45.47 cm), number of leaves (15.72) and branches (2.92), length of the largest leaf(8.45cm), breadth of the largest leaf(3.77cm) were observed when scions were defoliated 6 days before grafting and lowest graft height (38.72 cm), number of leaves (12.12) and branches (2.25), length of the largest leaf(5.60cm), breadth of the largest leaf(3.37cm) were observed when scions were defoliated on the day of grafting. In respect of retention of leaves on rootstock, the highest graft height (43.83 cm), number of leaves (15.62) and branches (2.82), length of the largest leaf(7.47cm), breadth of the largest leaf(3.78cm) were found when grafting was done on rootstock with leaves and lowest graft height (39.78 cm), number of leaves (11.32) and branches (2.48), length of the largest leaf(6.57cm), breadth of the largest leaf(3.40cm) were found when grafting was done on rootstock without leaves. Therefore, the maximum growth in grafted lime seedlings can be achieved if scion defoliated 6 days prior to grafting operation and leaves are kept on root stock below graft union.Asian J. Med. Biol. Res. March 2018, 4(1): 44-48

Darwin's Pangenesis and Graft Hybridization.

Although there were many records of graft-induced variations in ancient China, it wasDarwin who coined the term "graft hybridization", the formation of hybrids between distinct species or varieties, through plant grafting, without the intervention of the sexual organs. He described many cases of the so-called "graft hybrids", in which shoots produced from grafted plants exhibited a combination of characters of both rootstock and scion, and explained their formation by his Pangenesis. Michurin invented "mentor-grafting" and "preliminary vegetative approximation" methods, which greatly increased the production of graft hybrids, thus providing a solution to Darwin's puzzle. Over the past decides, the existence of graft hybrids has been extensively documented, and graft hybridization is considered to be a simple and efficient means of plant breeding, and would be especially significant in the improvement of fruit trees. Graft hybridization is now explained by horizontal gene transfer and DNA transformation. In addition, the long-distance transport of mRNA and small RNAs is also considered to be involved in the formation of graft hybrids.

Effect of Fungicides and Plant Extracts in the Management of Foliar, Twig and Fruit Diseases of Citrus (Citrus limon)

A research work was conducted on citrus plants raised at GPC, of Fruit Tree Improvement Project (FTIP) at Horticulture Farm, Bangladesh Agricultural University, Mymensingh, to investigate the effect of fungicides and plant extracts in controlling the scab, die-back and canker. Three fungicides viz. Cupravit 50 wp (0.4%), Dithane M-45 (0.3%), Rovral 50 WP (0.2%) and extracts of 3 plants viz. Neem {Azadirachta indica), Ginger {Zingiber officinale) and Garlic {Allium sativum) were applied for controlling the citrus (C. limon) diseases (scab, die-back and canker). All the fungicides showed significant effect in the control of the above mentioned citrus diseases. The highest reduction of the scab, die-back and canker diseases was recorded applying Rovral 50 WP. Neem leaf extract was the most effective in controlling canker of leaf and fruit. Garlic extract and Neem leaf extract were the most effective in controlling die-back of twig and branches of citrus, respectively. From the above results it can be concluded that Rovral 50 WP is the most effective chemical for controlling all citrus (C. limon) diseases and citrus canker can successfully be controlled specially by Neem leaf and garlic extract.J. Environ. Sci. & Natural Resources, 10(1): 93-100 2017

New Biotechnological Tools for the Genetic Improvement of Major Woody Fruit Species.

The improvement of woody fruit species by traditional plant breeding techniques has several limitations mainly caused by their high degree of heterozygosity, the length of their juvenile phase and auto-incompatibility. The development of new biotechnological tools (NBTs), such as RNA interference (RNAi), trans-grafting, cisgenesis/intragenesis, and genome editing tools, like zinc-finger and CRISPR/Cas9, has introduced the possibility of more precise and faster genetic modifications of plants. This aspect is of particular importance for the introduction or modification of specific traits in woody fruit species while maintaining unchanged general characteristics of a selected cultivar. Moreover, some of these new tools give the possibility to obtain transgene-free modified fruit tree genomes, which should increase consumer's acceptance. Over the decades biotechnological tools have undergone rapid development and there is a continuous addition of new and valuable techniques for plant breeders. This makes it possible to create desirable woody fruit varieties in a fast and more efficient way to meet the demand for sustainable agricultural productivity. Although, NBTs have a common goal i.e., precise, fast, and efficient crop improvement, individually they are markedly different in approach and characteristics from each other. In this review we describe in detail their mechanisms and applications for the improvement of fruit trees and consider the relationship between these biotechnological tools and the EU biosafety regulations applied to the plants and products obtained through these techniques.

Effect of scion defoliation period and methods of grafting on success and survivability in mango

This study was conducted in order to investigate the effect of scion defoliation period and methods of grafting on the success and survivability of mango (var. Amrapali) at Bangladesh Agricultural University Germplasm Centre (BAU-GPC) of Fruit Tree Improvement Program (FTIP) of the Department of Horticulture, Bangladesh Agricultural University, Mymensingh. The experiment consisted of four scion defoliation periods, viz., defoliation before 9, 6, 3 days of grafting and defoliation on the day of grafting and two grafting methods namely cleft grafting and whip grafting. The study was laid out in randomized complete block design with three replications. The results revealed that scions defoliated 9 days before grafting showed the highest success (91.59%) and survivability (88.75%) and took the lowest time for bud breaking and first leaf opening (11.10 days and 14.22 days, respectively)whereas the lowest success rate (85.82% ) and survivability (83.60%) were observed when scion defoliation was performed on the day of grafting. In respect of grafting methods, higher graft success and survivability (89.68% and 86.89%, respectively) were found in cleft method, however, this method took longer time for bud breaking (11.92 days) and first leaf opening (15.90 days). The combined influence of scion defoliation period and grafting method exhibited the best performance on graft success and survivability when cleft grafting method was used with scion defoliated 9 days before grafting operation. Therefore the results of this investigation suggested that scions defoliated 9 days before grafting operation and cleft grafting method would be better for propagation of mango, yet the performance of cleft grafting with scion defoliated 6 days before grafting was also good with the hope of getting 85% success and survivability.Progressive Agriculture 27 (3): 242-248, 2016

Effects of rooting media and varieties on rooting performance of dragon fruit cuttings (Hylocereu sundatus Haw.)

The experiment was carried out to investigate the effects of different rooting media on rooting performance, plant growth and development of two varieties of Pitahaya (dragon fruit) cuttings at the Fruit Tree Improvement Project (FTIP), Germplasm Centre (GPC) of Bangladesh Agricultural University (BAU), Mymensingh during the period from May 2014 to August 2014. The two factors experiment consisted with of two different varieties of dragon fruit viz., BAU Dragon fruit-1 (V1) and BAU Dragon fruit-2 (V2) with 14 rooting media. viz. control (soil 100%) (T0), 50% cow dung + 50% soil (T1), Saw dust (100%) (T2), Compost (100%) (T3), 50% soil + 50% sand (T4), 50% soil + 50% saw dust (T5), Sand (100%) (T6), Indole-3 Acetic Acid (IAA) 500 ppm solution + soil (100%) (T7), 300 ppm solution + soil (100%) (T8), 200 ppm solution of IAA + soil (100%) (T9), 500 ppm solution of Indole-3 Butyric Acid (IBA) + soil (100%) (T10), 300 ppm solution IBA + soil (100%) (T11), 200 ppm solution IBA + soil (100%) (T12), (IBA+IAA) 200 ppm solution of each + soil (100%) (T13). All the parameter showed significant effect except number of branches per plant. In case of variety less time was needed for first root initiation (22.33 days) with the longest plant height (34.02 cm). The better result regarding number of roots per cutting (6.00) was found in case of BAU dragon fruit-2 (V2) where the highest root length (15.22 cm). In case of different treatment, the better result regarding number of roots per cutting (8.17) at 100 DAP was counted from the combination of (IAA+IBA) 200 ppm solution + soil (100%) (T13). The highest root length (25.38 cm) was observed in IAA 200 ppm solution + soil (100%) (T9). In case of combined effect, the minimum time was required for first root initiation (20.78 days) with IAA 300 ppm solution + soil (100%) (T8). The highest root length (25.87 cm) was observed in BAU Dragon fruit-1 with IAA 200 ppm solution + soil (100%) (V1T9). Number of roots per cutting was noticed (9.67) in BAU Dragon fruit-2 200 ppm solution of each IAA and IBA + soil (100%) (V2T13).Res. Agric., Livest. Fish.3(1): 67-77, April 2016

In Vivo Fast Induction of Homogeneous Autopolyploids via Callus in Sour Jujube (Ziziphus acidojujuba Cheng et Liu)

Polyploidization has been demonstrated as a very effective approach in fruit tree improvement. Sour jujube (Ziziphus acidojujuba Cheng et Liu) is a promising diploid wild, traditional fruit species (2n = 2x = 24) that is rich in vitamin C, which is the main rootstock of Chinese jujube (Z. jujuba Mill.). The novel method we developed for rapid in vivo induction of homogeneous autopolyploids (IVIHA) via callus in Chinese jujube was first applied and further optimized in sour jujube. Under optimized conditions, an average of one pure autotetraploid shoot could be regenerated from one treated branch, thereby indicating a relatively high efficiency rate. A total of 9 pure autotetraploid genotypes were created, and one of these was released as a new cultivar named ‘Zhuguang’ in 2015. Moreover, unexpected octoploids and hexaploids were also simultaneously created and detected. The leaves of tetraploids were thicker, broader, and darker in color than those of the original diploids, whereas the leaf sizes of octoploids were much smaller compared to that of diploids. However, stoma size increased with the occurrence of ploidy, mainly from diploid to octoploid. The well grown ploidies of jujube included diploids, triploids, and tetraploids. Anatomical observation indicated that adventitious buds/shoots emerged from the callus that formed on the cut, which was then followed by the development of connective vascular tissues between the adventitious bud and the stock plant tissue. This study demonstrates the universality of the IVIHA method that was initially developed in Chinese jujube, as well as provides a foundation for high-efficiency pure polyploid induction in sour jujube.

Generation of chemically induced mutations using in vitro propagated shoot tip tissues for genetic improvement of fruit trees

Mutagenesis via treatment of seeds with chemical mutagens such as ethyl methanesulfonate (EMS) has been widely used for crop improvement. However, this approach is not suitable for some crop species such as clonally propagated crops and allogamous perennial plants characteristically with high levels of genome heterozygosity and a long life cycle. Here, we report direct treatment of in vitro-induced peach shoot tip tissues with EMS for generation of mutations in peach, a perennial, woody fruit tree. We optimized EMS dosage and exposure time and found that treatment of the explants with 0.2 % EMS for 16 h was optimal for generation of genetic variations. So far we have generated nearly 2000 peach seedlings. Typical EMS-induced phenotypic variations were present in the seedlings. Next generation sequencing and subsequent data analyses were performed to monitor the efficiency of mutagenesis. The mutation rate was estimated to be one mutation per 150 kilobase pairs in the mutagenized population, suggesting effectiveness of this method in inducing mutagenesis in peach. Taken together, our data open an avenue for the generation of mutant populations suitable for crop improvement in allogamous perennial plants including fruit trees and clonally propagated plants.

MicroRNAs in fruit trees: discovery, diversity and future research directions.

Since the first description of microRNAs (miRNAs) 20 years ago, the number of miRNAs identified in different eukaryotic organisms has exploded, largely due to the recent advances in DNA sequencing technologies. Functional studies, mostly from model species, have revealed that miRNAs are major post-transcriptional regulators of gene expression in eukaryotes. In plants, they are implicated in fundamental biological processes, from plant development and morphogenesis, to regulation of plant pathogen and abiotic stress responses. Although a substantial number of miRNAs have been identified in fruit trees to date, their functions remain largely uncharacterised. The present review aims to summarise the progress made in miRNA research in fruit trees, focusing specifically on the economically important species Prunus persica, Malus domestica, Citrus spp, and Vitis vinifera. We also discuss future miRNA research prospects in these plants and highlight potential applications of miRNAs in the on-going improvement of fruit trees.

Propagation of Jackfruit by Modified Cleft Grafting as Influenced by Time of Operation

The experiment was conducted to study the effect of time (season) of grafting on the performance of modified cleft grafting of Jackfruit at the BAU Germplasm Centre (GPC) of Fruit Tree Improvement Project (FTIP) of the Department of Horticulture, Bangladesh Agricultural University, Mymensingh. The experiment consisting ten levels of grafting times, viz., 30th March, 15th April, 30th April, 15th May, 30th May, 15th June, 30th June, 15th July, 30th July, 15th August, was laid out in RCBD with three replications. The results revealed that grafting done on 14th August showed the highest success (39%) and took the lowest time to first flush and first leaf opening (4.66 and 5.00 days, respectively) whereas the success rates were very low at the months of March, April and May. Likewise the highest vegetative growth of the grafted plants in terms of height, diameter, number of leaves, length and breadth of the leaves was found with grafting done on 14th August.DOI: http://dx.doi.org/10.3329/pa.v19i2.16930 Progress. Agric. 19(2): 67 - 74, 2008

Effect of Shoot Bending and Fruit Thinning on Productivity of Guava

The study was carried out at the Germplasm Centre of Fruit Tree Improvement Programme (GPC-FTIP), Bangladesh Agricultural University, Mymensingh during the period February, 2011 to March, 2012 to find out the effect of shoot bending and fruit thinning on productivity of guava. The treatments of the experiment were four varieties of guava viz., Swarupkathi, BAU piyara-5, Chiang Mai (round) and Chiang Mai (long) and six different management practices viz., (i) control (no shoot bending + no fruit thinning); (ii) shoot bending; (iii) 25% fruit thinning; (iv) 50% fruit thinning; (v) 75% fruit thinning and (vi) 100% fruit thinning. The ages of the plants were 4-5 years. Results revealed that the variety Chiang Mai (round) showed superiority over BAU piyara-5, Chiang Mai (long) and Swarupkathi in respect of fruit yield (15.63 kg/plant) and fruit retention (72.92%) during on-season but during off-season, Swarupkathi showed superiority over Chiang Mai (round), BAU piyara-5 and Chiang Mai (long) in case of number of flowers set per plant (127.44), number of fruits set per plant (75.28), fruit retention (88.66%) and yield (11.78 kg/plant). Different management practices had significant effect on all studied parameters in both seasons. Fifty percent fruit thinning treatment showed the highest fruit yield (20.46 kg/plant) and 75% fruit thinning treatment performed lowest fruit yield (10.06 kg/plant) during on-season but during off-season shoot bending performed highest fruit yield (13.50 kg/plant). Highest fruit retention in both seasons (on-season 89.28% and off-season 90.47%) was observed in 50% fruit thinning treatment. In case of combined effect of variety and different management practices, 50% fruit thinning treatment combined with Chiang Mai (round) produced highest yield (23.15 kg/plant) and fruit retention (92.72%) during on-season, but shoot bending treatment combined with Swarupkathi gave the highest yield (16.06 kg/plant) and 50% fruit thinning combined with Swarupkathi showed highest fruit retention (94.12%) during off-season.DOI: http://dx.doi.org/10.3329/jesnr.v5i2.14808 J. Environ. Sci. & Natural Resources, 5(2): 167-172 2012

Field performance of transgenic citrus trees: assessment of the long-term expression of uidA and nptII transgenes and its impact on relevant agronomic and phenotypic characteristics.

BackgroundThe future of genetic transformation as a tool for the improvement of fruit trees depends on the development of proper systems for the assessment of unintended effects in field-grown GM lines. In this study, we used eight transgenic lines of two different citrus types (sweet orange and citrange) transformed with the marker genes β-glucuronidase (uidA) and neomycin phosphotransferase II (nptII) as model systems to study for the first time in citrus the long-term stability of transgene expression and whether transgene-derived pleiotropic effects occur with regard to the morphology, development and fruit quality of orchard-grown GM citrus trees.ResultsThe stability of the integration and expression of the transgenes was confirmed in 7-year-old, orchard-grown transgenic lines by Southern blot analysis and enzymatic assays (GUS and ELISA NPTII), respectively. Little seasonal variation was detected in the expression levels between plants of the same transgenic line in different organs and over the 3 years of analysis, confirming the absence of rearrangements and/or silencing of the transgenes after transferring the plants to field conditions. Comparisons between the GM citrus lines with their non-GM counterparts across the study years showed that the expression of these transgenes did not cause alterations of the main phenotypic and agronomic plant and fruit characteristics. However, when comparisons were performed between diploid and tetraploid transgenic citrange trees and/or between juvenile and mature transgenic sweet orange trees, significant and consistent differences were detected, indicating that factors other than their transgenic nature induced a much higher phenotypic variability.ConclusionsOur results indicate that transgene expression in GM citrus remains stable during long-term agricultural cultivation, without causing unexpected effects on crop characteristics. This study also shows that the transgenic citrus trees expressing the selectable marker genes that are most commonly used in citrus transformation were substantially equivalent to the non-transformed controls with regard to their overall agronomic performance, as based on the use of robust and powerful assessment techniques. Therefore, future studies of the possible pleiotropic effects induced by the integration and expression of transgenes in field-grown GM citrus may focus on the newly inserted trait(s) of biotechnological interest.

Genetic transformation of fruit trees: current status and remaining challenges

Genetic transformation has emerged as a powerful tool for genetic improvement of fruit trees hindered by their reproductive biology and their high levels of heterozygosity. For years, genetic engineering of fruit trees has focussed principally on enhancing disease resistance (against viruses, fungi, and bacteria), although there are few examples of field cultivation and commercial application of these transgenic plants. In addition, over the years much work has been performed to enhance abiotic stress tolerance, to induce modifications of plant growth and habit, to produce marker-free transgenic plants and to improve fruit quality by modification of genes that are crucially important in the production of specific plant components. Recently, with the release of several genome sequences, studies of functional genomics are becoming increasingly important: by modification (overexpression or silencing) of genes involved in the production of specific plant components is possible to uncover regulatory mechanisms associated with the biosynthesis and catabolism of metabolites in plants. This review focuses on the main advances, in recent years, in genetic transformation of the most important species of fruit trees, devoting particular attention to functional genomics approaches and possible future challenges of genetic engineering for these species in the post-genomic era.

The genome of Prunus mume.

Prunus mume (mei), which was domesticated in China more than 3,000 years ago as ornamental plant and fruit, is one of the first genomes among Prunus subfamilies of Rosaceae been sequenced. Here, we assemble a 280M genome by combining 101-fold next-generation sequencing and optical mapping data. We further anchor 83.9% of scaffolds to eight chromosomes with genetic map constructed by restriction-site-associated DNA sequencing. Combining P. mume genome with available data, we succeed in reconstructing nine ancestral chromosomes of Rosaceae family, as well as depicting chromosome fusion, fission and duplication history in three major subfamilies. We sequence the transcriptome of various tissues and perform genome-wide analysis to reveal the characteristics of P. mume, including its regulation of early blooming in endodormancy, immune response against bacterial infection and biosynthesis of flower scent. The P. mume genome sequence adds to our understanding of Rosaceae evolution and provides important data for improvement of fruit trees.

Biotechnological advances in guava (Psidium guajava L.): recent developments and prospects for further research

Guava (Psidium guajava L.), an important fruit crop of several tropical and sub-tropical countries, is facing several agronomic and horticultural problems such as susceptibility to many pathogens, particularly guava wilting caused by Fusarium oxysporium psidii, low fruit growth, short shelf life of fruits, high seed content, and stress sensitivity. Conventional breeding techniques have limited scope in improvement of guava owing to long juvenile period, self incompatibility, and heterozygous nature. Conventional propagation methods, i.e., cutting, grafting or stool layering, for improvement of guava already exist, but the long juvenile period has made them time consuming and cumbersome. Several biotechnological approaches such as genetic transformation may be effective practical solutions for such problems and improvement of guava. The improvement of fruit trees through genetic transformation requires an efficient regeneration system. During the past 2–3 decades, different approaches have been made for in vitro propagation of guava. An overview on the in vitro regeneration of guava via organogenesis, somatic embryogenesis, and synthetic seeds is presented. Organogenesis in several different genotypes through various explant selection from mature tree and seedling plants has been achieved. Factors affecting somatic embryogenesis in guava have been reviewed. Production of synthetic seeds using embryogenic propagules, i.e., somatic embryos and non-embryogenic vegetative propagules, i.e., shoot tips and nodal segments have also been achieved. Development of synthetic seed in guava may be applicable for propagation, short-term storage, and germplasm exchange, and distribution. An initial attempt for genetic transformation has also been reported. The purpose of this review is to focus upon the current information on in vitro propagation and biotechnological advances made in guava.

Functional characterization and mapping of two MADS box genes from peach (Prunus persica)

Previously an AGAMOUS gene homologue PpMADS4 and a FRUITFULL gene homologue PpMADS6 were isolated from peach (Prunus persica), and both genes were shown to express in the developing floral and fruits. To gain insight into their function, the two genes were constitutively expressed in Arabidopsis thaliana and their effects on plant growth and floral organ development were studied in this work. The transgenic plants all displayed early flowering and conversion of inflorescence to floral meristem. However, the two genes had different effects on the floral organ structures in A. thaliana. The transgenic plants overexpressing PpMADS4 displayed homeotic conversion of floral organs, and particularly the perianth abscission was inhibited. The plants overexpressing PpMADS6 showed early flowering, produced higher number of carpels, petals, and stamens than nontransgenic plants, and pod shatter was prevented; significantly, the transgenic plants yielded more than one siliques from a single flower. A SSR molecular marker was developed for PpMADS4, and it was then assigned into the G5 linkage group of Prunus sp. Both PpMADS4 and PpMADS6 genes were located at the same region in the G5 linkage group. Our results showed the potential application of these two MADS box genes for crop and fruit tree improvement.

DEREGULATION OF PLUM POX RESISTANT TRANSGENIC PLUM 'HONEYSWEET'

Genetic engineering (GE) has the potential to revolutionize fruit tree breeding. It is an approach that can specifically target genetic improvements and allow for the development of novel, useful traits. While GE does not provide a panacea for all of the difficulties associated with fruit tree breeding, it can be a useful approach to increase the efficiency and effectiveness of breeding programs. In spite of the potential utility of GE for fruit tree improvement, the technology has not, to date, been widely exploited in these species. Of over 11,000 field tests of transgenic plants in the United States between 1987 and 2004, less than 1% have involved fruit tree species. Transgenic plum trees that are highly resistant to Plum pox virus (PPV) are one example of GE that can be of significant benefit to growers and consumers while providing unique genetic material for use in conventional breeding programs. The development and testing of this plum has spanned 15 years and included researchers in five countries. Currently this plum, 'HoneySweet', is being evaluated for deregulation by U.S. regulatory agencies so that it may possibly be released in the future to breeders and growers who are concerned about the threat of PPV to U.S. stone fruit production.