Direct Somatic Embryogenesis in Carica papaya L. Genotypes for Genetic Modification Purposes.

This chapter presents an efficient protocol for regenerating Carica papaya plants via somatic embryogenesis from immature zygotic embryos from economically important papaya genotypes. To achieve regenerated plants from somatic embryos, in the present protocol, four induction cycles are required, followed by one multiplication cycle and one regeneration cycle. With this optimized protocol, 80% of somatic embryos can be obtained in only 3.5 months. At this stage, calli containing more than 50% globular structures can be used for transformation (via agrobacterium, biobalistics, or any other transformation method). Once transformed, calli can be transferred to the following steps (multiplication, elongation, maturation, rooting, and ex vitro acclimatization) to regenerate a transformed somatic embryo-derived full plant.

Effect of Vitis vinifera zygotic embryo cryopreservation and post-cryopreservation on the gene expression of DNA demethylases.

Grapevine (Vitis vinifera L.) crops are continuously exposed to biotic and abiotic stresses, which can cause genetic and epigenetic alterations. To determine the possible effects of grapevine cryopreservation on the regulation of DNA demethylase genes, this work studied the expression of DNA demethylase genes in cryopreserved and post-cryopreserved grapevine tissues. V. vinifera DNA demethylases were characterized by in silico analysis, and gene expression quantification was conducted by RT‒qPCR. Three DNA demethylase sequences were found: VIT_13s0074g00450 (VvDMT), VIT_08s0007g03920 (VvROS1), and VIT_06s0061g01270 (VvDML3). Phylogenetic analysis revealed that the sequences from V. vinifera and A. thaliana had a common ancestry. In the promoters of responsive elements to transcription factors such as AP-2, Myb, bZIP, TBP, and GATA, the conserved domains RRM DME and Perm CXXC were detected. These responsive elements play roles in the response to abiotic stress and the regulation of cell growth. These data helped us characterize the V. vinifera DNA demethylase genes. Gene expression analysis indicated that plant vitrification solution 2 (PVS2) treatment does not alter the expression of DNA demethylase genes. The expression levels of VvDMT and VvROS1 increased in response to cryopreservation by vitrification. Furthermore, in post-cryopreservation, VvROS1 was highly induced, and VvDML3 was repressed in all the treatment groups. Gene expression differences between different treatments and tissues may play roles in controlling methylation patterns during gene regulation in tissues stressed by cryopreservation procedures and in the post-cryopreservation period during plant growth and development.

Long-Term Conservation for the Safeguard of Abies nebrodensis: An Endemic and Endangered Species of Sicily.

The combined approaches between ex situ and in situ conservation are of great importance for threatened species in urgent need of protection. This study aims to develop concrete actions to preserve the relic of 30 adult trees of the Sicilian fir (Abies nebrodensis) from extinction using long-term germplasm conservation in liquid nitrogen (LN, -196 °C). Pollen grains were collected, and their moisture content (MC) was measured. Then, viability (2,3,5-tryphenyl tetrazolium chloride, TTC), in vitro germinability, and enzymatic antioxidant activity (ascorbate peroxidase, APX; catalase, CAT) were evaluated before and after cryopreservation. Seeds collected from mature cones underwent X-ray analysis, and only full seeds were used to excise the zygotic embryos (ZEs) for cryopreservation. The MC percentage of ZEs was determined, and then they were plunged in LN with (+PVS2) or without (-PVS2) Plant Vitrification Solution 2; untreated ZEs were used as a control. Viability (TTC test) and in vitro germination were assessed for all ZEs (+PVS2, -PVS2, and control). Embryogenic callus (EC) lines obtained from mature ZEs were cryopreserved applying the 'encapsulation-dehydration' technique. This study has allowed, after optimizing cryopreservation protocols for pollen, ZEs, and EC of A. nebrodensis, to establish the first cryobank of this endangered species in Polizzi Generosa (Palermo, Italy), inside the 'Madonie Regional Park'. The strategy developed for Sicilian fir conservation will pave the way for similar initiatives for other critically endangered conifer species.

Somatic Embryogenesis from Immature Olive Zygotic Embryos.

The effects of plant growth regulators (PGRs) and the explant type on the embryogenesis and plant regeneration of olive (Olea europaea L. ssp europaea var. sativa) cv. "Chetoui" were studied using immature zygotic embryos. Embryogenic callus induction was achieved on OMc medium supplemented with different concentrations of BAP and NAA at low levels. Immature zygotic embryos as juvenile tissues are competent for somatic embryogenesis independently of PGRs supplementation. Repetitive somatic embryogenesis was obtained on PGRs-free media or at low concentrations in the dark.

Effect of copper and silver ions on sequence and DNA methylation changes in triticale regenerants gained via somatic embryogenesis.

Somatic embryogenesis is a plant regeneration method that can be exploited in tissue culture systems for a variety of tasks, such as genetic modification or the selection of somaclones with advantageous characteristics. Therefore, it is crucial to create efficient regeneration procedures and comprehend how medium components affect regeneration effectiveness or the degree of variation created in plant tissue cultures. The level of tissue culture-induced variation in triticale regenerants was examined in the current study in relation to the concentration of copper and silver ions in the induction media as well as the length of time immature zygotic embryo explants were incubated on these media. The high degree of variation (45%) revealed by the methylation-sensitive amplified fragment length polymorphism approach for estimating variation included 38% DNA sequence alterations, 6% DNA demethylation, and 1% de novo DNA methylation. Different levels of variance were found in relation to various DNA sequence settings. The CHG context had the most alterations, whereas CG experienced the fewest; sequence variation predominated in each sequence context. Lower copper ion concentrations showed the most variance. However, it could not be connected to the duration of in vitro culture or the effect of silver ions. Accordingly, we think that altering the concentration of copper ions in the induction medium may throw off the equilibrium of the metabolic processes in which copper is involved, resulting in tissue culture-induced variation.

Analysis of the Distribution of Symplasmic Tracers During Zygotic and Somatic Embryogenesis.

Plasmodesmata (PD) are membraneous channels that span cell walls of adjacent cells to establish the symplasm. These connections are unique to plants and enable the cell-to-cell exchange of information via the symplasm. However, not every plant cell is connected to its neighbor. Absence of PD and lack of communication (symplasmic isolation) are important regulators of cell differentiation. To determine cell-to-cell symplasmic connectivity, the distribution of fluorescent tracers can be analyzed. Here, we describe in detail the entire procedure for conducting such analysis using fluorescence and confocal microscopy to study molecular fluxes in fluorescence recovery after photobleaching (FRAP) experiments. Studies using fluorochromes and fluorescent-labeled dextrans successfully inform the degree of symplasmic connectivity between cells in zygotic and somatic embryos. Small molecules, such as water and ions, travel through PD but also transcription factors and different types of RNA. Studies of symplasmic communication are important to determine the spatio-temporal correlation between cell differentiation and the exchange of information between cells. This information is necessary to determine the role of symplasmic communication during embryogenesis, which is a very important stage in plant development and morphogenesis.

Cryopreservation of carnation (Dianthus caryophyllus L.) and other Dianthus species.

MAIN CONCLUSION: This paper reviews the cryopreservation of the ornamental, carnation (Dianthus caryophyllus L.), as an important method for the long-term preservation of this plant's germplasm. Carnation (Dianthus caryophyllus L.) is an important ornamental plant that is used as a potted plant as well as a cut flower. Important Dianthus germplasm would benefit from long-term strategies such as cryopreservation. Unlike the in vitro tissue culture literature of this ornamental, which has been studied in considerable detail, and with several genetic transformation protocols, surprisingly, the literature on its cryopreservation is still fairly scant, with barely two dozen or so studies, mostly having employed shoot tips. Early (< 2007) and more recent (2007-2020) cryopreservation techniques for carnation, including ultra-rapid cooling, encapsulation-vitrification, and encapsulation-dehydration, efficiently replaced programmed slow cooling processes used in early studies in the 1980s. Two large gaps (1997-2006, and 2016-2020) in which no carnation cryopreservation studies were published, requires future studies to cover new knowledge to fill gaps in information. Carnation cryopreservation research would benefit from testing a wide range of in vitro explants, new techniques such as the cryo-mesh, improved regeneration protocols for post-cryopreserved material, and the use of low-temperature storage as a mid- to long-term complementary germplasm storage strategy. This mini-review provides details of what has been achieved thus far and future objectives that could fortify cryopreservation research of this ornamental, as well as provide a robust long-term germplasm repository.

Somatic Embryogenesis from Mature Embryos of Olea europaea L. cv. 'Galega Vulgar' and Long-Term Management of Calli Morphogenic Capacity.

Several olive cultivars, characterized by high-quality olive oil show agronomical issues such as excessive vigor, high susceptibility to biotic and abiotic stresses, and low propagation ability. They are strong candidates for breeding based on new technologies to improve their performance in a short period of time. For this reason, the first step is developing efficient somatic embryogenesis (SE) protocols. Somatic embryogenesis in olive is highly genotype-dependent for both adult tissues and mature embryos as initial explants, requiring the development of specific protocols for each genotype. Trials using cotyledons and radicles as initial explants, isolated from ripe seeds from the Portuguese olive cv. 'Galega vulgar', gave more than 95% calli development. Radicles proved to be the most responsive tissue for SE induction, with an average of 2 embryos per callus after callus transfer to expression medium, and 14 embryos per callus after subculture on the olive cyclic embryogenesis medium (ECO). Embryogenic competence could be recovered after several subcultures on ECO medium that maintained cyclic embryogenesis for an indeterminate period of time. Embryo conversion and plant acclimatization were also attained with high success rates. Media management for cyclic embryogenesis maintenance is of general importance for SE protocols in any olive genotype. Somatic embryogenesis was thus attained for the first time in embryo-derived explants of cv. 'Galega vulgar'.

Protocol for Rescuing Young Cassava Embryos.

Embryo rescue (ER) in cassava breeding has several relevant applications, from the recovery of broad crosses to the recovery of seeds from the standard pollination program. Cassava fruit setting may drop from 100%, during the 1st week after pollination, to less than 40% during the 2nd week after pollination due to the abscission of fruits depending on genotypes. Therefore, the availability of an ER protocol for early stages of embryo development, in particular during the first 2 weeks after pollination (prior the cotyledonary stage), could have practical implications for cassava breeding. Until now, attempts to recover cassava immature embryos at stages of development earlier than the cotyledonary stage failed. The earliest successful rescue reported in cassava is from embryos excised 32-36 days after anthesis (DAA). However, limited information was available regarding embryo development in cassava. This work studied and documented the stage of embryo development in histological sections of hand-pollinated ovules fixed from 1 to 30 days after anthesis (DAA). At 7 DAA, zygotes were just at the first stages of cell division (pro- embryo stage). At 14 DAA, embryos were at the pre-globular stage. Embryos at the early globular stage were observed in sections fixed at 21 DAA, and at the proper globular stage at 24 DAA. Samples at 30 DAA contained cotyledonary embryos that easily developed after ovule culture into viable plants using existing protocols. A second contribution of this work is the development of a protocol for the recovery of fully developed plants from immature embryos rescued and cultured in vitro as early as 7-14 DAA. Since embryos collected at this age are at the pro-embryo to pre-globular stage, ovary/ovule culture was necessary. A method is described whereby ovules were cultured to allow the development of pro-embryos and pre-globular stage embryos into the cotyledonary stage. Subsequently, these mature embryos were excised from the ovules to induce germination and the recovery of fully developed plants.

Assessment of genetic stability in somatic embryo derived plantlets of Pterocarpus marsupium Roxb. using inter-simple sequence repeat analysis.

An efficient plantlet regeneration protocol using immature zygotic embryos (IZEs) via somatic embryogenesis has been developed in Pterocarpus marsupium Roxb. The regenerated plantlets were evaluated for their genetic stability. IZEs were incubated on Murashige and Skoog (MS) media augmented with 1.07-16.11 µM naphthalene acetic acid (NAA) or 0.90-13.97 µM 2,4-dichlorophenoxyacetic acid. The optimum callus induction (96.6%) was observed on MS medium augmented with 5.37 µM NAA. Induction of somatic embryos (SEs) was observed after sub-culture of calli on medium with decreased concentrations of NAA (0.54-5.37 µM), either alone or 2.69 µM NAA in combination with 2.22-8.90 µM benzyladenine (BA) or 2.32-9.30 µM Kinetin. Maximum number (33.4 ± 0.85) of SEs occurred on MS medium augmented with 2.69 µM NAA + 4.40 µM BA + 3% sucrose. Highest percentage (67.3 ± 0.37) of SEs matured and developed into cotyledonary stage by subsequent subculture on the same medium. SE formation and maturation decreased when sucrose concentrations were higher than 3%. Seventy percent of mature somatic embryos developed into plantlets on half strength MS medium augmented with 5.80 µM gibberellic acid. The various stages of development during somatic embryogenesis include  globular, heart, torpedo and mature stages as revealed by the stereomicroscopic and histological studies of explants. Plantlets derived from SEs were successfully acclimatized in the greenhouse with a survival rate of 78%. Among the survived plantlets, 9 plantlets were randomly selected for inter-simple sequence repeat (ISSR) analysis. Of the 13 primers used, 8 produced reproducible and monomorphic bands. ISSR analysis revealed a homogenous amplification profile for all regenerated plantlets analyzed validating the genetic stability of somatic embryo derived plantlets.

Protocol of in vitro Jojoba (Simmondsia chinensis (Link) Schneider) Callus Induction.

BACKGROUND AND OBJECTIVES: Presently, determination of optimum protocol for callus induction of any plant is an important issue in tissue culture technology. Therefore, the main objective of this study was to find out an optimum protocol for callus induction from in vitro cultured jojoba by determining the optimum explant and the best growth regulators mixture for callus induction. MATERIALS AND METHODS: The study used three variant explants namely the leaf disks, seeds and nodal segments for callus formation. Different culture media containing basic Murashige and Skoog (MS) medium components supplemented with various concentrations of 2,4-dichlorophenoxy acetic acid as an auxin (2,4-D) and Kinetin (Kin) as a cytokinin with various concentrations ranging from 0.0, 0.5, 1.0 and 2.0 mg L-1 were used. The total number of treatments were 16. The callus was induced from all explants on MS medium containing the lowest concentration of 2,4-D 0.5 mg L-1 with any concentration of Kin. RESULTS: The results showed that nodal segments were the best for callus formation followed by the leaf disks (leaves) and seeds, respectively. While, the best concentration of proliferation and development of the used explant was 2.00 followed in descending order by 1.00, 0.5 and 0.0 mg L-1, respectively. CONCLUSION: The study find out that the best concentration of 2,4-dichlorophenoxy acetic acid as an auxin (2,4-D) and Kinetin (Kin) as a cytokinin was 2.00 followed in descending order by 1.00, 0.5 and 0.0 mg L-1, respectively for callus induction.

Electrophoresis-Based Proteomics to Study Development and Germination of Date Palm Zygotic Embryos.

Proteomics has become an important and powerful tool in plant biology research. To establish a proteomic reference map of date palm zygotic embryos (ZE), we separated and identified proteins from zygotic embryos during different developmental and germination phases using one, two-dimensional polyacrylamide gel electrophoresis and mass spectrometry. Proteins are extracted with trichloroacetic acid (TCA)/acetone-phenol and resolved by gel electrophoresis. Gel images are captured and analyzed by appropriate software and statistical packages. Quantitative or qualitative variable bands or spots are subjected to MS analysis in order to identify them and correlate differences in the protein profiles with the different stages of date palm zygotic embryo development, maturation, and germination.

Somatic Embryogenesis in Olive (Olea europaea L. subsp. europaea var. sativa and var. sylvestris).

Protocols for olive somatic embryogenesis from zygotic embryos and mature tissues have been described for both Olea europaea sub. europaea var. sativa and var. sylvestris. Immature zygotic embryos (no more than 75 days old), used after fruit collection or stored at 12-14 °C for 2-3 months, are the best responsive explants and very slightly genotype dependent, and one single protocol can be effective for a wide range of genotypes. On the contrary, protocols for mature zygotic embryos and for mature tissue of cultivars are often genotype specific, so that they may require many adjustments according to genotypes. The use of thidiazuron and cefotaxime seems to be an important trigger for induction phase particularly for tissues derived from cultivars. Up to now, however, the application of this technique for large-scale propagation is hampered also by the low rate of embryo germination; it proves nonetheless very useful for genetic improvement.

Effect of coconut water on growth of olive embryos cultured in vitro / Efeito da água de coco no crescimento de embriões de oliveira cultivados in vitro

The experiment was carried out to determine the appropriate dose of coconut water as supplement for in vitro cultivation of zygotic embryos from 19 olive genotypes. The isolated embryos of the olive seeds were immersed on culture medium containing 0 (control), 25, 50, and 100mL L-1 of fresh and sterile coconut water and kept for 45 days under controlled environment. The percentage of germination, shoot length, number of roots, number of leaves and number of internodes were measured for all 19 olive genotypes. The ANOVA of the parameters evaluated showed significant genotypes x doses of coconut water interaction for shoot length, number of leaves and number of internodes and the dose of 100mL L-1 produced the best results overall as indicated by the means of measured parameters. However, the study showed the importance of determining the appropriate dose of coconut water for each genotype under consideration as shown by significant genotype x dose of coconut water interaction effect.

O experimento foi realizado para determinar a dose adequada de água de coco como suplemento para cultivo in vitro de embriões zigóticos de 19 genótipos de oliveira. Os embriões isolados das sementes de oliveira foram imersos em meio de cultura contendo 0 (controle), 25, 50, e 100mL L-1 de água de coco fresca e estéril, em condição de ambiente controlado durante 45 dias. A porcentagem de germinação, comprimento da parte aérea, número de raízes, número de folhas e número de internódios foram medidos para todos os 19 genótipos de oliveira. A ANOVA dos parâmetros avaliados apresentou interação significativa entre genótipos e dose de água de coco para o comprimento da parte aérea, número de folhas e número de internódios, e a dose de 100mL L-1, de forma geral, produziu os melhores resultados, como indicado pelas médias dos parâmetros analisados. No entanto, como mostra a interação significativa observada entre genótipos e tratamentos, é importante determinar a dose adequada de água de coco para cada genótipo.

Respuesta de Zamia incognita L. al cultivo in vitro, una alternativa para su conservación / In vitro culture response of Zamia incognita, an alternative for preservation

Las Zamiaceas son plantas relictuales consideradas fósiles vivientes. En Colombia, el 65% de esta familia se encuentra en alguna categoría de amenaza, por la destrucción del hábitat e intensa recolección. Teniendo en cuenta que entre las ventajas de la propagación in vitro está la conservación ex situ de germoplasma, el presente trabajo tuvo como objetivo evaluar el potencial de regeneración de plantas de Z. incognita a partir de explantes foliares y embriones cigoticos. Se evaluó el efecto de diferentes combinaciones de Auxinas (2,4-D y ANA) y citoquininas (KIN, BAP y TDZ) sobre la formación de callo y la regeneración de brotes (directa o indirecta), utilizando como medio basal MS (MB1) y medio basal B5 modificado (MB2). La formación de callo se presentó sobre un amplio rango de concentraciones de 2,4-D con KIN y 2,4-D con BAP, independientemente del medio basal, pero no en los explantes tratados con ANA más KIN o TDZ. Para los explantes foliares no hubo respuesta a la formación de embriones somáticos y/o brotes con las combinaciones y concentraciones hormonales evaluadas, no obstante los callos inducidos en MB2 con 2,4-D (0,22 mg/l) y BAP (0, 1, 2, 3 mg/l) fueron diferentes, su aspecto nodular, color crema y apariencia proembriogénica coincidió con una gran cantidad de células meristemáticas potenciales para el proceso de regeneración. A partir de embriones cigoticos inmaduros se logró la formación de embriones somáticos en el medio MB2 exento de reguladores o conteniendo 2,4-D solo (0,22 mg/l) y en combinación con BAP (1 mg/l), sin lograr el proceso de conversión a plántulas.

Zamiaceas are relict plants considered living fossils. In Colombia, 65% of this family is under some threat category due to their habitat destruction and their intense collection. Given that the advantages of in vitro propagation is ex situ conservation of germoplasm, this study aimed to evaluate the regeneration potential of Z incognita plants from leaf explants and zygotic embryos. The effect of different combinations of auxin (2.4-D and NAA) and cytokinins (KIN, BAP and TDZ) was evaluated on the formation of callus and shoot regeneration (direct or indirect), using MS (MB1) basal medium and B5 (MB2) basal modified medium. The callus formation was presented over a wide concentration range of 2.4-D with KIN and 2.4-D with BAP, regardless of the basal medium, but not in explants treated with ANA more TDZ or KIN. For leaf explants there was no response to the formation of somatic embryos or shoots with hormonal combinations and concentrations evaluated; however, MB2 calluses induced with 2.4-D (0.22 mg / l) and BAP (0. 1 , 2. 3 mg / l) were different, their nodular aspect, cream color and pro-embryogenic appearance coincided with a lot of potential meristematic cells for the regeneration process. From immature zygotic embryos, somatic embryo formation in the MB2 medium was achieved without growth regulators or containing 2.4-D alone (0.22 mg /l) or 2.4-D in combination with BAP (1 mg/l) without achieving the conversion process to seedlings.

Aplicação de análogo de brassinosteroide (Biobras 16®) sobre a germinação e crescimento in vitro de embriões zigóticos e aclimatização de plântulas de bocaiuva / Application of analogue brassinosteróide (Biobras 16®) germination and growth in vitro culture of zygotic embryos and acclimatization of bocaiuva

Apresentam-se resultados de pesquisa experimental que avaliou o crescimento in vitro de embriões zigóticos e aclimatização de plântulas de bocaiuva (Acrocomia aculeata) cultivadas em diferentes concentrações (0,0; 0,001; 0,005; 0,01; 0,05; 0,1; 0,5 e 1mg L-1) de análogo de brassinosteroide (Biobras 16®). O trabalho buscou verificar se a aplicação de Biobras 16® influencia positivamente na taxa de germinação dos embriões zigóticos de Acrocomia aculeata e se promove o crescimento e desenvolvimento das plântulas e, consequentemente, afeta o número de plântulas normais. A aplicação de Biobras 16® não promoveu acréscimo no percentual de germinação, porém, estimulou a formação de plântulas normais. -O efeito positivo de Biobras 16® foi observado apenas na primeira fase, não sendo observado nas demais fases de crescimento avaliadas.

The results of an experimental research evaluating the in vitro growth of zygotic embryos and acclimatization of bocaiuva (Acrocomia aculeata) grown under different concentrations (0.00, 0.001, 0.005, 0.01, 0.05, 0.1, 0.5 and 1mg. L-1) of a brassinosteroid analogue (Biobras 16®) are presented. The objective was to determine whether the application of 16 Biobras ® positively affects the germination of zygotic embryos of Acrocomia aculeata and promotes the growth and development of seedlings and thereby affects the number of normal seedlings. The application of Biobras 16® did not promote an increase in the percentage of germination but stimulated the formation of normal seedlings. The positive effect of Biobras 16® was observed only in the first phase, not observed in other growth stages evaluated.

Induction of somatic embryogenesis in Pinus roxburghii Sarg.

Embryogenic calli were initiated from embryonic explants of Pinus roxburghii using female gametophytes containing immature pre-cotyledonary embryos. Zygotic embryos were collected at different developmental stages and cultured on various media. Initiation of embryogenic calli was achieved in pre-cotyledonary zygotic embryos of a 0.1-mm to 1.2-mm embryonal head on Douglus fir cotyledon revised medium (DCR) medium supplemented with 2,4-D or NAA and BA. Embryogenic callus development was initiated from the suspensor region of immature embryos. The method of immature embryo culture was significant as rapid embryogenic callus development occurred in megagametophytes where the suspensor was stretched onto the medium from the cut micropylar end. Sixty embryogenic lines were established from 2500 explants cultured during one season. A pro-embryo with six to eight meristematic cells and suspensor of six to ten long, vacuolated cells dominated the early phase of the callus development. Cleavage polyembryony occurred in proliferating callus, constituting a method of multiplication of these somatic embryos. Somatic embryos developed to stage-I and stage-II embryos on DCR medium supplemented with 5 µM 2,4-D or 10 µM NAA.

The Resistance of Mango (Mangifera indica) Cultivars to Tip Dieback Disease in Florida.

The resistance of Mangifera indica to tip dieback disease caused by Botryosphaeria ribis, anamorphic state Fusicoccum sp., was determined on 361 trees of 122 mango cultivars and relatives planted in the mango germ plasm collection at the University of Florida, Tropical Research and Education Center, Homestead. Three trees from each cultivar were evaluated on a 1 to 5 scale ranging from those free of tip dieback to those with extensive branch necrosis. Each cultivar was assigned to one of eight major systematic groups based on race or geographic origin. Resistance to tip dieback disease was not associated with any of the groups. No significant differences in mean disease severity were found among the Indian, Southeast Asian, West Indian, Haden, or Sandersha parts of the Haden-Sandersha Complex, Turpentine types, or a group of unclassified cultivars. Two Mangifera species (M. odorata and M. zeylanica) showed the lowest mean disease rating. Cultivars were also grouped into monoembryonic and polyembryonic types. Although several mango cultivars, mainly found in the monoembryonic group, appeared to be free of the disease, resistance to tip dieback was not associated with embryony. This study provides the first indication that field resistance to tip dieback may be present in some mango cultivars.