Polyembryony is a type of sporophytic apomixis common in citrus species. Previous studies discovered that embryo traits relate to their sexual or asexual origin. Smaller embryos at the micropyle end are considered zygotic embryos, whereas larger embryos are nucellar. Early embryogenesis in the ovule of apomictic citrus promotes the development of nucellar embryos. The chalaza region inhibits the early development of the zygotic and nucellar embryos; thus, both embryos must grow at the micropyle end. Numerous researchers agree that highly polyembryonic cultivars produce nucellar seedlings more often as the zygotic embryos cannot survive field conditions. Thus, the selection of polyembryonic genotypes facilitates clonal propagation. This chapter analyzes the factors that affect polyembryony in citrus.

Determining the sample size in a scientific investigation is important because it gives reliability in the results together with the efficiency in the use of resources and optimization of time. Polyembryony is a characteristic that allows to obtaining clonal and zygotic plants in the same seed. In mango this characteristic is presented, however, there is no information that mentions which is the adequate sample size to evaluate it. The objective of the present work was to determine the optimum sample size by means of the maximum curvature method for future polyembryony studies. Mangoes from the cultivar Manila and Ataulfo were collected from the states of Guerrero and Nayarit, Mexico. In each state, two orchards of each cultivar were chosen, and in each one three trees were selected. In the Fruit Biotechnology laboratory of the Colegio de Postgraduados, Campus Montecillo, five fruit variables were evaluated: weight of fruit, seeds (endocarp and embryos), embryos, weight of the largest embryo and number of embryos. In all the variables evaluated, except for the weight of the largest embryo, the inflection point of the curve was in 6 fruits and an optimal sample size of 8 fruits was determined. The minimum variation coefficients (CV) for fruit weight were from 17.9 to 19.1%, for seed weight 12.7 to 19.3%, embryo weight 12.3 to 17.1% and number of embryos 6.7 to 16.7%. In the case of larger embryo weight, it was determined that 20 fruits are the optimal sample size, obtaining CV from 7 to 22.6%. The fruit and seed weight characteristics were the least variation, and number of embryos with higher CV. The cultivar Manila of Nayarit presented the highest CV in all the variables studied.

By virtue of the knowledge of the beneficial effect of the warm and dry storage, for the growth of the chincuya seed embryo, defined as morphological dormancy. The effect of the same type of storage was studied for the seed viability and germination by soaking gibberellic acid. Also, fatty acids and their kinetics were identified during the warm and dry storage. The following treatments were evaluated: storage time (0, 3, 6, 9 and 12 months), seed soaking in gibberellic acid at 350 mg L-1, and for the control, imbibition in distilled water, both for 72 h. The seed viability was evaluated through the stain test with tetrazolium chloride. The embedded seeds were germinated on absorbent paper towels and incubated at different temperatures of 30 ° C during the day and 25 ° C at night and 12 hours of photoperiod. The lipid profile was developed by gas chromatography. Seeds were held at constant temperature of 25 ± 3 ° C, in darkness, during the storage time. Results demon-strated that the high initial viability was maintained until the ninth month, when it decreases and is statisti-cally different from the other treatments. The smaller germination percentage (26.1 %) was observed in the freshly harvested seeds and, the higher one corresponded to the six months (65.6 %), with these differences being statistically significant. Regarding the identified fatty acids and their average content, it was found that 33.41 % corresponded to palmitic acid, 7.72 % to stearic acid; the arachidic acid with 1.30 %, making a total of saturated fatty acids of 42.44 %. The detected unsaturated fatty acids were: palmitoleic acid 1.52 %, oleic acid 43.37 % and linoleic acid 7.24 %, in total, 52.15 %. No significative changes were observed in the fatty acids content that are the largest part of the total seed reserves; although the higher concentrations matched with the longest germination (three months), with an average of 92.84 % total fatty acids. Specified regressions indi-cated with statistical robustness that palmitoleic and palmitic acids increased while the oleic acid decreased during the dry storage. The arachidic acid showed a slightly downward trend. Also, the concentrations of fat-ty acids were significatively different between unstored and unincubated seeds (intact) and unstored and in-cubated, but without germinating seeds (dormant), in the latter, the total fatty acids content was significantly lower. Given that the application of gibberellic acid and warm dry storage favored germination, as well as the change in fatty acid content during warm dry storage, added to the results already reported on morphological changes and embryonic growth as an effect of the same type of storage, it is established that Annona purpurea seeds present morphophysiological dormancy, also this is the first identification report of arachidic and pal-mitoleic acids in chincuya seeds and the higher germination percentage reported (65.6 %).

There is sufficient knowledge of the beneficial effect of warm-dry storage on breaking the morpho-logical dormancy of the chincuya (Annona purpurea Moc. & Sessé ex Dunal) seed embryo. Chincuya is an underutilized, tropical wild species native to Mexico, with potential as a biopesticide. The impact of warm-dry storage and gibberellic acid treatment on seed viability and germination was determined to improve that knowledge further. Also, the content and kinetics of fatty acids in chincuya seeds were profiled during warm-dry storage. Seed treatments included storage time (0, 3, 6, 9, and 12 months), seed imbibition for 72 h in gibberellic acid at 350 mg L-1, and distilled water im-bibition for 72 h for the control treatment. Seed viability was determined using the TTZ classic test. Imbibed seeds were germinated on paper towels and incubated at 30 °C during the day and 25 °C at night in a 12:12 h dark:light photoperiod. The lipid profile was obtained by gas chromatography. During the storage treatment, seeds stayed in darkness at 25 ± 3 °C. Results showed that high viability remained up to month 9 in storage when it significantly decreased. Freshly harvested seeds germi-nated at a statistically significantly lower rate (26.1 %) than six-month-old seeds (65.6 %). The profile of fatty acids breaks down as palmitic acid (33.41 %), stearic acid (7.72 %), and arachidic acid (1.30 %), for a total of 42.44 % of saturated fatty acids. The detected unsaturated fatty acids (52.15 %) were palmitoleic acid (1.52 %), oleic acid (43.37 %), and linoleic acid (7.24 %). No significant changes were detected in fatty acid content; however, the highest fatty acid content (92.84 %) occurred with the highest germination rate. Regression analysis showed significant content changes: palmitoleic and palmitic acid increased while oleic acid decreased during dry storage. Arachidic acid showed a slight downward trend. Also, fatty acid content significantly differed between intact seeds (unstored and unincubated) and latent seeds (unstored, incubated, and ungerminated). The total fatty acids content for latent seeds was significantly lower. These results show that Annona purpurea seeds present morphophysiological dormancy. Also, we document the highest germination rate reported (65.6 %) and report the presence of arachidic and palmitoleic acids in chincuya seeds.

Despite ample knowledge of the effect of warm-dry storage on breaking dormancy in chincuya (Annona purpurea Moc. & Sessé ex Dunal) seeds, this paper investigates an important new aspect of this process—the applicability of seed treatment with gibberellic acid and its influence on seed viability and fatty acid profile. Chincuya is an underutilized, tropical wild species native to Mexico, with potential as a biopesticide. The impact of warm-dry storage and gibberellic acid treatment on seed viability and germination was determined to improve that knowledge further. Also, the content and kinetics of fatty acids in chincuya seeds were profiled during warm-dry storage. Seed treatments included storage time (0, 3, 6, 9, and 12 months), seed imbibition for 72 h in gibberellic acid at 350 mg L⁻¹, and distilled water imbibition for 72 h for the control treatment. Seed viability was determined using the TTZ classic test. Imbibed seeds were germinated on paper towels and incubated at 30 °C during the day and 25 °C at night in a 12:12 h dark/light photoperiod. The lipid profile was obtained by gas chromatography. During the storage treatment, seeds stayed in darkness at 25 ± 3 °C. Results showed that high viability remained up to month 9 in storage when it significantly decreased. Freshly harvested seeds germinated at a statistically significantly lower rate (26.1%) than six-month-old seeds (65.6%). The profile of fatty acids breaks down as palmitic acid (33.41%), stearic acid (7.72%), and arachidic acid (1.30%), for a total of 42.44% of saturated fatty acids. The detected unsaturated fatty acids (52.15%) were palmitoleic acid (1.52%), oleic acid (43.37%), and linoleic acid (7.24%). No significant changes were detected in fatty acid content; however, the highest fatty acid content (92.84%) occurred with the highest germination rate. Regression analysis showed significant content changes: palmitoleic and palmitic acids increased while oleic acid decreased during dry storage. Arachidic acid showed a slight downward trend. Also, fatty acid content significantly differed between intact seeds (unstored and unincubated) and latent seeds (unstored, incubated, and ungerminated). The total fatty acids content for latent seeds was significantly lower. These results show that Annona purpurea seeds present morphophysiological dormancy. Also, we document the highest germination rate reported (65.6%) and report the presence of arachidic and palmitoleic acids in chincuya seeds.