Kernel size and weight affected by three plant bioregulators applied at bloom to Non Pareil and Carmel almond cultivars

Background: The yield of almonds [Prunus dulcis (Mill.) D.A. Webb] could be low due to climatic problems and any factor improving kernel size and weight, such as the use of plant bioregulators (PBRs), should be beneficial. Results: Three plant bioregulators: 24-epibrassinolide (BL), gibberellic acid (GA3) and kinetin (KN) were applied at three spray concentrations to Non Pareil and Carmel cultivars, at two phenological stages during bloom, in the 2014 and 2015 seasons. The results showed significant differences (P b 0.0001). For total dry weight of Non Pareil, the best treatment was BL (30 mg·L-1), with an average of 1.45 g, while the control was 1.30 g, at pink button during 2015. For Carmel, the best dry weight was 1.23 g, achieved with BL (30 mg·L-1) at fallen petals in both seasons. The average dry weight of the controls varied between 1.13 and 1.18 g. The greatest almond lengths and widths in Non Pareil were 24.98 mm and 15.05 mm, achieved with BL (30 mg·L-1) and KN (50 µL·L-1) treatments, respectively, applied at pink button in 2015. In Carmel, the greatest length and width were 24.38 and 13.44 mm, obtained with BL (30 mg·L-1) applied at the stages of pink button and fallen petals, respectively, in 2015. The control reached lengths between 22.33 and 23.38 mm, and widths between 11.99 and 12.93 mm. Conclusions: The use of the bioregulators showed significant favorable effects on dry weight, length and width of kernels at harvest, in both cultivars.

The effect of three plant bioregulators on pollen germination, pollen tube growth and fruit set in almond [Prunus dulcis (Mill.) D.A. Webb] cvs. Non Pareil and Carmel

Background In commercial almond [Prunus dulcis (Mill.) D.A. Webb] orchards in Chile, the percentage of fruit set is low and commonly reaches 5–30%. As almond trees bloom during a cool period and also suffer from self-incompatibility, any factor that can improve pollination, pollen germination and pollen tube growth or extend the effective pollination period, such as the application of plant bioregulators (PBRs), should be beneficial for fruit production. Results Three plant bioregulators (PBRs): brassinolide (BL), gibberellic acid (GA3) and kinetin (KN) were evaluated for pollen germination and pollen tube growth in vitro, as well as for fruit set in almond cultivars Non Pareil and Carmel, in central Chile, during the 2013 and 2014 seasons. For pollen germination in vitro, the BL concentration of 10 mg L- 1 had the highest value in Non Pareil (97.7%), after 4 h germination in 2014 growing season (the control was 90.9%). KN at a concentration of 50 µL L- 1 induced the longest pollen tube growth of 1243.4 µm in Carmel after 8 h germination in 2013 (the control was 917.7 µm). In Non Pareil, the highest percentage of fruit set (31.0%) was achieved in 2014 by spraying during bloom at pink bud stage with KN at 50 µL L- 1 (the control was 16.7%). Conclusions A significant favorable effect of the tested PBRs was observed in pollen germination and pollen tube growth in vitro, as well as on fruit set in Non Pareil and Carmel almonds.

An efficient regeneration and rapid micropropagation protocol for Almond using dormant axillary buds as explants.

An efficient in vitro protocol was standardized for Almond (Prunus dulcis) propagation using dormant axillary buds as explants. Explants were cultured on Murashige and Skoog (MS) and woody plant medium (WPM) supplemented with different concentration/combination(s) of phytohormones. MS basal medium showed lowest shoot induction and took longest duration for shoot initiation. Multiple shoots were induced in MS medium supplemented with the combination of BAP (0.5 mgL-1). Cultures showed poor response for rooting in all combinations of plant growth regulators (PGRs) and took 90 days for initiation. Rooting was higher in half strength of MS than in full-strength. The highest root induction (33.33%) was recorded in half MS medium supplemented with 0.1 mgL-1 IBA (indole-3-butyric acid) followed by full strength of MS medium (20%) supplemented with IBA (0.1 mgL-1). α-Naphthalene acetic acid (NAA) was less effective for rooting than IBA. The highest root induction (25%) was found in half strength of MS medium supplemented with 0.1 mgL-1 NAA followed by full strength of MS medium (20%). The protocol developed would be of use in mass propagation of almond and also support in vitro conservation.