Molecular and histological validation of modified in ovulo nucellus culture based high-competency direct somatic embryogenesis and amplitude true-to-the-type plantlet recovery in Kinnow mandarin

Kinnow (Citrus nobilis Lour. × Citrus deliciosa Ten.) needs to be genetically improved for traits such as seedlessness using biotechnological tools. Indirect somatic embryogenesis (ISE) protocols have been reported for citrus improvement. However, its use is restricted due to frequent occurrences of somaclonal variation and low recovery of plantlets. Direct somatic embryogenesis (DSE) using nucellus culture has played a significant role in apomictic fruit crops. However, its application in citrus is limited due to the injury caused to tissues during isolation. Optimization of the explant developmental stage, explant preparation method, and modification in the in vitro culture techniques can play a vital role in overcoming the limitation. The present investigation deals with a modified in ovulo nucellus culture technique after the concurrent exclusion of preexisting embryos. The ovule developmental events were examined in immature fruits at different stages of fruit growth (stages I-VII). The ovules of stage III fruits (>21-25 mm in diameter) were found appropriate for in ovulo nucellus culture. Optimized ovule size induced somatic embryos at the micropylar cut end on induction medium containing Driver and Kuniyuki Walnut (DKW) basal medium with kinetin (KIN) 5.0 mg L^-1 and malt extract (ME) 1,000 mg L^-1. Simultaneously, the same medium supported the maturation of somatic embryos. The matured embryos from the above medium gave robust germination with bipolar conversion on Murashige and Tucker (MT) medium + gibberellic acid (GA₃) 2.0 mg L^-1 + ά-naphthaleneacetic acid (NAA) 0.5 mg L^-1 + spermidine 100 mg L^-1 + coconut water (CW) 10% (v/v). The bipolar germinated seedlings established well upon preconditioning in a plant bio regulator (PBR)-free liquid medium under the light. Consequently, a cent percent survival of emblings was achieved on a potting medium containing cocopeat:vermiculite:perlite (2:1:1). Histological studies confirmed the single nucellus cell origin of somatic embryos by undergoing normal developmental events. Eight polymorphic Inter Simple Sequence Repeats (ISSR) markers confirmed the genetic stability of acclimatized emblings. Since the protocol can induce rapid single-cell origin of genetically stable in vitro regenerants in high frequency, it has potential for the induction of solid mutants, besides crop improvement, mass multiplication, gene editing, and virus elimination in Kinnow mandarin.

Hydrolysable tannins, physicochemical properties, and antioxidant property of wild-harvested Terminalia ferdinandiana (exell) fruit at different maturity stages

Terminalia ferdinandiana Exell., also known as Kakadu plum, is a wild-harvested native Australian fruit with limited information on how maturity is affecting the phytonutritional properties and bioactivities of the fruit. Thus, this study investigated changes in hydrolysable tannins, phenolic acids, sugar profile, standard physicochemical parameters, and antioxidant-scavenging capacity of wild-harvested Kakadu plum fruits at four different maturity stages, from immature to fully mature. Fruits harvested <25, 25-50, 50-75, and 75-100% degree of fullness were classified as highly immature (stage 1), immature (stage 2), semi-mature (stage 3), and fully mature (stage 4), respectively. Results showed that chebulagic acid, geraniin, chebulinic acid, castalagin, punicalagin, and gallic acid continuously decreased during fruit maturity, while elaeocarpusin, helioscopin B, corilagin, 3,4,6-tri-O-galloyl-S-glucose, and ellagic acid increased at the beginning of fruit growth (from stage 1 to 2), but decreased when the fruits reached their full maturity (stage 4). The levels of hydrolysable tannins and phenolic acids in fully mature fruits (stage 4) were significantly (p ≤ 0.05) lower than that in their immature counterparts (stages 1 and 2). Total phenolic content (TPC) and DPPH antioxidant radical-scavenging activity did not vary significantly between different maturity stages. Pearson's correlation coefficient test indicated that TPC and DPPH positively (p ≤ 0.05) correlate with most of the studied tannin compounds. Sugars (glucose, fructose, and sucrose), total soluble solid content, and titratable acidity increased during the fruit development. Furthermore, principal component analysis (PCA) revealed the difference between the immature and mature samples, based on their nutritional profile and bioactive compounds. The PCA results also suggested a considerable variability between the individual trees, highlighting the challenges of wild-harvest practice.

Bioactive Potential of Minor Italian Olive Genotypes from Apulia, Sardinia and Abruzzo

This research focuses on the exploration, recovery and valorization of some minor Italian olive cultivars, about which little information is currently available. Autochthonous and unexplored germplasm has the potential to face unforeseen changes and thus to improve the sustainability of the whole olive system. A pattern of nine minor genotypes cultivated in three Italian regions has been molecularly fingerprinted with 12 nuclear microsatellites (SSRs), that were able to unequivocally identify all genotypes. Moreover, some of the principal phenolic compounds were determined and quantified in monovarietal oils and the expression levels of related genes were also investigated at different fruit developmental stages. Genotypes differed to the greatest extent in the content of oleacein (3,4-DHPEA-EDA) and total phenols. Thereby, minor local genotypes, characterized by stable production and resilience in a low-input agro-system, can provide a remarkable contribution to the improvement of the Italian olive production chain and can become very profitable from a socio-economic point of view.