Huanglongbing (otherwise known as HLB or greening) is currently the most devastating citrus disease worldwide. HLB is primarily associated with the phloem-inhabiting bacterium ‘Candidatus Liberibacter asiaticus’ (CLas). Currently, there are no citrus species resistant to CLas. Genetic transformation is one of the most effective approaches used to induce resistance against plant diseases. Antimicrobial peptides (AMPs) have shown potential breakthroughs to improve resistance to bacterial diseases in plants. In this paper, we confirm the Agrobacterium-mediated transformation of Pera sweet orange expressing the AMP sarcotoxin IA (stx IA) gene isolated from the flesh fly Sarcophaga peregrina and its reaction to CLas, involving plant performance and fruit quality assessments. Four independent transgenic lines, STX-5, STX-11, STX-12, and STX-13, and a non-transgenic control, were graft-inoculated with CLas. Based on our findings, none of the transgenic plants were immune to CLas. However, the STX-5 and STX-11 lines showed reduced susceptibility to HLB with mild disease symptoms and low incidence of plants with the presence of CLas. Fruit and juice quality were not affected by the genetic transformation. Further, no residues of the sarcotoxin IA protein were found in the juice of the STX-11 and STX-12 fruits, though detected in the juice of the STX-5 and STX-13 lines, as revealed by the immunoblotting test. However, juices from all transgenic lines showed low traces of sarcotoxin IA peptide in its composition. The accumulation of this peptide did not cause any deleterious effects on plants or in fruit/juice. Our findings reinforce the challenges of identifying novel approaches to managing HLB.

Studies on rootstocks and scions are of major importance for citrus crop production. The goal of this study was to evaluate vegetative growth, yield performance, and fruit quality of ‘Navelina’ sweet orange trees grafted on five different rootstocks in Northern Parana state, Brazil. The experimental design was completely randomized blocks, with six replications, two plants per plot, and five treatments: ‘Rangpur’ lime; ‘Cleopatra’ mandarin, ‘Sunki’ mandarin; ‘Swingle’ citrumelo; and ‘Fepagro C-13’ citrange. Tree vegetative growth, yield performance, and fruit physical-chemical characteristics were analyzed. ‘Sunki’ mandarin provided the largest canopy volume for ‘Navelina’ sweet orange trees, whereas ‘Swingle’ citrumelo, ‘Fepagro C-13’ citrange, and ‘Rangpur’ lime provided a smaller volume for tree canopy. Compared to Rangpur lime, ‘Swingle’ citrumelo provided higher accumulated yield and production efficiency for ‘Navelina’ sweet orange trees. All rootstocks induced good physical and chemical quality to ‘Navelina’ sweet orange fruits.

The use of natural-based coatings is an eco-friendly approach that can be applied in citrus postharvest to preserve fruit quality and to prolong shelf life. Additionally, the study of antioxidant capacity of obtained by-products from fruits is of great value to mitigate better practices to manage the residues left from the juice processing industry. Under this context, the aim of this study was to investigate the use of carnauba wax/wood resin-based coating and cold storage on postharvest life of Valencia Late and Natal IAC sweet oranges, as well as the physicochemical quality and antioxidant capacity of its by-products. Mature fruits were harvested in 2019 and 2020 seasons. Initially, fruits were assessed for physicochemical quality and antioxidant capacity. Then, fruits were treated with carnauba wax and wood resin mixture and stored for 0, 15, 30, 45 and 60 days in a cold chamber. Fruit color index, weight loss, physicochemical quality and sensory profile of the fruits were monitored at harvest and during each cold storage period. Evaluations were performed in triplicates of 10-fruit. Valencia Late and Natal IAC fruits had proper quality in both years, attending the requirements of the fresh market and processing industry. Flavedo and albedo section displayed the highest concentration of bioactive compounds such as phenolics, flavonoids and antioxidant activity. The coating treatment associated with cold storage was efficient to preserve fruit color and to retard weight loss for both varieties up to 60 days. The sensory profile and quality of the carnauba wax/wood resin treated fruits were preserved all over the cold storage period, while uncoated fruits ranked low for most of the sensory attributes. Together, Valencia Late and Natal IAC fruits contain a high level of healthy beneficial compounds, which may be exploited as a natural source of low-cost antioxidants. Further, carnauba wax/wood resin coating associated with cold storage effectively reduce weight loss and color progression in sweet orange fruits, in addition to preserving overall physicochemical and sensory quality.

Evaluation of the physiological potential of seeds by fast and efficient methods is an important step in the process of production and commercialization of sweet corn seeds. The aim of this study was to discriminate sweet corn seed lots by applying multivariate methods regarding the usual vigor tests to verify the sensitivity of these seeds to flood conditions and to verify if the submersion test has potential for classifying lots of this species regarding vigor. Five seed lots of sweet corn were tested for moisture content and physiological potential. Cluster analysis and principal component analysis were performed on the data to discriminate the seed lots regarding initial vigor. Subsequently, two of these lots were selected for the water submersion test, performed with four replicates of 150 seeds, which were submerged in 100 mL of distilled water for 0, 24, 48, 72, and 96 hours at 25 ºC, and they then underwent the germination test. Discrimination of sweet corn seed lots is possible through multivariate analysis. Sweet corn seeds are sensitive to submersion in water; however, the test did not allow seed lots to be differentiated for vigor.

The diversification of Citrus spp. orchards, for both scion and rootstock genotypes, is essential to prevent outbreaks of insects and diseases, improve yield and fruit quality, and extend harvesting and industrial juice processing. Furthermore, this enables growers to obtain higher off-season profits. Citrus plantings were prohibited in most regions of the state of Paraná in the past due to the spread of citrus canker disease. Therefore, this study aimed to evaluate the agronomic performance of distinct early- and mid-season sweet orange cultivars (C. sinensis (L.) Osbeck) regarding vegetative growth, fruit quality, and yield under the Brazilian humid subtropical climate in order to select new alternatives of sweet orange for the industrial and fresh fruit markets. The experimental orchard was planted in 2012 with 15 sweet orange cultivars (early-maturing: Bahia Cabula, Diva, Cadenera, Marrs, Midsweet, Paulista, Rubi, and Westin; mid-season maturing: Berna Peret, Jaffa, Khalily White, Fukuhara, Seleta do Rio, Seleta Tardia, and Shamouti) grafted on Rangpur lime (C. limonia (L.) Osbeck). The experimental design was randomized blocks with three replicates and five trees per plot, analyzed between each maturation group. Data were submitted to analysis of variance followed by Tukey’s test (p ≤ 0.05). Regarding the early-season cultivars, Diva had the tallest trees with largest canopy diameter and volume, differing from Marrs, which had the smallest trees. Shamouti and Khalily White trees were greatly different from all other mid-season cultivars and produced low fruit load over the evaluated period. The early-season Midsweet scored the highest yield and technological index, similar to the mid-season Berna Peret, producing fruits of high juice quality. These genotypes are more effective under the current situation faced by the citrus industry, as the economic life of orchards has been reduced due huanglongbing (HLB). Altogether, Midsweet and Berna Peret genotypes, previously reported as being less susceptible to citrus canker under the same soil–climate condition, are precocious and exhibit higher agronomic potential to be planted in humid subtropical climates, including Brazil and other similar areas around the world.