Eduardo Augusto Girardi

Rootstock-induced physiological and biochemical mechanisms of drought tolerance in sweet orange

The poorly understood physiological and biochemical drought responses induced in sweet orange by citrus rootstocks of contrasting drought tolerance were investigated during a drought/rewatering cycle under controlled conditions. Long-term exposure of the grafted trees to a gradually increasing water deficit and subsequent recovery revealed distinct strategies of drought acclimation that were induced by the different rootstocks. Trees grafted onto the drought-tolerant rootstock ‘Cravo’ rangpur lime were less water conservative, exhibiting an increased cell-wall elasticity that contributes to turgor maintenance and its related processes of growth and photosynthesis over a wider range of soil–water potentials. On the other hand, the drought-tolerant ‘Sunki Tropical’ mandarin and drought-sensitive ‘Flying Dragon’ trifoliate orange rootstocks induced a water conservation strategy by increasing tissue rigidity under drought. ‘Sunki Tropical’ was also able to induce osmotic adjustment, conferring thereby a more efficient water conservation strategy than ‘Flying Dragon’ by allowing for turgor maintenance at lower soil–water potentials while attenuating cell dehydration and shrinkage. In contrast to ‘Cravo’ and ‘Sunki Tropical’, trees grafted onto ‘Flying Dragon’ exhibited a significant photoinhibition of the photosystem II reaction centers, as well as an increased H2O2 production and lipid peroxidation under drought treatment. A significantly higher activity of the antioxidant enzyme GPX was also observed in drought stressed trees grafted onto ‘Flying Dragon’. Collectively, these results support the involvement of elastic and osmotic adjustments, as well as the control of oxidative stress, as functional leaf traits associated with the rootstock-induced drought tolerance in sweet orange.

TAMANHO ÓTIMO DE AMOSTRAS DE FRUTOS E DE SEMENTES PARA DETERMINAÇÃO DA POLIEMBRIONIA EM CITROS

ABSTRACTPolyembryony and nucellar apomixis are important traits for citrus rootstocks breeding and selection and for commercial multiplication. This study evaluated the polyembryony and estimated the optimal sample size of citrus rootstocks fruits and seeds for fruit seed number, seed embryo number and polyembryony rate, respectively. Fruits and seeds were collected from mother plants in the experimental field of Embrapa Manioc and Fruitculture, in Cruz das Almas, state of Bahia, Brazil. Rootstock species evaluated were: ‘Sunki Tropical’, ‘Sunki Maravilha’,‘Sunki da Florida’, ‘Sunki Comum’, ‘Dancy’ and ‘Cleopatra’ mandarins; ‘Rugoso Jambhiri’, ‘Rugoso da Florida’, ‘Rugoso Comum’ and ‘Volkameriano Lagoa Grande’ lemons; ‘Santa Cruz’ Rangpur lime; and the hybrids ‘Rangpur’ lime x ‘Sunki Maravilha’ mandarin, ‘Sunki da Florida’ mandarin x citrangequat ‘Thomasville’ and an open pollinated hybrid of ‘Tahiti’ lime. Data was submitted to descriptive analysis and equations of maximum curvature were estimated for determination of fruit and seed sample optimal size using 20 or 100 fruits and 156 seeds per genotype, respectively. Seed production and polyembryony varied significantly among the genotypes, which could be grouped by seed production and by polyembryony rate in five classes, respectively comprising intervals of 2 to 28 seeds and 12 to 100%. Optimal size sample was respectively of nine uniform fruits, ten and 23 seeds to determine fruit seed mean number, seed embryo mean number and polyembryony rate by direct counting, because these sample levels were sufficient for all genotypes evaluated.

Genetic variation of Citrus and related genera with ornamental potential

The interest in Citrus and related genera as ornamental plants has increased in recent years, motivating studies aimed at identifying genotypes, varieties and hybrids suitable for this purpose. The Citrus Active Germplasm Bank of the Embrapa Cassava & Fruits, a research unit of the Brazilian Agricultural Research Corporation—Embrapa, contains more than 750 accessions with wide genetic variability, and their utilization for ornamental purposes is the objective of this study. For this purpose, we characterized 37 accessions with ornamental potential, classified in four categories for use in floriculture: potted plants, minifruit, hedges and landscaping. Through the use of 39 quantitative and qualitative morphological descriptors, the following accessions stood out for use landscaping and as potted plants: ‘Variegated’ calamondin, ‘Nasnaran’ mandarin, ‘Chinotto’ orange, ‘Trifoliate limeberry’, ‘Papeda Kalpi’, ‘Talamisan’ orange, ‘Wart Java’ lime, and ‘Chinese box-orange’, besides accessions of the genera Fortunella, Poncirus and Microcitrus. Among the accessions identified as having potential for use as minifruit plants, the common ‘Sunki’ mandarin was the most suitable, and in the hedge category, ‘Chinese box-orange’ and ‘Trifoliate limeberry’ stood out. The results obtained provide information to support citrus breeding programs for ornamental purposes.

Poliembrionia e atributos morfológicos de sementes de porta-enxertos de citros

Seed polyembryony is an important trait for breeding and commercial multiplication of citrus rootstocks. This study evaluated relationships of polyembryony with different morphological seed traits of 12 citrus genotypes selected as rootstocks. The following traits were evaluated individually on 50 seeds per genotype: seed mass, height, width and embryo number, polyembryony level, difficulty for seed coat extraction, and seed color, which was estimated by a two-grade scale representing predominant colors on the endosperm. Data was submitted to variance analyses and the means were compared by the Scott-Knott Test (P < 0.05). Pearsons Correlation Coefficients were determined among all variables for all genotypes and individually. Citrus rootstocks had significantly distinct seed traits and could be classified in three polyembryony groups, with three Rangpur lime selections presenting polyembryony lower than 50% and the citrandarins as totally polyembryonic. Other trifoliate hybrids showed low to intermediate polyembryony. Seed coat extraction was more difficult in smaller seeds. For majority of genotypes, the number of embryos in the seed had positive correlation to the seed mass, height and width and negative correlation to the color ratio, which was calculated by the division of the lowest and highest color grades. This result suggests that the whole seed color analysis may be an alternative method for a rapid visual evaluation of polyembryony manifestation.

PERFORMANCE OF ‘TUXPAN VALENCIA’ SWEET ORANGE GRAFTED ONTO 14 ROOTSTOCKS IN NORTHERN BAHIA, BRAZIL

In the State of Bahia, Brazil, the citrus industry is located on the north coast with the prevalence of the combination ‘Pera’ sweet orange on ‘Rangpur’ lime. Scion-rootstock diversification may contribute to the increase of yield and the extension of harvest season, as long as to decrease the risk associated to abiotic and biotic stresses. Therefore, the performance of ‘Tuxpan Valencia’ sweet orange grafted onto 14 rootstocks was evaluated in Rio Real – BA. Planting was performed in 2006 under rainfed cultivation on cohesive ultisol and tree spacing of 6.0 m x 4.0 m. Tree size, yield and fruit quality were evaluated in the period of 2010-2014, in addition to tree survival at nine years old and drought tolerance in the field based on leaf wilting. In the evaluated conditions, ‘Sunki Tropical’ and ‘Sunki Maravilha’ mandarins led to the highest scion canopy volume. The highest accumulated yield in five harvests was recorded on ‘Santa Cruz Rangpur’ lime, ‘Volkamer’ lemon, ‘Riverside’ and ‘Indio’ citrandarins, ‘Sunki Tropical’ mandarin and the hybrid TSKC x (LCR x TR) – 001. ‘Riverside’ and TSKFL x CTSW – 049 induced higher yield efficiency on the canopy. The rootstocks did not influence the tree survival nine years after planting except for lower survival of TSKFL x CTSW – 049. Drought tolerance was not affected either. Regarding to the fruit quality of ‘Tuxpan Valencia’, the rootstocks influenced the juice content, soluble solids and technological index with the citrandarins, ‘Santa Cruz Rangpur’ lime, ‘Volkamer’ lemon and ‘Sunki Tropical’ mandarin presenting higher performance in general.

Evaluation of photodegradable tape on grafting in citrus nursery trees

RESUMO - O trabalho avaliou os efeitos do uso de fita fotodegradavel de enxertia em mudas de laranjeira ‘Valencia’ enxertadas em limoeiro ‘Cravo’ e citrumeleiro ‘Swingle’, em viveiro telado, em Bebedouro-SP, durante os meses de setembro a novembro de 2009. Para cada porta-enxerto, foram avaliados tres tratamentos, que incluiram o uso da fita convencional de polietileno para a fixacao da borbulha e a fita fotodegradavel, por sua vez aplicada sob duas formas: com e sem envolvimento completo da gema. As variaveis avaliadas foram: tempo consumido na operacao de amarrio da fita, porcentagem de borbulhas brotadas, comprimento e diâmetro do enxerto e porcentagem de mudas prontas para comercializacao. O delineamento experimental adotado foi o de blocos ao acaso, com seis tratamentos e quatro repeticoes. Cada parcela foi representada por 12 plantas. Os tratamentos com a fita fotodegradavel, com e sem envolvimento da gema, anteciparam a brotacao do enxerto, apesar de o tempo gasto no amarrio da fita ser significativamente maior em relacao ao metodo convencional. Quando o porta-enxerto utilizado e o citrumeleiro Swingle, menos vigoroso, recomenda-se manter a gema descoberta para evitar reducao acentuada da brotacao do enxerto. Termos de indexacao: Citrus spp.; propagacao; borbulha.

Desenvolvimento do pessegueiro 'Flordaprince' sob duas intensidades de poda verde

‘FLORDAPRINCE’ PEACH BEHAVIOUR AFTER TWO INTENSITIES OF GREEN PRUNING ‘Flordaprince’ peach [Prunus persica (L.) Batsch] was submitted to two levels of green pruning intensity (mild and renewal), 45 days after harvest, with the objective of evaluating its effects on plant development, production, fruit quality and soluble carbohydrates in roots and branches. The experiment was carried out at University of Sao Paulo, Piracicaba, Brazil, in the 2003/2004 season. The experimental designed was entirely randomized, with two treatments and twelve replicates. Experimental unit comprised two plants at the 3,0 m x 1,2 m spacing and was conducted in central leader system. Biometric data collected were: effective flowering, sprouting, shoot length after green and winter pruning, quality and production of fruits, and soluble carbohydrates in roots and branches. Renewal pruning leads to lower soluble carbohydrate concentrations in the roots during dormancy. Renewal pruning also decreases fruit retention and Brix, even though it increases individual fruit weight. Green pruning intensities do not influence soluble carbohydrates concentration in branches, fruit growth or shoot growth after winter pruning. Soluble carbohydrate concentrations are always higher in the roots.

Initial horticultural performance of nine ‘Persian’ lime selections grafted onto Swingle citrumelo

‘Persian’ lime (PL) [Citrus latifolia (Yu. Tanaka) Tanaka] is an important species both for domestic fresh fruit consumption in Brazil as well as the export market, since the country is one of the largest producers in the world despite the fact that, in commercial plantations, it is still not uncommon to find trees with low productivity and high plant vigor of unknown origin. Selections of Persian lime ‘CNPMF–2000’, ‘CNPMF–2001’, ‘CNPMF–01’, ‘CNPMF–02’, ‘IAC–5’, ‘IAC–5.1’, ‘Bearss’, ‘Persian–58’, and ‘5059’, were therefore grafted onto Swingle citrumelo [C. paradisi Macfad. cv. Duncan × Poncirus trifoliata (L.) Raf.] rootstocks and evaluated in Cruz das Almas, Bahia, Brazil in a field experiment conducted in a completely randomized block design with five replications and two trees per plot. The biometric attributes (canopy height, diameter and volume), yield parameters (yield during the off-season harvest period, yield per plant, production efficiency), and fruit quality traits, were evaluated. The ‘CNPMF–2001’, ‘CNPMF–01’, ‘CNPMF–02’, ‘IAC–5’, and ‘Bearss’ selections had 5-11 % shorter trees than the other cultivars. ‘CNPMF–01’, ‘CNPMF–02’, ‘Persian–58’, and ‘5059’ presented higher yield efficiency values, between 3.1-3.4 kg m−3, and higher yield levels during the off-season harvest periods. The ‘Bearss’, ‘Persian–58’, ‘CNPMF–2000’, ‘IAC–5.1’ and ‘5059’ selections had more acid fruits and the latter three, smaller fruits. Based on their horticultural performance up to eight years of age, ‘CNPMF–01’, ‘CNPMF–02’, ‘Persian–58’ and ‘5059’ selections were the most promising varieties of Persian lime.

Estádio de maturação de frutos e influência de ácido giberélico na emergência e crescimento de Passiflora spp.

The aim of this work was to evaluate emergence and initial growth in plants of Passiflora spp. from seeds obtained from fruit at different stages of maturation and treated with different concentrations of gibberellic acid (GA3). The species under evaluation were Passiflora alata, P. cincinnata, P. setacea, P. edulis and P. gibertii. For the first trial, the seeds were extracted from fruits at different stages of maturation, and sown in polyethylene bags in a completely randomised design with a 4 x 3 factorial scheme (species x stage of maturation), with five replications. A second and third experiment evaluated respectively, seeds stored for 11 months and seeds collected from freshly picked fruit of the same species, immersed in a solution of GA3 (0, 250, 500 and 1000 mg L-1) and transferred to an agricultural substrate. The experimental design was of randomised blocks in a 5 x 4 factorial scheme (species x GA3 concentration), with four blocks and twenty-five seeds per lot to analyse emergence. In P. cincinnata, P. alata, P. edulis and P. setacea, fruit at the pre-ripe stage can be harvested with no harm to the physiological quality of the seeds. A solution of GA3 up to 1000 mg L-1 did not increase emergence or initial growth in plants of Passiflora spp. stored for 11 months. Seeds from ripe, freshly picked fruit of Passiflora spp. display greater and faster emergence, and greater initial plant growth after soaking in a 500 to 1,000 mg L-1 solution of GA3.

PRODUÇÃO DE MUDAS DE CITROS COM DIFERENTES COMBINAÇÕES COPA E PORTA-ENXERTO EM VIVEIRO PROTEGIDO

The aim of this study is to evaluate the performance of sweet orange seedlings ‘Pera’ and ‘Westin’, mandarin-Murcott ‘Piedmont’ and acid lime ‘Tahiti’ grafted on 14 citrus rootstocks in protected nursery. The citrus nursery tree production of ‘Pera D-6’ and ‘Westin’ sweet oranges, ‘Piemonte’ tangor and ‘CNPMF-02’ Persian lime was evaluated in screen house after budding onto 11 hybrid rootstocks: ‘Indio’, ‘Riverside’ and ‘San Diego’ citrandarins, ‘Swingle 4475’ citrumelo and HTR-051, TSKC x (LCR x TR)-040 and 059, LVK x LCR-010 and 038, TSKC x CTTR-002 and TSKC x CTSW-041, besides ‘Flying Dragon’ trifoliate, ‘Santa Cruz’ Rangpur lime and ‘Tropical’ Sunki mandarin. Biometric and physiological variables were collected, and the experimental design was split-plot randomized blocks in 4 x 14 factorial, with three replications and ten trees in the unit. ‘CNPMF-02’ Persian lime was the most vigorous scion variety, followed by ‘Piemonte’ tangor and the sweet oranges for the last, regardless of the rootstock. Citrus nursery trees budded onto ‘Tropical’ Sunki mandarin had higher vegetative and root system growth in combination to all scion varieties evaluated. Citrus nursery trees budded onto ‘Flying Dragon’ trifoliate and the HTR-051 hybrid need longer period to complete adequate growth due to their lesser vigor induced to all scion varieties. No incompatibility symptoms were observed in the nursery.