ABSTRACT The search for alternative rootstocks to the ‘Rangpur’ lime tree is a challenge to the sustainability of citrus in the Tabuleiros Costeiros (Coastal Tablelands) of Northeastern Brazil. New varieties should meet high drought tolerance with water deficit, cohesive soils, resistance to citrus diseases and inducing high production of fruit. In this work, the performance of ‘Pera’ sweet orange was evaluated on ‘Tropical Sunki’ mandarin and 27 hybrid citrus rootstocks in Umbaúba, Sergipe. A local selection of the ‘Rangpur’ lime was the control. Planting was in 2013 at tree spacing of 6.0 × 3.0 m, without irrigation. Tree size, fruit yield and quality, tree survival rate and graft-compatibility were assessed until 2019. Experimental design was completely randomized blocks with 29 treatments, three replicates and four plants in the plot. Two selection indices were applied to the data to assist in decision making. The ‘Tropical Sunki’ mandarin induced similar cumulative fruit yield in relation to the ‘Rangpur’ lime, suggesting a good drought tolerance of the former rootstock. The TSKC × (LCR × TR) - 073 induced slightly lower productivity, compensated by higher productive efficiency and higher concentration of soluble solids, whereas LCR × TR - 001 and HTR - 166 were highly efficient dwarfing rootstocks. The multiplicative and the rank sum indices showed high correlation, both classifying ‘Tropical Sunki’ mandarin, ‘Santa Cruz Rangpur’ lime, LVK × LCR - 010 and - 038, HTR - 127, in addition to the three aforementioned hybrids, as superior to the local selection of ‘Rangpur’ lime.

Resumo: O objetivo deste trabalho foi avaliar cinco índices de seleção não paramétricos para a seleção de citros híbridos como porta-enxertos, enxertados com laranjeira 'Valência', com base em atributos horticulturais relevantes para a indústria de processamento de suco. Avaliaram-se 46 porta-enxertos em delineamento de blocos ao acaso, com três repetições e cinco plantas na parcela, no período de 2009-2015, em cultivo de sequeiro. As médias das variáveis altura de planta, produção acumulada de frutos, eficiência produtiva de frutos, concentração de sólidos solúveis totais, rendimento de suco e tolerância à seca foram utilizadas para calcular os seguintes índices: multiplicativo (IEi), soma de classificação (IMMi), distância genótipo-ideótipo (DiI) e ranqueamento (IRKi, baseado em médias simples; e IRKii, baseado em normalização linear). Os índices foram eficientes em classificar os híbridos em relação ao desempenho geral. A correlação de Spearman mostrou alta similaridade entre a maioria dos índices não paramétricos, notadamente entre IRKi e IRKii. Os índices de ranqueamento, principalmente o IRKii, fornecem uma classificação mais coerente dos híbridos, o que permite a seleção de porta-enxertos mais produtivos e tolerantes à seca, para a produção de frutas de alta qualidade para processamento.

Abstract: The objective of this work was to evaluate five nonparametric selection indices for the selection of hybrid citrus rootstocks grafted with 'Valência' sweet orange, using horticultural traits relevant for the juice processing industry. Forty-six rootstocks were evaluated in a randomized complete block design, with three replicates and five trees in the plot, in the period from 2009-2015, in a rainfed cultivation. The means of the variables plant height, accumulated fruit yield, fruit yield efficiency, total soluble solids concentration, juice yield, and drought-tolerance were used to calculate the following indices: multiplicative index (IEi), sum of classification (IMMi), genotype-ideotype distance (DiI), and ranking indices (IRKi, based on simple means; and IRKii, based on linear normalization). The indices were efficient to classify the hybrids in relation to general performance. Spearman’s correlation showed a high similarity between most nonparametric indices, notably between IRKi and IRKii. The ranking indices, mainly IRKii, provide a more coherent classification of the hybrids, which allows of the selection of more productive and drought-tolerant rootstocks to produce high-quality fruit for processing.

O efeito do estresse salino de intensidade e duração conhecida nos parâmetros de fluorescência da clorofila em plantas de girassol foi estudado objetivando selecionar genótipos tolerantes e sensíveis à salinidade. O delineamento experimental utilizado foi o inteiramente casualizado em um arranjo fatorial entre 10 genótipos e 2 níveis de salinidade, com quatro repetições. As sementes foram semeadas em areia lavada e, após a germinação, foram transplantadas para vasos contendo solução nutritiva ou solução nutritiva com 100 mM de NaCl, em casa de vegetação. Após 27 dias nessas condições, foram avaliadas a fluorescência basal (F0), a eficiência quântica potencial do fotossistema 2 - PS2 (Fv/Fm), a razão Fv/F0 e a eficiência quântica efetiva do PS2 (Y). Os coeficientes dos "quenching" fotoquímico (qP) e não fotoquímico (qN, qCN e NPQ) também foram calculados. O estresse salino aumentou F0 e diminuiu Fv/Fm, Fv/F0 e Y, sugerindo injúrias na estrutura dos tilacóides causadas pela salinidade. Esses efeitos foram mais pronunciados no genótipo AG-960 e menos pronunciados no AG-975. O genótipo AG-960 também apresentou os maiores aumentos em qN, qCN e NPQ, em contraste com o observado para o AG-975. Dessa forma, AG-975 e AG-960 foram caracterizados como tolerante e sensível à salinidade, respectivamente. Os demais genótipos apresentaram tolerância intermediária ao estresse salino. Os resultados indicam que a fluorescência da clorofila pode ser utilizada como uma ferramenta para a seleção de genótipos de girassol tolerantes à salinidade.

The effect of salt stress of known intensity and duration on chlorophyll fluorescence in sunflower plants was studied aiming to identify salt-tolerant and salt-sensitive genotypes. The experimental design was a completely randomized in a factorial arrangement among 10 genotypes and two salt levels, with four replications. Seeds were sown in sand, and after germination were transplanted to plastic pots with nutrient solution or nutrient solution containing 100 mM of NaCl and placed in a greenhouse. After 27 days, ground fluorescence (F0), maximum quantum yield of PS2 Fv/Fm, the Fv/F0 ratio and effective quantum yield of photosystem 2 - PS2 (Y) were evaluated. The photochemical (qP) and non-photochemical (qN, qCN e NPQ) coefficients were also calculated. Salt stress increased F0 and reduced Fv/Fm, Fv/F0, and Y, suggesting salt-induced structural damage in the thylakoid membranes. These effects were more pronounced in genotype AG-960 and lowest in AG-975. The highest increases in qN, qCN and NPQ were also found in genotype AG-960 in contrast with that observed in AG-975. Thus the AG-975 and AG-960 genotypes were characterized as the most salt-tolerant and salt-sensitive, respectively. The other genotypes showed intermediate tolerance to salt stress. Our results suggest that chlorophyll fluorescence could be used as a tool for the screening of sunflower genotypes for salinity tolerance.