Respostas agronômica e ecofisiológica de genótipos de meloeiro submetidos à salinidade para desenvolvimento de estratégias de seleção

Abstract

Melon is a vegetable of great economic importance for the semiarid region of Brazil, but this region has edaphoclimatic characteristics that favor the salinization of soils and water, negatively influencing the crop. Several alternatives can be used for cultivation in soil and saline water, but most of them are economically unfeasible, the best alternative is the use of tolerant cultivars. For the development of new cultivars it is essential to identify and characterize genotypes that can be gene donors to increase tolerance to salinity. The breeding process takes a long time from identification to the release of cultivars, so to reduce the breeding process time it is necessary to develop strategies by means of technologies that allow the identification of tolerant genotypes efficiently. Currently, some areas such as phenomena have been gaining attention due to their high precision and efficiency. The objective of this research was to evaluate the agronomic and ecophysiological responses of melon genotypes submitted to salinity to develop selection strategies. The first step was the identification and characterization of melon genotypes. The objective of this work was to perform the agronomic and physiological characterization of melon genotypes submitted to salinity in hydroponic system. The research was conducted at the Federal Rural University of Pernambuco, from September to November 2017. The experiment was conducted in a randomized block design with four replications, in which 12 genotypes were evaluated, seven accessions of caxi melon (Cucumis melo var momordica) and five commercial cultivars: SF 10/00, Al Mel, Gladial, Torreon and Sancho. These genotypes were subjected to 6.5 dS.m-1 electrical conductivity provided by nutrient solution. Growth, flowering, fruit characteristics, yield and physiological characteristics were evaluated. Variance analysis, Skott Knott cluster test at 5% probability and canonical correlations were performed. For yield and average fruit weight, three groups were formed; the highest yield group was formed by genotypes A1, A6, A8, A14, A16, A18, SF10 / 00, Gladial and Sancho, with an average of 2.56. kg.plants-1. The intermediate group was formed by genotypes A4 and AL Mel, with an average of 2.24 kg.planta-1. The Torreon genotype (1.89 kg.planta-1) was the representative of the lowest productivity group. The genotypes belonging to the botanical groups momordica and inodorus presented the highest yields in hydroponic system using saline water in nutrient solution. The physiological characteristics showed no significant difference between genotypes submitted to salinity. Yield, percentage of shoot dry matter, plant height, beginning of female flowering and number of male flowers at 40 days and female at 45 days can be used to choose salinity tolerant melon genotypes. The second step was to evaluate the agronomic and physiological responses of saline genotypes submitted to salinity: the objective of this work was to evaluate the agronomic and physiological responses of saline genotypes. The research was carried out at the Federal Rural University of Pernambuco in Recife, between May and July 2018. The experiment was carried out in a randomized block design in a split plot (10 x 2) with three replications, and 10 genotypes were evaluated. of melon (subplots) in two electrical conductivities (plots). Each plot was represented by four plants. The genotypes used were: SF 10/00, Torreon, AL Mel and seven accessions of the momordica group, A1 São José do Egipto, A4 Petrolina, A6 Ibimirim, A8 Serra Talhada, A14 Belo Jardim, A16 Juazeiro, A18 Santa Tereza do Oeste. The two electrical conductivities were 2 dS.m-1 (± 0.10) and 6.5 dS.m-1 (± 0.10) provided in the nutrient solution. Vegetative, physiological and productive characteristics of melon were evaluated. The genotypes A8 Serra Talhada, A16 Juazeiro, Torreon and Al Mel did not differ statistically in the two ECs, presenting respective losses of productivity in the order of 15,29; 17.44; 24.85 and 17.80% when comparing the EC 2 and 6.5 dS.m-1. The genotypes with the highest yield losses were A1 São José do Egipto, A4 Petrolina, A6 Ibimirim, A14 Belo Jardim, A18 Santa Tereza do Oeste and SF 10/00, with respective loss averages compared to EC 2.0 and 6. 0.5 dS.m -1 of 39.04; 30.41; 50.39; 37.77; 44.57 and 31.59%. Excess salt in nutrient solution promoted reduction in growth, development and productivity of melon. The A8 Serra Talhada, A16 Juazeiro, Torreon and Al Mel genotypes showed low yield losses in response to salt stress. The third stage used the same experiment as step two, and only the evaluations were changed: only the reflectance characteristics that presented variation between treatments were used in the analyzes. Canonical correlation was used to determine the contribution in the relationship of the main variables (Plant Height, Percentage of Dry Matter and Productivity) and the contribution of the secondary variables (Photosynthesis, Conductance, Chroma, Green NDVI, NIR / G (gray), Green channel (gray), NIR channel and Canopy (gray), Canopy (blue). From the results obtained, the equations for the estimation of the main characteristics as a function of the secondary characteristics were determined. Vegetative, physiological and productive characteristics of melon were evaluated. The third canonical pair showed high correlations for the three main characteristics, associating the increase of AP,% MS and PR with the reduction of photosynthesis, Green NDVI and NIRG Gray, increase of conductance, increase of Chroma value and NIRG Gray. The use of multispectral images associated with physiological characteristics is a viable strategy for salinity tolerant melon breeding programs.