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Combining ability among tetraploid and diploid lines of watermelonCombining ability of three tetraploid (LT7-48.1, LT9-24.1 and LTCC-24) and four diploid lines of watermelon ('Crimson Sweet', 'Pérola', 'New Hampshire Midget' and 'Charleston Gray') was evaluated using a partial diallel scheme. A randomized block design, with three replications and seven plants in each field plot was used. Parents and F 1 's were evaluated regarding the number of days to the set of the first male and female flower, the number of fruits per plant and the length of the main vine, fruit mean weight, total soluble solids, transversal and axial fruit diameter, rind thickness at the stem and at the scar flower regions, flesh color and hollow heart. The tetraploid and diploid parents were diversified regarding the traits studied. The GCA effects were much higher than the SCA effects for most of the characters analyzed, particularly, for characters related to plant yield, showing the major relevance of the additive genetic effects. However, some traits like earliness and hollow heart presented non-additive genetic effects and, therefore, evaluation and selection of lines in hybrid combinations will allow the synthesis of superior watermelon triploid hybrids.

Allelic patterns and genetic similarity among 17 watermelon cultivars were established using microsatellite markers. For visualization of the genetic similarity, the dendrogram UPGMA (Unweighted Pair Group Method with Arithmetic Means) was generated by the similarity matrix of the Jacquard coefficient, based on 34 alleles of ten microsatellite loci. Total DNA was extracted by the CTAB 2x method and PCR (Polymerase Chain Reaction) products were analyzed in denaturing polyacrylamide 6% gels, stained with silver nitrate. The number of base pairs was estimated by the method of inverse mobility, based on known size product regression. Similarity ranged from 34 to 100%, reflecting high genetic variability. Analyzed loci were not enough to distinguish all 17 watermelon cultivars. The pairs 'Sugar Baby' and 'Omaru Yamato', 'Charleston Gray' and 'Sunshade', 'Crimson Sweet' and 'Nova Crimson' presented 100% of similarity. In dendrogram two groups were observed at 0.42 similarity cut point, with Citrullus colocynthis, positioned as an out group. One watermelon group was formed predominantly by cultivars derived from 'Crimson' and another group was formed by cultivars of different types such as 'Sugar Baby', 'Charleston Gray' and 'Pérola'. Allele pattern and base pair (bp) estimates for the 34 alleles in the 10 microsatellite loci revealed in the present study are a first endeavor to use microsatellite markers in situations of cultivar protection for the watermelon agribusiness in Brazil. They can also be used in situations of commercial disputes regarding certification of the main watermelon cultivars used in the country.

The development and validation of a standard area diagram set (SADs) was proposed in this study to assess the severity of powdery mildew (Podosphaera xanthii) in watermelon (Citrullus lanatus) leaves. The SADs proposed has twelve levels of severity, varying from 0.07 to 100%. The SADs were validated by 16 raters who had no previous experience in evaluating plant disease severity. Initially, the estimation of severity was performed without the use of the SADs in leaves with different levels of severity. In a second moment, the same raters estimated the disease severity using the SADs proposed. By Lin’s concordance correlation analysis, there was an improvement in precision (coefficient of correlation, r = 0.878 and r = 0.959, without and with SADs, respectively) and accuracy (bias correction factor, Cb = 0.830 and 0.982, without and with SADs, respectively) using SADs when compared to the non-use of SADs. The agreement (Lin’s concordance correlation coefficient, ρc = 0.734 and 0.952 without and with SADs, respectively) also improved using SADs. Severity estimates inter-rater were more reliable when using SADs (coefficient of determination, R2 = 0.681 without and R2 = 0.864 with SADs; Intra-class correlation coefficient, ρ = 0.759 and ρ = 0.928, without and with SADs, respectively). Therefore, SADs improved precision, accuracy and reliability of powdery mildew severity on watermelon leaves.

Acerola (Malpighia emarginata DC.) is one of the most important fruit produced in the São Francisco Valley, a Semi-arid region in the Northeast of Brazil. This study aimed to evaluate the physicochemical quality of thirty-five acerola genotypes produced during two growing seasons in a Semi-arid region and to identify the best ones with potential for fresh consumption based on a multivariate selection index. Fruit of each genotype were harvested during two growing seasons at the maturity stage red-ripe, characterized by full red skin color. After harvest, the fruit were evaluated for diameter, mass, flesh firmness, soluble solids (SS), titratable acidity (TA), SS/TA ratio, ascorbic acid content and skin color. A multivariate selection index (SI) was applied for scoring and ranking the genotypes for fresh consumption based on red-ripe fruit physicochemical quality. According to the results, all physicochemical attributes had high variability among genotypes. The SI was a powerful tool for identifying genotypes with high potential for fresh consumption, since it allowed selecting genotypes with multiple desirable traits. In the first and second growing seasons, the SI identified the genotypes PROG 052 (SI = 76.1 and 78.9), BRS Rubra (SI = 74.1 and 99.5), Cabocla (SI = 72.3 and 70.7), Costa Rica (SI = 61.2 and 73.8) and PROG 069 (SI = 68.1 and 72.4) as the most promising ones for fresh consumption due to the presence of multiple desirable traits such as high diameter, mass, flesh firmness, SS, and SS/AT ratio, as well as lower acidity.