ABSTRACT This study aimed to find sources of resistance to damping-off and to determine the inheritance of resistance in watermelon. Firstly, 72 watermelon accessions were inoculated with CMM 1053 isolate of Rhizoctonia solani. Only two accessions (BGH 29 and BGH 76) were considered moderately resistant to the disease. The inoculated plants without symptoms from accession BGH-29 identified as resistant were self-fertilized and the inbred line S1 was used for the crosses. The reaction to R. solani after inoculation of the segregating populations of the cross and backcrosses between susceptible cultivar Crimson Sweet and the inbred line BGH-29 was evaluated. In other experiment eight S1 lines of watermelon were inoculated with six different isolates of R. solani and the reaction was evaluated by partial diallel analysis using the Griffing’s method IV to obtain estimates of general resistance ability (GRA), general aggressiveness ability (GAA), and specific interaction ability (SIA). According to ratings of the susceptible and resistant parents, generations F1, F2, BC1 (F1 × P1) and BC2 (F1 × P2), resistance to damping-off was conferred by at least nine genes with additive effect and low heritability which indicates polygenic inheritance. The results of the diallel analysis corroborate with the analysis of segregating population, indicating inheritance of resistance was horizontal, since 46.1% of the total sum of squares of the variation observed in the crosses was due to GRA, while the SIA corresponded to only 20.39% of variation. This is the first report about inheritance of resistance to damping-off caused by R. solani in watermelon.

Resumo O objetivo deste trabalho foi comparar diferentes métodos para estimar a herdabilidade em 30 linhagens de guandu das gerações F3, F4, F5 e F6, para nove variáveis. O delineamento experimental foi em blocos ao acaso, com três repetições e 20 plantas por parcela. Estimou-se a herdabilidade no sentido amplo por meio de análise de variância (ANOVA) [h2b-E(MS)], máxima verossimilhança restrita/melhor predição linear não viciada (REML/BLUP) (h2b-REML), regressão pai-filho (h2PO) e unidade do desvio-padrão (h2UP). As estimativas de h2b-E(MS) e h2b-REML foram de magnitude próxima para sete das variáveis analisadas. Para maior controle genético e facilidade na seleção, valores de h2b-E(MS) e h2b-REML >0,70 foram estimados para duas variáveis em quatro gerações, duas variáveis em três gerações, três variáveis em duas gerações e uma variável em uma geração. Valores de h2UP e h2PO >0,70 foram obtidos para quatro e cinco variáveis, respectivamente. As estimativas via regressão ou correlação pai-filho mostraram alguns valores fora da variação esperada de 0 a 1. Os métodos ANOVA [h2b-E(MS)] e REML/BLUP [h2b-REML] são os melhores para estimar a herdabilidade em guandu.

Abstract The objective of this work was to compare different methods to estimate heritability in 30 pigeon pea families from the F3, F4, F5, and F6 generations, for nine variables. The experimental design was a randomized complete block with three replicates and 20 plants per plot. Broad-sense heritability was estimated by the analysis of variance ( A N O V A) [ h 2b-E(MS)], restricted maximum likelihood/best linear unbiased prediction (REML/BLUP) (h2b-REML), parent-offspring regression (h2PO), and standard deviation unit (h2UP). The h2b-E(MS) and h2b-REML estimates were similar for seven of the analyzed variables. For a higher genetic control and easier selection, values of h2b-E(MS) and h2b-REML >0.70 were estimated for two variables in four generations, two variables in three generations, three variables in two generations, and one variable in one generation. Values of h2UP and h2PO >0.70 were obtained for four and five variables, respectively. The estimates via regression or parent-offspring correlation showed some values outside the expected range of 0 to 1. The ANOVA [h2b-E(MS)] and REML/BLUP [h2b-REML] methods are the best to estimate pigeon pea heritability.

Abstract Fifty-five watermelon accessions were inoculated in pots using Fusarium oxysporum f. sp. niveum chlamydospores in a completely randomized design with five replications. Among the 42 accessions that were resistant, twelve accessions with a mean score ≤1 were selected for morpho-agronomic characterization. ‘Sugar Baby’ and ‘Charleston Gray’ were used as controls. Field research was conducted over two production cycles in a randomized block design with three replications and five plants per plot. For the characterization 13 quantitative agronomic traits were used. The dissimilarity measures were obtained by the sum of the matrices of standardized mean Euclidean distance. Coefficients of variation ranged from 5.33% (number of days until 50% of plants with at least one female flower) and 17.20% (mass of characterized fruit). In the second cycle, a reduction in days was observed for the flowering. For soluble solids content, the accession BGH-UNIVASF 40 was statistically equal to the commercial cultivars in the second cycle. Accessions were grouped similarly using two grouping methods, Tocher and the farthest neighbor method. The most promising accessions were BGH-UNIVASF 40, 169, 177 and 210 for use in future hybridizations. BGH-UNIVASF 76, 128 and 185 (Citrullus lanatus var. citroides) can be used as resistant Fusarium wilt rootstocks.