Search

Abstract: The objective of this work was to estimate the stability and genotypic adaptability of advanced lines and cultivars of curled green-leaf lettuce (Lactuca sativa), in different growing environments and seasons, using the REML/Blup mixed model. Ten genotypes, seven cropping environments, and two growing seasons were studied in 2015. Plant yield traits were evaluated, and data were subjected to the Selegen-REML/Blup software. Genotype stability and adaptability were analyzed using the harmonic mean of genotypic values (HMGV) and the relative performance of genotypic values (RPGV), respectively. The harmonic mean of RPGV (HMRPGV) was used to simultaneously estimate the stability, adaptability, and yield of breeding lines or cultivars. Considering the combined analysis of the two seasons for the set of traits, the lines L6, L7, and L8 were selected as promising ones and recommended for planting. The breeding lines selected for all season exhibit good yield and are considered superior to the commercial cultivars Vanda and Vera.

Genetic resistance is one of the most suitable strategies to control cucurbit powdery mildew (CPM) on melon, incited by Podosphaera xanthii or Golovinomyces orontii. However, many races of these pathogens have been reported worldwide in recent years, what may compromise the effectiveness of this method. Thus, annual surveys of CPM races and the screening of germplasm for new sources of genetic resistance provide a vital support to melon breeding programs. This study aimed at identifying a natural population of CPM race under greenhouse conditions, as well as evaluating the reaction of local and exotic melon germplasm for CPM-resistance. CPM race identity was based on the reaction of eight race differentials: Védrantais, Nantais Oblong, PMR 45, PMR 5, WMR 29, Edisto 47, PI 414723 and PI 124111. Fifty-nine melon genotypes were evaluated, 53 of them being germplasm accessions, and six net melon elite-inbred lines, besides two net melon-type cultivars (Louis and Fantasy). Plants were evaluated using a visual scale for leaf lesions. The causal pathogen was confirmed to be P. xanthii, based on the presence of fibrosin bodies in conidia and the complete resistance response of winter melon (Benincasa hispida). Race 4 was identified for the first time in the São Paulo state, Brazil. Genotypes A19, A30, A32, C67, C384, JAB-3, JAB-7, JAB-9, JAB-11, JAB-18, JAB-20 and Solarking showed to be resistant to the race 4.

Melon is one of the most economically important crops cultivated in Brazil, especially in the Northeast region. However, as its cultivation increases, phytosanitary problems arise, including those caused by nematodes, which are most effectively controlled using resistant cultivars. This study aimed at assessing the reaction of muskmelon genotypes, in terms of resistance to Meloidogyne incognita and M. javanica infestation. The experiment was conducted under greenhouse conditions using a completely randomized design, in a 2 x 15 factorial scheme, with six replications. A total of 15 muskmelon genotypes were evaluated and the 'Santa Cruz Kada' tomato was used as a susceptible control. The total number of eggs and juvenile nematodes in the roots and the reproduction factor were used to assess the genotype reaction. None of the genotypes was resistant to M. incognita. Eight genotypes were classified as resistant to M. javanica and promising for use in melon breeding programs.