Watermelon [ Citrullus lanatus (Thunb.) Matsum. and Nakai] seedlings are the main product of the seedling companies in China. With the increases in the cultivation area of watermelon (2.2 million ha in China and 3.8 million ha in the world
objective of this study was to evaluate clomazone tolerance in a diverse germplasm collection of watermelon cultivars and germplasm accessions of Citrullus lanatus and closely related species. Subsequent greenhouse and field experiments were conducted to
, and reproductive indices for selected PIs of Citrullus lanatus var. citroides , C. lanatus var. lanatus , and C. colocynthis and control watermelon cultivars inoculated with M. incognita race 3 in replicated greenhouse tests. z
Watermelon [ Citrullus lanatus (Thunb.) Matsum. and Nakai] is an important cucurbit crop, occupying 7% of the worldwide area allocated for vegetable production ( Guo et al., 2013 ). China, as the largest producer of watermelons in the world
effective in controlling this soilborne disease. Finding resistant germplasm sources and incorporating the resistance into watermelon cultivars should be the most effective strategy for controlling FW in watermelon. Two U.S. PIs of Citrullus lanatus var
.T. Vodouhe, R.S. Coulibaly, O. Ahanchede, A. 2008 Importance and practices of egusi crops [ Citrullus lanatus (Thunb.) Matsum. & Nakai, Cucumeropsis mannii Naudin and Lagenaria siceraria (Molina) Standl. cv. ‘Aklamkpa’] in sociolinguistic areas in Benin
). Fig. 1. High-performance liquid chromatography. Spectral patterns of flavonoids and caffeoyl-quinic acid (CQA) derivatives found in ‘Charleston Gray’ and ‘Mickey Lee’ watermelon, Citrullus lanatus var. lanatus . Refer to Table 1 for the meaning of
watermelon. Rootstock genotypes. Seedless watermelon ‘Tri-X 313’ was grafted onto five wild watermelon ( Citrullus lanatus var. citroides ) germplasm lines developed at the U.S. Vegetable Laboratory (RKVL 301, RKVL 302, RKVL 303, RKVL 316, and RKVL 318
Simple sequence repeats (SSRs) were isolated from a size-fractionated genomic DNA library of watermelon (Citrullus lanatus L. cv. New Hampshire Midget). Screening of the library with five oligonucleotide probes, including (GT)11, (AT)11, (CT)11, (GC)11, and (TAA)8, detected the occurrence of 96 positive colonies among ≈8000 recombinants. Automated DNA sequencing revealed the presence of SSRs. PCR primer pairs homologous to the regions flanking the SSR loci were synthesized commercially and used to screen 56 watermelon genotypes for the occurrence of SSR polymorphisms. Amplification products were separated using nondenaturing PAGE. Eighty percent of the primer pairs produced amplification products of the expected size and detected polymorphisms among the genotypes examined. The use of SSRs for watermelon germplasm characterization is discussed.
In triploid (seedless) watermelon [Citrullus lanatus var. lanatus (Thunb. Matsum. and Nakai)], hollow heart (HH) is a disorder that is expressed as a crack in the center of the fruit that expands to an open cavity. Although HH incidence and severity is part of a screening process for marketable watermelon fruit during cultigen evaluations, HH incidence is highly variable with growing season, even when the best cultural practices are used. Placental tissue firmness is also measured because firmness is related to the marketability of watermelon and may be related to HH. Genetic and environmental factors can influence watermelon HH development, including plant genetics, pollen amount and viability, pollinator activity, and temperature and rainfall fluctuations. We used seedless watermelon cultigen evaluation data collected over 3 years (2012–14) to determine the relationship between germplasm HH and tissue firmness. Transplanted watermelon representing 30 to 44 cultigens per year were grown at the Central Crops Research Station, Clayton, NC, and interplanted with pollenizers ‘Ace’ and/or ‘SP-6’. Harvested fruit were cut length-wise and rated for HH incidence and severity. Flesh firmness was determined by a handheld penetrometer at five locations in the flesh (stem end, top side, ground spot, blossom end, and heart). A common cultigen subset, consisting of 13 cultigens that were grown in all three experiments, was used for analysis of HH severity and incidence, and placental firmness. The presence of HH was negatively correlated with tissue firmness in both the large multiyear cultigen set (R 2 = −0.32; P = 0.0001) and the common cultigen set (R 2 = −0.78; P = 0.0001). Cultigens with lower watermelon tissue firmness values had higher HH incidence and severity. By using multiyear cultigen studies and logistic regression, we were able to detect trends for cultigen susceptibility to this highly variable disorder. Using logistic regression, the probability of HH development was highest for ‘Bold Ruler’, ‘Liberty’, and ‘Affirmed’, and lowest for ‘Maxima’ and ‘Captivation’. The identification of cultigens with a tendency for higher or lower rates of HH will be useful for further research of the causes of HH. Measurements of placental flesh firmness may be useful indicators of susceptible cultigens.