The past 10 years has seen a steep increase in production of seedless watermelon (Citrullus lanatus) in the United States. Seedless fruit is produced on triploid plants that require pollination from diploid pollenizers for fruit set. Synchronization of the staminate flowers on the pollenizers with the appearance of pistillate flowers on the triploids is a fundamental requirement for this production system. Previous research suggested that pistillate flowers reach peak production early in the season, but data are only available for a small number of triploid cultivars. We compared the flowering patterns of 29 triploid cultivars and 20 pollenizers, including 10 harvested pollenizers, during the first 6 weeks after transplanting over 2 years. The average number of days from transplanting (DAT) to the first staminate flower was between 5.3 days and 19.1 days in 2012 and 9.7 days and 24.4 days in 2013 for the pollenizers and between 18.7 days and 27.6 days and 22.1 days and 32.7 days for the pistillate triploid flowers in the 2 years, respectively. K-means clustering of the weekly percentage of plants with staminate and pistillate flowers for the different cultivars shows that different triploid and pollenizer cultivars have different flowering patterns and that some combinations have better synchronized flowering than others. Growers should take particular care when choosing pollenizers for early-flowering triploid cultivars. Harvested pollenizers are better suited to late-flowering triploids and growers should choose triploid and pollenizer cultivar combinations with flowering patterns that best satisfy their specific production goals.

U.S. watermelon (Citrullus lanatus) production is worth ≈$0.5 billion annually to growers and nearly all of them are dependent on reliable synchronized flowering time of triploid cultivars and diploid pollenizers in their production fields. One aspect of this synchronization is time to flowering, the change from the vegetative to reproductive phase of a plant. Flowering time has emerged as one of the key traits in horticultural and agronomic crops to breed for escape from biotic and abiotic stresses. However, very little is known about the control of flowering time in watermelon. The number of genes involved, mode of inheritance, heritability, and the possible candidate genes are all unknown. In this study, quantitative trait loci (QTL) associated with days to first male flower (DMF), days to first female flower (DFF), and the female-male flower interval (FMI) were identified in a ‘Klondike Black Seeded’ × ‘New Hampshire Midget’ recombinant inbred line population over 2 years. Heritability for DMF, DFF, and FMI were 0.43, 0.23, and 0.10, respectively. Control of flowering time was oligogenic with a major, stable, colocalized QTL on chromosome 3 responsible for ≈50% of the phenotypic variation observed for DMF and DFF. This region of the draft genome sequence contains 172 genes, including homologs of the flowering locus T (Cla009504) and tempranillo 1 (Cla000855) genes associated with flowering time in other species. Cla009504 and Cla000855 represent excellent candidate genes toward the development of a functional marker for marker-assisted selection of flowering time in watermelon. In addition to the major QTL on chromosome 3, two other QTL were identified for DMF (chromosomes 2 and 3) and DFF (chromosomes 3 and 11) and one for FMI on chromosome 2. Understanding the genes involved in this trait and the ability to select efficiently for flowering time phenotypes is expected to accelerate the development of new watermelon cultivars in changing environmental conditions.

Greenhouse studies were performed to determine the reactions of 10 "California Wonder" (Capsicum annuum) accessions to the three forms of Phytophthora blight (root rot, stem blight and foliar blight) caused by Phytophthora capsici. Differences in root rot, stem blight and foliar blight severities among accessions were significant. The accessions consistently differentiated into two groups across the three disease syndromes. Simple sequence repeat (SSR) markers showed variability both within and between accessions of California Wonder. The variability in the responses to the three forms of Phytophthora blight does not warrant its usefulness as a standard susceptible control in studies involving the Capsicum-P. capsici pathosystem.

ABSTRACT. Genomic tools for watermelon breeding are becoming increasingly available. A high throughput genotyping system would facilitate the use of DNA markers in marker-assisted selection. DNA extraction from leaf material requires prior seed germination and is often time-consuming and cost prohibitive. In an effort to develop a more efficient system, watermelon seeds of several genotypes and various seed sizes were sampled by removing ⅓ or ½ sections from the distal ends for DNA extraction, while germinating the remaining proximal parts of the seed. Removing ⅓ of the seed from the distal end had no effect on seed germination percentage or seedling vigor. Different DNA extraction protocols were tested to identify a method that Seed-based genotyping system for watermelon breeding could yield DNA of sufficient quality for amplification by polymerase chain reaction. A sodium dodecyl sulfate extraction protocol with 1% polyvinylpyrrolidone yielded DNA that could be amplified with microsatellite primers and was free of pericarp contamination. In this study, an efficient, non-destructive genotyping protocol for watermelon seed was developed.

Developing high levels of resistance to Phytophthora blight (Phytophthora capsici Leonian) of pepper (Capsicum annuum L.) is a goal of many pepper breeding programs. Genetic diversity and plant characteristics were evaluated on 21 pepper accessions previously identified as having high levels of Phytophthora root rot resistance. Accessions were evaluated for plant height, fruit size and shape, pericarp thickness, and pungency. Accessions varied widely from very unadapted material to those with more obvious breeding potential. Genetic diversity among the accessions was estimated using 22 simple sequence repeat (SSR) loci. Phytophthora capsici resistant accessions were identified that were not closely related to previously described sources of resistance. This information will allow breeders and researchers to further identify and incorporate novel sources of resistance to P. capsici into breeding programs. Accessions PI 201237 and PI 640532 appear to have the most potential for introgressing P. capcisi resistance into bell pepper.