Drought stress and weed competition are two of the most important threats to corn production in the northeastern United States. Both pressures have the potential to worsen under climate change. In a 2-yr field study in Ithaca, NY, we tested the effects of drought and burcucumber, an increasingly problematic annual vine, on silage corn. Burcucumber seedlings were transplanted into corn rows at densities of 0, 0.5, 2, and 3 plants m−2 and a drought treatment was later imposed with rainout shelters constructed from steel frames and high-clarity plastic. Available soil moisture was lower in drought plots (47% ± 1% in 2018 and 52% ± 2% in 2019) than no-drought plots (69% ± 1% in 2018 and 68% ± 1% in 2019). Burcucumber planting density (P = 0.008) reduced fresh silage yield. Drought also reduced fresh silage yield (P < 0.001) with a drought-by-year interaction (P = 0.007): drought reduced fresh weight by 29% in 2018 (48,000 ± 2,000 kg ha−1 to 34,000 ± 3,000 kg ha−1) and by 9% in 2019 (38,000 ± 3,000 kg ha−1 to 34,000 ± 3,000 kg ha−1). Burcucumber planting density and drought did not interact. Overall, our findings indicate that drought and competition from burcucumber may have additive effects on silage corn in New York State. Regardless of water availability, active weed management is required to prevent yield losses due to burcucumber. Yield losses may be similar or greater in grain corn and might increase under climate change.

Gac is a dioecious tropical and perennial climber. The fruit is a rich source of carotenoids and is used in traditional cuisine and medicine. Improving propagation methods using simple techniques would increase production and improve conservation in regional areas. This study evaluated temperature requirements for seed germination, the use of rooting hormones to strike female cuttings and the grafting of female scions onto seedling rootstock. Seed germination was optimised between 25 and 35 °C, with a maximum germination percentage of 91% at 30 °C. However, increasing storage time from 6 to 18 months under laboratory conditions (21 ± 1°C and 60% relative humidity) reduced germination and this was associated with seed weight loss, highlighting the need to develop storage guidelines, particularly for the higher temperature and humidity conditions where Gac is grown. Survival of softwood cuttings was improved from 53 to 77% with indole-3-butyric acid (IBA) (3–5 g/L) and semi-hardwood cuttings did not require IBA treatment. Both splice and wedge grafting techniques achieved a survival rate > 53% and with the youngest rootstock (4 and 8 weeks) this increased to > 85%. Further work could investigate the production potential of crops using cuttings and grafted plants.

Watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] grafting is commonly used for management of diseases caused by soilborne pathogens; however, little research exists describing the effect of grafting on the weed-competitive ability of watermelon. Field experiments determined the response in yield, fruit number, and fruit quality of grafted and nongrafted watermelon exposed to increasing densities of Palmer amaranth (Amaranthus palmeri S. Watson). Grafting treatments included ‘Exclamation’ triploid (seedless) watermelon grafted on two interspecific hybrid squash rootstocks ‘Carnivor’ and ‘Kazako’, with nongrafted Exclamation as the control. Weed treatments included A. palmeri at densities of 1, 2, 3, and 4 A. palmeri plants per watermelon planting hole (0.76-m row) and a weed-free control. Increasing A. palmeri densities caused significant reductions (P <0.05) in marketable watermelon yield and marketable fruit number. Watermelon yield reduction was described by a rectangular hyperbola model, and 4 A. palmeri plants planting hole−1 reduced marketable yield 41%, 38%, and 65% for Exclamation, Carnivor, and Kazako, respectively. Neither grafting treatment nor A. palmeri density had a biologically meaningful effect on soluble solids content or on the incidence of hollow heart in watermelon fruit. Amaranthus palmeri seed and biomass production was similar across weed population densities, but seed number per female A. palmeri decreased according to a two-parameter exponential decay equation. Thus, increasing weed population densities resulted in increased intraspecific competition among A. palmeri plants. While grafting may offer benefits for disease resistance, no benefits regarding weed-competitive ability were observed, and a consistent yield penalty was associated with grafting, even in weed-free treatments.

William Griffith wrote an account of the plants collected by Theodore Cantor in 1840 while on a military expedition to Chusan in China. This was published posthumously in 1854, but was also distributed in 1844 or 1845 as a preprint. The 14 new names at species rank appearing in the paper are reviewed (including the often overlooked Leucopogon ophirensis and Corylopsis grata) and their typification considered. Lectotypes are designated for 10 of these names, one second-stage lectotypification is proposed, and Corylopsis griffithii Hemsl. is also lectotypified.

In this study, the genetic variability among 130 accessions of the Portuguese germplasm collection of Cucurbita pepo L. maintained at the Banco Português de Germoplasma Vegetal was assessed using AFLP (amplified fragment length polymorphism) and RAPD (random amplified polymorphic DNA) techniques for the identification of a genetically diverse core group of accessions for field phenotypic analysis. The surprisingly completely different molecular patterns exhibited by multiple accessions was later confirmed in the distribution of the putative C. pepo plants into two clusters drastically separated at a very low level of genetic similarity (DICE coefficient = 0.37). Additional analyses with RAPD and ISSR (inter single sequence repeat) markers and the introduction of standard genotypes of C. maxima L. and C. moschata L. into the analyses allowed the identification of multiple accessions of the last species wrongly included in the C. pepo collection. This study is a good example of the usefulness of DNA markers in the establishment and management of plant germplasm collections.

Aphis gossypii Glover is a polyphagous aphid pest with a worldwide distribution. However, there is evidence that on a global scale the name A. gossypii is being applied to a number of forms with different life cycles and/or host-plant associations. Morphometric variation of A. gossypii samples from crops and non-cultivated plants in many parts of the world was examined, to determine whether this variation is correlated with the hosts from which the aphids originated. Samples of A. gossypii were collected from Cucurbitaceae and Malvaceae in Europe, and from Compositae in various parts of the world. Morphometric data for 13 parameters measured from 97 clonal lineages (728 specimens) and 27 field-collected samples (313 specimens) were analysed by a series of canonical variates analyses, using the field sample/clonal lineage as grouping factor. Clonal lineages were reared on a common host in controlled conditions to standardize the effect of host and environment on morphology. The analyses provided a clear morphometric separation of the aphids originating from Compositae and those collected on Cucurbitaceae and Malvaceae, regardless of the geographical origin of the aphids and the host plant on which they were reared. This indicates that within A. gossypii there are two widely distributed host races or subspecies with different plant family associations. The taxonomic implications are discussed.

Pollination ecology was investigated in Citrullus lanatus (Thunb.) Matsum. & Nakai, which is a species vulnerable to pollinator loss. It was found that this species depends heavily on the honeybee, Apis mellifera L., as the main pollinator. Other pollen vectors identified include Xylocopa bees, halictid bees, Hypotrigona bees, flies and beetles. Phenologically, the plant was found to promote male fitness by producing numerous male flowers, which serve as pollinator attracting structures. Blooming sequence and A. mellifera visitation rates to these flowers are presented. This will enable farmers and pollination managers to better understand visitation patterns and to safeguard pollinators during pesticide application schedules.