Grafting is an effective way to increase plant tolerance to biotic and abiotic stressors, it is widely used in watermelon production. However, grafting is labor intensive due to the additional time is required, such as the management of rootstock regrowth. This study used a new grafting tool to destroy (remove) the epidermis of pumpkin and bottle gourd rootstock cotyledon base during grafting, we called this a new grafting method. Compared with the traditional grafting (100%), the new grafting method had significantly lower rate of rootstock regrowth (2-23%), higher watermelon scion dry weight and leaf area. In addition, the time used for the new hole insertion and one cotyledon grafting method to destroy (remove) the epidermis of rootstock cotyledon base (4.2 s/plant, 4.2 s/plant) is significantly shorter than the time required to remove the rootstock regrowth manually in the traditional grafting (9.3 s/plant, 8.8 s/plant). Thus, this study developed a new grafting method for watermelon to inhibit rootstock regrowth and enhance scion growth, and this new method is cost-effective for grafted watermelon seedlings.

Salinity substantially affects plant growth and crop productivity worldwide. Plants adopt several biochemical mechanisms including regulation of antioxidant biosynthesis to protect themselves against the toxic effects induced by the stress. One-year-old Pistachio rootstock exhibiting different degrees of salinity tolerance were subjected to sodium chloride induced salt stress to identify genetic diversity among cultivated pistachio rootstock for their antioxidant responses, and to determine the correlation of these enzymes to salinity stress. Leaves and roots were harvested following NaCl-induced stress. Results show that a higher concentration of NaCl treatment induced oxidative stress in the leaf tissue and to a lesser extent in the roots. Both tissues showed an increase in ascorbate peroxidase, superoxide dismutase, catalase, glutathione reductase, peroxidase and malondialdehyde. Responses of antioxidant enzymes were cultivar dependent, as well as temporal and dependent on the salinity level. Linear and quadratic regression model analysis revealed significant correlation of enzyme activities to salinity treatment in both tissues. The variation in salinity tolerance reflected their capabilities in orchestrating antioxidant enzymes at the roots and harmonized across the cell membranes of the leaves. The study provides a better understanding of root and leaf coordination in regulating the antioxidant enzymes to NaCl induced oxidative stress.

Crown gall (Agrobacterium tumefaciens), crown/root rot (Phytophthora spp.), root lesion disease (Pratylenchus vulnus), and tree vigor are key traits affecting productivity and quality of walnuts in California. Non-inoculated hybrid rootstocks were analyzed by RNA-seq to examine pre-formed factors affecting these traits. Enrichment analysis of the differentially expressed genes revealed that increased expression of cell wall biogenesis-related genes plays a key role in susceptibility to A. tumefaciens, Phytophthora spp., increased vigor, but not P. vulnus. Analysis of the predicted subcellular loci of the encoded proteins revealed that many gene products associated with vigor and susceptibility were targeted to the plasma membrane and extracellular space, connecting these traits to sustaining barrier function. We observed that RNA processing and splicing, along with predicted nuclear targeting, were associated with resistance to A. tumefaciens, Phytophthora spp., low vigor, but not P. vulnus. Four genes within the J. microcarpa QTL region for resistance to A. tumefaciens and Phytophthora spp. were represented among our transcripts, with two of the genes being differentially expressed in association with resistance to A. tumefaciens and decreased vigor. No differential expression related to Phytophthora spp. or P. vulnus traits was observed in this region. Additionally, the J. microcarpa haplotype expressed more transcripts associated with resistance to A. tumefaciens, Phytophthora spp., and low vigor, but not P. vulnus than the J. regia haplotype. We also report unique and shared hormone and defense responses associated with each trait. This research suggests a link between cell wall biogenesis, vigor, and critical root diseases of walnut.

Late pear cultivars, such as ‘Conference’, can be stored for a long period, with their storability depending on storage conditions. A three-year study (2011-2013) compared the impact of half-year storage using four technologies – normal atmosphere, normal atmosphere + 1-methylcyclopropene (1-MCP), controlled atmosphere, controlled atmosphere + 1-MCP – on the quality parameters of ‘Conference’ pears, such as mass loss, firmness, total soluble solids, acidity, antioxidant capacity, and the incidence of diseases and disorders. Additionally, the study analysed different storage conditions in terms of profitability, based on the market prices for pears in the seasons during which the pears were stored. The storage conditions had a very strong influence on the fruit quality parameters, and was found to affect most visibly the mass loss and the incidence of postharvest diseases and disorders. The storage of ‘Conference’ pears for 180 days in normal atmosphere is not economically viable, even if the fruit is subjected to 1-MCP treatment.