Watermelons are grafted to prevent soil-borne diseases such as Fusarium wilt (FW) and increase their resistance to abiotic stress. Root-knot nematodes (RKN) are a contributing factor to economic loss in several cucurbits, including watermelon. Growing resistance varieties is an effective way to reduce the damage caused by soil-borne diseases. Resistance evaluation was performed on 50 watermelon lines to select rootstocks resistant to FW and RKN. Fusarium oxysporum f. sp. niveum race 2 was inoculated into 10-day-old seedlings using a root dipping method, and resistance was evaluated for four weeks. The 37-day-old watermelon seedlings were inoculated with Meloidogyne incognita and evaluated 60 days later. Three lines (IT199860, PI296341-6, and PI532811) were resistant to FW race 2, while one line (PI494527) was moderately resistant. Three lines (PI296341-5, PI457916-2, and PI457916-5) were RKN resistant. The PI296341-6 line was selected for its resistance to FW and moderate resistance to RKN. These findings imply that the identified resistant lines can be used in rootstock breeding programs against FW and/or RKN.

The range of peach rootstocks currently available worldwide has increased dramatically in the last few decades. However, peach rootstocks in Republic of Korea still primarily use mainly seeds of different species imported from China. This kind of rootstocks is not ideal for clonal production and uniformity since it is a varietal blend of genotypes with differing physical characteristics. We collected genetic resources of 214 native peaches and determined 156 native peaches for breeding the suitable peach rootstock with easy propagation, uniform growth habit, and the resistance to biotic and abiotic stresses under domestic conditions. ‘PR1’ peach rootstock [Prunus persica (Batsch) L.] was originated from open-pollinated seeds of ‘PHJN0129’ collected in 2001 at Suncheon. ‘PR1’ peach rootstock was preliminarily designated as ‘PH193’ in 2002 and then grafted onto ‘Maotao’ (P. persica) wild peach seedling rootstocks. In Hwasung, three grafted trees were observed from 2005 to 2009 and seen to have the properties of ‘PH193’. In Suwon, one-year- old seedlings were observed from 2010 to 2014 and showed to have the commercial availability of ‘PH193’ when compared with 5 peach rootstocks (Tsukuba No.4, GF677, Nemaguard, Yumyeong, and imported peach seeds from China). ‘PH193’ was finally selected in 2014, owing to its superior seed germination, graft compatibility, resistance to nematodes and crown gall, and low mortality. It was named ‘PR1’ to indicate the first peach rootstock in Republic of Korea and was released for commercial use in 2015. (Grant Number 5896).

FT-IR spectroscopy, combined with multivariate analysis, was used to determine whether 67 different wild and rootstock peach accessions could be discriminated from each other. Genomic DNA was isolated from leaves, and the purified genomic DNA was analyzed by FT-IR spectroscopy in the spectral region from 1800 to 800 cm^-1. FT-IR spectra showed that typical spectral differences existed in the frequency regions of N-H stretching (amide I), C=O stretching vibrations (amide II), and PO₂⁻ ionized asymmetric and symmetric stretching. Principal component analysis (PCA) was able to discriminate three groups. The partial least squares discriminant analysis (PLS-DA) yielded more clear discrimination among the three groups of peach accessions. The FT-IR spectral differences might be directly related to subtle changes in the base functional group and backbone structures of genomic DNA. This technique could provide a research foundation for FT-IR spectral-based rapid diagnosis, selection, and discrimination of peach accessions for rootstock.