This paper reviews the status of the use of grafting in two solanaceous crops of global importance, tomato and eggplant, for the control of biotic and abiotic stresses. Flooding and soil-borne diseases cause severe crop losses of tomato during the hot and wet summer months in the lowland tropics. Asian Vegetable Research and Development Center (AVRDC) recommended since 2003 the use of eggplant rootstocks VI046103 (EG195) and VI045276 (EG203) for grafting tomato scions to provide a high degree of tolerance and resistance against flooding, bacterial wilt, root-knot nematodes and other soil-borne diseases. These two eggplant rootstocks and the tomato rootstock VI043614 (Hawaii 7996) are widely used in Southeast and East Asia for successful tomato production in both the tropical lowlands and highlands, providing significant economic returns to farmers. Given the rapid evolution of plant pathogens that might cause a breakdown of the limited rootstocks currently available, as well as the challenges of other abiotic stresses such as salinity and supra-optimal temperatures, it is necessary to expand the search for new rootstocks and evaluate new rootstock-scion combinations. Breeding and evaluation of appropriate rootstocks is still a matter of trial and error because desired rootstock traits, especially for abiotic stresses, are quite complex and regulated by multiple genes. Physiological and genetic markers to guide the selection process are still lacking but are essential to fast-track the identification of rootstocks with multiple benefits. This review supports an initiative to upgrade grafting technology through evaluation of a new and wider range of rootstocks sourced from the AVRDC genebank.

Intercropping and soil amendment experiments were conducted to determine if they reduced populations of Pseudomonas solanacearum and bacterial wilt of tomato at the Asian Vegetable Research and Development Center (AVRDC) and at three other locations in Taiwan. At AVRDC, intercropping tomato with cowpea planted within the row significantly reduced bacterial wilt (P < 0.05) compared to when tomato was cropped alone. The P. solanacearum population in soil was not affected by intercropping with cowpea, soybean, or Welsh onion.At the same site, however, a preplanting soil amendment consisting of urea (200 kg ha−1 N) and CaO (5000 kg ha−1) significantly reduced the pathogen population and tomato bacterial wilt (P < 0.001). The effect of the soil amendment was not consistent when applied to soil from three other sites in Taiwan; in soil from two sites no reduction of the pathogen population occurred. At these sites, tomato bacterial wilt in the field was not reduced significantly after amending. In comparison with a non‐amended control, the addition of only CaO reduced the P. solanacearum population in AVRDC soil significantly (P < 0.05), but the reduction was significantly greater when the complete soil amendment was added. In contrast, urea alone did not affect the survival of P. solanacearum in the soil. In a greenhouse experiment with AVRDC soil, P. solanacearum was undetectable 2 weeks after soil amendment, but in the same treatment tomato yield was significantly reduced by 48% (P < 0.05) compared with non‐amended treatments. The suppressive effect of the soil amendment on the P. solanacearum population was probably due to the generation of one or several toxic substances during the transformation of urea in the presence of CaO.

Saposhnikovia divaricata (Turcz) Schischk, a perennial plant in the Umbelliferae, is widely cultivated in north China. As a traditional Chinese medicine, it can be used to cure colds and rheumatism (1). During disease surveys on medicinal plants in August 2010, a bacterial leaf blight was discovered with a general incidence of 40 to 60% on S. divaricata farms in Longxi, Weiyuan County in Gansu China. In young plants, tiny yellowwhite points were visible on the backs of the leaves. They then expanded to 2-to 3-mm oil-soaked lesions; leaves appeared crimped and deformed. Later the leaves shriveled; black-brown oil-soaked lesions appeared on the vein and the tissue around it; and black streaks appeared on the stems. Ten diseased leaf and stem tissues were cut into 4-to 5-mm squares, surfacesterilized in 1% sodium hypochlorite for 1 min, rinsed three times, and macerated for 5 min in sterilized distilled water. They were then streaked onto nutrient agar (NA) medium and incubated at 28°C for 3 days. Colo nies on NA were round, smooth, translucent, and yellowish green. They were Gram negative and induced a hypersensitive response on tobacco {Nicotiana tabacum L.) leaves. The strain was positive for gelatin, cata lase, oxidase, and utilization of glucose and saccharose. Pathogenicity tests were performed by spraying bacterial suspension containing 107 CFU/ml on six leaves of three healthy potted S. divaricata plants and injecting it into another six leaves on three plants. Plants inoculated with sterile distilled water alone served as controls. They were placed in a growth chamber at 25°C and bagged for 24 h to maintain >95% humidity. Thirty-six hours after inoculation, the inoculated leaves appeared watersoaked; 10 days later, the symptoms were apparent on leaves and the plant wilted. The negative control appeared normal. Finally, Koch's postulates were verified by re-isolating P. viridiflava from the leaves with typical blight. The genomic DNA of the isolate was extracted, and the partial 16S rDNA sequence was amplified with a universal bacterial primer set (27f and 1492r) (2). The sequence was deposited in GenBank as KM030291. BLAST search yielded 99% identity with P. viridiflava strains, including the strains KNOX209 (AY604847), RMX3.1b (AY574911), ME3.1b (AY574909), and UASWS0038 (AY919300). Based on the symptoms, colony morphology, biochemical tests, and 16S rDNA sequence identity, the pathogen was identified as P. viridiflava. To our knowledge, this is the first report of leaf blight of S. divaricata by P. viridiflava in Gansu prov ince of China. In Jilin province, the same disease was reported in 2008 (3). The impact of P. viridiflava on S. divaricata production is not yet known.