A new destructive apple disease, causing black spots and necrotic lesions on leaves and defoliation on cvs. Gala and Golden Delicious (Malus × domestica Borkh.), was observed in August 2011 in Fengxian, Jiangsu Province, China. More than 90% of trees of those cultivars in the area were defoliated by the disease and almost no leaves were left on trees before harvest. The disease was similar to Glomerella leaf spot reported first in Brazil in 1988 (2) and in the United States in 1998 (1) on cvs. Gala and Golden Delicious. The initial symptom was small black lesions on leaves. Above 30°C, the lesions developed quickly and grew to 2 to 3 cm, with a blurred edge. Diseased leaves became dark and were shed. At lower temperatures, the black lesions stopped enlarging after 5 to 6 days and formed large necrotic spots with clear edges; these leaves gradually grew yellow and were shed. When incubated at 30°C and 100% relative humidity for 1 to 2 days, the black lesions produced a mass of saffron-yellow conidia. On fruit, the pathogen only caused circular, necrotic, sunken, red-bordered lesions 2 to 3 mm in diameter, which was different from bitter rot. Three monospored cultures were isolated from diseased leaves and new conidia were obtained from isolates. The colony, with abundant mycelium, was white but turned gray to black. Conidia were 12 to 17 × 5 to 7 μm, and were cylindrical with rounded ends. After germination, conidia formed appressoria, oval, or circular cells with black thick walls 7 to 12 × 5 to 7 um. Based on morphological characteristics, the pathogen was putatively identified as Glomerella cingulata. The conidia were inoculated in vitro on leaves of cvs. Gala and Fuji by dripping a suspension of about 104 conidia/ml of water onto upper leaf surfaces. Dark necrotic lesions were observed on all inoculated Gala leaves, which were similar to those observed in orchards, after 4 days incubation in a chamber at 30°C with 100% humidity. Only small black lesions, about 1 to 2 mm in diameter, were observed on Fuji leaves. No symptoms developed on leaves inoculated with distilled water. The internal transcribed spacer (ITS) region of ribosomal DNA and part of the 18S and 28S ribosomal RNA of the three isolates were amplified with the universal primers ITS1 (5′-TCCGTAGGTGAACCTGCGG-3′) and ITS4 (5′-CCTCCGCTTATTGATATGC-3′). The amplified ITS sequences confirmed that the three isolates belonged to the same species, with only one base pair variation among sequences. The nucleotide sequence of isolate 1 and 2 was deposited in GenBank (JN714400 and JN714401). BLAST analysis showed that the sequence had 99% homology with the sequence of G. cingulata (EU008836), the causal agent of Glomerella leaf spot. However, the sequence of isolate 1 had 100% homology with that of G. cingulata (HQ845103.1) isolated from walnut in Shandong, China, while the sequence of isolate 2 had 100% homology with that of G. cingulata (HM015004.1) isolated from sweet pepper in Taiwan. Results suggested the disease is Glomerella leaf spot and the causal agent is G. cingulata. The disease will eliminate sensitive apple cultivars, such as Gala, from wet, warm production areas if effective control measures are not developed within a few years. To our knowledge, this was the first finding of the disease in China and will provide useful information for developing effective control strategies. References: (1) E. González and T. B. Sutton. Plant Dis. 83:1074, 1999. (2) T. B. Sutton and R. M. Sanhueza. Plant Dis. 82:267, 1998.

A dynamic model, called VenInf, was developed to forecast infection of pear leaves by conidia of Venturia nashicola. By simulating conidial infection processes following a rain event, the model estimates % conidia that successfully infected leaves at the end of an infection period. The model is mainly derived from logistic models developed from recent laboratory and glasshouse experimental results on infection of pear seedlings to estimate the rates of infection and mortality. It simulates the conidial infection process at 5 min intervals using temperature, relative humidity (RH), surface wetness and rainfall as input. The model was evaluated against pear scab in four unsprayed orchards in China over a 4-year period. In all orchards, all significant disease increases were associated with infection periods predicted by the model. In one orchard, in 2004 the incidence of leaf infection remained very low (<3%) during the entire season despite the model forecasting several severe infection periods. Results of orchard evaluation suggest that the model is able to identify all important potential infection periods. Thus, further field studies should be carried out to determine whether and how the model can be used in practice to assist farmers in making decisions on fungicide applications.

Maize, as a glycophyte, is hypersensitive to salinity, but the salt response mechanism of maize remains unclear. In this study, the physiological, biochemical, and molecular responses of two contrasting inbred lines, the salt-tolerant QXH0121 and salt-sensitive QXN233 lines, were investigated in response to salt stress. Under salt stress, the tolerant QXH0121 line exhibited good performance, while in the sensitive QXN233 line, there were negative effects on the growth of the leaves and roots. The most important finding was that QXH0121 could reshift Na+ from shoots into long roots, migrate excess Na+ in shoots to alleviate salt damage to shoots, and also improve K+ retention in shoots, which were closely associated with the enhanced expression levels of ZmHAK1 and ZmNHX1 in QXH0121 compared to those in QXN233 under salt stress. Additionally, QXH0121 leaves accumulated more proline, soluble protein, and sugar contents and had higher SOD activity levels than those observed in QXN233, which correlated with the upregulation of ZmP5CR, ZmBADH, ZmTPS1, and ZmSOD4 in QXH0121 leaves. These were the main causes of the higher salt tolerance of QXH0121 in contrast to QXN233. These results broaden our knowledge about the underlying mechanism of salt tolerance in different maize varieties, providing novel insights into breeding maize with a high level of salt resistance.