Volume 11, Issue 1 (1-2022)
Abstract
Downy mildew is one of the most important diseases of cucurbits in the world and Iran. The development of the disease was investigated in a commercial variety (Sakata® F1 Hybrid Saso), three hybrids and eight pure lines of cucumber, four pure squash lines, and one commercial cultivar of watermelon (Sakata® F1 Charleston Gray 243) in two consecutive years (2017 and 2018 spring and summer) at the experimental field of the University of Guilan, Iran to identify the sources of resistance. Plants were regularly inspected until the downy mildew symptoms appeared. The disease was measured using standard scale and Image J software at five stages in the plant growing season. Comparison of disease progress curves, final severity of the disease, and area under the disease progress curve (AUDPC) showed that cucumber B10 and A12 pure lines were the most susceptible and resistant in both years, respectively. None of the squash lines were infected in the first year, but in the second year, two lines showed the disease symptoms, and the severity of the disease in these lines was close to each other. The commercial cultivar of watermelon was not infected in both years.
T. Anand, A. Chandrasekaran, S. Kuttalam, T. Raguchander, R. Samiyappan,
Volume 11, Issue 2 (4-2009)
Abstract
The compatibility studies of Pseudomonas fluorescens (Pf1) with azoxystrobin at differ-ent concentrations viz., 100, 150, 200, 250 and 300 ppm revealed that it was compatible with all the concentrations of azoxystrobin tested and the growth of the bacterium was unaffected even at the maximum concentration of 300 ppm. The field experiment revealed a foliar application of Pf1 (2.5 kg ha-1) and azoxystrobin (250 ml ha-1) combined, reduced downy mildew as well as powdery mildew disease severities more than azoxystrobin (250 and 500 ml ha-1) alone. An application of Pf1+azoxystrobin treatment recorded only 2.22 and 1.00 Percent Disease Index (PDI) of downy mildew and 1.85 and 0.50 PDI of powdery mildew during the first and second seasons, respectively. The treatment also recorded a maximum fruit yield of 14.30 and 15.65 tonnes ha-1 for the first and second seasons, re-spectively. Application of Pf1 along with azoxystrobin significantly increased the survival of Pf1 in the phylloplane of cucumber crop. In addition, there was multifold increase in peroxidase, polyphenol oxidase, phenylalanine ammonia lyase, ß-1, 3 glucanase, chitinase and phenolics in plants treated with Pf1+azoxystrobin.
