India during winter season of 2013-14 to study the efficacy of exogenous application of salicylic acid (SA) on growth and yield in onion var. Agrifound Light Red. The experiment was laid out in RBD with four replication having six treatments of different sprays of SA including control. The results revealed exogenous application of SA significantly increased the better vegetative growth in terms of plant height (68.18 to 71.08 cm), collar thickness (16.90 to 18.51 mm) with higher level of chlorophyll content of leaves (31.53 to 33.01 SPAD) than untreated control (61.71 cm, 15.29 mm, 26.77 SPAD, respectively). Further among different times of SA application, foliar spray of SA at 30 days after sowing (DAS) in nursery, 30 and 45 or 60 days after transplanting (DAT) recorded significantly maximum vegetative parameters than rest of spray schedule. Similar trend was also recorded for bulb yield and yield attributing parameters. Spraying of SA at 3 times had better efficacy than 2 times of spraying in terms of bulb diameter (polar: 65.60 to 67.94 mm and equitorial: 49.10 to 49.80 mm), bulb weight (59.50 to 69.25 g), marketable bulb yield (180.91 to 183.10 qha-1) and total bulb yield (266.99 to 290.91 q ha-1). Hence, it may be concluded that application of SA at 30 DAS, 30 DAT and/ or 45 or 60 DAT not only increased the vegetative growth but also bulb yield in onion variety ALR.

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Purple blotch, caused by Alternaria porri (Ellis) Cifferi, is a serious disease incurring heavy yield losses in the bulb and seed crop of onion and garlic worldwide. There is an immediate need for identification of effective resistance sources for use in host resistance breeding. A total of 43 Allium genotypes were screened for purple blotch resistance under field conditions. Allium cepa accession ‘CBT-Ac77’ and cultivar ‘Arka Kalyan’ were observed to be highly resistant. In vitro inoculation of a selected set of genotypes with A. porri, revealed that 7 days after inoculation was suitable to observe the disease severity. In vitro screening of 43 genotypes for resistance to A. porri revealed two resistant lines. An additional 14 genotypes showed consistent moderate resistance in the field as well as in vitro evaluations. Among the related Allium species, A. schoenoprasum and A. roylei showed the least disease index and can be used for interspecific hybridization with cultivated onion. Differential reaction analysis of three A. porri isolates (Apo-Chiplima, Apn-Nasik, Apg-Guntur) in 43 genotypes revealed significant variation among the evaluated Allium species (P = 0.001). All together, the present study suggest that, the newly identified resistance sources can be used as potential donors for ongoing purple blotch resistance breeding program in India.

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