Evaluation of the Susceptibility of Some Lettuce Cultivars to Natural Infection by Powdery Mildew (Erysiphe Cichoracearum)

Abstract

l(evwor&: Lettuce, powdery mildew, Erysiphe cichoruceurum, susceptibility Indroductipn Lettuce (Lactuca sutivu Linn.) is cultivated throughout India. Studies on host pathogen relationships of this crop have been carried out in U.S.A. and Europe (1,3,4). In Europe powdery mildew occurs sporadically on lettuce cultivars (1,3). Literature on the response of lettuce cultivars to powdery mildew (Erysiphe cichoruceurum) is limited (2). and Me-During 1992-94, twenty two commercial cultivars as follows; Avondefiance, Black seeded, Black seeded simpson, Californian wonder, Chinese Wong Bok, Elephants trunk, Green and Paris White, Honeydew, Hungarian wax, Himalyan grandeur, Iceberg, Italian sprouting, Lake Nyah, Maruraj, Pride of Fuji, Paris white cos, Suttons A-1, Suttons little gem, Suttons improved unrivalled, Suttons golden ball, Suttons white gem and Wayahead obtained from Sutton & Sons (India) Pvt. Ltd., 13-D Russel St, Calcutta, 700 071 and Cooper's Seed Co. 77/78 A, SahaneySujan Park, Pune, 41 1 040 were tested. The seeds were sown on 2 September 1992. Threeweek old seedlings of each cultivar were transplanted singly in 15 cm earthern pots containing a sterilised soiVcompost mixture (3:l). Trials were conducted in a glasshouse from the third week of September until February or March. The infected area of thirty leaves selected randomly from 15 replicate plants were assessed. Severity of infection was recorded using a 0-4 scale for assessments as follows: 0 = plants without powdery mildew infection; 1 = maximum leaf infection of 25%; 2 = 25-50% leaf infection; 3 = 50-75% leaf infection; 4 = 75-100% leaf infection. Powdery mildew infection occurred naturally in the glasshouse. &su! . &The results presented in Table 1, were recorded in 1992-93 when the powdery mildew infection was severe. Cultivars Suttons A-1 and Maruraj were the only cultivars which remained free of powdery mildew infection throughout the trial. Cultivars Black seeded, Black seeded simpson, Elephants trunk, Honeydew, Lake Nayh, Pride of Fuji and Suttons little gem showed sporadic occurrence of powdery mildew. Whereas cultivars Chinese Wong Bok, Green and paris white, Italian sprouting, Himalayan grandeur and Suttons white gem were severely infected by powdery mildew infection. In these cultivars nearly the whole plant was infected with powdery mildew.Observations in this trial support the results of earlier workers (1, 5), who have shown that there are resistant types among lettuce cultivars. Present studies therefore have shown preliminary results, further investigations should be carried out to determine lettuce resistance to E. cichoruceurum after artificial or natural infection. The cultivars showing some resistance could probably be utilised effectively in lettuce cultivation programmes where this pathogen causes heavy losses.-76 -

Evaluation and QTL mapping of resistance to powdery mildew in lettuce

“…However, Imperial 850 still possesses a certain level of resistance ( z = −0·66, six tests), probably either due to a residual effect of the defeated R gene or presence of another resistance gene(s). Resistance was previously reported in cvs Bath Cos (Schnathorst & Bardin, ), Big Green Cos (Matheron & Porchas, ), Susan (Knight et al ., ), Suttons A‐1 and Maruraj (Husain & Akram, ), and Colorado (Lebeda & Mieslerová, ; Lebeda et al ., ), that were not tested in this study.…”

Taxonomy, distribution and biology of lettuce powdery mildew (Golovinomyces cichoracearum sensu stricto)

“…Clearly, many authors have studied interactions between cultivated lettuce ( L. sativa ) and powdery mildew ( G. cichoracearum ) (Schnathorst & Bardin, 1958; Crute & Burns, 1983; Lebeda, 1985a,b,c, 1994; Knight et al. , 1986; Husain & Akram, 1996; Matheron & Porchas, 2001, 2003). Most cultivated lettuce was found to be susceptible.…”

“…Arctic King, Big Boston, Salad Bowl and Bath Cos (Schnathorst & Bardin, 1958); Two Star and Big Green Cos (Matheron & Porchas, 2003), Amanda Plus and Bremex (Lebeda, 1985a), Cindy, Clarion Corelli, Sabine, Soraya and Suzan (Knight et al. , 1986); Suttons A‐1 and Maruraj (Husain & Akram, 1996). According to Knight et al.…”

“…In Asia, there have been relatively few published reports of this disease on lettuce or other crops (e.g. Husain & Akram, 1996).…”