Evaluation of bell pepper (Capsicum anrzuzcm ...

India11Jourr~alofAgricultura1 Scietzces 77 (4) : 267-9, April 2007

Evaluation of bell pepper (Capsicum anrzuzcm) germplasm for resistance to leaf blight and fruit rot caused by PhytupAth ora riic~tianaevar n icotiarzae S K GUPTA', KUMUD JARIAL2,SANDEEP KANSAL" M C THAKUR.', AMIT VIKRAM and SEEMA MEHTA6

Dr Yashwant Singh Parmar University ofHorticulture aizd Foresti?, Nauizi, HinlacAal Pr~n'eshi 73 230 Received : 28 August 2006 Key words: Germplasm evaluation, Resistance, Bell pepper, Capsicum m7nuzlm. Phytoplzthora ~zicotiailae var nicotianae

Leaf blight and fruit rot (PJzytophthora~zicotianaeB. de. Hann var. nicotianae Waterhouse) is an important disease of bell pepper (Capsicum annuum L.) in mid hills of Himachal Pradesh causing huge losses to the farmers. Leaf blight severity and fruit rot incidence have been reported to vary between 35.0 to 62.7 and 30.4 to 68.7%, in the State. The pathogen is both seed as well as soil borne and spreads through rain splashes (Gupta et al. 2002). The disease can be kept under check with chemicals (Bhardwaj et al. 1985) but use of resistant varieties if available can lower the cost of production and help to check the environmental pollution. No reliable screening technique under laboratory conditions is available against the disease. Keeping this in view, 28 cultivars / lines of bell pepper were screened against leaf blight and fruit rot under natural epiphytotic conditions. Incubation and latent periods were also recorded by inoculating the lines with pathogen under laboratory conditions. Twenty eight cultivarsl lines of bell pepper were evaluated against leaf blight and fruit rot under natural epiphytotic conditions during cropping season of the year 2005 followed by artificial inoculation with pathogen under laboratory conditions. Bell pepper germplasm was transplanted in the second fortnight of April so that fruiting coincides with the onset of monsoon rains. Twelve plants of each cultivar/ line were transplanted in a 5.4 m long row at a recommended spacing of 60 cm x 45 cm and replicated thrice. Highly susceptible cultivar 'California Wonder' was planted in two rows around the experimental plots as well as in a single row alternating with 10 rows of germplasm lines. The severity and incidence of leaf blight and fruit rot was recorded on 0-4 scale (Verma 1997). The per cent disease severity was calculated by the *Short note I Scientist, *ResearchAssociate, Department of Mycology and Plant Pathology; 3 Scientist, Senior Vegetable Breeder, ' Assistant Scientist, Senior Research Fellow, Department of Vegetable Crops

fomula given below: Disease severity (%) =

Sum of all ratings Total number of ratings x maximum disease grade

x

100

The genotypes1 lines were classified as resistant, moderately resistant, moderately susceptible, susceptibleand highly susceptible depending upon 0.0-5.0, 5.1-10.0, 10.125.0,25.1-50.0and >50.0% leafblight severity respectively. In case of fruit rot, genotypes / lines exhibiting 0.0-5.0,5.110.0, 10.1-25.0,25.1-40.0 and >40.0% incidence were rated as resistant, moderately resistant, moderately susceptible, susceptible and highly susceptible, respectively. Additionally, apparent infection rate (r) was also calculated in each cultivarl line by the following formula: In [xJ(l-x,)] = In [x,/(l-x,)] + r(t;t,)

where r is apparent infection rate (per unit per day) and x, and x, are the disease severity (per unit) at time t, and t, respectively. All cultivars I lines evaluated under field conditions were further screened for resistance under laboratory conditions by artificial inoculation. The pathogen was isolated from the diseased fruits and purified on oatmeal agar plates. The identity of the pathogen was got confirmed as Phytophthora nicotiatzae var nicotianae from ITCC, New Delhi (Acc. No. 4200). For the production of sporangia the fungus culture was raised on oatmeal agar medium. Oneweek-old mycelial mat of the fungus was scrapped from the petri-plates with the help of a sterilized scalpel and placed in 0.01 M KNO, solution and incubated for 72 hr at 2@1°C. Sporangia were then harvested in sferilized distilled water with the help of a camel hairbrush and suspension so obtained was adjusted to a concentration of 9 x lo4sporangiaJm1with the help of a haemocytometer.Ten detached leaves and h i t s of each cultivar 1 line were swabbed with 70% ethanol, washed with sterilized distilled water, air dried and placed in enamel trays lined with moist blotting paper covering the moist cotton. Leaves (adaxial surface) and fruits (stem end)

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GUPTA ETAL.

[lr~tiintlJorri.tra1 qj'Agrici~ltrrraScie~~ces 77 (4)

tzicotiat~aevar ~licotinilneboth under natural and laboratory conditions Table 1 Reaction of bell pepper cultivars ;lines to Pl~~,toplit/lorn Reaction Apparent Incubation period (hr) Latent period (hr) Cultivar !line Leaf blight Fruit rot infection rate on leaves severity (YO) incidence (%) On fruits on fruits (per unit per day) 48.00 65.00 45.3 1 MS 0.175 'Arka Gaurav' 70.00 41 .OO 42.00 S 0.203 'Bell Orange' 43.00 68.00 40.50 S 0.185 'California Wonder' 42.00 96.00 96.00 R 'DW' No symptoms No symptoms NO symptoms R 'DG' No sporulation 252.00 120.00 0.203 S (MR*) 'Feroz' 54.00 76.00 141.50 0.131 MS (S*) 'HC-201' 50.00 66.00 48.00 0.171 MS 'Mid Way' 60.00 77.00 48.00 0.235 HS 'Sel-4' 75.00 66.00 62.50 MS 0.149 'SeI-9' 124.00 74.83 108.00 MS 0.135 'Sel-10' 60.00 72.00 43.00 HS 0.295 'Sel 1-2-4' 66.00 96.00 110.17 MS 0.176 'Sel 17-1-1' No sporulation No symptoms 186.00 R 'Sel 22-1 ' 80.00 45.00 62.00 S 0.199 'Sel 12-2' 65.00 89.00 34.00 HS 0.335 'Sel 64 -1-1-4' 49.00 67.00 42.75 HS 0.367 'Sel 104 -1-1-4' 160.00 62.66 120.00 HS 0.302 'Solan Bharpur' 67.00 49.33 42.00 S 0.186 'Solan Local' 46.00 67.00 121.00 R 'SP-14' 55.00 67.00 HS 0.294 42.25 'SP-602' 45.00 71.00 HS 0.296 42.00 'SP-6 13' 48.00 71.00 HS 0.279 40.87 'SP-620' HS 0.283 41.75 54.00 69.00 'SP-628' 5 1.OO 80.00 MS 0.237 45.25 'SP-633' MS 0.179 44.75 96.00 103.00 'SP-70 1' HS 0.296 42.00 94.00 103.00 'SP-705' 260.00 45.75 240.00 HS 0.386 'Yollow wonder'

*Reaction for fruit rot

were inoculated by placing a drop (10~1)of sporangial suspension with the help of a micropipette. The trays were covered with polythene sheet internally sprayed with sterilized distilled water to ensure high relative humidity (>go%) and incubated at room temperature (25*1 T). Observations were recorded in terms of incubation period (h) on both leaves and fruits and latent period (h) on fruits. Out of 28 cultivars I lines evaluated under field conditions, 4 lines viz 'DW', 'DG', 'SP 14' and 'Sel-22-1' completely resisted both leaf blight as well as fruit rot and were rated as resistant (Table 1). Eight lines were rated as moderately susceptible to leaf blight while rest were susceptible to highly susceptible. However, lline, ie 'Feroz' was rated as moderately resistant to fruit rot and 7 as moderately susceptible while rest were susceptible to highly susceptible.Apparent infection rate (r) ranged between 0.13 11 unitlday in 'HC 20 1 ' showing moderately susceptiblereaction to 0.386lunitlday in 'Yollow Wonder' showing highly susceptible reaction. Cultivar 'Feroz' moderately resistant to fruit rot showed moderate rate of infection (0.2031 unitfday). Artificial inoculation of the leaves and fnlits of bell

pepper germplasm indicated that out of twenty eight cultivars / lines, two lines viz DG and Sel-22-1 resisted the leaf blight while rest were susceptible to hghly susceptible (Table 1). 1 line, 'DG' was found resistant to fruit rot while, 2 lines 'Feroz' and 'Sel 22-1 ' showed a sparse sporulation along with symptom expression. These 2 lines were then rated as moderately resistant to fruit rot. Only 'DG' was rated as resistant to both leaf blight and fruit rot. Lines 'SP 14' and 'DW' resistant under field conditions were found susceptible under laboratory conditions. Out of 4 lines exhibiting resistant reaction under field conditions, 2 lines, ie 'DG' and 'Sel22-1' were found resistant to leaf blight and line 'DG' was resistant to fruit rot. However lines 'Sel 22-1' and 'Feroz' were moderately resistant to fruit rot as indicated by longer incubation periods and nonsporulation on inoculated fruits. Lines 'SP 14' and 'DW' which were resistant to leaf blight and fruit rot in the field were susceptible under laboratory conditions. So only 'DG' can be rated as resistant to leaf blight and fruit rot as concluded from present investigations. Delay in infection process on fn~itsof lines 'Sel22-1' and 'Feroz' can be attributed to high degree of horizontal resistance in these lines as compared to

April 20071

GERMPLASM REACTION

other susceptible lines. Verma et nl. (2001) also inferred higher degree of horizontal resistance in bell pepper cultivars exhibiting longer incubation periods. Line 'HC 201' exhibiting slowest rate of disease development in the field also exhibited longer incubation period on leaves under artificial inoculation conditions and 'Feroz' also had moderate rate of infection under field conditions besides longer incubation periods on leaves and fruits under laboratory conditions. These findings also indicate the presence of some horizontal resistance in them against the disease as it is a well known fact that any genotype having horizontal resistance will exhibit slower rate of infection in the field.

SUMMARY Out of twenty eight cultivars / lines evaluated for resistance to leaf blight and h i t rot (Phytophthora nicotianae B. de. Hann var. nicotianae Waterhouse) of bell pepper under field as well as laboratory conditions, only 1 line, ie DG was found resistant while rest were moderately resistant to highly susceptible. Higher degree of horizontal resistance was present in the moderately resistant lines 'HC 201' and 'Feroz' as reflected by slowest and moderate apparent infection rate, respectively under field conditions besides

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comparatively longer incubation periods under laboratory conditions. ACKNOWLEDGEMENT Authors are grateful to ICAR, New Delhi for providing financial assistance in the form of adhoc project to undertake the studies. REFERENCES Bhardwaj S S, Sharma S L and Dohroo N P. 1985. Role of meteorologicai.factors in development of bell pepper fruit rot (PIzytoplzthorarlicoiianae var riicotlanae Waterhouse). Indian Journal ofMycology and PIant Patl~ology15: 328-9. Gupta S K, Shyam K R and Bhardwaj S S. 2002. Leaf bliglzt arid fnlit of bell pepper. Research ~nformation~ulietin-NO.4,

Department of Mycology and Plant Pathology, Dr Y S Parrnar University of Horticulture and Forestry, Nauni, Solan (HP), 24 p. Verma S. 1997. 'Epidemiology and management of leaf blight and fruit rot of bell pepper'. M Sc thesis, UHF, Solan. Verma S, Shyam K R,Gupta S K and Sharrna H R. 2001. Evaluation of bell pepper (Capsicunz annuuni L.) germplasm for resistance against leaf blight and fruit rot (Phyfoplzfhoranicotianae var. nicoiianae). Indian Journal of Agricultz~ralSciertces 71(3): 219-21.