Chapter-3. Screening for varietal resistance of brinjal against Phomopsis vexans

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1 Chapter-3 Screening for varietal resistance of brinjal against Phomopsis vexans

2 Introduction Brinjal being native to India is one of the most common vegetable crops of the country and it is also called poor man s vegetable. Brinjal is grown for its unripe, immature fruits, which are used as cooked vegetable and in curries. In the areas experiencing high temperature and humidity during rainy season, the production of brinjal suffers immensely due to the attack of disease and insect pests. Among the diseases threatening the cultivation of brinjal, Phomopsis leaf blight and fruit rot are the most serious disease as this can affect at any stage of its development and lead to complete loss of the crop. The pathogen usually soil as well as seedborne and therefore it is very difficult to manage the disease by chemical control method alone. Chemical management of the disease also leaves behind the many toxic residues in the soil affecting the consumers health. In view of these, there is need for search for innate durable resistance in brinjal cultivars, so that same cultivars could be used for growing as well as breeding purpose for further improvement. Studies conducted to screen for resistant varieties of brinjal against P.vexans met with little success. Hence in the present study an attempt has been made screen popular varieties of brinjal for durable resistance against Phomopsis vexans. Materials and Methods Collection of Brinjal Samples A total of 16 cultivars were collected from different sources including agrotraders and farmers. The most widely cultivated cultivar in Karnataka is Brinjal cv. purple pusa long, Manju (F1 Hybrid) Hybrid, Ankush green long, MEBH9, MEBH10, Brinjal Seeds (Green round) and Kalpataru hybrid seeds. The list of brinjal cultivars used in the present study for varietal resistance is presented in Table-3.0.

3 Preparation of fungal inoculum Fourteen (14) day old culture of Phomopsis vexans was isolated on Potato Dextrose Agar medium from fruit rot and leaf blight affected brinjal sample. The pure culture was used for inoculum preparation. Using sterile needle, pycnidia were dislodged into sterile distilled water. The suspension was filtered through cheese cloth to remove bigger particles. The alpha conidial suspension was adjusted to 1x10 5 conidia/ml using Haemocytometre and used for foliar spray using glass automizer. Screening for resistant cultivars of brinjal under green house conditions A total of 16 commercial cultivars of brinjal seeds were used in the present investigation for screening for the resistance under green house condition. Seedlings were raised in nursery and were transferred to pots filled with sterilized soil, farmyard manure and sand (2:1:1). Twenty five 25 day old seedlings were sprayed with conidial suspension of Phomopsis vexans and initiation of leaf blight and fruit rot symptoms were recorded after 10 days post inoculation until the crop reached harvest stage. Based on the incidence of leaf blight and fruit rot disease on each cultivar, disease incidence and nature of resistance of each cultivar was determined. The disease resistance/susceptibility of each cultivar was recorded. Seedlings inoculated with sterile water served as control. Evaluation of varietal resistance against P. vexans in field condition A total of 16 commercial cultivars used earlier in green house experiment were also evaluated under field conditions in farmer fields situated near Mysuru (Marayyanahundi). The field blocks were 2.5x3m (length and width). Seedlings of all 16 cultivars were raised in nursery and 35days old seedlings were transferred to fields. A total of 90 seedlings were planted for each cultivar (9 rows and 10plants/row). After 30 days of transplantation and with all agronomic practices, conidial suspension of P. vexans was sprayed and initiation of leaf blight and fruit rot symptoms were observed after 10 days post inoculation until

4 the crop reached harvest stage. Development of fruit rot disease was observed after days of post inoculation. Table: 3.0. List of Brinjal cultivars used in the present investigations for screening resistant cultivars. Sl. No Cultivar/Variety Origin/Producer 01 Hybrid Brinjal seeds MEBH 10-Super 10 Mahyco, Mumbai, India 02 Malapur -Mrityunjaya seeds Mrityunjaya Seed corporation, Dharwad, Karnataka, India 03 Hybrid Brinjal seeds- Kamadhenu Tanindo Seed Pvt. Ltd. Banglore, India. 04 Hybrid Brinjal seeds MHB 11 (Improved) Mahyco, Mumbai, India 05 Hybrid Brinjal Ankush- BRANK Srujana Seeds Pvt. Ltd. Banglore, India. 06 Hybrid Egg Plant- Manju (F1 Hybrid) Syngenta India Limited, Mumbai, India. 07 Brinjal F1- Hybrid Jyothi Prabhakar Hybrid Seeds, Banglore, India 08 Brinjal- Brinjal Varikathri Nethra Seeds Corporation, Banglore, India. 09 Hybrid Brinjal Seeds- MEBH 11 Mahyco, Mumbai, India 10 Brinjal Seeds (Green round) Sagar Hybrid Seeds Company, Hyderabad, India. 11 Brinjal- Pusa Purple Long. National Seed Corporation Ltd. New Delhi, India 12 Brinjal seeds- Ruchika Pradham Biotech Pvt. Ltd Hyderabad, India 13 Kalpataru- Hybrid Brinjal Seeds MEBH10 Mahyco, Mumbai, India 14 F1 Hybrid Brinjal SBH- Sarpan brinjal Seeds SARPAN Hybrid seeds Co. Pvt. Ltd, Dharwad, Karnataka 15 Local Brinjal Seeds* Doddamaragowdanahally, Mysuru, Karnataka, India

5 16 Local Brinjal Seeds* Netkalu, Malavally, Mandya, Karnataka, India. *Seed samples processed by farmers for recycle purpose were procured directly and were preserved at 4 C for further use. Disease scale for calculating leaf blight disease and fruit rot disease As there is no disease assessment scale available for brinjal, a disease scale has been developed to calculate the leaf blight disease and fruit rot disease. For the assessment of leaf blight disease, a disease scale of 0-5 was used (0- highly resistant, 1-5-resistant, 6-15-moderately resistant, intermediate, suseptible, > 61-Highly susceptible respectively. Similarly, a disease scale of 0-5 was used for fruit rot disease assessment. The disease scale of 0-5 (0-highly resistant, 1-20 resistant, moderately resistant, intermediate, 51-70, susceptible, highly susceptible was used. This scale has been used to calculate disease incidence on leaf and fruit of brinjal. The disease scale used for assessing leaf blight and fruit rot disease is presented in Table-3.1 (Mrindha et al. (2007). Table: 3.1. Disease scale for leaf blight and fruit rot disease of brinjal against Phomopsis vexans. Severity Scale for leaf Leaf surface affected (%) Nature of resistance/ susceptibility Fruit surface affected (%) Severity Scale for fruit 0 0 Highly Resistant (HR) Resistant (R) Moderately Resistant MR Intermediate (I) Susceptible (S)

6 Highly Susceptible (HS) Results Screening for resistance under green house condition The results of cultivar screening for leaf blight disease of brinjal are provided in Table 3.0 and Fig. 3.1 respectively. A total of 16 cultivars were screened under green house condition with conidial application of P. vexans. The study revealed that, very high incidence of leaf blight disease of 84% and 82% was recorded in two local cultivars of brinjal followed by 78% in Malapur cultivar. Low incidence of leaf blight disease of 11% and 22% were recorded in MEBH10 and MEBH11 cultivars respectively. Similarly the incidence of fruit rot disease was also evaluated on 16 cultivars based on the fruit rot disease incidence. The study showed that high incidence of fruit rot disease of 72% and 69% was recorded in two local cultivars of brinjal followed by incidence of 64% in Malapur cultivar. Very low incidence of fruit rot disease of 14% and 22% were recorded in two hybrid cultivars namely MEBH10 and MEBH11 respectively. Based on the screening method adapted under green house condition for leaf blight disease all the 16 cultivars were classified as 4-highly susceptible cultivars (> 61%), 7-susceptible (31-60%), 4-intermediate (16-30%) and 1 moderately resistant (6-15%) respectively for leaf blight disease. More or less similar trend was observed in all the 16 cultivars when screened against fruit rot disease under green house condition. Out of 16 cultivars, 4-highly susceptible (71-80%), 7- susceptible (51-70%), 4-intermediate (41-50%) and 1-moderately resistant (21-30%) cultivars were found. No cultivar was found resistant or blight resistant among 16 cultivars screened against fruit rot disease. Screening for varietal resistance under field condition

7 The results of field evaluation of brinjal cultivars for leaf blight and fruit rot disease is presented in Table-3.2 and Fig. 3.3, 3.5 & 3.4 respectively. Out of 16 cultivars screened for leaf blight disease four cultivars were highly susceptible to leaf blight disease. The study revealed that, very high incidence of leaf blight disease of 68% and 74% was recorded in Malapur and one local cultivars of brinjal. Lower incidence of leaf blight disease of 9% was recorded in MEBH10 cultivar. Similarly the incidence of fruit rot disease was also evaluated on 16 cultivars based on the fruit rot disease incidence. The study showed that high incidence of fruit rot disease of 83 and 84% was recorded in one local cultivar and Malapur seeds of brinjal followed by incidence of 79% in Local brinjal seeds 16. Very low incidence of fruit rot disease of 10% was recorded in MEBH10 cultivar. Based on the screening method adapted under field evaluation, for leaf blight disease all the 16 cultivars were classified as 4-highly susceptible cultivars (>61%), 7-susceptible (31-60%), 4-intermediate (16-30%) and 1 moderately resistant (6-15%) respectively for leaf blight disease. More or less similar trend was observed in all the 16 cultivars when screened against fruit rot disease under green house condition. Out of 16 cultivars, 4-highly susceptible (71-80%), 7- susceptible (51-70%), 4-intermediate (41-50%) and 1-moderately resistant (21-30%) cultivar was found. No cultivar was found resistant or highly resistant among 16 cultivars screened against fruit rot disease.

8 Discussion Plants are endowed with different types of resistance, so also many crop plants. Durable resistance is the resistance that remains effective in a cultivar that is widely grown for a long period of time. It cannot be identified immediately, as it should be grown for a long time. Durable resistance can be identified based on relative performance of other cultivars during evaluation or screening. Searching for durable disease resistance in crop plants has been a continuous process by which host itself plays the role of an antagonist (Singh, 1975). As many plant pathogens including fungal pathogens coming with varied degrees of virulence these days, resistant varieties can be the most simple, practical and effective and economical method of plant disease control. They also ensure protection against diseases and also save time, energy and money. For many diseases such as wilts, rusts, and other viral diseases, resistant varieties are the only practical method of disease control. The terms monogenic, polygenic, vertical, horizontal, specific and general resistance are being used to explain the type of resistance in plants against invading plant pathogens. Two basic types of resistance mechanisms have been recognized in plants, they are specific and general resistance. When the defense mechanism in plants is controlled by a single gene pair it is known as monogenic resistance. Varieties with monogenic resistance remain completely free from pathogen attack in different environments. This type of resistance is stable only until new races of pathogen emerge. When the resistance is controlled by synergistic action of more than one minor group of supplementary genes, the type of resistance is known as generalized or polygenic resistance. The polygenic resistance is likely to disappear with change in the environments. However, it is more tolerant to evolution of new races of the pathogen. It remains useful for a longer period. However, resistance developed by

9 combination of many dominant and recessive genes is more desirable in crop plants. During crop improvement programme for disease resistance, three common methods are employed, namely; selection, mutation and hybridization. Screening for disease resistance is pre-requisite for breeding programme. As brinjal is one of the important vegetable crops, and is largely grown in different parts of the country, it is desirable to have stocks of resistance cultivars for cultivation in different agro-climatic regions of India, so that the crop could be protected from existing and new races of pathogen. However, no studies have been conducted for varietal screening for disease resistance in brinjal against fungal, bacterial or viral plant pathogens. In view of the above, in the present study, 16 popular cultivars of brinjal collected from different sources were screened against P. vexans. Among these very low incidence of leaf blight disease (11%) was recorded only on Brinjal Hybrid MEBH10. Similarly the low incidence of fruit rot disease (14%) was also recorded in cultivar MEBH10. Hence the study showed that cultivar MEBH10 to certain extent showed moderate resistance against P. vexans the causative agent of leaf blight disease. Similarly, among 16 cultivars of brinjal screened under field evaluation for leaf blight and fruit rot disease, low incidence of leaf blight and fruit rot disease were recorded in MEBH10 cultivar. None of the other cultivars exhibited some degree resistance to leaf blight and fruit rot disease. The present study clearly identified the moderately resistant MEBH10 variety only to certain extent against P. vexans. Similar studies on resistance to Phomopsis fruit rot in brinjal was investigated by Datar and Ashtaputre (1988). Studies on resistance to Phomopsis blight in brinjal were also studied by Kalda et al. (1976). Phomopsis blight in brinjal and sources of resistance was also studied by Pandey et al. (2002). Test on brinjal resisting to Phomopsis rot was studied by Ren and Zhang (1993). Further, control of Phomopsis fruit rot of brinjal with different fungicides and also economics was studied by Grewal and Jhooty (1987); Islam and Pan

10 (1989 and 1993). Efficacy of certain fungicides in controlling Phomospsis vexans causing fruit rot of Brinjal was studied by Mohanty et al. (1994). However no durable resistance was discovered. Brinjal is the leading vegetable in the country in terms of hectare and volume of production in India. It is a very versatile vegetable which can be taken alone as a dish or mixed with other vegetables. Its production constraint is the Phomopsis blight which is caused by Phomopsis vexans (Sacc and Syd) Harter. The disease is seed-borne and can cause disease in the next season. Host resistance is the most practical and environment-safe method against this pathogen. The present study, though identified MEBH10 cultivar is moderately resistant to P. vexans. The degree of resistance may not be sufficient to protect the brinjal crop against fungal pathogen. Therefore, further, work needs to be carried out to identify the durable resistance to P.vexans.

11 Sl. No. Table: 3.2. Brinjal cultivars inoculated with conidial suspension of Phomopsis vexans to record the disease incidence and severity under green house condition for leaf blight and fruit rot disease. Cultivar/Variety Source Leaf Blight (%) Mahyco, Mumbai, 01 Hybrid Brinjal seeds MEBH 10-Super Malapur -Mrityunjaya seeds India Mrityunjaya Seed corporation, Dharwad, Karnataka, India 03 Hybrid Brinjal seeds- Kamadhenu Tanindo Seed Pvt. Ltd. Banglore, India. 04 Hybrid Brinjal seeds Mahyco, Mumbai, MHB 11 (Improved)- India Bulldozer 05 Hybrid Brinjal Ankush- Srujana Seeds Pvt. Ltd. BRANK Banglore, India. 06 Hybrid Egg Plant- Manju Syngenta India (F1 Hybrid) Limited, Mumbai, India. 07 Brinjal F1- Hybrid Jyothi Prabhakar Hybrid Seeds, Banglore, India 08 Brinjal- Brinjal Varikathri Nethra Seeds Corporation, Banglore, India. 09 Hybrid Brinjal Seeds- MEBH Brinjal Seeds (Green round) 11 Brinjal- Pusa Purple Long. Mahyco, Mumbai, India Sagar Hybrid Seeds Company, Hyderabad, India. National Seed Corporation Ltd. New Delhi, India 12 Brinjal seeds- Ruchika Pradham Biotech Pvt. Ltd Hyderabad, India 13 Kalpataru- Hybrid Brinjal Mahyco, Mumbai, Seeds MEBH10 India 14 F1 Hybrid Brinjal SBH- SARPAN Hybrid seeds Sarpan brinjal Seeds Co. Pvt. Ltd, Dharwad, Karnataka 15 Local Brinjal Seeds Doddamaragowdanahal ly, Mysuru, Karnataka, India 16 Local Brinjal Seeds Netkalu, Mandya, Malavally, Karnataka, India. Values given are mean of three replicates Nature of resistance Fruit Rot Disease (%) 11 MR 14 MR 78 HS 64 HS 23 I 22 I 52 S 39 S 24 I 18 I 42 S 54 S 51 S 36 S 64 HS 65 HS 22 I 24 I 46 S 37 S 59 S 49 S 27 I 25 I 55 S 38 S 58 S 42 S 82 HS 72 HS 84 HS 69 HS Nature of Resistance (Hybrid Brinjal seeds MHB 11 (Improved)-Bulldozer, Hybrid brinjal- Manju (F1 Hybrid), Brinjal F1- Hybrid Jyothi, Brinjal Seeds (Green round)

12 Table: 3.3. Brinjal cultivars inoculated with conidial suspension of Phomopsis vexans to record the leaf blight and fruit rot disease under field evaluation. Sl. No Cultivar/Vari ety 01 Hybrid Brinjal seeds MEBH 10-Super Malapur - Mrityunjaya seeds 03 Hybrid Brinjal seeds- Kamadhenu 04 Hybrid Brinjal seeds MHB 11 (Improved)- Bulldozer 05 Hybrid Brinjal Ankush- BRANK Hybrid Egg Plant- Manju (F1 Hybrid) 07 Brinjal F1- Hybrid Jyothi 08 Brinjal- Brinjal Varikathri 09 Hybrid Brinjal Seeds- MEBH Brinjal Seeds (Green round) 11 Brinjal- Pusa Purple Long. 12 Brinjal seeds- Ruchika 13 Kalpataru- Hybrid Brinjal Seeds MEBH10 14 F1 Hybrid Brinjal SBH- Sarpan brinjal Seeds 15 Local Brinjal Seeds 16 Local Brinjal Seeds Origin/Producer Leaf Blight Disease incidence Nature of the cultivar Fruit Rot disease Mahyco, Mumbai, India 9 MR 10 MR Mrityunjaya Seed corporation, Dharwad, Karnataka, India Tanindo Seed Pvt. Ltd. Banglore, India. 68 HS 84 HS 25 I 29 I Mahyco, Mumbai, India 44 S 46 S Srujana Seeds Pvt. Ltd. Banglore, India. Syngenta India Limited, Mumbai, India. 21 I 22 I 38 S 53 S Prabhakar Hybrid Seeds, Banglore, India 47 S 58 S Nethra Seeds Corporation, 69 HS 78 HS Banglore, India. Mahyco, Mumbai, India 26 I 21 I Sagar Hybrid Seeds Company, Hyderabad, India. 39 S 52 S National Seed Corporation 41 S 57 S Ltd. New Delhi, India Pradham Biotech Pvt. Ltd 19 I 19 I Hyderabad, India Mahyco, Mumbai, India 55 S 42 S SARPAN Hybrid seeds Co. Pvt. Ltd, Dharwad, Karnataka Doddamaragowdanahally, Mysuru, Karnataka, India Netkalu, Mandya, Malavalli, Karnataka, India. 47 S 54 S 66 HS 83 HS 74 HS 79 HS Nature of the cultivar

13 Figure: 3.0. Brinjal seedlings in nursery for varietal screening for resistant cultivars of brinjal before they are transplanted to fields.

14 Figure-3.1: Evaluation of brinjal cultivars for varietal screening for resistance under green house condition.

15 Figure -3.2 :Evaluation of Brinjal cultivars for varietal screening for resistance underfield condition near Mysuru.

16 Figure -3.3: Evaluation of Brinjal cultivars for varietal screening for resistance under field condition near Mysuru showing leaf blight disease on local cultivar.

17 Figure-3.4: Evaluation of Brinjal cultivars for varietal screening for resistance under field condition near K. R. Nagar, Mysore District showing leaf blight disease on local cultivar.

Breeding for Disease Resistance

Breeding for Disease Resistance Resistance refers to the ability of the host to interfere with the normal growth and for development of the pathogen. The plant affected by the disease is known as host