The most important commercial citrus species grown in India include mandarin (Citrus reticulata Blanco), sweet orange (Citrus sinensis Osbeck.) and acid lime (Citrus aurantifolia Swingle). Citrus industry in India is the third largest fruit industry covering 0.99 million ha with annual production of 9.64 million tonnes (http://data.gov.in/dataset/ all-india-and-state-wise-area-and-production-fruits). India is the sixth largest citrus producing country in the world, contributing 4.69% of world citrus production. In Punjab, citrus fruits rank first, over an area of 44.724 thousand ha and annual production of 9.005 lakh tonnes (http://data.gov.in/ dataset/all-india-and-state-wise-area-and-production-fruits). Kinnow is the leading citrus fruit under an area of 31.788 thousand ha and annual production of 5.913 lakh tonnes. Area under kinnow is increasing rapidly due to its precocious bearing habit and very high economic returns to growers. The major problem raising citrus in Punjab and surrounding states is non-availability of quality planting material. Nursery is one of the basic inputs in citrus industry, and attention should be focused on large scale, rapid multiplication of true- to-type, healthy planting material. Therefore, production of disease-free plant material is a pre-requisite for a bright future for the citrus industry. For raising healthy plant material of citrus, a thorough understanding of mother Germination and growth of rough lemon (Citrus jambhiri Lush.) seedlings under protected environment Lakesh K. Sharma1 and H.S. Dhaliwal Department of Horticulture, Punjab Agricultural University Ludhiana, Punjab - 141004, India Email : dhaliwal_mandhali@yahoo.com ABSTRACT Production of disease-free plants is necessary for a healthy future for the citrus industry. Therefore, a study was designed to compare growth of direct-sown and transplanted rough lemon seedlings under controlled conditions. Rough lemon rootstock seedlings were grown under screen-house, shade-net house, glasshouse, and open field conditions. Seeds were planted in seed beds, propagation trays and black polythene bags. Germination was significantly higher (94.30%) in propagation trays under shade-net house except that in screen-house. Minimum germination (62.45%) was recorded in open-field seed-beds. Seedling height, stem diameter, leaf number and leaf area was found to be maximum (i.e., 55.26cm, 0.63cm, 33.43 and 24.75cm2 respectively) in direct-sown seeds in polybags under screen-house which were transferred to glasshouse during winter. Minimum values observed were 41.33cm, 0.44cm, 18.29 and 15.47cm2, respectively, in conventionally raised seedlings. On the basis of our study, it is concluded that rough lemon nursery is best raised in polybags under screen-house or glasshouse conditions. Key words: Screen-house, g lasshouse, shade-net house, rough lemon J. Hortl. Sci. Vol. 8(1):91-94, 2013 Short communication rootstock plant selection, seed sowing, raising seedlings, transplanting seedlings and budwood selection is essential. To raise quality planting material of kinnow, the most important step is to produce healthy and vigorous seedlings of rough lemon for propagation in the shortest possible time. Therefore, the present study was planned to compare growth performance of direct-sown and transplanted rough lemon seedlings. The present investigation was carried out during 2006- 07 in College Orchard, Department of Horticulture, Punjab Agricultural University, Ludhiana. Rough lemon seeds were extracted from healthy fruits collected from single-tree source and treated with Ridomil MZ 72 WP. These were sown in seed beds, propagation trays and black polythene bags filled with sterilized farm soil + FYM (2:1) in the second fortnight of August. After seed sowing, the polythene bags and propagation trays were divided into three sets. Of these, one set was placed under screenhouse, the second in shade- net house and the third under open field conditions. Seed- beds and propagation trays could not support larger seedlings. Therefore, seedlings from seed-beds were transplanted into nursery beds and in polythene bags when these attained a height of 10cm. Seedlings from propagation 1Department of Soils, North Dakota State University, Fargo, ND-58108, USA 1E-mail: lakesh.sharma@ndsu.edu or lkpau2010@gmail.com 92 trays were also transferred to polybags. In mid-November, polythene bags from each treatment were divided into three sets. One set of each treatment was transferred to polyhouse, the second to glasshouse up to the end of February, while, the third remained in place. In the first week of March, the polythene bags placed in glasshouse and polyhouse were again shifted to their original place for further growth until seedlings reached the buddable stage. Observations were recorded on seed germination in the second fortnight of September, before transplanting. Data on seedling height, seedling diameter, number of leaves and leaf area were recorded at the time of budding during May. Germination data were recorded one month after sowing and per cent germination was calculated as under: No. of germinated seeds Per cent germination = ——————————— x 100 Total number of seeds sown Height of the seedlings was measured from soil surface to the plant tip in centimeters with a meter scale, while diameter was intimated with Vernier calipers at 5 cm- above ground at the time of budding. Fully developed green leaves were counted starting from the base of the stem at the time of budding, and leaf size was calculated using a graph sheet. There were three replications per treatment, with 50 seedlings constituting a replication. Data were analyzed in this completely randomized block design (Singh et al, 1998). Maximum mean seed germination (94.30%) was obtained in treatment T 2 , where seeds had been sown in propagation trays under shade net-house. This value was significantly higher than seed germination obtained in all other treatments, except in T 1 93.35% , where seeds were sown in propagation trays under screen-house conditions. This was followed by 89.41% and 85.55% seed germination recorded in T 5 (seeds sown in polybags under shade-net house) and T 4 (seeds sown in polybags under screen-house), respectively. Minimum seed germination (62.45%) was obtained in T 7 (Control), where seeds were sown in seed beds in open-field. This value was significantly lower than in all other treatments (Table 1). Data on seed germination was recorded 30 days after sowing. It is clear that shade improves germination percentage compared to open-field conditions, and germinations rate increases with increase in shade, i.e., from screen-house to shade-net house. Optimum temperature range for rough lemon seed germination was recorded as 20-400C (Rouse and Sherrod, 1996). Present results are in accordance with findings of Dhaliwal and Mehan (2006) who reported 85-90% seed germination in rough lemon (Citrus jambhiri Lush.) in seeds sown in black polythene bags/plastic trays under 50% shade- net house with polycarbonate sheet roof, under Ludhiana (Punjab) conditions. Similarly, Singh et al (1970) found germination of citrus rootstock seeds (C. jambhiri, C. pseudolimon, C. limonia, C. magaloxycarpa and Poncirus trifoliata) under alkathene cover (65-85%) to be distinctly superior to that in open-field conditions (25-52%). Maximum mean seedling height, stem diameter, number of leaves and leaf area of 55.26cm, 0.63cm, 33.43 and 24.75cm2 were obtained, respectively, in treatment T 12 where seeds were sown directly in polybags under screenhouse conditions and seedlings were then shifted to glasshouse in winter (November to February). This was significantly higher than seedling height, stem diameter, number of leaves and leaf area obtained in all other treatments, except for stem diameter (0.61cm) obtained in treatment T 11, where seeds were sown directly in polybags under screenhouse and were shifted to polyhouse during winter. This was followed by seedling height (54.10cm and 53.46cm) in T 15 and T 11 , respectively; for stem diameter, this was followed by T 11 (0.61cm) and T 3 (0.60cm). In the case of number of leaves, this was followed by T 3 (30.10) where seeds were sown in propagation trays and transplanted to polybags under screen-house and shifted to glasshouse during winter (November to February). In leaf area, this was followed by treatment T 11 (22.08cm2), and T 3 (21.33cm2). Minimum mean seedling height, stem diameter, number of leaves and leaf area of 41.33cm, Table 1. Effect of sowing method on seed germination in rough lemon (Citrus jambhiri Lush.) under modified environment Treatment Seed germination (%) T 1 -Seed sowing in PT and transplanting 93.35 in PB under SH T 2 -Seed sowing in PT and transplanting 94.30 in PB under SNH T 3 -Seed sowing in PT and transplanting 69.40 in PB under open T 4 -Seed sowing in PB under SH 85.55 T 5 -Seed sowing in PB under SNH 89.41 T 6 -Seed sowing in PB under open 65.52 T 7 -Seed sowing in seed beds (Control) 62.45 Standard Error of mean (SEm) 5.19 CD (5%) 2.2 PB = Polybag, SH = Screen house, PT = Propagation trays SNH = Shade-net house J. Hortl. Sci. Vol. 8(1):91-94, 2013 Sharma and Dhaliwal 93 0.44cm, 18.29 and 15.47cm2 were recorded in T 22 (Control) respectively, where seeds were sown in seed beds and transplanted to nursery beds in open-field conditions. Maximum seedling height (53.43cm), stem diameter (0.60cm), number of leaves (30.10) and leaf area (21.33cm2) were obtained when seeds were sown in propagation trays and seedlings then transplanted into polybags under screenhouse, and which were shifted to glasshouse during winter (Nov-Feb) compared to all other similar type of treatments. Greater seedling height, stem diameter, number of leaves and leaf area were recorded in treatments T 3 , T 6 , T 9 , T 12 , T 15 , T 18 and T 21 , where seedlings were shifted to glasshouse in winter (November to February) compared to treatments where seedlings were transferred to polyhouse (T 2 , T 5 , T 8 , T 11 , T 14 , T 17 and T 20 ) or those that were not shifted from their original place (T 1 , T 4 , T 7 , T 10 , T 13 , T 16 and T 19 ). This might be due to modification in environmental conditions like temperature and humidity, which were favourable for growth of seedlings under screenhouse compared to shade-net house and open field conditions. Also, there is less attack of insect-pests on seedlings under screenhouse. Open-field conditions may have more harmful effects on seedling growth due to high temperature. These findings are in accordance with results of Dhaliwal et al (2003a) who recorded significantly higher seedling height, stem diameter and number of leaves under screen house compared to open-field under Ludhiana, Punjab conditions. In another trial, Dhaliwal et al (2003b) also recorded maximum seedling height, stem diameter and number of leaves in rough lemon seedlings germinated under glasshouse and placed in screenhouse conditions, compared to those germinated in glasshouse and placed in openfield; germinated and kept in screenhouse or those that were germinated and placed in open-field, under Ludhiana, Punjab conditions. Singh et al (1970) also recorded increase in seedling height, stem diameter, number of leaves and leaf area of rough lemon and rangpur lime seedlings under alkathene cover compared to open-field, under Delhi conditions. In the case of seedling height, similar results were reported by Muller (1988) in citrus rootstocks under South African conditions; by Chaturvedi and Bajpai (1999) in Bridelia retusa and Holarrhena antidysenterica under Madhya Pradesh (India) conditions; West et al (2002) in saw tooth oak (Quercus acutissima), white oak (Quercus alba), green ash (Fraxinus pennsylvanica) and flowering dogwood (Cornus florida) under Auburn, Alabama, U.S.A, Table 2. Effect of direct-sown and transplanted rough lemon (Citrus jambhiri Lush.) seedlings on seedling height, stem diameter, number of leaves and leaf area under modified environmenta Treatments Seedling Stem Number Leaf height (cm) diameter (cm) of leaves area (cm2) T 1 Seed sowing in PT and transplanting in PB under SH 50.01 0.56 26.03 19.32 T 2 -Seed sowing in PT and transplanting in PB under SH + PH 52.49 0.59 27.89 20.35 T 3 -Seed sowing in PT and transplanting in PB under SH + GH 53.43 0.60 30.10 21.33 T 4 -Seed sowing in PT and transplanting in PB under SNH 47.82 0.55 25.56 17.52 T 5 -Seed sowing in PT and transplanting in PB under SNH + PH 49.05 0.56 26.21 18.09 T 6 -Seed sowing in PT and transplanting in PB under SNH + GH 49.63 0.57 26.57 19.57 T 7 -Seed sowing in PT and transplanting in PB in open 45.28 0.49 24.61 16.59 T 8 -Seed sowing in PT and transplanting in PB in open + PH 45.95 0.51 25.34 17.21 T 9 -Seed sowing PT and transplanting in PB in open + GH 46.58 0.52 26.64 18.66 T 10 -Direct sowing of seeds in PB under SH 50.29 0.59 27.36 20.09 T 11 -Direct sowing of seeds in PB under SH + PH 53.46 0.61 29.56 22.08 T 12 -Direct sowing of seeds in PB under SH + GH 55.26 0.63 33.43 24.75 T 13 -Direct sowing of seeds in PB under SNH 49.92 0.56 26.56 18.22 T 14 -Direct sowing of seeds in PB under SNH + PH 51.85 0.57 26.88 18.91 T 15 -Direct sowing of seeds in PB under SNH + GH 54.10 0.58 27.95 20.38 T 16 -Direct sowing of seeds in PB in open 48.28 0.51 25.28 17.23 T 17 -Direct sowing of seeds in PB in open + PH 49.42 0.53 26.34 18.13 T 18 -Direct sowing of seeds in PB in open + GH 50.80 0.53 27.76 20.11 T 19 -Seed sowing in seed beds and transplanting in PB in open 43.69 0.48 20.93 15.62 T 20 -Seed sowing in seed beds and transplanting in PB in open + PH 45.26 0.49 22.60 16.25 T 21 -Seed sowing in seed beds and transplanting in PB in open + GH 45.37 0.51 23.55 16.37 T 22 -Seed sowing in seed beds and transplanting in nursery beds (control) 41.33 0.44 18.29 15.47 Standard Error of mean (SEm) 0.77 0.11 0.69 0.59 CD (5%) 0.95 0.02 0.96 1.08 PB = Polybag, SH = Screen house, PT = Propagation trays, SNH = Shade-net house, GH = Glass house, PH = Poly house J. Hortl. Sci. Vol. 8(1):91-94, 2013 Studies on rough lemon seedlings under protected environment 94 conditions. Similar results were recorded by Chaturvedi and Bajpai (1999) in Bridelia retusa Spieng. and Holarrhena antidysenterica Wall. under Madhya Pradesh, India conditions; Kumari et al (2001) in Nagpur mandarin under Nagpur, Maharashtra conditions; Singh (2003) in rough lemon under Ludhiana, Punjab conditions; Kumar (2004) in rough lemon under Ludhiana, Punjab conditions and Hazarika et al (2005) in seedlings of Khasi mandarin under Tinsukia (Assam) conditions in the case of number of leaves. REFERENCES Chaturvedi, S.K. and Bajpai, S.P. 1999. The effect of light conditions on root, shoot and plant length on selected forest-tree species. Ind. Forester, 125:725-729 Dhaliwal, H.S., Kanwar, J.S., Rattanpal, H.S. and Arora, N.K. 2003a. Effect of growing media on seed germination and growth of rough lemon (Citrus jambhiri Lush.) under protected conditions. All- India Seminar on Potential and Prospects for Protective Cultivation Dec.12 13, pp. 193-196 Dhaliwal, H.S., Kanwar, J.S., Rattanpal, H.S. and Arora, N.K. 2003b. Seed germination and growth studies on direct sown rough lemon (Citrus jambhiri Lush.) under protected conditions. All-India Seminar on Potential and Prospects for Protective Cultivation, Dec.12-13, pp. 155-156 Dhaliwal, H.S. and Mehan, V. K. 2006. Latest propagation techniques in citrus under phytosanitory conditions. Seminar on Kinnow, Abohar pp 8-9. Hazarika, N., Saikia, A.J., Borah, S.C. and Barbora, A.C. 2005. Effect of shade on growth and development of Khasi mandarin seedlings in nursery. Crop Res. Hisar, 2:446-448 http://data.gov.in/dataset/all-india-and-state-wise-area-and- production-fruits Kumar, J. 2004. Effect of media composition on growth and buddability of rough lemon (Citrus jambhiri Lush.) seedlings. M.Sc. Thesis, Punjab Agricultural University, Ludhiana, Punjab, India Kumari, N.V., Singh, A.K.S., Das, D.K., Ghosh, and Dhurjati, T. 2001. Performance of microbudding under different green house structures in Citrus reticulata cv. Nagpur mandarin. South Ind. Hort., 49:335-337 Muller, P. 1988. Optimum shade requirement of citrus nursery tree. Citrus and Sub-tropical Fruit Research Institute, South Africa, 190:12 Rouse, R.E. and Sherrod, J.B. 1996. Optimum temperature for citrus seed germination. Proc. Flo. State Hort. Soc., 109:132-135 Singh, R., Saxena, S.K. and V.P. Sharma. 1970. An improved method of raising citrus rootstocks. The Punjab Hortl. Journal 10:166-171 Singh, S., Bansal, M.L., Singh, T.P. and Kumar, K. 1998. Statistical Methods for Research Workers, Kalyani Publishers, New Delhi Singh, R. 2003. Propagation studies on the Kinnow mandarin under screen-house conditions. M.Sc. Thesis, Punjab Agricultural University, Ludhiana, Punjab, India West, D.H., Chappelka, A.H., Tilt, K.M., Ponder, H.G. and Williams, J.D. 2002. Effect of tree shelters on growth and gas exchange of four tree species under field and nursery conditions. J. Envin. Hort., 20:96-100 (MS Received 06 August 2012, Accepted 04 December 2012, Revised 19 December 2012) J. Hortl. Sci. Vol. 8(1):91-94, 2013 Sharma and Dhaliwal