IA. Genetic Resources

• A total of 17 accessions at Ludhiana, 120 at Rahuri, 37 at Sriganganagar, 139 at Tinsukia, 117 at Tirupati and 614 at Nagpur are conserved. Efforts to eliminate the duplicate have been in progress.

B. Crop Improvement

 

• In clonal selections, clone No.5 of Nagpur mandarin at Akola, 8 clones of Nagpur mandarin at Nagpur, Clone-6 of Coorg mandarin at Chettalli and CRS-4 of Khasi mandarin at Tinsukia continue to be superior yielders over the respective checks.

• The sweet orange clone TS-7 identified at Tirupati showed precocity of flowering. At Rahuri, 10 promising clones of sweet orange were selected and are under evaluation. Himakuntla selection-1 in sweet orange at Tirupati has been found superior. Sweet orange clone Sathgudi (CIP) continued to record higher yield with attractive fruit shape and storability.  Among the sweet orange varieties, Kodur Sathgudi performed well with respect to yield/plant (124.69 kg/tree).

• Promising genotypes viz., RHR-L-122 at Rahuri and TAL-94-14 (New) at Tirupati in acid lime are consistent to show its superiority. Further, acid lime elite clone No.2 at Akola and Acc.009 at Periyakulam continue to be promising, whereas the Rahuri centre has identified six clones that are being evaluated. The PDKV Chakradhar seedless lime with unique characters like thorn less and seed lessness acidic, with very thin fruit rind is recommended for cultivation.

• Recently two varieties of acidlime (Phule Sharbati from Rahuri cente and Balaji from Tirupati centre) and one variety of sweet orange (Phule mosambi from Rahuri) has been released under AICRP and have been popular in the respective regions.

•  

  Crop Production

• In old declining acid lime orchard and Nagpur mandarin orchard medium type of pruning in first week of June (removal of terminal shoots up to 45 cm) is recommended for maximum yield of superior quality. It was also observed that immediately after pruning, a recommended dose of fertilizer and spraying of fungicide and insecticide are essential.

• Rangpur lime followed by Rough lemon were found superior for mandarin and sweet orange at most of the locations. For high yield, survival per cent, minimum tree decline, good quality fruits with maximum monetary returns, the rootstock Marmalade orange (Rangpur lime Rahuri) is recommended for Nucellar mosambi at Rahuri, Further, it was also reported that the spray of GA3 20 ppm or Thiourea 0.1 % four times at monthly interval starting from 45 days after transplanting of Jambheri rootstock seedlings which were stunted and not up to mark for scion budding in Nagpur mandarin was found effective for vigorous growth of rootstock and scion.

• Plant spacing of 6 x 6m is ideal for superior quality fruit production having less pest and disease problem though the yield was less than 6 x 3m spacing for Nagpur mandarin. Plant spacing of 6x3m accommodating 550 plants/ha was found ideal for getting higher yields of Kinnow mandarin at Ludhiana and acid lime at Rahuri. 

• Application of 1200g N, 400g P2O5 and 400g K2O per plant per year for matured trees of Nagpur mandarin was ideal at Akola. .  The fertilizer should be applied in two split up doses, i.e. 600 g N +400 g P2o5 + 400 g K2o at the time of release of water stress before flowering and remaining half dose of N should be applied two month after fruit setting.  Inclusion of 7.5 kg neem cake along with 600g N, 300g P2O5 and 600 g K2O per plant was profitable in Khasi mandarin. 

•  

• Zinc-the most critical micronutrient in Citrus and preferred to apply in foliar form (0.5% ZnSO4). Further it was also observed that combined spray of zinc, manganese, magnesium, copper and boron were recommended on young flush to check the micro nutrient deficiency at most of the locations.

• Drip irrigation was found superior over other methods and ensured 30 per cent saving of irrigation water over traditional irrigation method. Fertigation with 75% RDF is productive for sweet orange at Rahuri and Tirupati. 

• D. Crop Protection

• Survey and surveillance of pest and natural enemies were carried out and seasonal abundance was correlated with weather parameters. Leaf miner incidence was serious at all the centres, whereas psylla affected the Chettalli, Ludhiana and Sriganganagar centres.

• Trunk borer was reported from the Akola and Tinsukia areas. Rust mite was reported as serious mostly at Rahuri and Tirupati. Fruit-sucking moths were observed to be more in Maharashtra and Punjab. Based on the population dynamics of the major pests, the centres have developed pest calendar and effective startegies for the mangements of insect pests, nematodes and diseases have been worked out besides developing prediction models.

•  

• The healthy and productive sweet orange orchards in Rahuri areas contain 2.62, 1.25 and 0.52 % N, K and Mg as against 1.77, 0.80 and 0.40 % respectively in semi crippled orchards. To achieve the maximum yield of sweet orange, the optimum concentration of NPK should be maintained within the range of 2.23 to 2.40 % N, 0.23 to 0.27 % P and 0.82 to 0.97 % K while the critical levels of NPK are 2.22, 0.22 and 0.81 per cent, respectively below which growth rate, yield and quality declines. Orchard efficiency analysis results revealed that in Kinnow mandarin, the status of available nutrients (P, K, Fe, Mn, Zn and Cu) in the soil was invariably higher in high-yielding orchards compared to low- and medium-yielding orchards. The soils of the high-yielding orchards of Khasi mandarin were moderately acidic (pH 5.1) with high organic matter content (1.04%), whereas low-yielding orchards were strongly acidic (pH 4.5) with low organic matter content (0.51%). 

• In first five years of planting intercroping with cowpea in Rabi at Akola or soybean followed by chickpea in Nagpur mandarin, green gram or onion seed production in acid lime orchard at Akola, groundnut in Kharif, onion in Rabi and French bean in summer at Rahuri, French bean followed by mustard in Kinnow mandarin at Ludhiana, cowpea or French bean during Kharif and Toria during Rabi Tinsukia has been profitable.

• Integrated method of weed control (hoeing followed by two sprays of glyphosate @ 1 kg/ha and hand weeding) recorded highest weed control efficiency (77.90%) with highest cost benefit ratio in Sathgudi sweet orange and Khasi mandarin under Tirupati and Tinsukia conditions respectively. Further, growing cowpea, blackgram and greengram in young Khasi mandarin orchard resulted in weed free condition besides giving additional income under Tinsukia conditions. Application of three sprays of Gramoxone 1.8 l/ha + 0.2% Urea at an interval of one month is recommended for controlling the monocot and dicot weeds in Nagpur mandarin orchard.

•  The trial for rejuvenating old and senile Citrus orchards revealed that soil application of 25 kg FYM + 5 kg neem cake + multiple microbial culture of NRCC (T. harzanium, Pseudomonas flouroscense and Azotobacter/Azospirillum) + 1 kg Dolomite/plant/year + 50% RDF (comprising 100 g ZnSO4 + 50 g borax/plant) as soil application + 50% RDF (comprising 100 g ZnSO4 + 50 g borax/plant) as foliar application in two equal splits (pre- and post-monsoon) was effective in Khasi mandarin at Tinsukia. This treatment was effective in rejuvenating the old and senile Citrus orchards of Nagpur mandarin at Akola and Kinnow mandarin at Ludhiana, wherein the micronutrient mixture used was FeSO4, MnSO4 and ZnSO4 and the dose was 200 g each per plant for Nagpur mandarin and 100 g each per plant for Kinnow mandarin.

• Trials to standardize the stage-wise requirement of nutrients in mandarin revealed that application of 30:40:10, 30:35:10, 20:25:30, 10:0:25 and 10:0:25% of the recommended dose of N:P2O5:K2O during March, May, July, September and November, respectively, improved growth characters and recorded higher yields of Nagpur mandarin at Akola and Nagpur, Khasi mandarin at Tinsukia, Coorg mandarin at Chettalli and also acid lime at Rahuri. However, for Kinnow mandarin at Ludhiana, the treatment with 0:0:0, 40:50:0, 40:50:0, 20:0:50, 0:0:25 0:0:25% recommended dose of N:P2O5:K2O for stages I to VI, respectively, recorded higher yield. In sweet orange, application of 40:50:0, 40:50:0, 20:0:50, 0:0:25 and 0:0:25% at Rahuri and 0:0:0, 30:40:0, 30:35:0, 40:25:30, 0:0:35, 0:0:35% N:P2O5:K2O/plant/year during stages I to VI, respectively, at Tirupati was found to be an ideal combination for higher yields.

• In the organic cultivation of Citrus, application of  75% RDF by vermicompost (on N-equivalent basis of RDF) + Trichoderma harzianum (30−40 ml/plant) + azadirachtin (1% at 3−4 ml/l as spray) + Pseudomonas fluroscens (30–40 ml/plant) recorded better yield and quality attributes of Nagpur mandarin at Akola with a fruit yield of 72.83 kg/plant, juice content of 52.40%, TSS of 120B with minimum acidity (0.78%) and in sweet orange at Rahuri with a fruit yield of 42.43 kg/plant, juice content of 46.51%, TSS of 10.350B and minimum acidity of 0.5%.

• Efforts to identify critical stages of water requirement indicated that the fruit bud differentiation stage in Nagpur mandarin at Akola, from stage I (January−February) to stage III (May−June) for sweet orange at Rahuri and stage IV (March−April) and stage V (May–June) for sweet orange at Tirupati were critical.

• Soil moisture stress from 15th Sept. to 15th  Oct. followed by spray of 50ppm ascorbic acid at the time of stress alleviation resulted in summer crop of acidlime at Akola. In Nagpur mandarin, it is recommended that, 50 days soil moisture stress is sufficient for the trees grown on medium type of soil for obtaining maximum yield of Mrig bahar.

• Studies on regulation of flowering in acid lime revealed that application of GA3 at 50 ppm during June and Cycocel at 1000 ppm during September followed by KNO3 at 1 per cent (Akola) or KNO3 at 2 per cent (Periyakulam) during October recorded maximum number of flowers per shootduring summer and yield.

• Studies on regulation of fruit drop in Kinnow mandarin at Ludhiana revealed that application of copper oxychloride (0.3%) or carbendazim (0.1%) in combination with 2,4-D (10ppm) or NAA (10ppm) during August gave good fruit yield.

• Medium pruning (removal of terminal shoots of 15-25 cm) in old Nagpur mandarin recorded significantly highest yield of 114.39 kg/tree/year as against only 79.25 kg/tree/year in control.  Increased yield was due to more number of fruits and high average fruit weight.  Similarly, in acid lime also medium pruning resulted in significantly higher number of fruits (920) with higher fruit yield (29.99 kg/tree).