Assessment of inherent nodulation potential among chickpea accessions belonging to minicore set ABSTRACT: Chickpea (Cicer arietinum L.) has an inherent potential to fix atmospheric nitrogen through symbiotic association with Mesorhizobium. Response to Mesorhizobial inoculation is positive with yield increases of 9-33% over un-inoculated control. However, variable responses under field conditions due to plant genotype and soil properties type are reported. Hence, attempts were made to assess the symbiotic potential and plant growth of chickpea minicore under pot as well as field conditions. The study demonstrated a direct correlation between nodule numbers and plant growth in response of accessions to Mesorhizobium inoculation. About 17 genotypes with low nodulation (2-11 nodules plant-1), 18 genotypes (10-32 nodules plant-1) with intermediate nodulation and 39 genotypes (11-85 nodules plant-1) with high nodulation were found common at ICRISAT and IIPR using pot experiment. Similarly, some of the common genotypes showing low and high nodulation as well as plant growth pattern were also identified at both IARI and IIPR using field study. The high nodulating genotypes with high shoot growth will be useful for breeding cultivars that sustains plant growth under nutrient poor soils. INTRODUCTION Majority of high yielding and nutritive responsive chickpea varieties are evolved on soils with adequate supply of nutrients, especially phosphorus. Resource poor farmers cultivate chickpea on soils of low fertility status particularly low -P conditions. P-fertilizer use efficiency of Indian soils is also low due to high P-fixing capacity of soils which in turn reduce Symbiotic Nitrogen Fixation (SNF) as well as decrease in grain yield and its quality. Hence, identification of chickpea accessions with better SNF under limited soil P is important to identify effective cultivars that perform better under low available P. OBJECTIVE: Evaluating the inherent symbiotic potential of chickpea minicore accessions under in-vivo/in-situ conditions RESULTS: Nodulation variants of min-core lines found common at both IIPR and ICRISAT (In-vivo study ) In-situ study: Phosphorus acquisition from soil during early plant growth ranged from 0.21 to 1.36 mg P/plant with mean value of 0.56 mg P/plant. Low phosphorus acquisition was recorded in lines ICC 5879, ICC 3230, ICC 4182 and ICC 4495 while highest acquisition of 1.35 mg P/plant was recorded in ICC 15697, ICC 15435 and ICC 10755. Nodulation rating* Accession numbers 1 ICC-6294, ICC-9002 2 ICC-2065, ICC-9590, ICC-11764 3 ICC-2072, ICC-4363, ICC-6293, ICC-6537, ICC-9643, ICC-9712, ICC-12324, ICC-12492, ICC-13764, ICC-15248, ICC-15435, ICC-15612 4 ICC-2969, ICC-3325, ICC-4533, ICC-4639,ICC-5337, ICC-6279, ICC-6306, ICC-7272,ICC-10018, ICC-13719, ICC-15294 5 ICC-2580, ICC-2990, ICC-3421, RSG-888 *Ratings used for IIPR: 0 = No nodule; 1= 0.1 to 6 nodules; 2 = 7 to 12 nodules; 3 = 13 to 18 nodules; 4 = 19 to 24 nodules; 5= >24 nodules; *Ratings used for ICRISAT: 0 = No nodule; 1 = 0.1 to 1 nodule; 2 = 1 to 2 nodules; 3 = 2 to 4 nodules; 4 = 4 to 6 nodules; 5 = >6 nodules High biomass accumulating accessions Low biomass accumulating accessions Accessions Nodule dry weight (mg/plant) Shoot weight (mg/plant) ICC15762 38.0 1240 ICC 2210 9.0 190 ICC13357 16.5 1115 ICC 6571 7.5 ICC12328 16.0 1085 IG6154 6.5 185 ICC12947 12.5 ICC2679 6.0 180 ICC 9137 20.5 1080 ICC 1352 160 ICC12028 23.5 1035 ICC 7184 155 ICC13523 19.5 ICC2737 2.0 150 ICC16654 54.0 1025 ICC7052 5.5 145 ICC11584 15.5 1010 ICC12654 5.0 125 ICC3410 26.0 1005 ICC15610 17.0 70 Soil Improved crop growth and yield Mesorhizobium N Fixation Infection & Nodulation MATERIALS AND METHODS DISCUSSION: In-vivo study: A total of 35 chickpea mini-core lines showed similar nodulation behavior at ICRISAT and IIPR. A direct correlation was obtained between nodule numbers and shoot and root weights. In-situ study: There was also a positive relationship between nodule numbers /plant with plant dry weight and nitrogen uptake. Higher biomass accumulation and N-uptake was also associated with high P uptake. Therefore, under conditions of P-limitation, any chickpea genotypes efficient in P-acquisition from soil and its utilization will support high SNF activity and N2 fixation. This will result into greater biomass accumulation in shoot and grain yield under subsistence pulse production system. in-vivo Experiment in-situ Experiment Assessment of nodulation potential of chickpea accessions inoculated with Mesorhizobium ciceri (IC-76) under sterile conditions Locations: ICRISAT & IIPR Design: Completely Randomized Design (CRD) Sampling points: Vegetative stage (45 DAS) Assessment of inherent nodulation potential of chickpea accessions under field conditions Locations: IARI & IIPR Design: Augmented Design Vegetative stage (45 DAS), Flowering stage (75 DAS), Harvest stage Chickpea accessions used in this study: 211 mini-core lines, 68 land races, 10 wild accessions and 2 checks (BG-256 and RSG-888) Observations: Nodule No. /plant, Nodule dry weight/plant, biomass/plant , N & P uptake REFERENCES: Swarnalakshmi K, Gopalakrishnan S, Mohan Singh, Chopra P, Chaturvedi SK, Pooniya V, Upadhyaya HD, Basu PS. (2015) Assessment of genetic variation for nodulation potential in chickpea genotypes under field conditions. III International Plant Physiology Congress on “Challenges and Strategies in Plant Biology Research” held during Dec 11-14, 2015 at Jawaharlal Nehru University, New Delhi, pp. 272. Gopalakrishnan S, Swarnalakshmi K, Srinivas V, Upadhyaya HD, Mohan Singh, Basu PS, Chaturvedi SK. (2016) Assessment of genetic variation for nodulation potential in chickpea minicore genotypes under greenhouse conditions. Asian PGPR satellite workshop on “PGPRs for Sustainable Crop Productivity during Feb 25, 2016 NASC Complex, New Delhi, pp. 585. Leveraging legumes to combat poverty, hunger, malnutrition and environmental degradation Acknowledgement: CGIAR for extending financial support under CRP-GL; ICAR, New Delhi for providing the facilities to carry out the research. Swarnalakshmi K*1, Gopalakrishnan S2, Singh M3, Chaturvedi SK3, Rathore A2, Pooniya V1, Upadhyaya HD2 and Basu PS3. * swarna_micro@iari.res.in 1ICAR-IARI, New Delhi; 2ICRISAT-Patancheru; 3ICAR-IIPR, Kanpur, India