DOI: 10.1007/s11099-016-0642-7 PHOTOSYNTHETICA 55 (1): 41-49, 2017 41 Evaluation of wild Arachis species for cultivation under semiarid tropics as a fodder crop P.C. NAUTIYAL *,+ , A.L. RATHNAKUMAR * , G. KULKARNI ** , and M.S. SHESHSHAYEE *** Directorate of Groundnut Research, Post bag 5, Junagadh – 362001, Gujarat, India * Department of Botany, Junagadh Agricultural University, Junagadh – 362001, Gujarat, India ** Division of Crop Physiology, College of Agriculture, GKVK, UAS, Bangalore – 560065, Karnataka, India *** Abstract Wild Arachis genotypes were analysed for chlorophyll a fluorescence, carbon isotope discrimination (ΔC), specific leaf area (SLA), and SPAD readings. Associations between different traits, i.e., SLA and SPAD readings (r = –0.76), SLA and ΔC (r = 0.42), and ΔC and SPAD readings (r = 0.30) were established. The ratio of maximal quantum yield of PSII photochemistry (F v /F m ) showed a wider variability under water deficit (WD) than that after irrigation (IR). Genotypes were grouped according to the F v /F m ratio as: efficient, values between 0.80 and 0.85; moderately efficient, the values from 0.79 to 0.75; inefficient, the values < 0.74. Selected genotypes were evaluated also for their green fodder yield: the efficient genotypes ranged between 3.0 and 3.8, the moderately efficient were 2.6 and 2.7, the inefficient genotypes were of 2.3 and 2.5 t ha –1 per year in 2008 and 2009, respectively. Leaf water-relation traits studied in WD and IR showed that the efficient genotypes were superior in maintenance of leaf water-relation traits, especially, under WD. Potential genotypes identified in this study may enhance biomass productivity in the semiarid tropic regions. Additional key words: efficiency of photosystem II; green biomass; leaf water relation traits; water scarcity; water-use efficiency. Introduction The genus Arachis has evolved in some unusual niches, ranging from semiarid areas of northeastern Brazil to Carrado pockets in the Amazon forest, to low, deep-soil alluvial plains and humus clay swamps of the Gran Pantanal. Under such a wide ecological diversity, these species have been acclimatized for climate prevailing in the tropical and subtropical regions, especially water scarcity environments and poor soil conditions. In addition, these species could easily establish effective association with Bradyrhizobium in root nodules which increases soil fertility (Valls 1983). Wild Arachis species are considered best legumes for pasture improvement or forage crop. The most valuable attribute, which several wild species possess, is persistence under grazing that makes them special in development of permanent pastureland (Simpson 1991). On the other hand, genetic base of groundnut cultivars has become quite narrow and wild Arachis species are only source for variability in morphological, physiological, and genetic traits leading to detectable differences at an isoenzyme level under normal irrigation conditions (Lu and Pickersgill 1993). Moreover, these species have been identified as a donor source for various biotic (Subrahmanyam et al. 1985, Bera et al. 2014, Michelotta et al. 2015) and abiotic (Nautiyal et al. 2008, Upadhyay et al. 2011, Bera et al. 2013) stresses. The climate change scenario also demands to increase biomass production by developing pastureland or cultivation of wild Arachis species for fodder purpose (Nautiyal et al. 2008). Phenotyping for water use or photosynthetic efficiency requires a high throughput screening technology which is still in a stage of development. So far, in groundnut, water- use efficiency has been determined by analysing various traits, e.g., ∆C (Hubick et al. 1986), SLA (Nautiyal et al. 2002), and SPAD readings (Nageswara Rao and Wright ——— Received 19 March 2015, accepted 19 May 2016, published as online-first 27 May 2016. + Corresponding author; e-mail: prakashc@iari.res.in, pcnautiyal52@yahoo.co.in Abbreviations: ANOVA – analysis of variance; DM – dry mass; Chl – chlorophyll; E – transpiration rate; FM – fresh mass; F0 – minimal fluorescence yield of the dark-adapted state; Fm – maximal fluorescence yield of the dark-adapted state; Fs – steady-state fluorescence yield; Fv – variable fluorescence; Fv/Fm – maximal quantum yield of PSII photochemistry; F0/Fm – thylakoid membrane stability; gs – stomatal conductance; ICRISAT – International Crop Research Institute for Semi–arid Tropics; IR – irrigated (after irrigation); LA – leaf area; PCA – principal component analysis; PDB – PeeDee belemnite; RWC – relative water content; RCBD – completely randomized block design; SD – standard deviation; SPAD – soil plant analysis development; TM – turgid mass; WD – water-deficit (before irrigation); ψw – water potential.