Pak. J. Bot., 51(1): 73-80, 2019. DOI: 10.30848/PJB2019-1(28) CORRELATION AND PATH ANALYSIS OF MORPHOLOGICAL PARAMETERS CONTRIBUTING TO YIELD IN RICE (ORYZA SATIVA) UNDER DROUGHT STRESS MUHAMMAD ASIM BHUTTA 1 , SANA MUNIR 1 , MUHAMMAD KAMRAN QURESHI 1* , AHMAD NAEEM SHAHZAD 2 , KASHIF ASLAM 3 , HAMID MANZOOR 3 AND GHULAM SHABIR 3 1 Department of Plant Breeding & Genetics, Faculty of Agricultural Sciences & Technology, Bahauddin Zakariya University, Multan 2 Department of Agronomy, Faculty of Agricultural Sciences & Technology, Bahauddin Zakariya University, Multan 3 Institute of Molecular Biology & Biotechnology, Bahauddin Zakariya University, Multan * Corresponding author’s email: m.k.qureshi81@gmail.com Abstract Current experiment is conducted to study correlation and path analysis among morphological traits and their contribution towards yield under normal and drought stress using twenty diverse rice genotypes at Department of Plant Breeding and Genetics, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan. Genotypes were significantly varied ( p<0.01-0.05) in yield and yield related traits. In addition, growth (Plant height, r 2 = 0.17**) and yield attributes such as panicle length (0.49**), grains/ panicle (0.69**), grain weight/ panicle (0.99**), tillers/ plant (0.14) and 1000-grain weight (0.11*) were positively correlated in all genotypes under normal or drought stress conditions. Among genotypes, highest plant height was observed in Basmati-140 (43.13cm) comparatively to lowest was found in Sufaida 20 (26.27cm) under drought condition. Plant height was significantly reduced under drought stress than control condition in Munji 78B-1 from 64.71cm to 35.30cm, respectively. Drought drastically affected the yield/plant in different genotypes. Under drought stress, Harandi-379, Munji-78B-1 and Basmati-242 performed well for yield/plant with values of 7.54g, 7.69g and 9.28g, respectively. Grain weight/panicle showed highest positive effect (0.914 and 0.788) on yield/ plant and followed by spikelet fertility (0.022 and 0.056) under both drought and normal conditions, respectively. Results suggest that grain weight/panicle, 1000 seed weight and plant height can be used as selection indices for drought resistance. Key words: Correlation, Path analysis, Morphological traits, Yield, Oryza sativa, Drought stress. Introduction Rice, a cereal crop, ranks second among staple food crops in Pakistan. It is mainly grown for its grain containing about 80% starch, 7% protein and 12% water (Hossain et al., 2015). In addition to minerals such as copper, iron, calcium, magnesium, manganese and zinc, the rice grain contains niacin, riboflavin and thiamine (Oko et al., 2012). In international market, Pakistani rice is considered best on account of its aroma and good cooking quality. Basmati and coarse type shared 40% and 60% of total rice production, respectively in Pakistan. Rice shared 0.6% and 3.1% to cost added in gross domestic product and value addition in agriculture, respectively (Anon., 2016). About 42 stresses, both biotic and abiotic, affect the rice yield (Sarkar et al., 2006). Drought is a worldwide problem that affects the grain production and quality (Lafitte et al., 2002). Global climate changes manipulate the frequency and extent of hydrological fluctuations, causing floods and drought (Easterling et al., 2007). Drought refers to a condition in which deficiency of rainfall occurs for such a longer period that causes moisture depletion in soil and ultimately decreases in leaf water potential of plant (Kramer, 1980). Many breeders define drought as “a sufficient decrease in water availability in soil that can cause yield reduction” (Fukai & Cooper, 1995; Comas et al., 2013). Drought drastically affects grain quality and overall yield production by affecting its physiology, morphology, anatomy and biochemistry (Lima et al., 2015). Membrane structure, photosynthesis and pigments contents are affected by drought (Benjamin & Nielsen, 2006). Rice may suffer from water stress either at vegetative or at reproductive stage. During vegetative stage, decrease in plant height, biomass and number of tillers are affected and leaf rolling occurs in rice (Ji et al., 2012). Under water stress, phytohormones like ethylene are released by plant that inhibit leaf and root growth at initial phase (Basu et al., 2016) and stress occurring before flowering reduces plant yield. At reproductive stage, drought affects grain development and spikelet infertility results in unfilled grains (Kamoshita et al., 2004; Botwright et al., 2008). Drought is responsible for leaf shrinkage and it affects tillering capacity and photosynthesis in plants (Kramer & Boyer, 1995). During grain filling stage, water stress causes early senescence in plant which reduces its filling period (Plaut et al., 2004) leading to yield reduction (Qureshi et al., 2018). Developmental stage, specie type and drought severity influence the level of susceptibility in crop plant (Demirevska et al., 2009). Small root system and less cuticular wax make rice susceptible to drought (Hirasawa, 1999). Hence it is necessary to develop tolerant rice varieties which grow well and give better yield even under drought stress (Pantuwan et al., 2002). Several morphological traits, which are controlled by multiple genes, are genetically correlated with yield. Therefore, genotypic and phenotypic correlation estimates can provide facts to the breeders about type of association among yield and