Research Article Multivariate Analysis of Grain Yield and Its Attributing Traits in Different Maize Hybrids Grown under Heat and Drought Stress Fawad Ali, 1 Naila Kanwal, 1 Muhammmad Ahsan, 1 Qurban Ali, 2 Irshad Bibi, 3 and Nabeel Khan Niazi 3 1 Department of Plant Breeding and Genetics, University of Agriculture Faisalabad, Faisalabad 38040, Pakistan 2 Centre of Excellence in Molecular Biology, University of the Punjab, Lahore 54590, Pakistan 3 Institute of Soil and Environmental Sciences, University of Agriculture Faisalabad, Faisalabad 38040, Pakistan Correspondence should be addressed to Fawad Ali; fawadniazi a@yahoo.com and Naila Kanwal; nailakanwalpk@yahoo.com Received 29 June 2015; Revised 18 October 2015; Accepted 8 November 2015 Academic Editor: Karl-Josef Dietz Copyright © 2015 Fawad Ali et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Tis study was carried out to evaluate F1 single cross-maize hybrids in four crop growing seasons (2010–2012). Morphological traits and physiological parameters of twelve maize hybrids were evaluated (i) to construct seed yield equation and (ii) to determine grain yield attributing traits of well-performing maize genotype using a previously unexplored method of two-way hierarchical clustering. In seed yield predicting equation photosynthetic rate contributed the highest variation (46%). Principal component analysis data showed that investigated traits contributed up to 90.55% variation in dependent structure. From factor analysis, we found that factor 1 contributed 49.6% variation ( < 0.05) with primary important traits (i.e., number of leaves per plant, plant height, stem diameter, fresh leaves weight, leaf area, stomata conductance, substomata CO 2 absorption rate, and photosynthetic rate). Te results of two- way hierarchical clustering demonstrated that Cluster III had outperforming genotype H 12 (Sultan × Soneri) along with its most closely related traits (photosynthetic rate, stomata conductance, substomata CO 2 absorption rate, chlorophyll contents, leaf area, and fresh stem weight). Our data shows that H 12 (Sultan × Soneri) possessed the highest grain yield per plant under environmentally stress conditions, which are most likely to exist in arid and semiarid climatic conditions, such as in Pakistan. 1. Introduction Maize (Zea mays L.) is one of the most commonly cultivated crop worldwide [1, 2]. Heat and drought stress have emerged as a common problem worldwide which can reduce maize crop productivity [3]. Te right choice of maize genotypes for a given region is a crucially important practice to obtain high grain yield of diferent maize hybrids [4]. Quantitative evaluation of traits in the feld experiments is dependent on soil heterogeneity [5], genetic variability of the experimental material [6], and biotic and abiotic factors [7]. In addition to heat and drought stress, intraseasonal and interseasonal water availability variation are another common and signifcant problem that can lead to decrease grain yield of maize hybrids in various regions of the world [8]. Several studies have been conducted to understand the maize plant phenology (plant development rate) and physiology (functioning of internal processes) in diferent seasons and regions [9]. It is a well- known fact that high temperature stress and low irrigation regimes can limit certain factors in maize plant, thereby decreasing plant biomass below the target (7.5 tons/acre) levels [10, 11]. Considering these important, although partially resolved, research aspects, we conducted a feld study in four consec- utive crop growing seasons (2010-2011 and 2011-2012). Te objective of the present study was to demonstrate combined efect of seasonal variation on maize grain yield and its attributing traits in maize hybrids under high temperature (>45 ∘ C) and drought stress conditions. Te two-way hier- archical clustering was used for making clusters within and Hindawi Publishing Corporation Scientifica Volume 2015, Article ID 563869, 6 pages http://dx.doi.org/10.1155/2015/563869