INTRODUCTION Rice is a member of the Oryza genus in the Gramineae family and is a staple meal for over half of the world's population.High yield has become a main goal in rice breeding programmes as the world's population grows. The main source of carbohydrate production is flag leaf and its penultimate leaves (Al-Tahir, 2014).Flag leaf contributes 45% of rice grain yield because it mostly provides photosynthetic products to the panicle. Plant breeding may result in a significant improvement in grain output by improving flag leaf features. The length of the flag leaf has long been considered as one of the most important variables in the development of novel rice plant ideotypes with high yielding potential (Vangahun, 2012). Leaf length varies greatly in rice and is closely related to leaf angle. Droopyness is related with long leaves, whereas erectness is associated with short and tiny leaves (Vangahun, 2012). The angle of the flag leaf had a significant impact on rice grain output because of light interception will change with the angle (Prakash et al. 2011). Through ideotype breeding, the ideal leaf length, width, thickness, angle, and area were addressed for generating high-yielding rice cultivars (Peng et al. 2008). As a result, we assessed the flag leaf and its penultimate leaves for their association with grain yield. MATERIAL AND METHODS During kharif, 2017 eleven CMS lines along with their maintainer lines were raised at Rice Research Center, PJTSAU, Hyderabad. All the lines were grown in three replications in randomized block design with spacing of 20 x 15 cm. To raise a successful crop, the entire suggested package of practices was followed. Eleven Cytoplasmic male sterile lines and five local varieties were utilized as test subjects for determining the leaf features of the top three leaves (1st leaf or flag leaf, 2nd leaf or penultimate leaf and 3rd leaf), viz., length, width, angle, thickness SPAD and CCI of the leaves. At reproductive stage, the lengths of the top three leaves on the main culm were measured in centimeters (cm) using a coded measuring device and classified as: very short (<21 cm), short (21–40 cm), intermediate (41–60 cm), long (61–80 cm) and extra long (>80 cm) (Jockson 2010). At reproductive stage, the width of the top three leaves was measured in cm at the widest portion of the leaf blade with a coded measuring instrument and classified as: narrow (<1 cm), intermediate (1–2 cm) and broad (>2 cm) (Jockson, 2010). Palaniswamy and Gomez's (1972) formula was used to calculate the area of the flag leaf, second leaf, and third leaf: Leaf Area = (length × width) × K Constant (K)= 0.75 The leaf angle was calculated by marking the position of each leaf's tip and collar on the paper against the main culm, which served as a vertical line. A line was drawn between the two spots, and an angle was measured with a protractor between the line and the vertical axis (Yoshida et al. 1976) and The angle of the flag leaf at full bloom determines the categorization, where the flag leaf angle ranges from 0-30 degrees for upright, 31-60degrees for intermediate, 61–90 degrees for horizontal, and 91 degrees or greater for downward. (Chang et al., 1965). Digital callipers were used to measure leaf thickness, which was given in millimeters (Kiran et al., 2013). SPAD and CCI were captured at the blossoming stage utilisingMC-100 chlorophyll concentration meter. Panicles from 1 m2 were collected at physiological maturity, sun dried, threshed, cleaned, and the weight of grains was recorded and expressed in g m-2 then computed to q.ac-1 (Yang et al., 2007). RESULTS AND DISCUSSION The angle of the third leaf was greater than the angles of the second and first leaves among the top three leaves in CMS lines and checks (Table 1). CMS 64B has the highest flag leaf angle of 46.67o among the CMS lines and checks, followed by CMS 23B (33.33o) and CMS 59B (21.67o). JGL11470 had the maximum angle of 33.33o in the second leaf, followed by CMS64B (30o). The third leaf angle was the greatest in CMS 23B (43O) followed by RNR15048(41.67o). Among the genotypes CMS 23B and JGL18047 were intermediate type and remaining were had erect type flag leaves. Correlation studies revealed angle of flag leaf has significantly negatively associated with grain yield (Table 2). This could be because the most effective arrangement for optimal photosynthesis is erect leaves. When LAI is large or sunlight is abundant, erect leaves are the most efficient arrangement for maximum photosynthesis. They have a higher leaf area index, which increases light interception for photosynthesis, and more upright leaves, which allow solar energy to penetrate into the lower levels of the aerial structure of plants (Vangahun, 2012). The length of the third leaf was greater than the length of the second and first leaves among the top three leaves in CMS lines and checks (Table 1). JMS11B had the longest flag leaf of 36.60 cm among the CMS lines and checks, followed by CMS59B (35.87 cm) and MTU1010 (35.71 cm). JMS13B had the longest second leaf (49.40 cm), followed by CMS64B (48.37 cm). The longest 3rd leaf was present in JMS14B (51.70 cm), followed by CMS59B (48.13 cm). Because mutual shading is reduced and light interception is more efficient, many breeders discard lines with unusually long flag leaves extending 30 cm or more. Short leaves are more erect and evenly distributed throughout the canopy, so mutual shading is reduced and light interception is more efficient (Vangahun, 2012). The association between flag leaf length and yield was positive (r=0.832) and very significant; plants with longer flag leaf length may have elongated panicles, resulting in more primary and secondary rachis, and thus more grain in the panicle, which improved the cultivar's production (Rahman et al., 2013). The width of the first leaf is greater than the width of the second and third leaves among the top three leaves (Table 1). Among the CMS lines and checks, wider flag leaf was presentinJMS13B (1.93 cm), JMS17B (1.77 cm) and CMS14B (1.73 cm) that was on par with each other. In the instance of JGL11470, the width of the second leaf was the widest (1.53 cm) followed by CMS23B (1.37 cm), JMS17B (1.30 cm) JMS18B (1.30 cm) that was on par with each other. JMS18B has the widest 3rd leaf, measuring 1.33 cm. According to Tari et al. (2009), the flag leaf must be wide and upright in order to increase rice grain yield. Among the CMS lines and checks, the thickest flag leaf was present in JMS11B (0.23 mm), followed by CMS59B (0.20 mm). Flag leaf thickness has shown significantly positive correlation with SPAD, CCI (chlorophyll content index) and grain yield. This may be due to thicker leaves may accommodate more chlorophyll content per unit area which results in improved photosynthesis. Guru et al. (2017) also reported similar results. In rice, leaf thickness has a positive relationship with single-leaf net photosynthetic rate (Pn), while the Pn of the flag leaf after heading has a positive relationship with grain yield (Vangahun 2012). Flag leaf thickness has also shown significantly positive correlation with flag leaf length (r=0.557) and significantly negative correlation with flag leaf angle (r=-0.553). Liu et al. (2014) observed that leaf length and leaf thickness have a significant positive correlation, it showed that thicker leaves were good for increasing single leaf area and that leaf thickness was inversely linked with leaf angle, implying that thicker leaves were favorable to the upright canopy. Among the CMS lines and genotypes highest flag leaf area of 43.33 cm2 was recorded in JMS11B, followed by CMS59B (41.13 cm2) and MTU1010 (40.54 cm) which were on par. Flag leaf area has shown significantly positive correlation with grain yield. Flag leaf area was picked by Tari et al. (2009) as a factor for boosting rice grain output. Flag leaf chlorophyll content index and SPAD values has recorded maximum in JMS11B followed by CMS59B and JGL11470 (Table 1). Flag leaf chlorophyll content index (CCI) and SPAD values has shown that grain yield and flag leaf thickness have a substantial positive correlation (Table 3) significant differences were observed among the genotypes with respect to grain yield (Table 1). The genotype with the highest grain yield out of all the genotypes was JMS11B (47.04 q.ac-1), followed by CMS59B (46.98 q.ac-1) and MTU1010 (39.34 q.ac-1), which was on par and significantly superior to other genotypes. Flag leaf morphological parameters like size and shape, as well as physiological traits like chlorophyll content index and SPAD value, have long been thought to be major predictors of grain output in cereals (Xue et al., 2008).