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Genetic divergence is a useful tool for choosing the parents to employ in a hybridization program. The current study was conducted at Agricultural College, Aswaraopet, Telangana, to evaluate genetic diversity among 30 rice genotypes during Kharif 2021 using D2 analysis under a semi-dry system. Based on the analysis, thirty genotypes were divided into ten clusters based on D2 values. Cluster II was found largest with twelve genotypes followed by cluster I with ten genotypes and clusters III, IV, V, VI, VII, VIII, IX, and X had one genotype each, indicating that there was a sizable amount of variation among the genotypes. Cluster II (284.13) had the highest intra-cluster D2 value, followed by cluster I. (242.63) while the highest inter-cluster distance was found between Cluster VIII and IV (1503.42) followed by cluster VI and IV (1316.83), cluster VI and III (1316.15), cluster IX and IV (1303.55), cluster VIII and X (1261.09), cluster VIII and IX (1132.95), V and III (1113.91), and cluster VII and V (1101.7) suggesting that crosses involving lines from these clusters would produce wider and more desirable recombination. The average inter-cluster distance for Cluster VIII and VI was the lowest (231.01), followed by Cluster IX and X (394.3) and Cluster III and IV (397.72). The genotypes of these clusters have the most gene complexes, as shown by the shortest inter-cluster distance. The findings revealed that root biomass contributed the most to genetic divergence (24.59 percent), ranking first followed by total biomass (21.60%), root length (17.70%) and grain yield/plant (14.02%), culm strength (8.04%), plant height (5.74%), 1000 grain weight (4.36 %). The traits viz., root biomass, total biomass, root length, grain yield/plant, and culm strength contributed 85.95% of the total deviation and need to be exploited to develop varieties suitable for the semi-dry system in rice. The genotypes BPT 5204, WGL 697, RNR 21278, RNR 28361, WGL 915, PR 126, and JGL 28545 were to be better for further hybridization programs to develop varieties for the semi-dry system.

Thirty hybrids along with their parents (B and R lines) and standard checks viz., MTU 1001 and 27P63 were evaluated for grain yield and related traits to study combining ability and heterosis in rice. The mean performance of the hybrids for most of the characters was found higher than that of parents. The analysis of variance revealed significant differences among lines, testers and hybrids for most of the characters studied. SCA variances were found lower than GCA variances for most of the characters and average degree of dominance was far from unity indicating the predominance of additive gene action for these traits. However, for effective bearing tillers and spikelet fertility the average degree of dominance was very near to unity inferring the predominance of non-additive genetic components for these traits. The gca effects revealed that the lines, RNR 25783 and RP 5980-109-12-9-27 had significant gca effects in desired direction for yield and yield attributing traits whereas the tester, CMS 59A was a good general combiner. SCA effects showed that the hybrid, JMS 13A × RNR 19361 was found to be good specific combiner for grain yield per plant and spikelet fertility. Similarly, the hybrids, CMS 59A × SYE 503-78-34-2, CMS 46A × WGL 347 and JMS 13A × RP 5980-109-12-9-27 were identified as good specific combiner for grain yield and yield contributing characters. Based on heterotic estimates, five hybrids viz., CMS 59A × RNR 25783, CMS 59A × WGL 14, JMS 13A × RNR 25783, CMS 59A × RNR 25776, JMS 13A × RP 5980-109-12-9-27 were identified as promising with more than 5% and 20% yield advantage over hybrid and varietal checks, respectively.

In the present study genetic diversity among 40 rice genotypes was evaluated using Mahalanobis D2 statistic based on morphological markers. Based on cluster analysis, the germplasms were grouped into 4 clusters of which Cluster I comprising of 23 genotypes was the largest group followed by the cluster II comprising of 15 genotypes, the clusters III and IV were represented by single genotype indicating high degree of heterogeneity among the genotypes. Maximum intra cluster distance observed in cluster II is (146.8) followed by cluster I (112.9) indicating the existence of variability among the genotypes within these clusters. The highest inter-cluster distance was observed between cluster IV and III (606.5), While the lowest was noticed between cluster II and III (222.9), describing that the genotypes included in these clusters were closely related. The kernel length, kernel length after cooking, kernel breadth, gel consistency, days to 50% flowering and plant height together contributed 90.1% towards total divergence. Therefore, these characters should be given importance during hybridization and selection of segregating populations. The genotypes falling in different clusters with the high mean for grain yield and other component characters can be utilized for the hybridization programme to obtain elite segregants.

The present investigation was carried out for yield and quality related traits in the F2 and F3 populations of twenty eight rice cross combinations developed from five aromatic (Pusa 1121, Improved Pusa Basmati, Basmati 370, Sumathi and RNR 2354) and three non-aromatic (BPT 5204, Akshyadhan and NLR 145) parents. In F2 generation, among the yield characters, the highest values of phenotypic co-efficient of variation (PCV) and genotypic co-efficient of variation (GCV) were recorded for the number of filled grains/panicle followed by grain yield per plant while the lowest values were recorded for days to 50% flowering. However, for the grain quality characters the highest PCV and GCV values were recorded for head rice recovery and lowest for kernel breadth. In F3 population, higher magnitudes of PCV and GCV were recorded for the number of filled grains/panicle and panicle weight, indicating greater scope of obtaining high selection response for these traits. High heritability in narrow sense along with medium to high genetic advance was noticed for the traits like days to 50% flowering, 1000 grain weight and the kernel traits.

F3 generations of 28 crosses were evaluated for the genetic parameters in rice. The estimates of GCV were lower than the respective PCV, indicating the influence of environmental factors on the expression of the quantitative and qualitative traits studied. In F3 population, higher magnitudes of PCV and GCV recorded for no. of filled grains/panicle and panicle weight and indicated greater scope of obtaining high selection response for these traits. The high estimates of heritability in broad sense with moderate genetic advance were recorded for the yield components viz., panicle length, filled grains per panicle and 1000 grain weight and kernel traits viz., kernel length and L/B ratio, which suggested that additive genetic effects played greater role as such, the chances of obtaining desirable segregants with good yield potential and quality are very bright through direct selection.

The knowledge of genetic variability in a given crop species for characters under improvement is important in any plant breeding programme. Genetic parameters for yield and its correspondent characters in rice were estimated from a trial conducted at Rice Research Centre, Agricultural Research Institute, PJTSAU, Hyderabad during Kharif, 2017. In the present study, four Cytoplasmic Male Sterility lines, eight male lines and thirty-two hybrids and four checks were evaluated. The analysis of variance showed highly significant differences among the genotypes for all the characters, indicated the presence of enormous amount of genetic variability. High phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) was observed for number of grains per panicle (26.55, 23.16) and grain yield per plant (21.67, 21.24) indicating that these characters could use as selection for crop improvement. High heritability coupled with high genetic gain as percentage of mean was observed for number of grains per panicle (70.26, 41.61) and 1000 grain weight (61.9, 29.52) which showed presence of additive gene action and thus the chances of fixing by selection will be more to improve such traits through pure line selection in the evaluated genotypes.