Genetic variability is the fundamental requirement of any crop breeding program to develop superior cultivars. The objective of this study was to estimate the genetic variability and find out the correlation among the different quantitative traits of rainfed early lowland rice. The experiment was conducted consecutively two years during 2015 and 2016 in wet season across the four different locations in Regional Agricultural Research Station, Khajura, National Wheat Research Program, Bhairahawa, National Maize Research Program, Rampur, and National Rice Research Program, Hardinath, along the Terai region of Nepal representing subtropical agroclimate. Seven genotypes including Hardinath-1 as standard check variety were evaluated in the randomized complete block design with three replications. Various quantitative traits were measured to investigate the variability and correlation coefficients. All the genotypes and locations showed significant variations for all the traits considered. Genotypic coefficient of variation was lower than phenotypic coefficient of variation for all traits studied. The magnitudes of genotypic coefficient of variations were relatively higher for grain yield, 1000-grain weight, and days to heading. The highest broad sense heritability of 94% was recorded in days to maturity and the lowest heritability of 16% was observed in plant height. Positive and highly significant correlations were found both in genotypic and phenotypic levels between days to heading and days to maturity (r_g=0.9999⁎⁎, r_p=0.997⁎⁎), days to heading and grain yield (r_g =0.9999⁎⁎, r_p= 0.9276⁎⁎), and days to maturity and grain yield (r_g =0.9796⁎⁎, r_p=0.9174⁎⁎). However, negative and highly significant genetic correlation was observed between plant height and 1000-grain weight (r_g = -0.9999⁎⁎). Thus results indicated that days to heading, days to maturity, grain yield, 1000-grain weight demonstrating higher heritability and remarkable genetic advance could be considered the most appropriate traits for improvement and selection of trait to achieve stable and high yielding early rice genotypes under rainfed environments.

Genetic variability is the fundamental requirement of any crop breeding program to develop superior cultivars. The objective of this study was to estimate the genetic variability and find out the correlation among the different quantitative traits of rainfed early lowland rice. The experiment was conducted consecutively two years during 2015 and 2016 in wet season across the four different locations in Regional Agricultural Research Station, Khajura, National Wheat Research Program, Bhairahawa, National Maize Research Program, Rampur and National Rice Research Program, Hardinath along the Terai region of Nepal representing sub-tropical agro-climate. Seven genotypes including Hardinath-1 as standard check variety were evaluated in the randomized complete block design with three replications. Various quantitative traits were measured to investigate the variability and correlation coefficients. All the genotypes and locations showed significant variations for all the traits considered. Genotypic coefficient of variation was lower than phenotypic coefficient of variation for all traits studied. The magnitudes of genotypic coefficient of variations were relatively higher for grain yield, 1000-grain weight and days to heading. The highest broad sense heritability of 94% was recorded in days to maturity and the lowest heritability of 16% was observed in plant height. Positive and highly significant correlations were found both in genotypic and phenotypic levels between days to heading and days to maturity (r _g =0.9999**, r _p =0.997**), days to heading and grain yield (r _g =0.9999**, r _p= 0.9276**), days to maturity and grain yield (r _g =0.9796**, r _p =0.9174**). However, negative and highly significant genetic correlation was observed between plant height and 1000 grain weight (r _g = -0.9999**). Thus results indicated that days to heading, days to maturity, grain yield, 1000 grain weight demonstrated higher heritability and remarkable genetic advance could be considered for the most appropriate traits for improvement and selection of trait to achieve stable and high yielding early rice genotypes under rainfed environments.

Rice is the major food crop directly related to the livelihood of majority of rural people in Nepal. Aromatic rice is one of the fundamental groups that has great significance from the nutritional and market point of view all over the world. The main objective of this study was to emphasize on the determination of major genetic parameters, genotypic and phenotypic correlations, stability analysis for yield and major quantitative traits of aromatic rice landraces. Altogether 30 aromatic rice landraces were considered in this study and that were evaluated in three locations namely Hardinath, Tarahara and Khajura with three replications. Two years of multilocation data on nine morphological traits were collected and evaluated. The genetic parameters like genetic variance, phenotypic variance, genotypic coefficient of variation, phenotypic coefficient of variation, heritability and genetic advance were estimated using the statistical methods. The highest GCV and PCV was exhibited by grain yield (23.67 and 25.7) whereas lowest GCV and PCV was found in panicle length (4.9 and 5.6) respectively. Heritability of various traits was measured from 0.76 to 0.98 where the lowest heritability was observed in panicle length and the highest was observed in both heading and maturity days. The genetic advance as percentage of means value ranging from 8.8 to 45 representing panicle length and grain yield respectively. The genetic correlation of the measured traits showed highly significant positive correlation of heading days with maturity (r=1.0004**) and straw yield (r=0.787**) as well as correlation of maturity days with straw yield (r=0.79**). In case of phenotypic correlation, highly significant positive correlation of heading days with maturity (r=0.99**) and straw yield (r=0.7611**) was obtained however there is negative but significant correlation with tillers per meter square (r=-0.296*), filled grain weight (r=-0.305*), 1000 grain weight (r=0.3115*) and grain yield (r=-0.4*). According to the stability analysis, Gouriya and Karia Kamod (bi=1.1) were found more stable. Based on the value of coefficient of determination (R2), most of accessions; Lalka Basmati, Sugandhit Dha-1, Suhpat, Gouriya, Bayerni Masino, Kalo Nunia, Balamsari Dhan, Tilki, Tulsiful and Sunaulo Sugandha were obtained stable in all the three locations in both years. Based on the Superiority Measure (Pi), Samba Masuli Sub-1 and Sugandhit Dhan-1 showed lower Pi values of 132556.16 to 377994.35 hence identified as most stable varieties. This study identified the genetic parameters that provides the useful information for breeding of rice varieties, correlation among the major traits and stability of some aromatic landraces Gouriya and Karia Kamod obtained in all the environments. Thus, findings of this study are highly helpful for future studies to identify desirable traits and genotypes in the further varietal development works in coming days.

Aromatic group of rice comprises fine, medium, long and extra-long grain that has rich in agro-biodiversity, carries historical and cultural significance in Nepalese society. The objective was to identify stable, high-yielding aromatic rice landraces for Nepal Thirty aromatic rice landraces including two released varieties as standard checks were evaluated at three locations during 2020 and 2021. The experiment was laid out in a Randomized Complete Block Design with three replications. The combined analysis of variance indicated differences among genotypes and genotype-environment interactions for grain yield. The additive main effects and multiplicative interaction (AMMI) analysis revealed that genotypic effects for 69%, genotype × environment interaction effects for 28% and environmental effects accounted for 3% of the total sum of squares. Similarly, GGE biplot analysis showed that the principal components (PC1 and PC2) accounted for 53% and 47% of the GGE sum of squares, respectively. Based on AMMI1, AMMI2 biplots, and GGE biplots, the genotypes Samba Masuli Sub-1 and Sugandhit Dhan-1 were identified as the high yielding and stable fine and aromatic rice landraces. Other promising genotypes are Damari Dhan, Tilki, Hiupuri, Kalo Basmati, Gouriya, and Brahmamusi Dhan. Specifically, Samba Masuli Sub-1 demonstrated the highest grain yield performance at the NRRP, Hardinath, while Sunaulo Sugandha and Balamsari Dhan excelled in the Tarahara and Khajura environments, respectively. In PCA analysis, four PCs showed significant eigen value >1.0 contributing more than 84% of total variance. Biplot analysis reflected that 1000 grain weight, panicle length, heading and maturity days, and grain yield showed greater variation among the landraces. The results provide a robust basis for the further evaluation and verification of this findings in advance stage trials. The superior and outstanding landraces with higher yields and aroma are potential future varieties that can be either use directly as varieties after selection or utilize in future breeding programs for the development of new aromatic rice varieties.