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 (rg=0.9999 ⁎⁎, rp=0.997 ⁎⁎), days to heading and grain yield (rg =0.9999 ⁎⁎, rp= 0.9276 ⁎⁎), and days to maturity and grain yield (rg =0.9796 ⁎⁎, rp=0.9174 ⁎⁎). However, negative and highly significant genetic correlation was observed between plant height and 1000-grain weight (rg = -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 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 (rg=0.9999**, rp=0.997**), days to heading and grain yield (rg =0.9999**, rp= 0.9276**), days to maturity and grain yield (rg =0.9796**, rp=0.9174**).However, negative and highly significant genetic correlation was observed between plant height and 1000 grain weight (rg = -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.

Abstract-

A field experiment was conducted at National Maize Research Program (NMRP) in Rampur, Chitwan, Nepal during May-Nov 2013. The experiment was laid out in strip-split design with twelve treatments and three replications. Treatments consisted of two different tillage methods namely conventional tillage (CT) and zero tillage (ZT) as vertical factor, two different levels of residue (residue kept and residue removed) as horizontal factor and three different levels of cropping systems namely sole maize, sole soybean and maize + soybean intercropping system as sub plot factor. Manakamana-3 and Puja were the variety of maize and soybean used for the experiment respectively. The results revealed that the grain yield and yield attributing components of maize and soybean was significantly influenced by cropping systems but not by tillage methods and residue levels. The grain yield of maize obtained under sole cropping (4.76 t ha-1) was significantly higher than maize + soybean intercropping system (4.27 t ha-1). Similarly, the grain yield of sole soybean was significantly higher (1.99 t ha-1) than that of maize + soybean intercropping system (1.26 t ha-1). Moreover, the total grain yield equivalent of 6.45 t ha-1 obtained from sole soybean system was significantly higher and was followed by maize and soybean intercropping system with 4.99 t ha-1. Whereas, sole maize produced significantly the lowest maize grain yield equivalent of 3.47 t ha-1. Significantly, higher LER (1.38) was recorded with maize and soybean intercropping system over sole system (1.0). Tillage and residue levels did not affect the gross and net return and B: C ratio but the effect was found obvious due to intercropping system. Significantly higher net return (NRs.140.49 thousands ha-1) was recorded in intercropping of maize with soybean as compared to sole soybean (NRs. 89.85 thousands ha-1) which was at par with sole maize system (NRs. 80.91 thousands ha-1). Maize and soybean intercropping system produced significantly the higher (2.47) B: C ratio than sole soybean (2.28) and was at par with sole maize (2.18).

Abstract-