GENETIC VARIABILITY, CORRELATION AND PATH ANALYSIS OF RICE GENOTYPES IN RAINFED CONDITION AT LAMJUNG, NEPAL

An experiment on eleven rice genotypes was designed at field of Institute of Agriculture and Animal Science, Lamjung, under randomized complete block design with three replications from June-October, 2018 to study genetic variability and character association. Analysis of variance showed significant difference among the genotypes for all the characters studied except for grain yield and fertility percent which indicates the existence of sufficient genetic variability and potential for selection and further improvement. Grain yield was significantly positively correlated with panicle length while positively and non-significantly correlated with days of flowering, leaf area and straw yield except for plant height, SPAD60, fertility percent, thousand grain weight and effective tillers. Leaf area had maximum positive direct effect on grain yield followed by panicle length, thousand grain weight and effective tillers which indicates help for selection and improvement of rice genotypes. The higher value of correlation between panicle length and grain yield is due to the direct effect of panicle length which exhibit true relationship between them. The variability study showed that there was high genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PCV) for thousand grain weight. High heritability estimates coupled with high genetic advance as per percentage of mean (GAM) was found for thousand grain weight, days of flowering, leaf area and effective tillers which indicate the control of additive gene of action and a greater scope of selection for crop improvement. The results revealed considerable phenotypic and genotypic variance among the genotypes for the traits under consideration. The value of GCV was high for thousand grain weight, moderate for leaf area, effective tiller, straw yield, grain yield, panicle length and days of flowering and low for plant height, chlorophyll and fertility percent. The value of PCV was high for thousand grain weight, leaf area, effective tiller, straw yield and grain yield and moderate for panicle length, days of flowering, PH and chlorophyll and low for fertility percent. High GCV and PCV indicate that there is possibility of traits improved through selection. Low value indicates that there is need for creation of variability either by hybridization or mutation followed by selection


MATERIALS AND METHODS OF RESEARCH
Eleven rice genotypes (viz. KHUMAL-13, NR-B-B-31-3, IR87760-15-2-3-4, NR-11032-B-B-5-3, NR-11130-B-B-B-12, NR-11289-B-16-1, NR-11137-B-B-10, KHUMAL-7, KHUMAL-4, KHUMAL-8, ANADI (Check)) was carried out in Randomized Complete Block Design (RCBD) with 3 replication in a field of IAAS, Lamjung. The size of each block was 2m *1m and spacing between row to row and plant to plant was 20cm x 20 cm. The distance between two plots is 50 cm and distance between two replications was 1m. Each hill consists of 2-3 seedlings. Nitrogen 60kg ha -1 , phosphorous 20kg ha -1 , potassium 20kg ha -1 as general recommendation for rainfed low land condition. Half dose of Nitrogen and full dose of phosphorous and potash was applied as a basal dose at transplanting and remaining half dose nitrogen was applied as split doses at 30 DAT and 45 DAT. Five plants were randomly selected from each plot in each replication and their means were used for the statistical analyses. Observations were recorded on different traits like plant height, leaf area, chlorophyll content, effective tillers/m 2 , flowering days, panicle length, 1000 grain weight, grain yield (kg ha -1 ) and straw yield (kg ha -1 ).
Phenotypic and Genotypic coefficients of variation were calculated by the method suggested by Lush (1940) and Chaudhary and Prasad (1968). According to (Sivasubramanian and Menon 1973) PCV and GCV values more than 20% are regarded as high, whereas values less than 10% are considered to be low and values between 10 and 20 % to be moderate.
It was calculated by the formula given by Falconer (1996) which is as below:
Under selection expected genetic advances where for each character at 5% selection intensity was computed by the formula described by (Johnson et. al., 1955).
Genetic advances as percent of mean was calculated to compare the extent of predicted advances of different traits under selection, using the formula GAM= ×100 (Falconer, 1996), where GAM=genetic advances as percent of mean, GA = Genetic advances under selection, X = Mean of population in which selection will be employed.

RESULTS AND DISCUSSION
Plant height (cm). Significant result was observed for plant height and Khumal-4, khumal-7 and NR11137-B-B-10 were found to be significantly superior to all others genotypes and statistically at par with NR11115-B-B-31-3, NR11130-B-B-B-12 and NR11289-B-16-1.The average mean value was 139.53 whereas check value was 139.72.
Leaf area (cm 2 ). Significant result was observed. Check value was found to be significantly superior to other genotypes whereas Khumal-13 was found to be lowest. The average mean value was 35.
Fertility percentage. Significant result was not observed. The highest fertility percentage was found in NR11289-B-16-1 whereas lowest value was found in check variety (Anadi).The average mean value was 87.2. Thousand grain weight (gm). Significant result was observed. NR11032-B-B-5-3 showed highly significant value than other genotypes and Khumal-4 and NR11289-B-16-1 showed least thousand grain weight. The check variety value was 28.73 and the average mean value was 26.14.
Panicle length (cm). Significant result was observed. Panicle length of Khumal-8 was found to be significantly superior and statistically at par with IR87760    The results revealed considerable phenotypic and genotypic variance among the genotypes for the traits under consideration. The value of GCV was high for thousand grain weight, moderate for leaf area, effective tiller, straw yield, grain yield, panicle length and days of flowering and low for plant height, chlorophyll and fertility percent. The value of PCV was high for thousand grain weight, leaf area, effective tiller, straw yield and grain yield and moderate for panicle length, days of flowering, PH and chlorophyll and low for fertility percent. High GCV and PCV indicate that there is possibility of traits improved through selection. Low value indicates that there is need for creation of variability either by hybridization or mutation followed by selection  Genetic advance as percent of mean was, however, highest for thousand grain weight followed by days of flowering, leaf area and effective tillers. Moderate for panicle length, straw yield, panicle height and grain yield whereas low magnitude of genetic advance as percent of mean was observed for chlorophyll content and fertility percent which indicates control of non-additive gene action on these traits and heterosis breeding will be useful. High heritability coupled with high genetic advance as percent mean was observed for thousand grain weight and days of flowering, leaf area and effective tiller which indicate the control of additive gene of action and a greater scope of selection for these 4 traits. Similar result was observed by (Bose et al., 2007) for thousand grain weight.

CONCLUSION
In terms of grain yield no variation was found among genotypes and with check variety and selection should be done based on yield attributing traits for further trials. The highest value of leaf area at 60 DAT and panicle length showed positive direct effect and also showed positive correlation with grain yield. Therefore, it should be considered for selection in breeding program. High heritability coupled with high genetic advance as percent mean was observed for thousand grain weight, days of flowering, leaf area and effective tillers per m 2 which indicate the control of additive gene of action and these traits can be used in further trails as there is higher expression of traits and genotypes was recreated in each generation.