The present investigation was carried out with 150 rice genotypes and three check varieties namely Rajshree, Pankaj and Rajendra Neelam with the view of assessing the variability in traits related to productivity and studying the response of these varieties towards brown spot resistance under the aerobic condition. These genotypes were evaluated for brown spot incidence and yield potential by recording observation for 11 quantitative traits by using augmented randomized complete block design at Rice research farm of RPCAU, Pusa, Bihar, during Kharif season of 2019. Analysis of variance revealed significant differences amongst the genotypes for all the eleven traits studied. Based on the mean performance, 14 genotypes out of 150 genotypes were significantly superior to the best check, Rajendra Neelam, for three traits viz., grain yield/ plant, Percent Disease Intensity (PDI) and area under disease progress curve (AUDPC), which are considered key traits for the assessment of brown spot incidence. The genotypes viz., VLD 16 entry no. -5, Udyagiri entry no.-9, and SKL 6 entry no.-94 significantly exhibited high mean for majority of the traits under study. Based on the AUDPC values, genotypes Satabdi, PS-4, Haryana Basmati and SKL6 were resistant for brown spot incidence. For most of the traits studied, moderate to low value of phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) was recorded. Higher magnitude of broad sense heritability and genetic advance as per cent of mean (GAM) were perceived for days to 50% flowering, plant height, no. of tillers per plant, no. of panicles per plant, filled grains per panicle, grain yield per plant, PDI, AUDPC signifying that direct selection by these traits can be rewarding for achieving yield improvisation and resistance to brown spot disease

The present investigation was carried out including 10 parents and their 45 half diallel crosses with the objective to study the relationship between heterosis and diverse genotype. The Mahalonobis D2values resulted in grouping of 10 parents into 3 clusters. Cluster I was comprised of four genotypes, cluster II comprised of five genotypes while, cluster III was found monogenotypic. Cluster II and Cluster III had maximum mean values for 4 traits. Highest intercluster distance was also observed in these 2 cluster followed by cluster I and III . Maximum intra cluster distance was observed in cluster II followed by cluster I. The highest contribution in the manifestation of total genetic divergence was exhibited by grain iron content followed by grain zinc content. The relationship between parental diversity and heterosis indicated that majority of crosses belong to moderate divergence class. The cross P4×P5 exhibiting better parent heterosis for maximum traits also exhibited at par mean performance for 5 traits including grain yield per plant over the better parent. For grain zinc content, two crosses from high and low while, nine crosses from moderate divergence classes reported positive significant heterosis and SCA effects. For grain iron content, 1 cross with high, 2 crosses with moderate while four crosses with low divergence classes reported significantly positive heterosis and SCA effects.

Biofortification of food crops using conventional breeding or biotechnological approach is gaining momentum to alleviate micronutrient malnutrition. Rice is a nice choice for biofortification of grain iron and zinc content as this is a cheap and chief staple food for millions of peoples world-wide particularly the poor. In present study, generation mean analysis was done to estimate the nature and magnitude of gene effects for grain iron and zinc content in rice cross Khusisoi-RI-Sareku × IR 91175-27-1-3-1-3. Scaling test and Joint scaling test indicated the influence of epistasis on the expression of yield, its component traits and grain Fe and Zn content and inadequacy of additive-dominance model to explain the variation in different generations. Dominance [h] gene effect was of higher magnitude as compared to additive [d] gene effect for both grain iron and grain zinc content. Additive × additive, additive × dominance and dominance × dominance component was significant for both grain Fe and Zn content, whereas dominance × dominance component was predominant for both grain Fe and Zn content. Dominance [h] gene effect and dominance × dominance interaction acted in opposite directions, indicating duplicate type of gene action controlling the expression of both grain Fe and grain Zn content which could be a bottleneck to exploit heterosis. Heterosis breeding and recombination breeding with postponement of selection till later generations, could be effective in improving both grain Fe and grain Zn content in rice.

The present investigation was carried out to study the correlation and path analysis in thirty four genotypes of rice (Oryza sativa L.). Character association of the yield attributing traits revealed significant positive association of grain yield per plant with panicle length, number of tillers per plant, panicle length, panicle number per plant, number of grains per panicle and 1000 grain weight. Hence, selection for these traits can improve yield. The number of tillers per plant, filled grains per panicle, test weight, panicle length, total number of grains per panicle and days to maturity exhibited positive direct effect on yield. Among these characters, number of tillers per plant possessed both positive association and high direct effects. Hence, selection for this character could bring improvement in yield and yield components.

A field screening of thirty four drought tolerant rice genotypes was conducted during Kharif 2017 and Kharif 2018 with the objective to identify different genotypes under drought stress condition. Significant variation was observed among genotypes for all studied traits including leaf rolling, leaf drying and relative water content. The tolerant lines maintained high leaf water status, membrane stability and plant biomass under reproductive stage drought condition. All thirty four genotypes were distributed in nine clusters. Out of thirty four genotypes seventeen were placed in cluster I, eight in cluster II, three genotypes in cluster III while in rest of the clusters are mono genotype. The findings of this study indicate that the cluster III, IV, VI, VII and IX showed the higher distance under drought stress condition.

The present experimental work was carried out at Rice Breeding Section, Pusa, Samastipur, with twenty-two lowland genotypes which were shown in R.B.D. style and were analysed for genetic divergence with the help of Mahalanobis’s D2 statistics.Twenty-two genotypes of rice were grouped into six clusters using Tocher’s method. The cluster I consists of maximum number of genotypes forming the largest cluster followed by cluster VI having three genotypes. The intra cluster distance ranged from 0.00 to 84.45. The inter cluster distance ranged from 52. to 282.49.Thehighest intra cluster distance was observed in cluster VI (84.85) followed by Cluster Ι (67.75). Maximum inter cluster distance was observed between cluster ΙΙΙ and Cluster ΙV followed by cluster ΙΙΙ and cluster ΙV. Per cent contribution of 15 characters and towards total genetic divergence was found maximum for 1000 grain weight (35.5 per cent) followed by days to flowering (22.08 per cent), grain length (17.32 per cent). It was observed that 1000 grain weight ranked 1st maximum times (82) followed by days to flowering (51), grain length (40), plant height (36).The genotype in cluster III and cluster IV due to maximum inter cluster distance between them, exhibited high degree of genetic diversity and thus may be utilized in future for heterosis breeding programme for getting high yielding recombinants.

In view to overcome the major problem of ‘hidden hunger’ mainly caused by micronutrient deficiency, breeding for micronutrient enriched staple food crops is important. In developing countries, iron and zinc deficiencies are reported to be major health risk factor causing a high mortality rate. So, for overcoming these nutritional deficiencies through genetic improvement, F2 population of two rice crosses obtained by crossing diverse parents for micronutrients (mainly, Fe and Zn) were evaluated using randomised complete block design during Kharif, 2019 to study the relationship between different traits and to study the estimates of direct and indirect effect. Among the F2 population of cross-I, grain yield per plant exhibited significant and positive association with seeds per panicle, tillers per plant, flag leaf area, harvest index, test weight, days to 50% flowering and days to maturity while negative and significant correlation with canopy temperature. For cross-II, grain yield per plant exhibited significant and positive association with seeds per panicle, tillers per plant, plant height, flag leaf area, SPAD value, harvest index, test weight and days to maturity while significant and negative correlation with grain Zn content, grain Fe content and canopy temperature. Hence, selection for the traits showing positive and significant association with grain yield in both the crosses will be rewarding. Highest positive direct effect on yield was shown by harvest index in cross-I. So, selection based on harvest index for grain yield per plant would be the most effective strategy for improvement of grain yield. No direct positive or negative effect of grain Fe and Zn content on yield was found.

Reverse breeding (RB) is a novel plant breeding technique designed to achieve one of the most sought goal of plant breeding by directly producing parental lines for any heterozygous plant. RB generates perfectly complementing homozygous parental lines through engineered meiosis. The main objective of this review article is to understand the method of producing homozygous parental lines which is based on reducing genetic recombination in the selected heterozygote by eliminating meiotic crossing over. Male or female spores obtained from such plants contain combinations of non-recombinant parental chromosomes which can be cultured in-vitro to generate homozygous doubled haploid plants (DHs). From these DHs, complementary parents are selected and used to reconstitute the heterozygote. The main advantage of this breeding method is that it facilitates the selection of superior hybrid plants. Large population of plants can be generated and screened and superior performing plants can be regenerated indefinitely without prior knowledge of their genetic constitution. The technique will be particularly important for crops lacking large existing collections of breeding lines

The experiment was conducted at the Dr. Rajendra Prasad central agricultural university, pusa, Bihar in a randomized block design with three replications during kharif season, 2017.The present study revealed the effects of photo thermal response on rice yield to adapt better in changing climatic scenario. Thirty two genotypes of rice were evaluated to work out heritability and trait association among important morpho-physiological traits and agro-meteorological indices for yield and yield contributing traits under directly seeded condition. The results indicated that PCV was higher than the GCV for almost all the traits. High heritability was observed for spikelet fertility (95%) followed by 1000 grain weight (91%), relative water content (88%), days to fifty per cent flowering (87%), days to physiological maturity (87%), growing degree days (86%), helio-thermal unit (86%), photo-thermal unit (85%), grain yield per plant (80%) and heat use efficiency (76%) suggesting that these traits were primarily under genetic control. Correlation studies indicated a significant and positive association of grain yield with traits viz. plant height, panicle length, number of tillers per plant, number of panicles per plant and relative water content. Based on heritability and association analysis, plant height, panicle length, number of tillers per plant, number of panicles per plant, heat use efficiency and relative water content were found major contributing indices. Therefore, this should be considered as selection criteria for discrimination of outstanding rice genotypes under directly seeded condition. Original Research Article Kumari and Nilanjaya; CJAST, 31(1): 1-9, 2018; Article no.CJAST.45865 2

Selection for yield parameters is often difficult in crop breeding because yield is a complex inherited character controlled polygenically, contributed by several component traits.Twenty five genotypes of rice were evaluated under aerobic and normal conditions to study the path coefficient analysis based on fifteen morpho-physiological traits.Path analysis revealed at genotypic level that under aerobic and normal condition traits like days to 50% flowering (0.487), no. of spikelets panicle -1 (0.572), number of tillers plant -1 (0.688), relative water content in flag leaf (0.98) and maximum root length (0.832, 1.18) had highest positive direct effect whereas, proline accumulation in leaves(-0.31)had high negative direct effect under normal condition and these important plant traits must be taken into consideration when further breeding program for higher yield in rice under aerobic and normal conditions is to be planned.Characters like days to fifty percent flowering, relative water content, maximum root length and proline were noticed to exert high direct effects on grain yield plant -1 .Panicle length showed positive association with number of spikelets panicle -1 , 1000 grain weight and grain yield per plot, whereas it showed negative correlation with proline accumulation in leaves under both conditions.Hence, these traits may be helpful in selection of suitable parents for future breeding programmes.Grain yield per plot showed negative and non-significant association with days to fifty per cent flowering under control condition indicating early maturing genotypes should be preferred under water limited condition.It indicated that earliness enabled the cultivars to escape drought at the end of the growing season under water stress condition.High indirect effects of most of the traits were noticed mostly through panicle characters indicating importance of the trait as selection criteria in crop yield improvement programs.

Experiment was conducted to study heterosis for different morphological traits i.e. days to fifty per cent flowering (DFF), plant height (PH), chlorophyll content (CC), tillers per plant (TPP), relative water content (RWC), panicle length (PL), grains per panicle (GPP), 1000 grain weight (1000-GW), harvest index (HI) and yield per plant (GYP) under drought conditions with Randomized Block Design (RBD) at DRPCAU, Pusa Samastipur Bihar in 2016 Our results indicates that the maximum standard heterosis under drought condition i.e. 119.05% was recorded in (P 2 X P 8 ) for tillers per plant followed by 109.86% in (P 4 x P 10 ) for grain yield per plant, 73.53% in (P 4 x P 10 ) for grains perpanicle, 39.92% in (P 3 x P 7 ) for chlorophyll content, 27.72% in (P 1 x P 2 ) for harvest index, 27.08% in (P 3 x P 5 ) for 1000-grain weight, 24.40% in (P 3 x P 6 ) for panicle length and 10.78% in (P 1 x P 3 ) for relative water content.Some hybrids had good heterosis for specific traits such as tillers per plant, 1000 grain weight and yield per plant that can be used for the development of new hybrid rice varieties.It can be concluded that our recent genotype has great potential that can be used for development of new varieties.

The present investigation was planned to assess the principal component for yield, yield contributing traits and quality traits in thirty genotypes of rice suitable for aerobic condition. The genotypes were procured from Directorate of Rice Research, Hyderabad and were evaluated in randomized block design with three replication. Principal component analysis (PCA) indicated that three components (PC1 to PC3) accounted for about 78.809% of the total variation among traits. Out of total principal components retained PC1, PC2 and PC3 with values of 58.125%, 13.305% and 7.380% respectively contributed more to the total variation. The first principal component had high positive loading for 7 characters out of 18 viz.grain yield per plant (0.278), canopy temperature (0.278), 1000-grain weight (0.271), panicle length (0.270), critical temperature for reproductive stage (0.239), seedling vigour (0.213) and days to 50% flowering per plant (0.201) which contributed more to the diversity. Genotypes in cluster VI showed higher mean performance for most of the yield attributing characters. Therefore, selection of parents from this cluster for these traits would be effective. The result of present study could be exploited in planning and execution of future breeding programme in rice under aerobic condition.

Boro rice cultivation is a special system of rice cultivation in low productive, waterlogged, low-lying deepwater land during November-May in eastern India. In such land, neither kharif (Jul-Oct) rice nor rabi (Nov-Apr) wheat is successful because of excess water. The boro crop is usually sown in November and transplanted when the temperature starts rising from January onward. The average minimum temperature during this period varies from 8 to 12°C. Crop productivity is very high (Thakur and Mishra 1990); consequently, boro rice has become popular in Bihar and eastern Uttar Pradesh. The suitability of rice varieties for boro cultivation mainly depends on their germination, tolerance for low temperature at the seedling stage, and seedling vigor.