Heritability of Main Yield Traits in Red-seed Watermelon and Their Correlation Analysis

[Objectives]This study was conducted to provide a reliable theoretical basis for the correct formulation of breeding programs for red-seed watermelon and the effective breeding of hybrid offspring.[Methods]With local varieties and inbred lines of red-seed watermelon as test materials,the generalized heritability of fruit number per plant,single-fruit weight,single-fruit seed number,single-fruit seed weight,seed kernel weight,1000-seed weight,kernel-producing ratio,seed production ratio and seed volume were estimated by variance analysis;and the heritability,genetic variation coefficients,and correlation of the nine yield traits in 43 red-seed watermelon varieties were studied.[Results]The generalized heritability of fruit number per plant,single-fruit weight,single-fruit seed number,single-fruit seed weight,seed kernel weight,1000-seed weight,kernel-producing ratio,seed production ratio and seed volume were 12.86%,80.14%,75.96%,74.39%,48.01%,17.12%,24.97%,18.60%,and 37.07%,respectively.The heritability of single-fruit weight,single-fruit seed number and single-fruit seed weight was higher,and early-generation individual selection could achieve a better effect on them;and 1000-seed weight and kernel-producing ratio had a higher coefficient of genetic variation,indicating a high selection potential.[Conclusions]Indirect selection could be achieved for traits such as the single-fruit seed number,single-fruit seed weight,seed kernel weight,and seed volume by selecting the single-fruit weight.In the process of red-seed watermelon breeding,traits with high heritability can be selected in early generations of hybrids,thus playing the role of early-generation orientation.

Genetic Variability, Heritability and Correlation of Some Morphological and Yield Components Traits in Potato (Solanum tuberosum L.) Collections

The study was conducted with the main objective to evaluate the genetic variability, heritability, and clustering pattern exploration of morphological and yield related traits in potato (Solanum tuberosum L.) collections in the bimodal rainfall agroecological zone of Cameroon using a Randomized Complete Block Design (RCBD) with three replications. The data obtained on morphological and yield traits were subjected to analysis of variance (ANOVA). The results showed that the viability rate of the collections varied from 77.78% to 96.55% respectively for the Maffo and Desiree collections, while the greatest number of tubers per plant varied from 4 to 18 respectively for Synergie and Desiree. The emergence rate varies from 60% to 1.66% respectively for Maffo et Doza collections. However, Desiree presents the highest TL (96.55) while Maffo shows the lowest value (77.78%). The yield per hectare varied from 1.14 to 9.3 t/h for Maffo and Doza respectively. For all the characteristics observed, Phenotypic Coefficients of Variation (PCV) were higher than Genotypic Coefficients of Variation (GCV) suggesting the role of environment in the expression of traits under observation. The highest GCV and PCV 47.55 and 58.94 respectively were observed for Diameter at the collar (DC). Most of the traits showed high GAM (>20%)) except Average Tuber Length (ATL) with a moderate value (19.8). In terms of vegetative development, the Desiree variety showed the highest performance. Based on the growth and yield results, Doza seems to be the most recommendable crop in the study area.

Estimates of Heritability and Genetic Correlations for Growth Traits in Chinese Shrimp Fenneropenaeus chinensis

[Objective] The aim was to estimate the heritability and genetic correlations of growth traits of Chinese shrimp Fenneropenaeus chinensis so as to provide basis and technical parameters for the breeding and selecting of Chinese shrimp.[Method] 51 full-sib families（including 35 half-sib families）of the Chinese shrimp F.chinensis were obtained by artificial insemination.Four growth traits of these families were measured,including body length,cephalothorax length,abdorminal segment length and body weight.According to quantitative genetics theory,the heritability of each growth trait,genetic and phenotypic correlation among these traits was statistically studied.[Result] The heritability was 0.36-0.51 for body length,0.14-0.24 for cephalothorax length,0.25-0.50 for abdominal segment length,and 0.04-0.29 for body weight.High and positive genetic correlations were obtained among growth traits.The genetic correlation between body weight and abdominal segment length was the highest（0.92）,followed by body length and abdominal segment length（0.91）,body length and body weight（0.88）,body weight and cephalothorax length（0.87）,abdominal segment length and cephalothorax length（0.86）,while the genetic correlation between body length and cephalothorax length was the lowest（0.83）.[Conclusion] The phenotypic correlation of body length,cephalothorax length,abdorminal segment length and body weight of Chinese shrimp F.chinensis were from 0.80 to 0.90 with extremely significant difference（P0.01）among the four growth traits by t-test.

Analysis on the Combining Ability and Heritability of Main Agronomic Traits of Hybrid Glutinous Sorghum

Using 3 sterile lines and 12 restorer of glutinous sorghum as experimental materials,36 hybrid combinations（3×12 NCⅡ） were designed to analyze the combining ability and heritability of six main agronomic traits,including plant height,panicle length,growth period,1 000-grain weight,per panicle grains and per panicle grain weight.The results showed that except per panicle grain number all other five agronomic traits have remarkable or extremely remarkable general combining ability and specific combining ability.Six agronomic traits were found to be control by additive genetic effect.Most of these agronomic traits are more easily influenced by restorers than sterile lines,suggesting that more attention should be paid to select restores in hybrid glutinous sorghum breeding.The narrow-sense heritability of these agronomic traits were in order growth period plant height per panicle grain weight panicle length 1 000-grain weight per panicle grains.

Analysis of Heterosis, Combining Ability and Heritability of Cadmium Content in Brown Rice of Three-line Indica Hybrid Rice

Five cytoplasmic male sterile （CMS） lines were used as parents in an incomplete diallet cross and six restorer lines of rice design （Nc II design）. Thirty hybrid combinations with the same growth period were selected as experimental ma- terials to investigate the heterosis, combined ability and heredity of Cd content in brown rice of indica hybrid rice. According to the results, Cd content in brown rice showed a significantly negative heterosis; the general combining ability and specific combination ability of Cd content in CMS and restorer lines both reached extremely significant level （P〈0.01）, indicating that both genetic improvement of parents and e- valuation of combinations are important to the breeding of hybrid combinations with low accumulation of Cd; the broad-sense heritabitity and narrow-sense heritability of Cd content were both relatively high with slight differences, which respectively reached 97.73% and 80.10%, indicating that Cd content in brown rice mainly de- pends on the additive action of genes; in addition, parent improvement showed bet- ter effect on the selection of early generation.

Analysis on Combining Ability and Heritability of the Main Agronomic Characters for JA CMS in Brassica napus L.

Fifteen combinations crossed by five JA cytoplasmic male sterile lines （A1, A2, A3, A4, A5） and three restoring lines （R1, R2, R3） were selected to analyze the combining ability and heritability of nine main agronomic characters of Brassica na-pus L. to definite the application potential of these parent materials. The result showed that （i） the general combining ability （GCA） of male parents was R3＆gt;R2＆gt;R1 and that of female parents was A4＆gt;A1＆gt;A2＆gt;A5＆gt;A3; （i ） the special combining ability （SCA） of A2＆#215;R3 in plant height, number of branches, number of pods per plant and yield per plant was the best. The yield per plant of A2＆#215;R3, A1＆#215;R1 and A2＆#215;R1 ranked the first three places in the 15 combinations; （i i） the broad heritability of yield per plant was the highest, and that of the height of branches was the lowest. The com-prehensive characters of R3, A2 and A4 were better, which could be used to create new materials; （iv） good offspring were more likely to be chosen from the combina-tion with higher parental GCA, so the GCA and SCA should be considered com-prehensively when choosing parent and determining the optimal combinations.

Heritability and genetic correlation of survival in turbot(Scophthalmus maximus)

We analyzed the survival data of the offspring from 21 sires and 42 dams of turbot. The results show that the cumulative survival rates for turbot from 2 to 18 months range from 17.5% to 28.5% main mortality occurred during months 2-5; and the highest survival rates of families were 97.9%, 98.8%, 99.4%, 99.7% during months 2-5, 5-6, 6-8, 8-11, and ll-18, respectively, and 99.5%, being 53.5%, 23.8%, 19.5%, 14.9%, and 13.2% higher, respectively, than the mean values in each period. In all periods, the estimated heritabilities for survival were very low without significant difference from zero （P〉0.05） （values ranged from 0.06 to 0.12）, indicating low additive genetic effects. The genetic correlations of survival among families in different periods were all positive, but low in magnitude （values range from 0.03 to 0.31）. Genetic correlations between long-term survival and other periods＇ survival had negative values （-0.06 and -0.15） and three positive values （0.16, 0.12 and 0.14）. Genetic correlations between survival and weight were all positive, except for survival at months 2-5 and weight at 18 months, which was not significantly negative （-0.18）.

ZResponse to selection,heritability and genetic correlations between body weight and body size in Pacific white shrimp,Litopenaeus vannamei

To quantify the response to selection, heritability and genetic correlations between weight and size ofLitopenaeus vannamei, the body weight （BW）, total length （TL）, body length （BL）, first abdominal segment depth （FASD）, third abdominal segment depth （TASD）, first abdominal segment width （FASW）, and partial carapace length （PCL） of 5-month-old parents and of offspring were measured by calculating seven body measurings of offspring produced by a nested mating design. Seventeen half-sib families and 42 full-sib families ofL. vannamei were produced using artificial fertilization from 2-4 dams by each sire, and measured at around five months post-metamorphosis. The results show that heritabilities among various traits were high： 0.515±0.030 for body weight and 0.394±0.030 for total length. After one generation of selection, the selection response was 10.70% for offspring growth. In the 5th month, the realized heritability for weight was 0.296 for the offspring generation. Genetic correlations between body weight and body size were highly variable. The results indicate that external morphological parameters can be applied during breeder selection for enhancing the growth without sacrificing animals for determining the body size and breed ability; and selective breeding can be improved significantly, simultaneously with increased production.

Estimated reproductive success of brooders and heritability of growth traits for large yellow croaker (Larimichthys crocea) using microsatellites

We estimated the reproductive success of adult brood fish and the heritability of growthrelated traits for large yellow croaker （Larimichthys crocea）. We created two independent full-factorial cross groups （1 and 2） by crossing 4 malesx4 females and 4 males^3 females, respectively. We measured the body weight （BW）, body length （BL）, and body height （BH） of 281 individuals from group 1 and 318 individuals from group 2 at 20 months post hatch （harvest age）. We also collected a tissue sample from each individual. The parents and offspring were genotyped using six polymorphic mierosatellites. Of the 599 offspring, 99.2% were assigned to a single pair of parents. In both groups, some parent pairs produced a large number of offsprings while other pairs did not produce any offspring. The genetic diversity and putative No were lower in the offsprings than in the parents in both groups. The heritability estimates at 20-month age were 0.13±0.10 for BW, 0.19±0.13 for BL, and 0.09±0.06 for BH. The genetic and phenotype correlation between BW, BL, and BH was close to 1. The results provide basic information for selective breeding and further genetic characterization of large yellow croaker.

Variation and heritability of morphological and physiological traits among Leymus chinensis genotypes under different environmental conditions

Intraspecific trait variation and heritability in different environmental conditions not only suggest a potential for an evolutionary response but also have important ecological consequences at the population, community, and ecosystem levels. However, the contribution of quantitative trait variation within a grassland species to evolutionary responses or ecological consequences is seldom documented. Leymus chinensis is an important dominant species in semi-arid grasslands of China, which has seriously suffered from drought and high temperature stresses in recent decades. In the present study, we measured variation and heritability of 10 quantitative traits, namely the number of tillers, maximum shoot height, number of rhizomes, maximum rhizome length, rhizome mass, aboveground mass, root mass, maximum net photosynthetic rate(Pmax), specific leaf area(SLA), and leaf length to leaf width ratio(LL/LW), for 10 genotypes of L. chinensis under one non-stress(Ck) condition and three environmental stress conditions(i.e., drought(Dr), high temperature(Ht), and both drought and high temperature(DrHt)). Result indicated that(1) the interaction of genotype and environmental condition(G×E) was significant for 6 traits but not significant for the other 4 traits as shown by two-way analysis of variance(ANOVA), suggesting that different selection forces were placed for different traits on the factors dominating phenotypic responses to different environmental conditions. Moreover, these significant G×E effects on traits indicated significantly different phenotypic adaptive responses among L. chinensis genotypes to different environmental conditions. Additionally, individuals could be grouped according to environmental condition rather than genotype as shown by canonical discriminant analysis, indicating that environmental condition played a more important role in affecting phenotypic variation than genotype;(2) by one-way ANOVA, significant differences among L. chinensis genotypes were found in all 10 traits under Ck and Dr conditions, in 8 traits under Dr Ht condition and only in 4 traits under Ht condition; and(3) all 10 traits showed relatively low or non-measurable broad-sense heritability(H_2) under stress conditions. However, the lowest H_2 value for most traits did not occur under DrHt condition, which supported the hypothesis of 'unfavorable conditions have unpredictable effects' rather than 'unfavorable conditions decrease heritability'. Results from our experiment might aid to improve predictions on the potential impacts of climate changes on L. chinensis and eventually species conservation and ecosystem restoration.

Estimates of heritability and correlation for growth traits of Turbot(Scophthalmus maximus L.) under low temperature conditions

The objectives of this present research were to assess the heritability of growth traits under low temperature conditions in turbot（Scophthalmus maximus L.）, and to analyze the correlation between body weight（BW） and body length（BL）. There were 536 individuals from 25 full- and half-sib families involved in this study. During the entire 90-day period, which was initiated at 233 dph（day old） and ended at 323 dph, the individuals＇ BW and BL were weighed consecutively six times every 18 days. The heritability of BW and BL and the correlation between these two traits were estimated based on an individual animal model with the derivative-free restricted maximum likelihood（DFREML） method. These results showed that the specific growth rates（SGR） of 25 families was from 0.75±0.11 to 1.05±0.14 under water temperature of 10.5–12°C. In addition, the heritability of BW and BL estimated under low-temperature were 0.32±0.04 and 0.47±0.06, respectively. The BW had a medium heritability（0.2–0.4）, and the BL had a high heritability（〉0.45）, which suggested that selection for increased weight and length was feasible. Moreover, there was potential for mass selection on growth. The genetic and phenotypic correlations between BW and BL were 0.95±0.01 and 0.91±0.01（P 〈 0.01）, respectively. A significant correlation between BW and BL showed that BL could be instead of BW for indirect selection, which could be effectively implemented in the breeding program.

Heritability of body weight and resistance to ammonia in the Pacific white shrimp Litopenaeus vannamei juveniles

Ammonia,toxic to aquaculture organisms,represents a potential problem in aquaculture systems,and the situation is exacerbated in closed and intensive shrimp farming operations,expecially for Litopenaeus vannamei.Assessing the potential for the genetic improvement of resistance to ammonia in L.vannamei requires knowledge of the genetic parameters of this trait.The heritability of resistance to ammonia was estimated using two descriptors in the present study:the survival time(ST) and the survival status at half lethal time(SS_(50)) for each individual under high ammonia challenge.The heritability of ST and SS_(50) were low(0.154 4±0.044 6 and 0.147 5±0.040 0,respectively),but they were both significantly different from zero(P<0.01).Moreover,these two estimates were basically the same and showed no significant differences from each other(P>0.05),suggesting that ST and SS_(50) could be used as suitable indicators for resistance to ammonia.There were also positive phenotypic and genetic correlation between resistance to ammonia and body weight,which means that resistance to ammonia can be enhanced by the improvement of husbandry practices that increase the body weight.The results from the present study suggest that the selection for higher body weight does not have any negative consequences for resistance to ammonia.In addition to quantitative genetics,tools from molecular genetics can be applied to selective breeding programs to improve the efficiency of selection for traits with low heritability.

Using microsatellite markers to identify heritability of Pacific whiteleg shrimp Litopenaeus vannamei

Pacific whiteleg shrimp （Litopenaeus vannamei） is an economically relevant shrimp species in many Asian countries. The specific objective of the current research was to assess microsatellite markers in screening the fast- growth of domesticated L. vannamei stocks to establish a founder population for breeding-selection plans. The post.larvae produced by the reproduction of second generation broodstock were cultured in the same conditions throughout a five months growing period. Ninety juvenile shrimp were selected from the slow-, medium- and the fast-growth groups, and ten microsatellite markers were used to investigate their genetic diversity, and to understand the improvement of a breeding-selection scheme. Ten polymorphic loci （markers） （M1-M10） were produced at ten loci in this sample, among them Primer M8 was the highest polymorphic locus and M7 was the lowest one. A specific locus was found in the fast-growth group using Primer M5. The longest genetic distance （0.481） was determined between the fast- and medium-growth groups and the shortest （0.098） was between the slow- and medium-growth groups; therefore, the largest genetic identity （0.946） was observed between the slow- and medium-growth groups and the smallest （0.667） was observed between the medium- and fast-growth groups. The Unweighted Paired Group with Arithmetic Average （UPGMA） dendrogram based on Nei＇s genetic distances provided two different groups; the first consist of the slow- and medium-growth groups and the second the fast- growth group. Selection response and realized heritability for growth were 11.55% and 31.26%, respectively. Therefore, this set of microsatellite markers would provide a useful tool in shrimp breeding schemes.

Heritability of resistance-related gene expression traits and their correlation with body size of clam Meretrix petechialis

Gene expression variation can be considered as a phenotype,and it plays an important role in both acclimation and adaption.However,genetic variation of gene expression received much less attention than traditional commercial traits in aquaculture.To estimate the genetic variation and heritability of gene transcription in clam Meretrix petechialis,five Vibrio resistance-related genes were selected for gene expression analysis in the digestive gland,and an animal linear model was used to analyze data from quantitative real-time PCR(qRT-PCR).Among the five genes,BIRC7 showed significant additive genetic variations,the heritability of this gene of 12-month-and 15-month-old clams were 0.84±0.32 and 0.91±0.34,respectively.The heritability of other four genes(Bax,NFIL3,Big-Def,and CTL9)expression were low-tomoderate but not significantly expressed.Additionally,no significant phenotypic and genetic correlations between the BIRC7 transcription trait and body size were detected.This study highlights that certain gene expression variation is heritable and provides a reference for indirect selection of M.petechialis with high Vibrio resistance.

Heterosis and heritability estimates for the survival of the Pacific white shrimp(Litopenaeus vannamei) under the commercial scale ponds

The aim of the present study is to detect the potential of the base population from diallel crosses of eight introduced strains of the Pacific white shrimp（Litopenaeus vannamei） for improving the yield. Heterosis and heritability were estimated for pond survival at commercial farm conditions for the base population that included 207 full-sib families from a nested mating design by artificial insemination. Among all the hybrids,the heterosis ranged from –11.37%（UA1×UA2） to 20.53%（UA3×SIN） with an average of 0.953%. The results showed that more than half of the hybrids（51.85%） have negative heterosis for survival rate, but most of the hybrids with positive heterosis have high estimates. The high proportion of negative heterosis for survival rate reminders us that the survival trait also should be considered in the crossbreeding program to avoid yield decrease. However, high positive heterosis manifested in most of the hybrids for survival indicates the usefulness of these hybrids for improving the survival to obtain higher yield by crossbreeding in this breeding program. The heritability estimate for pond survival was 0.092±0.043 when genetic groups were included in the pedigree, and it was significantly different from zero（P〈0.05）. The results from this study also indicated that significant improvement for survival is possible through selection in L. vannamei.

Heritability estimations of ammonia tolerance and survival of ridgetail white prawn Exopalaemon carinicauda

Ridgetail white prawn Exopalaemon carinicauda is an important economic marine species in China.To improve the germplasm quality of cultured E.carinicauda,for the fi rst time,we estimated the heritability of ammonia tolerance and survival of E.carinicauda,covering 263 full-sib families in multiple generations.Analysis models including binary linear animal model(BLA),binary linear sire-dam model(BLSD),probit threshold animal model(PTA),and probit threshold sire-dam model(PTSD)were used.The estimated heritability of tolerance to ammonia in diff erent models ranged from 0.09 to 0.22,and that of survival rate ranged from 0.06 to 0.16.Concerning the tolerance to ammonia,both the PTSD and BLSD models showed comparatively better prediction accuracies(0.48 and 0.47,respectively)than PTA and BLA models(0.40 and 0.26,respectively),while to the survival rate,all four models presented relatively low predictive abilities(0.16-0.26).This study provided important information for the future breeding program of E.carinicauda.

Association and Heritability Studies for Drought Resistance under Varied Moisture Stress Regimes in Backcross Inbred Population of Rice

Drought stress is one of the major constraints affecting rice production and yield stability in the rainfed regions. To understand the physiological basis of drought resistance related component traits, we used a backcross inbred population of rice under three kinds of moisture regimes viz., non-stress, moderate （24.48%） and severe stress （73.97%） conditions which reflect the differential responses of the genotypes to varying stress intensities. The plot yield, 1000-grain weight, panicle exsertion and canopy air temperature difference exhibited high heritability under the control conditions, whereas spikelet sterility and single plant yield exhibited high heritability under the moderate stress conditions. Traits such as days to 50% flowering, plant height and osmotic potential showed high heritability under the severe stress conditions. Plot yield under stress was significantly and positively correlated with harvest index and 1000-grain weight, but negatively associated with leaf rolling score and days to 50% flowering. The drought susceptibility index and drought response index were negatively correlated between each other both under the moderate and severe stress conditions. The derived traits viz., difference in panicle length between the control and the severe stress was associated with osmotic adjustment measured under field conditions. Difference in plant height and panicle length was negatively associated with plot yield under stress.

Estimation of Variability, Heritability and Genetic Advance for Phenological, Physiological and Yield Contributing Attributes in Wheat Genotypes under Heat Stress Condition

The investigation was carried out in focusing the genetic variability for different traits of wheat influenced by heat tolerance mechanism to find out relationships among phenological, physiological and yield contributing traits. Spring wheat cultivar of 25 genotypes were selected and cultivated under late sowing condition at the Regional Wheat Research Institute, Shympur, Rajshahi, Bangladesh from December, 2016 to April, 2017. Significant variability among the genotypes exposed for different traits related to heat tolerance. Results showed that the genotypes G24, G10, G01, G13, G16, G25 and G14 ranked as better category considering maximum number of traits in mean performance indicating their tolerance to heat stress under late sowing condition. Phenotypic variances (σg2) of all traits were greater than those of genotypic variances (σg2). The same trends were also found in their co-efficient of variances. The phenotypic co-efficient of variances (PCV) of all traits were greater compare to those of genotypic co-efficient of variances (GCV) and their values were closer to each other. The heading days (HD), canopy temperature at vegetative stage (CTvg), canopy temperature at grain filling stage (CTgf), biomass, plant height (PH), spike/m2 (SPM), spikelet/spike (SPS), grain/ spike (GPS), thousand grain weight (TGW) and yield exhibited higher heritability (hb2) estimated under irrigated late sowing (ILS) condition. Under the same ILS condition SPAD, SPM, SPS, GPS, TGW and yield showed moderate to high genetic advance (GA) obtained through computing their mean percentage (%) and the rest traits HD, maturity days (MD), CTvg, CTgf, biomass, PH and harvest index (HI) exposed smaller genetic advance (% mean). The co-efficient of variation (CV%) of all attributes in all genotypes were significantly lower (1.36 - 6.96). Both heritability and genetic advance were found lower for MD, SPAD and HI indicated their non additive genetic effects for which these traits might not be recommended for selection. However, spike/m2, spikelet/spike, grain/spike, thousand grain weight and yield belonged to higher heritability and high to moderate genetic advance in mean percentage (%) along with wide genetic variation and lower environmental influence in heat stress situation indicated the most likely heritability due to the effects of additive genes that might be suggested as effective process of selection for these traits in heat stress condition.

Genetic variability,heritability and genetic advance in linseed(Linum usitatissimum L)genotypes for seed yield and other agronomic traits

The experiment was conducted using simple lattice design with two replication and the trails was totally consisted fifty six genotypes.Data on seed yield and other Agronomic traits were used to estimate the genetic variability parameters,heritability and genetic advance(GA).Analysis of variance revealed highly significant and significant difference for all studied traits.Evaluated characters were exhibited different levels of variability,heritability and genetic advance among the studied genotypes.Low to high phenotypic coefficient of variation(PCV)and genotypic coefficient of variation(GCV)were recorded.The highest GCV and PVC values were found particularly for lodging percent(76.65%and 90.63%),harvest index(42.26%and 47.92%)yield per hectare(41.23%and 48.19%)and number of capsule per branch(30.81%and 37.25%)respectively,whereas low GCV and PCV(8.27%and 9.73%respectively)manifested for days to maturate.The highest broad sense heritability value manifested for harvest index(77.78%)followed by seed yield per hectare(73.21%),while lowest heritability(3.78%)revealed only for seed per capsule.In present study low to moderate genetic advance were manifested and high heritability and genetic advance as percentage of mean(>50)was recorded for lodging percentage,number of capsule per branch,seed yield per hectare and harvest index,indicating predominance of additive gene action for these characters.Therefore the result of this study suggests existence of variability for seed yield and other agronomic traits in these linseed genotypes,which should be exploited in future breeding.

Variability, heritability and genetic advance in mulberry (<i>Morus</i>spp.) for growth and yield attributes

Genetic improvement of crop plants is brought about by manipulating the genetic makeup through systematic breeding techniques or by employing modern biotechnological tools. Application of systematic breeding technique to a large extent is decided by the knowledge on the genetic control of the traits. Keeping this in view, nine mulberry genotypes were evaluated for different growth and yield attributing traits viz., number of tillers (NT), plant height (PH), total shoot length (TSL), nodal distance (ND), leaf fall % (LF), number of leaves/plant (NLP), weight of 100 fresh leaves (WFL), weight of 100 dry leaves (WDL), single leaf area (LA), leaf area index (LAI), aboveground biomass (AGB), leaf harvest index (LHI) and leaf yield (LY) and estimated the magnitude of genotypic and phenotypic variation, heritability, genetic advance and correlation coefficients. The broad sense heritability for these traits ranged from 63.942 (WFL) to 13.261 (PH). High heritability coupled with high genetic advance was recorded for the characters WFL, LF, LA, WDL and LY suggesting the higher genetic control over these traits. Leaf yield showed significantly positive phenotypic and genotypic correlations with all other growth traits except PH and LF. Leaf fall had significant negative correlations with all the highly heritable yield attributes viz., ND (-0.379), WDL (-0.225), LA (-0.346), LAI (-0.233) at 1% level and AGB (-0.148), LHI (-0.122) and LY (-0.146) at 5% level. Likewise, it showed positive correlations with TSL (0.558), NLP (0.264) and PH (0.221). Since mulberry is mainly cultivated for leaf yield, genotypes having higher WFL, LA, WDL and LY and less LF must be given importance during parent selection to evolve high yielding varieties with less leaf fall across different seasons in mulberry.