Heterosis For Yield Research Articles

Heterosis for grain yield contributing traits in pearl millet (Pennisetum glaucum)

The general expectation of the pearl millet farmers is mainly focused on level of superiority of newly released hybrids than the local standard hybrids, which is grown widely. Hence, the standard check RHB-173, RHB-177 and MPMH-17 were used as standard hybrid. The hybrid namely RMS-7 × RIB-3135-18 expressed highest significant standard heterotic value for grain yield per plant and fourassociated traits out of nine studied traits including dry fodder yield per plot also showed positive significant standard heterosis. Similarly, another hybrid namely RMS-7 × RIB-16296 showed highest significant standard heterosis for dry fodder yield per plot. The showed cross combination, viz. ICMA-00444 × RIB-16S/110, ICMA-00111 × RIB-494, ICMA-00444 × RIB-16296 and ICMA-00444 × RIB-16328 were good for other studied traits. At the end, among 100 hybrids studied, one hybrid, viz. RMS-7 × RIB-3135-18 was selected as best cross since, it expressed high significant standard heterosis over best check for many of the traits including grain yield and dryfodder yield and may have potential to replace old cultivar in the future.

Comprehensive molecular evaluation of the histone methyltransferase gene family and their important roles in two-line hybrid wheat

BackgroundHistone methylation usually plays important roles in plant development through post-translational regulation and may provide a new visual field for heterosis. The histone methyltransferase gene family has been identified in various plants, but its members and functions in hybrid wheat related in heterosis is poorly studied.ResultsIn this study, 175 histone methyltransferase (HMT) genes were identified in wheat, including 152 histone lysine methyltransferase (HKMT) genes and 23 protein arginine methyltransferase (PRMT) genes. Gene structure analysis, physicochemical properties and subcellular localization predictions of the proteins, exhibited the adequate complexity of this gene family. As an allohexaploid species, the number of the genes (seven HKMTs orthologous groups and four PRMTs orthologous groups) in wheat were about three times than those in diploids and showed certain degrees of conservation, while only a small number of subfamilies such as ASH-like and Su-(var) subfamilies have expanded their members. Transcriptome analysis showed that HMT genes were mainly expressed in the reproductive organs. Expression analysis showed that some TaHMT genes with different trends in various hybrid combinations may be regulated by lncRNAs with similar expression trends. Pearson correlation analysis of the expression of TaHMT genes and two yield traits indicated that four DEGs may participate in the yield heterosis of two-line hybrid wheat. ChIP-qPCR results showed that the histone modifications (H3K4me3, H3K36me3 and H3K9ac) enriched in promoter regions of three TaCCA1 genes which are homologous to Arabidopsis heterosis-related CCA1/LHY genes. The higher expression levels of TaCCA1 in F1 than its parents are positive with these histone modifications. These results showed that histone modifications may play important roles in wheat heterosis.ConclusionsOur study identified characteristics of the histone methyltransferase gene family and enhances the understanding of the evolution and function of these members in allohexaploid wheat. The causes of heterosis of two-line hybrid wheat were partially explained from the perspective of histone modifications.

Optimizing use of U.S. Ex-PVP inbred lines for enhancing agronomic performance of tropical Striga resistant maize inbred lines

BackgroundTemperate maize inbred lines with expired Plant Variety Protection Act certificates (Ex-PVP) are potential sources of desirable alleles for tropical germplasm improvement. Up to now, the usefulness of the Ex-PVP inbred lines as a potential source of novel beneficial alleles for Striga hermonthica resistance breeding to enhance genetic gain in tropical maize has not been reported.ResultsThis study was thus conducted to characterize the combining ability of 24 Ex-PVP inbred lines in crosses with two tropical Striga resistant inbred testers under Striga-infested and non-infested conditions and across three locations for 2 years. Many testcrosses between Ex-PVP inbred lines and the first tester (T1) produced competitive or significantly higher grain yields compared to the hybrid between the two resistant testers under Striga infested and non-infested conditions and across multiple test locations. Also, most of the testcrosses with positive heterosis for grain yield and negative heterosis for Striga damage and emerged Striga count involved T1 as a tester. Our study identified six Ex-PVP inbred lines with positive GCA effects for grain yield under Striga infested and non-infested conditions and across multiple test locations. Amongst these, inbred lines HB8229-1 and WIL900-1 also displayed negative GCA effects for emerged Striga count and Striga damage rating. The inbred line HB8229-1 showed positive SCA effects for grain yield with T2, whereas WIL900-1 had positive SCA effects for grain yield with T1. Over 70% of the Ex-PVP inbred lines were consistently assigned to specific heterotic groups using yield-based classifying methods (mean grain yield and SCA effects).ConclusionsThese results could facilitate systematic introgression of the Ex-PVP inbred lines into the existing Striga resistant heterotic groups in IITA. The Ex-PVP inbred lines with positive GCA effects and producing high grain yields in hybrid combinations could be useful parents for enhancing Striga resistance and agronomic performance of tropical maize hybrids.

Prediction of Heterosis for Agronomic Traits in Half-Diallel Cross of Rice (Oryza sativa L.) under Drought Stress Using Microsatellite Markers.

Rice breeders are encouraged to classify potential F1-hybrids without crossing all viable mixtures by testing depending on genetic distance due to lack of labor and time in yield trials. The goals of this research were to establish heterosis and investigate the relationship between genomic distance and agronomic attributes under drought. Half-diallel mating design, 28 F1′s and 8 parents were evaluated under drought and genotyped using 11 microsatellite markers. In total, 39 alleles were detected. Results indicated that the greatest heterotic effects for grain yield were observed in Sakha 103 × Sakha 104 and GZ7576-10-3-2-1 × Giza 179, which gave 29.32–22.57% heterosis, respectively. Heterosis for grain yield in these crosses occurred as a rise in panicle weight, filled grains per panicle, low sterility and 100-grain weight. Correlations of marker-based genetic distance with mid-parent heterosis were positively and significantly correlated with sterility percentage (r = 0.390 *, p < 0.05). However, better-parent heterosis was positively and significantly correlated with sterility percentage (r = 0.352 *, p < 0.05) and grain yield per plant (r = 0.345 *, p < 0.05). Associations indicate that high grain yield and low sterility of rice crosses can be expected from microsatellite marker-defined distances of parents. This study indicated that genetic distance is very effective for heterosis prediction in breeding programs.

Combining ability and heterosis for yield and grain quality characters in rice (Oryza sativa L.)

Twelve F1 crosses derived from four lines and three testers, crossed in L x T mating design were utilized to estimate the combining ability and heterosis for 17 yield and grain quality traits and also to detect the superior crosses for the breeding program. Analysis of variance showed significant differences among all the traits under study except for plant height in lines. In the case of testers, the traits viz., the number of tillers per plant, the number of productive tillers per plant, hundred seed weight, single plant yield, alkali spreading value, amylose content, gel consistency, kernel length, kernel length breadth ratio, kernel length after cooking and kernel breadth after cooking showed significant values. The SCA variance was higher than the GCA variance for all the characters under study except the alkali spreading value indicating the predominance of non-additive gene action in the inheritance of all the characters. The parents TKM 13, CO 52, ADT 52 and IRBB 21 were adjudged as good general combiners with respect to single plant yield. Hence, these parents can be exploited through pedigree breeding to obtain better recombinants by selection in later generations. Based on the results of per se performance, standard heterosis, and sca effects, the hybrids viz., CO 52 × IRBB 60 and ADT 52 × IRBB 21 were identified as the best specific combiners and these could be used for future breeding. Keywords: Combining ability, Heterosis, SCA, GCA, Rice

Contextualization of Trait Nexus and Gene Action for Quantitative and Qualitative Characteristics in Indian Mustard

After soybean and palm oil, the world’s third largest oil seed crop is rapeseed mustard. Out of the seven consumable oil seed crops grown in India, rapeseed mustard is responsible for one-third of production. Mustard aphid (Lipaphis erysimi Kalt) is considered the primary pest causing mayhem in crop production. Understanding the genetics behind resistance will aid breeders in developing a resistant/tolerant strain. Appropriate parent selection and analyzing gene action contribute to economic benefit maximization. The aims of the current study are to use seven lines and five testers to determine the best-performing parents and crosses based on their general and specific capacity to combine and to examine the level of heterosis for yield and related features like mustard aphid resistance. Due to the self-pollination nature of Indian mustard, Kempthorne’s line X tester method is helpful to judge the combining ability. Therefore, seven lines and five testers of Indian mustard (Brassica juncea L.) were employed in the present study. The findings suggested that there was substantial genetic variation for all traits examined. The mean oil yield of R1 B2-26 × R1 B2-25, JD6 × R1 B2-25, and JD6 × R1 B2-29 hybrids was more significant than that of the ancestors. The results show that R1 B2-26 × R1 B2-25, JD6 × R1 B2-25, and JD6 × R1 B2-29 hybrids produced more oil than their parents. The variance explained by SCA was greater than that explained by GCA, as indicated by the Ϭ2 gca/Ϭ2 sca ratio being less than one for all characters, implying that nonadditive gene actions such as dominance, epistasis, and other interaction effects played an important role in the presence of these attributes. Punjab Local was discovered to be an excellent general merge for reducing crop duration, whereas JD6 was an excellent combiner for seed yield per crop, aphid infestation indicator, seed yield per crop, and oil production per plant. The predictability ratio was found to be less than 0.5 for almost all traits, denoting that the nonadditive gene measure is involved in controlling the nature except days to 50% flowering, aphid infestation index, oil content, and oil yield per plant. Thus, based on these four traits, selection for superior plants may be practiced in later generations.

Association of Heterosis and Heterobeltiosis for Yield and its Contributing Traits in Indian Mustard (Brassica juncea L. Czern &amp; Coss)

The heterosis breeding strategy is one of the most successful technological approaches for improving Indian mustard varieties for seed yield quality and quantity, as well as other yield contributing character. The present investigation was undertaken ten genetically diverse parents following diallel mating design excluding reciprocals. The resultant 45 F1s and all the ten parents were evaluated in a randomized complete block design with three replications under three different environments. Data on quantitative characters were recorded and heterosis and heterobeltosis were determined that showed sufficient degree of heterosis and heterobeltiosis for all the attributes. The crosses, RGN-13 x RH-406 was identified for days to 50 per cent flowering, days to maturity, number of secondary branches per plant, number of siliquae per plant, 1000-seed weight, oil content, leaf area index and harvest index and the cross RGN-303 x RGN-229 was identified for days to 50 per cent flowering, days to maturity, number of secondary branches, number of seed per siliqua and 1000-seed weight. Among the 45 crosses, RGN-13 × RH-406 emerged as good heterotic as well as heterobeltiotic crosses for seed yield and other contributing characters.

Combining Ability Estimates and Heterosis for Yield and Yield Components in Rice (Oryza sativa L.) in Nigeria

The study was carried out to determine the combining ability estimates and heterosis for yield and yield components in rice (Oryza sativa L.) in Nigeria. A seven plant diallel was planted across three locations using a randomized complete block design with three replications. Parameters assessed include days to 50% heading, plant heights, panicle lengths, panicle weights, number of seeds per panicle, number of productive tillers, number of panicle branches, yields per hectare, 100 grain weight. Assessment of GCA and SCA were carried out. Percentage heterosis were also determined for all traits studied. Significantly higher yield was recorded by P5, P4, P3, P6, P7, P2, and P1 with means of 5.86t/ha, 5.26 t/ha, 5.09 t/ha, 4.94 t/ha, 4.91 t/ha, 4.74 t/ha and 4.49 t/ha respectively across three locations studied. Hybrids P1xP5, P3xP6, P4xP7, P3xP5 produced significantly higher yields of 6.14 t/ha, 6.13 t/ha, 6.22 t/ha), 6.95 t/ha compared to their parental means. Similarly, significant difference were recorded in all other traits studied among parents and hybrids. GCA means squares were significantly higher than that of SCA for most of the traits studied. Additive variance was shown to predominate for plant heights and productive tillers while dominance was higher in yield per plants. Narrow sense heritability was higher on days to flowering, plant heights, panicle length and productive tillers. Yield in general was found to be significantly higher for combining ability in P5, P3 and P4. The overall GCA status for the ten agronomical traits studied showed that P5, P3, P1 and P2 are higher general combiners. Hybrids P3xP5, P5xP6, P2xP3, P5xP7 and P2xP7 produced higher total overall SCA, however, some produced more dominance on a particular trait than others. Both positive and negative heterosis for mid-parent, standard and better parent were also observed.

Dissection of two QTL clusters underlying yield-related heterosis in the cabbage founder parent 01–20

Cabbage has significant heterosis and most commercial cultivars are hybrids. To explore genetic basis of cabbage heterosis and promote cabbage heterosis utilization, we constructed two populations by crossing 100 DH lines derived from a cabbage hybrid 01–20 × 96–100 with two female parents. Hybrids exhibited different extents of heterosis, the mean value of economic yield was 2.6 times bigger than parents. We identified 66 and 73 QTLs associated with mid-parent heterosis and transgressive heterosis of twelve yield-related traits, respectively. Some QTLs could be detected under the two-year experiment existed in two populations with different testers, showing relatively high phenotypic contribution rate (15.8%–20.0%). Heterosis QTLs exhibited clustered distribution in several cabbage chromosome regions. Two dominant genetic regions, mk300–316 and mk258–268, originated from the elite parent 01–20, exhibited significant genetic effects for yield-related heterosis, which were first identified. Three elite DH lines (D22, D46, D83) harboring these two dominant regions were selected as having strong heterosis in cabbage production. Candidate gene analysis revealed that some genes participating in biosynthetic processes of carbohydrates and some responses to auxin might affect cabbage yield heterosis. QTL identification and genetic dissection of yield-related traits provide new insights into the genetic effects of cabbage heterosis.

Agro-morphological and molecular diversity analysis of new cytoplasmic male sterile lines in Indian cauliflower for their use in hybrid breeding

Cauliflower is a typical thermo-sensitive crop, highly responsive to heterosis for yield and stress tolerance. A diverse set comprising of 24 cytoplasmic male sterile (CMS) lines, developed across different maturity groups of Indian cauliflower, using refined Ogura, Can(napus) and Tour sterile cytoplasms was studied to understand the morphometric and molecular changes. The established Ogura-based CMS line of ‘84 series’ (in the nuclear background of snowball cauliflower) was used as an immediate source for conversion of fertile early- and mid-maturity groups lines. Observations on 18 agro-morphological traits revealed significant differences among the CMS lines, however they could not distinguish different CMS systems. The CMS system significantly reduced the floral traits (19) in almost all the transformed lines irrespective of the maturity group, however, the reduction was maximum in CMS line Tour(CMS 394–41–5) having Tour sterile cytoplasm. This CMS line had a peculiar feature of ‘gripping phenomena’ for the style which drastically reduced flower size and eventually seed yield. These CMS lines showed variation with 11 mtDNA markers and 36 genomic simple sequence repeats (gSSR), and of these, BnTR1 perfectly-identified Can(napus) and Tour CMS systems. This is the first detailed report on the extent of diversity observed in 24 new CMS lines developed using three diverse sterile cytoplasms in the nuclear background of different maturity groups of Indian cauliflower. The information will be of immense significance for immediate use in hybrid breeding and/or use as an immediate source of CMS trait for tropical cauliflowers in other regions.

Hybrid vigour studies for root yield traits across the environments in Ashwagandha (Withania somnifera L.)

In the present experiment, 45 F1 hybrids of Ashwagandha were included in relation to investigate extent of heterosis for dry root yield and its attributing characters. The pooled ANOVA depicted the valuable amount of diversity existed among genotypes for all the characters. The significant estimates of heterosis in desirable direction were recorded in 22 hybrids over the mid parent, six hybrids over the better parent and six hybrids against the superior check (JA-134) for dry root yield, out of which the cross, UWS-309 × RVA-100 exhibited highest useful heterosis (17.42 %) for dry root yield across the environments, hence, the cross may be gainfully utilized.

Heterosis response and combining ability (variance and effect) analysis for seed yield and its components in Indian mustard (Brassica juncea L.) under timely sown condition

Diallel analysis excluding reciprocal crosses comprising of seven parents and their 21 specific hybrids was carried out to identifyhigh heterotic combinations and their relationship in terms of general and specific combining ability (GCA and SCA) in Indian mustard. Highest economic heterosis for yield was observed in crosses namely; NRCHB-101 x Pusa M-21, Urvashi x Pusa Bold, NRCDR-2 x Urvashi, Maya x Pusa Bold, and Maya x NRCDR-2. The economic parents Urvashi, Pusa Bold, NRCHB-101, Pusa M-21, NRCDR-2, Maya and RGN-73 were the best parents for majority of the characters with Urvashi and Pusa Bold being the best economic parents for seed yield/plant and its contributing characters as their GCA and per se performances were high. Analysis of variance for GCA and SCA signified differences for majority of the characters. Ratio of GCA and SCA variances was below unity for majority of the characters except Days to 50% flowering and Days to maturity, which suggested superior role of non-additive genetic variance in the inheritance of these traits. The crosses namely Maya x NRCDR-2, Maya x Pusa Bold, NRCDR-2 x Urvashi, NRCHB-101 x Pusa M-21 and Urvashi x Pusa Bold showed high per se performance as well as SCA effects for seed yield and its contributing characters. The above best parents and best crosses could be used in hybridization and heterosis breeding respectively.

Systematic trait dissection in oilseed rape provides a comprehensive view, further insight, and exact roadmap for yield determination

BackgroundYield is the most important and complex trait that is influenced by numerous relevant traits with very complicated interrelations. While there are a large number of studies on the phenotypic relationship and genetic basis of yield traits, systematic studies with further dissection focusing on yield are limited. Therefore, there is still lack of a comprehensive and in-depth understanding of the determination of yield.ResultsIn this study, yield was systematically dissected at the phenotypic, genetic to molecular levels in oilseed rape (Brassica napus L.). The analysis of correlation, network, and principal component for 21 traits in BnaZN-RIL population showed that yield was determined by a complex trait network with key contributors. The analysis of the constructed high-density single nucleotide polymorphism (SNP) linkage map revealed the concentrated distribution of distorted and heterozygous markers, likely due to selection on genes controlling the growth period and yield heterosis. A total of 134 consensus quantitative trait loci (QTL) were identified for 21 traits, of which all were incorporated into an interconnecting QTL network with dozens of hub-QTL. Four representative hub-QTL were further dissected to the target or candidate genes that governed the causal relationships between the relevant traits.ConclusionsThe highly consistent results at the phenotypic, genetic, and molecular dissecting demonstrated that yield was determined by a multilayer composite network that involved numerous traits and genes showing complex up/down-stream and positive/negative regulation. This provides a systematic view, further insight, and exact roadmap for yield determination, which represents a significant advance toward the understanding and dissection of complex traits.

Heterosis for yield and quality traits in traditional and evolved Basmati

A study was undertaken on 36 F1s obtained from diallel (without reciprocals) mating design to explicate the genetic behavior of traditional and evolved basmati varieties for 14 traits. F1s were divided into traditional x traditional (T x T); evolved x evolved (E x E) and traditional x evolved (T x E) basmati types; amidst which E x E and T x E type of crosses exhibited high positive average heterosis in comparison to T x T type of crosses for yield per plant trait. Assessment of quality traits for average heterosis indicated that, all the three types of crosses were equally effective for KL, KB and LBR. Manifestation of average heterosis for KLAC was better in TxT type as none of the ExE type of crosses showed significant positive heterosis; likewise, among 20 T x E type of crosses only 3 crosses showed significant positive heterosis. Heritability in narrow sense was high for: MPL, 100-GW, NGP, YPP, KL, LBR, and KLAC.

Study of gene action for yield and quality traits in rice (Oryza sativa L.)

The present experiment was conducted to study the gene action, heterosis, inbreeding depression and heritability for different yield and quality traits in the cross WGL 48684 x IR 36. Analysis of heterosis revealed that most of the traits show duplicate type of epistasis which is non- fixable and cannot be exploited through the general breeding procedures of self pollinated crops. Additive gene effect and complementary epistasis plays a lead role for plant height, number of ear bearing tillers per plant, kernel breadth and amylase content and they can easily be exploited for developing fixed lines. Significant inbreeding depression was found for ear bearing tillers per plant, SPAD Chlorophyll Meter Reading (SCMR), harvest index, grain yield, head rice recovery and kernel elongation ratio. Therefore, few cycles of recurrent selection followed by pedigree method would be effective and useful to utilize all types of gene effects by maintaining considerable heterozygosity through mating of selected plants in early segregating generations.

Estimation of combining ability and heterosis for yield and its component traits for identification of promising red rice (Oryza sativa L.) hybrids developed from new WA-based CMS lines and red kernel breeding lines

Combining ability analysis and heterosis enables plant breeders in anticipating improvement in productivity through hybridization and selection. In this study, line × tester mating design was used to develop 42 red rice hybrids by utilizing newly developed six WA-based CMS lines and seven testers selected from red kernel breeding lines at Zonal Agricultural Research Station, V.C. Farm, Mandya during kharif, 2018. The phenotypic performance of hybrids along with parents and checks were evaluated for grain yield and yield contributing traits. Analysis of variance revealed that variance due to the line × tester was significant for almost all the characters studied. Combining ability analysis revealed the predominance of non-additive gene action for most of the characters studied. On the basis of gca effects, CMS 2 among the lines and MO-21 among testers were identified as good general combiners for most of the traits studied. High sca effects were observed in the crosses, viz., CMS-1 × ME-19, CMS-2 × IET-14757 and CMS-4 × MSN-98 and they were also found to be the best combinations for grain yield and its component traits. The crosses CMS 5 × MSN-10-3, CMS 2 × ME-19 and CMS 5 × IET-14757 exhibited high mean grain yield and high standard heterosis over the standard commercial check KRH-4. These hybrids further need to be evaluated in multi-location trails for commercial exploitation of heterosis in red rice hybrid breeding program. Keywords: Hybrid rice, CMS, Combining ability, Heterosis, GCA, SCA &nbsp

Hybrid Performance and Heterosis for Yield and Agronomic Traits of Quality Protein Maize (Zea mays L.) Inbred Lines Adapted to Mid-altitude Agroecology of Ethiopia

Maize is a primary crop in most farming systems and staple food of the rural population in abundant of the mid-altitude sub- humid agro-ecologies of Ethiopia. Nearly 88% of maize produced in Ethiopia is consumed as food, both as green and dry grain. Yet, it has low protein content since it is normal maize, with poor protein quality limited by deficiencies in lysine and tryptophan and has an excess of leucine and isoleucine. Suggestions on hybrid performance and heterosis of QPM inbred for grain yield and its components is vital to design suitable breeding strategies for the development of nutritionally enhanced maize varieties. A line x tester analysis involving 36 crosses generated by crossing nine elite maize inbred lines with four testers and four checks were evaluated for yield and yield related traits at Bako and Jimma. The objectives were to evaluate mean performance and the magnitude of heterosis for quality protein maize inbred lines, adapted to mid altitude agroecology of Ethiopia. The genotypes were evaluated in alpha lattice design replicated three times. Analyses of variances showed significant (p&lt;0.05 or p&lt;0.01) mean squares due to genotypes in each and across locations for most traits studied, indicating the existence of appropriate genetic variability. The crosses, L5xT2, L7xT2, L8xT1, L8xT2, L3xT2, L5xT1, and L1xT1 showed higher grain yield. The estimated mid and better parent heterosis for grain yield across locations for all crosses displayed positive and highly significant variances which ranged from 386.6% to 111.2% and 288.9% to 72.2%, respectively. From this study, about 77.78% of crosses had better potential for grain yield. The results attained in this experiment suggest that the hopeful potentials of the identified inbred lines for further breeding of QPM for the mid-altitude agroecology of Ethiopia.

Evaluation of heterosis through reciprocal crosses of inbred cucumber lines (Cucumis sativus L.)

The purpose of the study. The aim of the study was to determine the effect of heterosis in short-fruited parthenocarpic F1 cucumber hybrids by the main economically valuable characteristics, when grown using low-volume technology in industrial greenhouses of the Moscow region.Materials and methods. The object of the study is short-fruited parthenocarpic reciprocal hybrids of cucumber Druzhny (F1 I73514 x I74011), F1 I74011 x I73514 and their parent inbred lines I73514 and I74011 of selection by N.N. Timofeev Breeding Station LLC. F1 SV4097CV of foreign selection of Semenis company (Netherlands) was used as a control. The study was conducted in 2020-2021 in industrial greenhouses of the "V. I. Edelstein Vegetable Experimental Station" of the K.A. Timiryazev Russian State Agrarian University-Moscow Agricultural Academy in Moscow on low-volume hydroponics in peat bags. Parental lines and hybrid combinations were evaluated by earliness, early yield, yield, number of fruits per plant, average fruit weight and marketability.Results. According to the results of the study, F1 Druzhny (F1 I73514 x I74011) and the reverse hybrid I73514 x I74011 demonstrated high positive effects of heterosis in yield (MPH=19.4...22%; HPH=13.4...15.9%; CH=9.6...12%) and the number of fruits per plant (MPH=22.5...26.4%; HPH=12.5...15.8%; CH=11.7...15%). Negative indicators of the heterosis effect were noted for earliness from germination to flowering (MPH=-3.4...-1.1%; HPH=-6.5...-4.4%; CH=-4.4...-2.2%) and average fruit weight (MPH=-2.2...-1.3%; HPH=-5.3...-4.3%; CH=-3.4...-2.4%). The value of the degree of dominance indicates the presence of positive overdominance in the inheritance of such traits as yield (hp=2.7...3.2), the number of fruits from the plant (hp=1.5...1.9) and marketability (hp=1.6...2.3). Negative overdomination was observed in earliness from germination to flowering (hp= -2...-1.3) and average fruit weight (hp=-1.7...-1.2). According to the signs of earliness from germination to fruiting (hp =0) and early yield (hp=-0.1...0.5), intermediate inheritance was revealed. The Druzhny hybrid significantly exceeded the control hybrid SV4097CV in early yield, yield and number of fruits from the plant, and the reverse hybrid F1 I74011 x I73514 was at the control level, which indicates the prospects of growing these hybrids in the conditions of spring-summer turnover on low-volume hydroponics.

Stacking of Pup1 QTL for low soil phosphorus tolerance and bacterial blight resistance genes in the background of APMS6B, the maintainer line of rice hybrid DRRH-3

Phosphorus (P) is one of the macronutrients essential for plant growth and development. Rice (Oryza sativa L.) is sensitive to P starvation and its deficiency influences many key plant functions, resulting in crop yield penalties. Although the hybrid rice segment is well-known for its yield heterosis, P deficiency and bacterial leaf blight diseases are evident limitations. APMS6B, the female parent of DRRH-3 is susceptible to low P and bacterial blight disease. In the present study, the improvement of APMS6B to P starvation and resistance to bacterial leaf blight (BB) was carried out using the marker-assisted backcross breeding approach. Kasalath (+Pup1 QTL) was used as a donor, and a promising IL (ATR 594-1) at BC1F4 generation was identified with 81.15% of recurrent parent genome recovery. Concurrently, this IL was intercrossed with GU-2 (+Xa21 and Xa38). Intercross F1s (ICF1) hybridity was confirmed through foreground selection having maximum RPGR (88.29%) and was selfed to produce ICF2. The resultant progenies were phenotyped for BB using Xoo inoculum (IX-020), simultaneously genotyped with gene-specific functional SSR markers forXa21 and Xa38. The identified BB-resistant plants were subjected to foreground selection for Pup1. Four promising ICF3 plants (BP-10-1, BP-10-3, BP-10-5, and BP-10-15 with Xa21, Xa38, and Pup1) along with parents and checks were screened both in low P plot (< 2 kg P2O5 ha−1) as well as in normal plot (> 25 kg P2O5 ha−1) during dry and wet seasons 2018. The field evaluation identified four promising intercrossed lines with better root growth in the primary root length of extracted zone and root volume. In addition, fewer reductions in grain yield (39.10%) under P starvation and less susceptibility indices values (< 1) for BB were observed. These lines may be exploited in the CMS conversion and development of climate-resilient, biotic and abiotic stress-tolerant rice hybrids.

Assembly of yield heterosis of an elite rice hybrid is promising by manipulating dominant quantitative trait loci.

In the past, rice hybrids with strong heterosis have been obtained empirically, by developing and testing thousands of combinations. Here, we aimed to determine whether heterosis of an elite hybrid could be achieved by manipulating major quantitative trait loci. We used 202 chromosome segment substitution lines from the elite hybrid Shanyou 63 to evaluate single segment heterosis (SSH) of yield per plant and identify heterotic loci. All nine detected heterotic loci acted in a dominant fashion, and no SSH exhibited overdominance. Functional alleles of key yield-related genes Ghd7, Ghd7.1, Hd1, and GS3 were dispersed in both parents. No functional alleles of three investigated genes were expressed at higher levels in the hybrids than in the more desirable parents. A hybrid pyramiding eight heterotic loci in the female parent Zhenshan 97 background had a comparable yield to Shanyou 63 and much higher yield than Zhenshan 97. Five hybrids pyramiding eight or nine heterotic loci in the combined parental genome background showed similar yield performance to that of Shanyou 63. These results suggest that dominance underlying functional complementation is an important contributor to yield heterosis and that heterosis assembly might be successfully promised by manipulating several major dominant heterotic loci.