Non-additive Gene Action Research Articles

Genetics of nitrogen use efficiency and its component traits under nitrogen-rich environment in wheat (Triticum aestivum)

Minimizing the footprints of overuse of nitrogen (N) on the ecosystem is the need of an hour. There is little information on the genetic inheritance of NUE and its component traits. The present study was therefore designed to study the genetic behaviour of NUE traits under abundant N supply. Diallel analysis of 21 F1 along with 7 parents was carried out for NUE traits, viz. shoot dry weight (SDW), root dry weight (RDW), maximum root length (MRL), N% in shoot, gram N in shoot (gN) and nitrogen use efficiency (NUE) under high N in hydroponic condition. Analysis of variance revealed significance for both general combining ability (GCA) and specific combining ability (SCA) for all NUE traits indicating the importance of both additive and non-additive gene action for these traits. Baker's ratio revealed a preponderance of additive genes over non-additive for SDW, RDW and MRLsuggesting thereby effectivity of selection for SDW, RDW, gN, and MRL in the early segregating generation of high GCA lines can improve NUE under high N. Crosses with high SCA effects for SDW, RDW, gN and N% were from the parent combination of high × low GCA effects, whereas for MRL, low × low GCA parents resulted in crosses with high SCA effect indicating the dispersal of favourable alleles in the different parents. Our study indicates the feasibility of improvement of NUE through direct selection for the component traits under N rich environment.

Detection of Epistasis for Seed and Some Phytochemical Traits in Coriander under Different Irrigation Regimes

Coriander (Coriander sativum L.) is an annual herb mainly cultivated for its seed characteristics. Drought stress is a major problem which affects coriander behaviour through biochemical responses. This study aimed to determine the nature and magnitude of epistasis in inheritance of seed yield (SY), percent of dehulled seed (PODS), percent of seed hulls (POSH), essential oil content (EOC), essential oil yield (EOY), dehulled seed fatty acid content (DSFAC), hull fatty acid content (HFAC), fatty acid content (FAC), and fatty acid yield (FAY), and to estimate additive and dominance variance for the traits not influenced by epistasic effects. Three testers, TN-59-158 (highly drought-susceptible), TN-58-230 (highly drought-tolerant, but low-yielding), and their F1 hybrid were each crossed for six genotypes. The experiment was performed under different levels of water deficit: control (C), moderate water deficit (MWD), and severe water deficit (SWD) conditions. Epistasis affected the expression of SY, EOC, EOY, FAC, and FAY in all water conditions, PODS in C, POSH in SWD, HFAC in MWD, and DSFAC in both C and MWD conditions. Total epistasic effects were partitioned, showing that both [i] and [j + l] type interactions were significant, with a prevalent influence of [i] type interactions on these traits except for POSH and FAC in the SWD condition, which exhibited a higher value of the [j + l] type. Both additive and non-additive gene actions were significant for those traits not significantly affected by epistasis in C, MWD, or SWD conditions. An additive type of gene action was preponderant for PODS in MWD and SWD, POSH in MWD, DSFAC in SWD, and HFAC in C and SWD conditions.

Genetic Control and Combining Ability Effects of Certain Yield Traits in Cowpea (Vigna unguiculata L. (Walp)) under Conditions of Drought Stress

This research was undertaken to assess genetic control and combining effects of some essential traits of yield under drought stress. Forty-two hybrids under water-stressed and well-watered conditions were tested in field experiments for two years. Evaluation of the various genetic components of variation was performed. Both the additive (D) and the dominant (H1) variance components were important in most of the traits suggesting both additive and non-additive gene effects under both conditions. The study showed that the minimum number of genes under water-stressed (WS) conditions ranged from 0.02 for pod length to 16.13 for days to 50% flowering. The narrow-sense heritability ranged from 24% for the number of pods per plant and pod length to 66% for the number of days to 50% flowering under WS condition. The impacts of SCA and GCA have been determined. In both conditions IT93K-432-1 and IT97K-499-35 showed the strongest GCA results on both of the traits. Danila×IT93K-432-1, Danilla×IT97K-499-35, and TVu7778×IT99K-573-2-1 have been observed to have the best SCA effect under both conditions for most of the traits. In most traits, additive and non-additive gene effects plus additive × additive and additive × dominance gene interactions were common. In summary, additive and non-additive gene actions were detected; however, there was a preponderance of non-additive gene action in both conditions. As a result, the enhancement of these traits would involve a repetitive selection technique as a result of the prevalence of the dominant gene effect, which would allow favorable recombination of the genes in both conditions in later generations.

Assessment of Genitic Variability, Cause Effect and Interrelationship among Yield Components in Chickpea (Cicer arietinum L.)

The present investigation consists of 26 genotypes of Chickpea including one check, which were grown in the Field Experimentation Centre of the Department of Genetics and Plant Breeding, SHUATS, Prayagraj during Rabi 2020 following RBD with three replications. The data were recorded on 11 characters. Assessment of genetic variability, cause effect and interrelationship among yield components in chickpea. High significant variation was obtained for all characters studied. High GCV and PCV in chickpea germplasm were observed for Total no of pods per plant, number of effective pods per plant, biological yield, seed yield. High estimate of heritability coupled with high genetic advance as percent of mean was recorded for No. of primary branches, No. of secondary branches, Total no of pods per plant, No. of effective pods per plant, biological yield, Seed yield per plant, Harvest index, Seed index. High values for heritability indicates that it may be due to higher contribution of genotypic components. Traits exhibiting high heritability coupled with genetic advance as percent of mean suggest that the traits are governed by additive gene action, equal contribution of additive and non-additive gene action respectively. Correlation coefficient analysis revealed that seed yield per plant exhibited positive and significant association with Biological yield per plant, Harvest index and plant height at genotypic and phenotypic levels. Correlation coefficient analysis revealed that seed yield per plant exhibited positive and significant association with Biological yield per plant, Harvest index and plant height at genotypic and phenotypic levels. Path analysis revealed that characters plant height, number of primary branches, biological yield and harvest index have positive direct effect on seed yield per plant at genotypic and phenotypic level.

Combining ability and gene action for structural and economical traits in brinjal (Solanum melongena)

An experiment was undertaken to estimate GCA for 8 parents and SCA for 15 hybrids in brinjal (Solanum melongena L.) through line × tester analysis. The combining ability analysis revealed highly significant differences among the treatments for all the characters. The gca reveals that, parental lines L2 (IC- 433678), L5 (Raidurg Local) and T3 (Pusa Purple Cluster) were identified as good general combiners for fruit yield per plant. These lines and testers were also best combiner for yield component characters like number of primary branches per plant, days to first flower, medium and long styled flowers, fruits per plant and fruit length. The estimates of specific combining ability effects indicated that cross combinations, viz. IC-433678 × IC-89986, Tiptur Local × Vellayani Local, Jagaluru Local × Vellayani Local, IC-345271 × Pusa Purple Cluster and Raidurg Local × Pusa Purple Cluster were most promising for fruit yield per plant and its component attributes. Gene action analysis revealed preponderance of both additive and nonadditive gene actions for yield and its contributing characters.

Genetic analysis of biochemical, fiber yield and quality traits of upland cotton under high-temperature

ABSTRACT To understand the effect of heat stress on morphology and physiology of the cotton, eight cotton genotypes with their 15F1 hybrids (five lines, three testers) were grown in the field conditions under randomized complete block design (RCBD) with two treatments i.e. normal and high-temperature stresses with two replications followed by split-plot arrangement. Data were collected for biochemical and yield-related parameters. Mean values of all studied traits were reduced significantly under high-temperature stress whilst the mean value of lint%, catalase activity, total soluble proteins, peroxidase, and carotenoids were increased under high-temperature. Under both conditions, the number of bolls, boll weight, seed cotton yield, lint index, seed mass per boll, hydrogen peroxide content, catalase activity, total soluble proteins, carotenoids, and chlorophyll contents had high heritability values along with high genetic advance percent mean which revealed, these traits were controlled by additive gene action. The lint%, seed index, short fiber index, fiber strength, fiber fineness, upper half mean length and peroxidase activity had high heritability with moderate genetic advance under heat stress conditions which showed, these traits were controlled by non-additive gene action. Under both temperature conditions, FH-458, IUB-65, CRS-2, and FH-313 were good general combiners for physicochemical and yield-related traits. The cross combination of IUB-013× CRS-2 and FH-458× FH-313 were good specific combiner for plant height and seed cotton yield whilst for fiber quality and biochemical traits, the best specific combiners were VH-329× FH-313 and IUB-013× CRS-2. These identified parents and cross combinations might be used for improving already present commercial varieties under high-temperature stress.

English

Maize (Zea mays L.) is the most important cereal crop on which many smallholder farmers in sub-Sahara Africa (SSA) depend on as a sole source of calories, proteins, and vitamins. However, conventional maize is deficient in two essential amino acids, lysine, and tryptophan. Thereafter, Quality Protein Maize (QPM) developed to combat protein malnutrition. In SSA low soil nitrogen is also the most limiting factor in maize production and productivity. To determine the combining ability of QPM inbred lines for grain yield and other agronomic traits under low and optimum N environments, 121 genotypes generated using 11 QPM inbred lines in a complete diallel mating design with 5 checks were evaluated under both low and optimum N environments at 3 locations in the 2018 cropping season. Significant differences were observed among the genotypes for major characters under both low and optimum N environments. Under low and optimum N environments, non-additive gene actions were more important than additive gene action for grain yield, number of ears per plant, plant and ear height, ear length and diameter. Under low N environments, more contributions of reciprocal effects than GCA effects were observed for number of ears per plant, plant aspect, ear diameter. Parental lines TL156579, TL156583, and TL148288 were considered as a good general combiner for grain yield under low N environments. Parental line TL156612 showed higher positive GCA effects when used as female while parental line TL156612 showed higher negative GCA effects when used as a male parent for grain yield under low N environments.   Key words: Complete diallel, general combining ability, low soil nitrogen, lysine, optimum soil nitrogen, quality Protein maize, reciprocal effect, tryptophan.

Assessment of genetic variability, heritability and genetic advance of biparental progenies in okra [Abelmoschus esculentus (L.) Moench

In the present investigation, the four cross combinations of Punjab Padmini X Panruti local, Dharmapuri local X Panruti local, Punjab Padmini X Parbanikranthi and Dharmapuri local X Parbanikranthi and three bhendi populations, BIP, F2, and F3, were developed in 2019, and these populations were evaluated in 2020 to determine the extent of genetic variability, heritability, and genetic advance for twelve bhendicharacters. Significant variances in BIP compared to the population of F2 and F3 in most characters have been noted that showed high mean and wider variations in PCV and GCV in fruit length, number of fruits per plant and plant yield. High heritability of BIPS was revealed by Punjab Padmini x Parbanikranthi for the traits viz., days to 50 per cent flowering, number of fruits per plant, fruit length, fruit girth and fruit yield per plant which revealed the importance of additive gene action for these traits. This is indicative of both additive and non-additive gene action (dominance and epistasis). Hence, selection could not be practiced in the immediate segregating generations. These two characters also showed unfavourable association with fruit yield per plant in BIPs which indicated that all the unfavourable linkages were not broken down through intermating in the early segregating generation. Thus, selection should be postponed to later generations after intermating in one or two subsequent to obtain potential recombinants.

Combining ability analysis for seed yield and its attributes in Indian mustard [Brassica juncea (L.) Czern and Coss

The experimental material comprised of forty eight genotypes consisting of five Mori based CMS lines and seven Mori based fertile lines crossed in line x tester mating design. The resultant thirty five hybrids along with their twelve parents and standard check (GDM 4) were evaluated in randomized block design at Castor-Mustard Research Station, Sardarkrushinagar Dantiwada Agricultural University, Sardarkrushinagar during, rabi 2018-2019. The analysis of variance for combining ability revealed that variance due to gca was significant for all the characters except number of seeds per siliqua, seed yield per plant and 1000 seed weight. Whereas, variance due to sca was significant for all the traits. This indicates significant contribution of hybrids for specific combining ability variance component. The ratio of σ2gca/σ2sca below than unity for days to maturity, siliqua length, number of seeds per siliqua, seed yield per plant, 1000 seed weight and oil content which suggested greater role of non-additive gene action in the inheritance of these traits. Among the parents, female SKM 9928 and Kranti were good general combiner for seed yield per plant, total number of branches per plant and total number of siliquae per plant. Whereas, male parent Mori 'R' 1-18 was good general combiner for seed yield per plant, total number of branches per plant and total number of siliquae per plant. Best three hybrids which possessed significant positive SCA effects for seed yield per plant were SKM 301 x SKM 303, SKM 9928 x Pusa Agrani and Kranti x Mori ‘R’ 1-18.

English

A study was conducted to determine the mode of inheritance for grain shape and aroma traits of lines in the Uganda rice germplasm. Five aromatic and four non-aromatic rice lines were crossed in screen house using North Carolina Design II at the National Crops Resources Research Institute, Uganda. The resulting F2 seeds and their parents were planted in the field using complete randomized block design in two replications. The grain shape and aroma intensity of the harvested F3 seeds on per hill basis were determined in laboratory using instrumental and sensory evaluation procedures, respectively. The results revealed that the inheritance of grain shape and aroma traits were influenced by both additive and non-additive gene actions, but with the grain shape being dominated by additive gene action and the aroma by non-additive gene action. In addition, Supa 3, Supa 5 and Supa 1052 rice lines exhibited good general combining ability effects for the shape trait while Supa 3 and MET 13 were good general combiners for the aroma trait. The superior cross combination from Supa 3 x Supa 5 for grain shape and Supa 3 x MET 13 for aroma trait could be used for selection of the relevant traits at advanced stages of the breeding cycles. Key words: General combining ability effects, gene action, North Carolina design II, selection, sensory evaluation.

Combining ability and heterosis for root structure and graft-related traits of interspecific Cucurbita rootstocks

Interspecific hybrid Cucurbita rootstocks (Cucurbita maxima × Cucurbita moschata) are the most widely used rootstocks for Cucurbitaceous vegetables in the world. In recent years, scientists have focused on understanding and exploiting root architectures as new opportunities for crop improvement. Selection of parents and hybrids based on combining ability test is an effective approach in interspecific hybrid variety breeding. However, limited information is available on the combining ability tests for the rooting and graft-related traits in these rootstocks. Ondokuz Mayis University and Black Sea Agricultural Research Institute are conducting a program to breed Cucurbita rootstocks in Turkey for fifteen years. In this study, seven C. maxima (BC5F1 generation) lines as female parents and three C. moschata (S6 generation) lines as male parents were used to obtain 21 crosses. The watermelon grafted onto the interspecific hybrids and their parent rootstocks were analyzed in terms of general combining ability (GCA), specific combining ability (SCA), heritability, and heterosis for roots and graft-related traits including root volume (cm3), root length (m), root dry weight (g), hairy root rate (%), average root diameter (mm), shoot dry weight (g), graft success rate (%), and hypocotyl thickness ratio (%) by using line × tester mating design. The quotient of GCA/SCA effects for all root and hypocotyl traits were higher than 1, suggesting the preponderance of additive over non-additive gene action in the expression of these traits, whereas graft success was controlled by additive and non-additive gene effects. It was determined that average root diameter had high heritability (63.85%) and the other traits had intermediate heritability ranging from 40.59 to 58.98%. Combining ability analyses indicated that FTS5, GH12, and GRD17 lines were promising parents with greater general combining ability. Three crosses, GRD17 × FTS5, B12 × FTS5, and BH5 × CHI2 showed superior mid-parent heterosis and significant SCA for most studied characteristics. Present findings will provide significant contributions in understanding of root related characteristics and then achieving desirable improved rootstocks in C. maxima × C. moschata.

Study on combining ability for seed yield and its attributing traits in sunflower (Helianthus annuus L.)

Six CMS lines and nine restorers ofsunflower were used in a Line × Tester mating design at Zonal Agricultural Research Station, Bengaluru to determine the combining ability and mode of gene action. The traits studied were days to 50 % flowering, plant height, head diameter, stem diameter, seed yield/plant, 100 seed weight, volume weight and oil content. The gca and sca effects were not significant for all the traits. The SCA variance were greater than GCA variance for the traits viz., plant height, head diameter, seed yield/plant, stem diameter and 100 seed weight, which showed greater manifestation of non-additive gene action. Among the CMS line, BCB-43A and among the testers, LTRR-822, RHA-95C-1 and RHA-95C-2 were good general combiners for most ofthe traits. The cross combinations BCB-171A × RHA 95C-2, BCB-44A × RHA-92, BCB-44A × RHA-95C-1, BCB-43A × GKVK-2 and BCB-170A × LTRR-822 showed higher sca for seed yield/plant.

Studies on induced genetic variability in M1 generation for quantitative traits in chickpea (Cicer arietinum L.)

Mutations were induced in three chickpea genotypes, ICC-15936, BRC-1104-127 and C-108 using sodium azide (SA) as a mutagen. The immediate effects of mutagenic treatments were measured in terms of biological damage caused in M1 generation. All the mutagenic treatments brought reduction in seed germination, seedling length and plant survival. Such reduction, with an exception of plant survival, were found to be depended upon the dosage of the concentration.High GCV and PCV in chickpea germplasm were observed for number of effective pods per plant, number of secondary branches per plant, number of pods per plant, seed yield per plant, plant height, number of primary branches per plant, seed index, harvest index, biological yield per plant. High estimate of heritability coupled with high genetic advance as percent of mean was recorded for number of effective pods per plant, number of secondary branches, number of pods per plant and seed yield per plant. High values for heritability indicates that it maybe due to higher contribution of genotypic components. Traits exhibiting high heritability coupled with genetic advance as percent of mean suggest that the traits are governed by additive gene action, equal contribution of additive and non-additive gene action respectively.

Gene Action, Heterotic Patterns, and Inter-Trait Relationships of Early Maturing Pro-Vitamin A Maize Inbred Lines and Performance of Testcrosses under Contrasting Environments

Vitamin A deficiency is the leading cause of night blindness, total blindness, maternal and childhood mortality in developing countries. Drought, low soil nitrogen and Striga hermonthica parasitism are major constraints to maize production in sub-Saharan Africa (SSA). Thus, the development of multiple stress tolerant maize varieties with elevated levels of PVA is an economically feasible approach to simultaneously tackle malnutrition and food insecurity in SSA. The objectives of this study were to determine the gene action modulating the inheritance of grain yield and other traits, group the inbred lines, investigate inter-trait relationships among grain yield and other traits and assess the performance and stability of single-cross hybrids derived from a set of inbred lines under stress and non-stress environments. One hundred and ninety diallel crosses plus six hybrid checks were evaluated under managed drought at Ikenne during the 2016/17 and 2017/18 dry seasons, low soil N conditions at Mokwa and Ile-Ife, Striga infestation at Abuja and Mokwa, and optimal management conditions at Ikenne, Kadawa, Abuja, Bagauda and Mokwa during the 2016 and 2017 growing seasons. Both additive and non-additive gene actions were prominent in the inheritance of grain yield and other measured traits under stress and optimal management conditions. However, additive gene action was preponderant over the non-additive. The PVA inbreds were classified into three heterotic groups with TZEI 25 and TZEIOR 164 identified as inbred testers for heterotic groups 2 and 3, respectively. Plant and ear heights, ears per plant, plant and ear aspects were identified as reliable secondary traits for genetic enhancement of grain yield under both stress and non-stress conditions. Hybrids TZEIOR 4 × TZEIOR 158 and TZEIOR 119 × TZEIOR 158 were outstanding in performance and should be tested extensively for possible commercialization to combat malnutrition and food insecurity in SSA.

Combining ability studies for yield components, quality characters and relative susceptibility to fruit and shoot borer in brinjal

Six diverse brinjal lines were crossed in a diallel fashion,excluding reciprocals to obtain fifteen cross combinationsto study combining ability for yield components, qualitycharacters and relative susceptibility to brinjal fruit andshoot borer. Significant differences were observed amonggenotypes for most of the characters studied. Both additiveand non-additive gene action conditioned most of thecharacters while non-additive gene action was preponderantfor the control of total phenol content of fruit, seed proteincontent and shoot infestation by borer. Maximum significantgca effects in desired directions were registered by Garia for7 characters followed by BCB-40, BCB-50 and PunjabSadabahar for 6 characters. However, considering thesecond highest per se performance for marketable fruit yield/plant (2.59 kg/plant) along with second lowest severity offruit borer infestation (18.55%) together, the parental lineBCB-40 emerged as the best followed by BCB-30, being thehighest yielder (2.69 kg/plant) and low severity of fruit borerinfestation (22.07%). The most promising cross combinationGaria × Punjab Sadabahar registering the second highestmarketable fruit yield per plant (3.74 kg / plant) exhibited thehighest significantly positive sca effects for marketable fruityield/ plant along with high and significantly positive scaeffect for plant height, fruit pedicel length, fruit weight, fruitsper plant and total phenol content of shoot and significantlynegative sca effect for fruit infestation by brinjal fruit andshoot borer. Keeping in view of low narrow sense heritabilityfor some important characters viz., fruit weight, marketablefruit yield per plant, total phenol content of fruit and fruitinfestation by brinjal fruit and shoot borer selection shouldbe based primarily on replicated family testing in F3 andlater generations. In the perspective of importance of nonadditivegenetic variance along with additive geneticvariance for the conditioning of most of the characters,heterosis breeding to develop high yielding hybridspossessing better fruit size, colour, quality and lesssusceptibility to brinjal fruit and shoot borer may be thebest breeding strategy.

Gene action, combining ability and heterosis in rice genotypes of North Western Himalayas

Results of these studies revealed that both additive and non-additive gene actions were involved in the inheritance of all traits. Preponderance of additive gene action was observed in the inheritance of ten traits viz., days to 75% maturity, plant height, spikelets/panicle, grains/panicle, harvest index, grain length, grain breadth, L:B ratio, amylose content and grain yield/plant. Preponderance of non-additive gene action was observed in the inheritance of eight traits viz., days to 50% flowering, maturity period, total tillers/plant, effective tillers/plant, panicle length, spikelet fertility, biological yield/plant and test weight. Genotype HPR 3007 followed by HPR 1156 and Kasturi were identified as superior parents based on high grain yield/plant and general combining ability. HPR 3007 × HPR 2373 followed by HPR 3007 × HPR 2612, Kasturi × HPR 2612 and HPR 3007 × HPR 3010 were identified as promising crosses based on high grain yield/plant, heterosis and specific combining ability. Identified superior parents and crosses can be used as donor parents for the improvement of existing low yielding basmati cultivars.

Deciphering the combining ability and gene action for root yield and related traits in ashwagandha [Withania somnifera (L.) Dunal

Genetics and crop improvement aspects of medicinal plants in Ashwagandha should be taken consideration to meet the accelerating pharmaceutical demands. For a better understanding of the genetic basis of root yield and related traits, a 9 × 9 diallel analysis excluding the reciprocals was carried out using SKA 27, SKA 11, SKA 6, SKA 24, SKA 10, SKA 26, JA 20, JA 134 and AWS 1 as parents. The σ2gca/σ2sca denotes that the majority of the traits considered except plant height and the number of secondary branches were governed by non-additive gene action. The fresh root yield was governed by almost equal proportions of additive and non-additive gene actions with a slight increment in additive proportion. Even though none of the parents was a good general combiner for all the traits considered, SKA 27 and SKA 11 appeared to be the best general combiners for root traits. The crosses JA 20 × AWS 1, SKA 24 × SKA 26 and JA 134 ×AWS 1 were found to be appropriate for the heterosis breeding on the basis of the estimates of SCA effects. Key wordsAshwagandha, combining ability, GCA, SCA, gene action, half-diallel  

Heterosis and combining ability studies in sesame (Sesamum indicum L.)

A line × tester analysis was carried out in Sesame (Sesamum indicum L. ) with four lines viz., VRI 3, SVPR 1, TMV 6, and TMV 7 and six testers viz., Thilathara, Thilak, TKG 55, RT 125, RT 127 and Thilottama. A total of 24 cross combinations were made and ten biometrical characters viz., days to 50 % flowering, height to first capsule, plant height, the number of primary branches, the number of capsules per plant, the number of capsules on main stem, capsule length, days to maturity, 1000 seed weight and seed yield per plant were recorded and analysed for combining ability and heterosis. In this present investigation, the variance due to SCA was higher than the variance due to GCA, which indicates that the inheritance of seed yield/plant is governed by non-additive gene action. Combining ability was analysed based on gca and sca effects. VRI 3 was the best general combiner among lines and among testers Thilathara was the best general combiner. The sca effects showed that seven hybrids viz., VRI 3 × Thilak, VRI 3 × RT 127, VRI 3 × Thilottama, SVPR 1 × Thilathara, TMV 6 × Thilathara, TMV 7 × TKG 55 and TMV 7 × RT 125 exhibited significant and positive values and these crosses can be evaluated further in advanced generations. Heterosis over standard parent was estimated and the highest positive significant heterosis for seed yield per plant was registered by the cross TMV 6 × Thilathara (39.32 %) followed by VRI 3 × Thilottama (21.41 %). Key wordsSesame, nature of gene action, gca effects and sca effects, heterosis

Breeding Resistance for Post Flowering Stalk rot (Macrophomina phaseolina) in Maize Identification of Resistance against Post Flowering Stalk Rot (Macrophomina phaseolina) in Maize

Maize is one of the most important staple food crops in the World. However, the yields of maize have been affected by various fungal infestations. Post flowering stalk rot is one of the devastating diseases and so, we planned our study to order to identify suitable resistance maize genotypes against post flowering stalk rot (PFSR) complex caused by Macrophomina phaseolina through in-vivo screening and toothpick method for creating artificial epiphytotics. A total of 20 maize inbreds were screened and crossed in Line × Tester mating design (15 × 5) during Kharif 2019, Six resistant inbred lines were identified and generated the 75 F1s (SCHs) at MRC, ARI, Rajendranagar, Hyderabad. All these 20 parents and 75 F1s along with three checks were evaluated by raising the crop in disease sick plot accompanied by toothpick inoculation during Rabi, 2019-20, in a Randomized Block Design with two replications. The field screening of maize genotypes by the standard toothpick method which needs about 40 days for expression of plant drying symptoms due to PFSR and data are possible to record only at the time of crop harvesting using 1-9 rating scale of PFSR for scoring disease severity in-vivo condition by splitting the stem of each plant. As a result, most of the genotypes were exhibited disease reaction varying from resistant (score 2) to moderately resistant (score 5) against M. phaseolina. While studying the genetics of PFSR, we found that interaction of lines and testers were proportionally contributed towards resistant, and degree of dominance is preferably non-additive gene action, it shows that the magnitude of dominance was higher than additive effect indicating that PFSR resistance is largely governed by dominance effect i.e., non additive component is not fixable for resistance. It is also found that the resistant genotypes also exhibited highest significant positive heterosis and combining ability effects (GCA and SCA). A considerable yield reduction in grain yield (10.5 to 28.3%) over checks was observed in susceptible lines. Most of the genotypes were found resistant as the reduction in yield is low. Hybrids developed using such lines exhibited high yields which are promoted for extensive testing to know their stability before release as commercial hybrids.

A novel parent selection strategy for the development of drought-tolerant cotton cultivars

AbstractDrought is a devastating factor for crop production worldwide. Therefore, an experiment was conducted to study genetics for some agro-physiological traits in cotton under drought stress. The 13 parental cotton genotypes along with their 30 F1 hybrids were planted under normal and drought conditions. The mean performance of the genotypes was assessed through principal component and heat map analyses. The principal component analyses revealed 53.99 and 53.15% in the first two principal components of variability for normal and drought conditions, respectively. Heat map analysis revealed that three cotton genotypes i.e. FH-207 × NS-131, FH-207 × KZ-191 and S-15 × AA-703 attained higher values for all the traits except for canopy temperature under drought conditions. These crosses may proliferate to further filial generations to identify transgressive segregates for drought tolerance. The heritable differences of F̅1 and mid-parent showed dominance and non-additive gene action under drought conditions. Heritable differences between F̅1 and P̅1 showed over dominance and partial dominance under drought conditions. Heritable differences between F̅1 and P̅2 indicated negative over dominance and partial dominance for all traits under drought conditions. Proline contents and the bolls per plant showed high heritability and genetic advance through additive gene action. Therefore, these two traits can be used as a means of selection in future breeding programmes of drought tolerance.