Diverse Parental Lines Research Articles

Evaluation of Genetic Diversity in Sorghum Genotypes for Drought Tolerance Using Mahalanobis’ D2 Analysis

Genetic diversity is vital in plant breeding and crop improvement, enabling the development of varieties resilient to biotic and abiotic stresses. Mahalanobis' D² analysis is a robust multivariate statistical method for assessing genetic diversity, offering precise measures of genetic divergence. This study aimed to evaluate the genetic diversity of twenty sorghum (Sorghum bicolor L. Moench) genotypes under rainfed and irrigated conditions using Mahalanobis’ D² statistics. The experiment was conducted at the Main Agricultural Research Station (MARS), Dharwad, involving twenty genotypes sourced from the AICRP sorghum, Dharwad, India. The genotypes were sown in medium black soil under two moisture levels: rainfed and irrigated. Morphological, physiological, phenological, and yield-related traits were recorded to identify drought-tolerant genotypes. Genetic divergence was estimated using D² statistics, and genotypes were grouped into clusters using Tocher’s method. Under rainfed conditions, the genotypes were classified into six clusters, while under irrigated conditions, they were grouped into three clusters. The intra-cluster distances ranged from 7.79 to 12.14 under rainfed conditions and from 8.14 to 15.74 under irrigated conditions. The inter-cluster distances revealed significant genetic variation, with the highest divergence observed between Clusters III and V under rainfed conditions and Clusters II and III under irrigated conditions. These findings highlight the presence of substantial genetic diversity among sorghum genotypes, facilitating the selection of diverse parental lines for breeding programs aimed at enhancing drought tolerance. The insights gained from this study contribute to the development of resilient sorghum varieties capable of withstanding water scarcity, ensuring sustainable agriculture, and promoting food security in drought-prone regions.

Bulk Segregant Analysis for the Identification of Shoot Fly Resistance Linked Molecular Marker in Sorghum [Sorghum bicolor (L.) Moench

Sorghum (Sorghum bicolor (L.) Moench) is one of the most important crops in the semi-arid regions of the world. One of the important biotic constraints to sorghum production in India is the shoot fly which attacks sorghum at the seedling stage. The study was undertaken during 2021–22 at the Centre for Millets Research, Sardarkrushinagar Dantiwada Agricultural University, Deesa, Gujarat, India to assess linked molecular markers for sorghum shoot fly resistance using the bulk segregant analysis (BSA) method with simple sequence repeat (SSR) marker from developed F2 mapping population with two genetically diverse parental lines, SWARNA (susceptible to shoot fly) and IS 18551 (resistant to shoot fly). Sixty-five SSRs primers pair were used for the parental polymorphism survey using two contrasting parents to detect the primers exhibiting polymorphism. Eight out of sixty-five primers showed polymorphism (12.30%) between two contrasting parental lines in sorghum. Two out of eight polymorphic SSRs primer pairs i.e., Xtxp 67 and Xgap 88 were found polymorphic between resistance and susceptibility in parents and bulks and thus reported to be putatively linked with shoot fly. Bulk segregant analysis (BSA) was extended to identify the traits controlled by minor genes with additive effects, which increased the power and efficiency of this molecular technique to construct genetic map in the sorghum crop improvement program. The identified SSRs markers i.e., Xtxp 67 and Xgap 88 might be useful to screen resistance for shoot fly infestation in future sorghum improvement program.

Genetic Diversity of Cowpea Parental Lines Assembled for Breeding in Uganda

Cowpea is a grain legume that is commonly grown in Sub-Saharan Africa (SSA) for a variety of uses including food, feed, and soil fertility enhancement through nitrogen fixation. Genetic improvement in cowpea can be accomplished by creating breeding populations from high-performing but genetically diverse parental lines. The goal of this study was to use single nucleotide polymorphic markers (SNPs) to estimate genetic diversity and population stratification among cowpea parental genotypes from five countries. A total of 2,746 SNP markers were used to analyze 62 cowpea genotypes that differed in key characteristics. Only 55% of the SNP markers were polymorphic across the 62 genotypes and met the selection requirement. The gene diversity varied from 0.52 to 0.57 with an average of 0.55, while the polymorphic information content ranged from 0.46 to 0.51 with an average of 0.49, showing that the cowpea parental lines are genetically diverse. The analysis of molecular variance (AMOVA) found high significant (p < 0.001) variation among genotypes and non-significant variation across genotypes depending on country of origin. The cluster analysis for the 62 genotypes using the unweighted pair group procedure with arithmetic mean approach divided the genotypes into two distinct groups. Genotypes from the same geographical regions tended to cluster together and there was a significant level of genetic variation among genotypes from Uganda and Nigeria. The SNP markers utilized in this study were effective at distinguishing genotypes and may be used to estimate the diversity in the cowpea core collection. The genetic diversity in this collection is important for future development of improved varieties of cowpea in Uganda.

Characterisation of bell pepper (Capsicum annuum L. var. grossum Sendt.) accessions for genetic diversity and population structure based on agro-morphological and microsatellite markers

Bell pepper (Capsicum annuum L. var. grossum Sendt.) is a leading Solanaceous vegetable crop across the world with immense therapeutic and export potential. Such wide cultivation exposes the crop to various biotic and abiotic stresses. Genetic diversity is one of the major prerequisites for any crop breeding programme. Hence, in this study, an attempt was made to evaluate the genetic diversity and population structure of 24 bell pepper genotypes using 25 agro-morphological [9 distinctness, uniformity and stability (DUS) descriptors; 13 quantitative traits; and 3 quality traits] and 82 microsatellite or simple sequence repeat (SSR) markers. Eight DUS descriptors showed polymorphism with maximum morphological variation (H = 1.29) for fruit shape in longitudinal section. Multivariate analysis using Mahalanobis D2 statistic distinguished the genotypes into 11 clusters. With a mean of 4.08 alleles per locus, a total of 151 alleles were generated from 37 polymorphic SSR primers. The polymorphic information content (PIC) ranged from 0.14 (CAMS 451) to 0.76 (CA 525390) with an average of 0.54. The genotypes were divided into two major clusters based on cluster analysis using the unweighted pair group method with arithmetic mean (UPGMA) algorithm, whereas the cluster tree using the neighbour-joining (NJ) method identified three major groups. The population was classified into three groups based on structure analysis. On comparing agro-morphological and molecular clusters, 11 genotypes viz., BWT-39, BWT-39-BR, BWT-39-DR, BWT-29, BWT-3Y, BWT-3Y-4L, Kandaghat Selection, BWT-48-AC, BWT-49-AC, EC-464107, and EC-464115, were found common. These genotypes also exhibited considerable resistance to bacterial wilt disease. Mantel's test showed a moderate positive correlation between agro-morphological (DUS descriptors) and molecular data. Therefore, a combined approach of agro-morphological and molecular evaluation can facilitate the selection of diverse parental lines followed by subsequent hybridisation between them to introduce new traits in bell pepper.

Genetic diversity analysis of Eggplant Germplasm from Iran: assessments by morphological and SSR markers.

Eggplant is an important vegetable that has long been cultivated in different parts of Iran. The major objectives of the eggplant breeding program are to improve fruit quality, increase yield performance through heterosis breeding, and introduce abilities of pest and disease resistance from wild relatives. In order to select suitable parents for breeding purposes, with respect to the genetic and morphological diversity of eggplant cultivars, it is necessary to have sufficient knowledge of genetic diversity and classification of germplasms. This experiment was conducted in a randomized block design at the Seed and Plant Improvement Institute (SPII) in Karaj, Iran. Here, morphological diversity was assessed among a collection of eggplants which comprised four Iranian lines and 13 non-Iranian genotypes. For this purpose, 16 morphological traits were analyzed in the plants. Given the weakness of morphological analysis in providing precise characterizations of genetic divergence, a molecular study was also carried out by using five Simple Sequence Repeat (SSR) markers. In addition to the univariate analysis, the multi-descriptor variation was studied among the genotypes using two methods of multivariate analyses. The genotypes differed significantly in terms of the morphological traits. The multivariate analyses of morphological data indicated that eggplants from two different origins were clearly differentiated. Three main clusters were distinguished by a morphological UPGMA dendrogram in which non-Iranian genotypes, with the exception of 11,212, constituted cluster I and required the maximum number of days to flower, days to fruit set, and days to first harvest. Cluster II was identified with two Iranian lines BJ30, Y60, and one non-Iranian genotype (11,212) which showed the highest values of stem diameter, fruit diameter, fruit length, fruit length-to-width ratio, number of fruits per plant, and yield. Cluster III comprised two Iranian lines, D1 and D7, and showed the maximum plant height, number of internodes, number of nodes, number of leaves, number of stems, fruit weight, and fruits weight per plant. The highest and lowest intra-cluster genetic distances were observed in cluster I and cluster II, respectively. Based on SSR analysis, high levels of similarity were detected between several genotypes, namely, Y60 and 13,411; BJ30 and 1111; D7 and 13,521; 21,881 and 13,421. High levels of heterozygosity and polymorphism information content (PIC) were observed in this study. This not only indicated high levels of polymorphism and an equal distribution of the evaluated loci but also suggested that these genotypes can be considered for the development of diverse parental lines which are of interest in breeding programs.

Review on Heterosis and Combining Ability Study for Yield and Morphological Characters of Coffee (Coffea arabica L) in Ethiopia

Ethiopia is both the center of origin and diversification of Coffee arabica. Despite the existence of high genetic diversity in coffee population that provides immense opportunities for improvement program, shortage of improved varieties (pure line and hybrid varieties) is the major one. It is obvious that research work carried out so far on coffee genetics and breeding was not adequate to address these diverse agro-ecologies of the country. Heterosis and combining ability studies are some of the basic breeding tools to address such problems. Some studies had been focused on assessment of heterosis and combining ability analysis for yield and morphological characters of coffee in Ethiopia and the presence of heterosis was reported in crosses of selected indigenous C. arabica L. varieties in Ethiopia under different set of studies mainly due to presence of diverse parental lines. These results clearly suggested that the possibility to bring significant coffee improvement through heterosis and combining ability analysis. Therefore, continuous crossing program should be required to acquire many more cross combinations for intensive and extensive evaluation to develop better performing and high yielding hybrids for Ethiopian origin coffee. Keywords: Coffee Arabica, morphological traits, yield, Heterosis and combining ability DOI: 10.7176/JEES/12-7-02 Publication date: July 31 st 2022

Heterosis and combining ability for yield traits and its relationship with gene action in muskmelon (Cucumis melo)

Twenty-one F1 hybrids were developed from seven diverse parental lines of muskmelon (Cucumis melo L.) from two horticultural groups, viz. inodorous and cantalupensis through half-diallel mating system and evaluated at ICARIndian Agricultural Research Institute, New Delhi, during 2017 and 2018. The component of variance for sca (σ2s) was higher than gca component of variance (σ2g) for all the characters, except average fruit weight, which indicated the importance of non-additive gene action for improvement of many traits. The predictability ratio and average degree of dominance was less than 0.5 and more than 1 for all the yield related traits, except average fruit weight, which further confirmed the predominant role of non-additive component of variance. The parent DHM-163 (P1) was identified as good general combiner for earliness, whereas parent DCM-31 (P4) for fruit length, average fruit weight and yield per plant. The parent Pusa Madhuras (P5) also exhibited highest gca effects for number of fruits per plant, number ofprimary branches per plant, fruit diameter and negative gca effects for days to first fruit harvest. The hybrid DCM-31 × Kashi Madhu (P4 × P6) exhibited highest heterotic value for days to first male flower anthesis, days to first female flower anthesis and days to first fruit harvest. Three crosses, DMM-159 × Pusa Madhuras (P3 × P5), DHM-163 × Kashi Madhu (P1 × P6) and DMM-159 × DCM-31 (P3 × P4) were found to be best heterotic combinations for yield related traits. These promising heterotic hybrid combinations may be tested under multi-location trials to assess their potential as commercial hybrids.

Heterosis and Per se performance studies in sesame (Sesamum indicum L.)

The present study comprised of a full diallel set of eight diverse parental lines and their 56 F1s including reciprocals. The data were recorded for ten quantitative traits. The analysis of variance revealed highly significant differences due to genotypes for all the characters. Mean performance of parents revealed a significant difference for all the traits under study excluding days to 50 per cent flowering and seed yield. The parent TBS-3 was top in seed yield per plant followed by TBS-10 and TBS-105. Length of the capsule was found highest in the parent TBS-10. Parental line V-29 recorded the maximum number of seeds per capsule while 1000 seed weight and oil content were recorded as the highest in TBS-105. Regarding the mean performance of hybrids exhibited significant difference for all the traits under study. Hybrid TBS-105 x R-09 was the top yielder followed by TBS-105 x V-29 and TBS-7 x V-29. Hybrid TBS-12 x TBS-105 had displayed a maximum 1000-seed weight whereas, the highest oil content was recorded in hybrid TBS-105 x V-29. Among the 56 F1s TBS-105 x R-09, TBS-105 x V-29 and TBS-7 x V-29 were top rankings crosses manifested highly significant and desirable heterosis for seed yield and either of the component traits viz., plant height, the number of branches, the number of capsules, capsule length and the number of seeds per capsule over mid, a better parent and standard check. Key words: Mid parent heterosis, heterobeltiosis, standard heterosis, reciprocals, sesame

Omics advances and integrative approaches for the simultaneous improvement of seed oil and protein content in soybean (Glycine max L.)

Genetic improvement of soybean, one of the major crops providing edible oil and protein-rich food, is important to ensure balanced nutrition for the growing world population. To make soybean cultivation more rewarding, an increase in seed oil and protein content is most desirable. Here, a critical review of the efforts employed over a half-century to accomplish the improvement of soybean oil and protein content has been presented. Many studies have used diverse parental lines to map and characterize quantitative trait loci (QTL)/genes regulating these two essential traits. Here, we highlighted such genomic loci that were consistently identified with different mapping approaches, like QTL mapping, genome-wide association studies (GWAS), and meta-QTL analysis. In addition, the information generated through efforts utilizing omics approaches, such as genomics, transcriptomics, and proteomics has also been compiled to anticipate the molecular mechanism. Several innovative approaches like multi-parental mapping, induced mutagenesis, genomic selection, transgenics, and genome-editing have been discussed in terms of effective utilization of technological advances to improve the oil and protein content in soybean. Information provided here will be helpful for better understanding and designing an effective strategy for simultaneous improvement in seed oil and protein content in soybean.

Genetic Diversity Assessment in Dolichos Bean (Lablab purpureus L.) Based on Principal Component Analysis and Single Linkage Cluster Analysis

Background: Dolichos bean occupies a unique position among the legume vegetables of Indian origin for its high nutritive value and wider climatic adaptability. Despite its wide genetic diversity, no much effort has been undertaken towards genetic improvement of this vegetable crop. Knowledge on genetic variability is an essential pre-requisite as hybrid between two diverse parental lines generates broad spectrum of variability in segregating population. The current study aims to assess the genetic diversity in dolichos genotypes to make an effective selection for yield improvement.Methods: Twenty genotypes collected from different regions were evaluated during year 2016-17 and 2017-18. Data on twelve quantitative traits was analysed using principal component analysis and single linkage cluster analysis for estimation of genetic diversity.Result: Principal component analysis revealed that first five principal components possessed Eigen value greater than 1, cumulatively contributed greater than 82.53% of total variability. The characters positively contributing towards PC-I to PC-V may be considered for dolichos improvement programme as they are major traits involved in genetic variation of pod yield. All genotypes were grouped into three clusters showing non parallelism between geographic and genetic diversity. Cluster-I was best for earliness and number of cluster/plant. Cluster-II for vine length, per cent fruit set, pod length, pod width, pod weight and number of seed /pod, cluster III for number of pods/cluster and pod yield /plant. Selection of parent genotypes from divergent cluster and component having more than one positive trait of interest for hybridization is likely to give better progenies for development of high yielding varieties in Dolichos bean.

Development of random mating population for genetic enhancement of yield traits in sunflower (Helianthus annuus L.)

As in any crop, in sunflower, to develop improved breeding lines having superior yield, oil content and resistantto biotic and abiotic stresses, it is essential to have genetically diverse parental lines. In this study, we used six trait specific inbred lines and allowed random mating in isolation. Through population improvement a total of 150 new restorer lines have been developed. Significant variation was observed for different traits among the lines studied. The progenies RGP-11-P1-S2 (39.89%), RGP-58-P4-S2 (39.31%), RGP-58-P4-S1-1 (39.31%) were promising for oil content. RGP-58-P4-S2 (32.1 g/plant), RGP-85-P1-S1 (31.3 g/plant), RGP-85-P1 (30.1 g/plant) for high seed yield. Based on survival under stress condition, the progenies RGP-21-P5, RGP-21-P6, RGP-32-P1 and RGP-61-P2 were identified as best genotypes under moisture stress conditions. RGP-21-P4-S1-3 and RGP-50-P2-S1 were completely free from powdery mildew.

Progress of Coffee (Coffea arabica L) Hybridization Development Study in Ethiopia: A Review

Ethiopia being the center of origin and genetic diversity of Arabica coffee is lucky in this regard. Despite the existence of high genetic diversity in coffee population that provides immense opportunities for improvement program, shortage of improved hybrid varieties is the major one. It is obvious that research work carried out so far on coffee genetics and breeding was not adequate to address these diverse agro-ecologies of the country. Hybridization study through heterosis and combining ability analysis are some of the basic breeding tools to address such problems. Some studies had been conducted on assessment of heterosis and combining ability analysis for yield and morphological characters of coffee in Ethiopia and the presence of heterosis was reported in crosses of selected indigenous C. arabica L. varieties in Ethiopia under different set of studies mainly due to presence of diverse parental lines. These results clearly suggested that the possibility to bring significant coffee improvement through heterosis and combining ability analysis. Therefore, continuous crossing program should be required to acquire many more cross combinations for intensive and extensive evaluation to develop better performing and high yielding hybrids for Ethiopian origin coffee. Keywords: Coffee Arabica, Hybrid, Heterosis and combining ability DOI : 10.7176/FSQM/92-03 Publication date: December 31 st 2019

Review on Heterosis and Combining Ability Study for Yield and Morphological Characters of Coffee (Coffea arabica L) in Ethiopia

Ethiopia is both the center of origin and diversification of Coffee arabica. Despite the existence of high genetic diversity in coffee population that provides immense opportunities for improvement program, shortage of improved varieties (pure line and hybrid varieties) is the major one. It is obvious that research work carried out so far on coffee genetics and breeding was not adequate to address these diverse agro-ecologies of the country. Heterosis and combining ability studies are some of the basic breeding tools to address such problems. Some studies had been focused on assessment of heterosis and combining ability analysis for yield and morphological characters of coffee in Ethiopia and the presence of heterosis was reported in crosses of selected indigenous C. arabica L. varieties in Ethiopia under different set of studies mainly due to presence of diverse parental lines. These results clearly suggested that the possibility to bring significant coffee improvement through heterosis and combining ability analysis. Therefore, continuous crossing program should be required to acquire many more cross combinations for intensive and extensive evaluation to develop better performing and high yielding hybrids for Ethiopian origin coffee. Keywords: Coffee Arabica, morphological traits, yield, Heterosis and combining ability DOI : 10.7176/JEES/9-12-03 Publication date: December 31 st 2019

Combining Ability Analysis for Yield, Quality, Earliness, and Yield-Attributing Traits in Tomato

ABSTRACTDevelopment of hybrids and varieties for better yield and quality traits requires identification of good specific and general combiners. Combining ability studies provide reliable information for selection of parents for hybrid combination by revealing the nature and magnitude of gene actions involved in expression of quantitative traits. Ten diverse parental lines of Tomato (Solanum lycopersicum L.) from the Canadian gene bank were crossed with four testers in a Line × Tester mating design. All 40 F1 hybrids, along with their parents, were evaluated. Analysis of variance for combining ability indicated variation for all traits under study due to lines. Crosses for all traits indicated availability of sufficient diversity to choose the best crosses for yield, quality, and yield-attributing traits. Variation due to testers occurred for days to first fruit set, average fruit weight, and average fruit diameter. Among lines and testers, EC95 (line) and ‘CLN 2264F’ (tester) exhibited desirable general combining ability effects for yield and quality and yield-attributing traits. Cross-combinations EC93 × ‘CLN 2264F’ and EC95 × ‘CO3’ exhibited higher specific combining ability for yield and yield-attributing traits; crosses EC86 × ‘CO3’, EC89 × ‘CLN 2264H’, and EC95 × ‘Punjab Chhuhara’ were good for quality attributing traits and crosses EC86 × ‘CO3’, EC88 × ‘Punjab Chhuhara’, EC89 × ‘Punjab Chhuhara’, EC93 × ‘CLN 2264H’, and EC94 × ‘CO3’ were good for earliness, indicating that these crosses may be further tested for commercial utilization.

Molecular-agronomic characterization and genetic study reveals usefulness of refined Ogura cytoplasm based CMS lines in hybrid breeding of cauliflower (Brassica oleracea var. botrytis L.)

Cytoploasmic male sterility (CMS) is the most widely used system for hybrid seed production in vegetable brassicas. Information of morphological and molecular divergence in combination with combining ability is instrumental in selecting suitable parent in hybrid development. Twenty five CMS lines developed after more than 9 generations of backcrossing were analysed for different agronomic and floral traits. Besides, they were also evaluated for combining ability to reveal their breeding potential. Two CMS lines, Ogu402-6A and Ogu76-4A were distantly placed from rest of the CMS genotypes based on morphological characterization. Molecular analysis through SSR primers also revealed the genetic distance of the CMS lines Ogu402-6A from rest of the CMS pool. Three genotypes (Ogu402-6A, Ogu76-4A and Ogu119-2A) with early maturity were identified for their use in development of short duration hybrids. Similarly, 3 CMS lines Ogu118-2A, OguHL-3A and Ogu126-1A were identified with yield potential of more than 60t/ha. Based on 13 polymorphic SSR markers 25 CMS lines were grouped into 4 major clusters. Molecular diversity in combination with agronomic characterization will be very useful in diverse parental lines. Introgression of Ogura cytoplasm into cauliflower nuclear background caused variety of flower deformities. However, these deformities were genotype specific. General combining ability (GCA) of the CMS lines revealed their potential for use in hybrid breeding. Few genotypes were identified based on combining ability for their use in development of short duration and high yielding F1 hybrids.

Heterosis study in Okra [Abelmoschus esculentus (L.) Moench] genotypes for pod yield attributes

A study was conducted at Vegetable Research Farm, Department of Horticulture, Institute of Agriculture Sciences, Banaras Hindu University, Varanasi during Spring-Summer and Rainy season of 2012 and 2013 using 12 diverse parental lines of okra and their 66 F1 hybrids (through diallel cross-excluding reciprocals) with the objective to measure the extent of heterosis over better parent and standard commercial check varieties for the purpose of judging the extent up to which heterosis can be exploited in commercial okra breeding. The extent of heterosis for five best crosses over better parent and check (48.32 % to 82.42 % and 7.13 % to 35.66 %, respectively) for yield per hectare suggested the great scope of realizing higher yield in okra through heterosis breeding. Other economic traits also recorded moderate to high level of heterosis over the better parents. The cross combination IC -282280×EC – 329380showed high heterosis over better parent and standard check for pod yield (82.42 % and 35.66 %), number of pods per plant (62.82 % and 48.54 %) and respectively. This particular cross combination eventually resulted the height magnitude of heterobeltiosis and standard heterosis for the most of the desirable growth parameters as well as yield attributing characters which may be taken for further breeding programme.

Genetic Characterization of Self-incompatible Lines and Strategies for Heterosis Breeding in Cauliflower

ABSTRACTCauliflower (Brassica oleracea var. botrytis L.) is a thermosensitive crop grown almost all year-round in North Indian plains due to development of genotypes for production under different temperature regimes. Comparatively, varieties of early and mid-maturity group cauliflowers exhibit low yield compared to that of late maturing snowball types. Despite the presence of a higher level of heterosis in Indian cauliflower, development of hybrids in India is lacking due to nonavailability of strong self-incompatibility-based hybrids suitable for different seasons. To identify diverse parental lines for breeding in early and mid-maturity Indian cauliflower, genetic characterization of self-incompatible inbred lines was carried out based on quantitative and molecular analyses. To study heterotic performance of these lines in relation to divergence, 80 and 54 F1 hybrids of early and mid-maturity groups, respectively, were developed into a Line × Tester mating design and evaluated for yield and related traits. The mid-maturity group had higher diversity compared to that of early maturity group. Of 32 random amplified polymorphic DNA (RAPD) and 38 simple sequence repeat (SSR) primers, 25 RAPD and 3 SSRs exhibited polymorphism and generated a total of 164 reproducible amplicons, of which 37 were polymorphic. The average number of amplicons per primer was 6.71 and the maximum number of polymorphic amplicons (three) was obtained from RAPD primer SK-14. In SSR markers, the average number of polymorphic amplicons was 1.48 per primer. The SSR marker BoREM-1b indicated heterozygosity in the self-incompatible lines ccm-8 and cc-35L and further inbreeding may produce homozygosity in these lines. Lines cc-32E (early) and cc-22 (mid-maturity) had the most heterotic crosses for marketable curd weight and moderate diversity at the molecular level could be utilized for heterosis breeding. The molecular makers with quantitative analysis may be utilized for assessment of genetic diversity, testing of hybrid purity, and protection of superior lines and hybrids.

Genetics of resistance to downy mildew in muskmelon (Cucumis melo L.)

To identify parents and specific combination of parents for resistance to downy mildew, thirty Ft hybrids were developed by crossing six female parents with five male parents in a line x tester mating design. Adult muskmelon plants of parents and hybrids were evaluated in greenhouse and field conditions. Significant variances for general combining ability (GC A) and specific combining ability (SC A) indicated the importance of both additive and non-additive gene actions for the expression of resistance. Inbred lines IIHR 352 (Cucumis melo var. reticulatus), IIHR 190 (Cucumis melo var. reticulatus) and IIHR 122 demonstrated consistently high and negative GCA effects in both screening conditions. Arka Jeet x IIHR 121, Arka Jeet x IIHR 122, Punjab Sunehri x IIHR 190, Punjab Sunehri x IIHR 718, IIHR 681 x IIHR 121, IIHR 681 x IIHR 122 and IIHR 352 x IIHR 616 were the hybrids expressed high per se performance, high midparent heterosis and high SCA effects. The study highlights the importance of harnessing useful genes from diverse parental lines to improve resistance to Pseudoperonospora cubensis in adapted muskmelon varieties/cultivars.

Heterosis for yield and yield contributing characters in cowpea genotypes

Fifteen F&lt;sub&gt;1&lt;/sub&gt; hybrids obtained by crossing 6 diverse parental lines of cowpea through diallel excluding reciprocals method was studied to investigate the extent of heterosis for yield and yield contributing characters during &lt;italic&gt;kharif&lt;/italic&gt;, 2007 and &lt;italic&gt;spring&lt;/italic&gt;&lt;italic&gt;summer&lt;/italic&gt;, 2008 season. Among the various components pods per plant and seeds per pods are important factor contributing to yield. IT-97K-1042 and IT-93K-452 were observed to be the top performing parents for total seed yield per plant. The crosses IT-97K-1042 X IT-98K-1111 and IT-97K-1042 X Pusa Komal were best heterotic crosses for seed yield and other characters.

Prediction of hybrid performance based on the genetic distance of parental lines in two-line rice (Oryza sativa L.) hybrids

A total of six TGMS (thermosensitive genic male sterile lines) and nine pollinator lines were subjected to molecular characterization using 48 genome-wide SSR (simple sequence repeat) markers. Cluster analysis revealed clear differentiation among the TGMS lines according to their source of origin. The SSR-based genetic distance between the hybrids of the parental lines ranged from 0.36 to 0.79 suggesting a high degree of genetic divergence. Among a set of 54 hybrids generated using parental lines, 32 showed better parent heterosis (+21.7%) while 19 showed mid-parent heterosis (+15.0%). For the trait yield per plant genetic distance (GD) was negatively correlated with F1 performance (r = −0.202), mid-parent heterosis (r = −0.325*; P < 0.05), and better parent heterosis (r = −0.261), while it was positively correlated with specific combining ability (r = 0.042). Based on the grouped genetic distance (GGD), the hybrid combinations were divided into four groups. The GGD showed linear correlation with hybrid performance within the group (GGD = 40–50: r = −0.07; GGD = 70–80: r = 0.32). This information can be utilized in the development of higher yielding, two-line rice hybrids through selection of intermediately diverse parental lines using GGD.