Wide Genetic Base Research Articles

IDENTIFICATION OF OUTSTANDING SALADETTE TOMATO LINES WITH A WIDENED GENETIC BASE

The “bell pepper” or “chino criollo” tomato is a native Mexican variety with similar characteristics to the “Saladette” tomato and the potential to be used as a source of germplasm to generate commercial hybrids of this type. The aim of this investigation was to identify and select advanced lines with a wide genetic base, derived from crosses between Saladette tomatoes and native populations to generate free pollination varieties and potential parents of Saladette tomato hybrids. The hypothesis was that crosses between native populations and Saladette commercial hybrids generate outstanding offspring. The 103 genotypes evaluated included 10 native parents, three parents derived from commercial hybrids, one commercial hybrid control (“El Cid”) and 89 S4 advanced lines. The evaluation was carried out in a greenhouse and hydroponics during the 2020 spring-summer cycle, using a randomized complete block experimental design with three replications and four plants per replication. The total weight and number of fruits were recorded based on the sum of the two cuts performed. The days to flowering of the first cluster, average fruit weight, and total soluble solids were also determined. Analyses of variance were carried out for each variable, as well as orthogonal contrasts and correlations between different combinations of the materials of interest. The comparison of means was carried out using Tukey’s test (p ≤ 0.05). Nine advanced lines with similar or greater characteristics to the control were identified and are recommended to be recombined genetically in a diallelic cross scheme to identify new outstanding offspring. The advanced line 2051 (LOR85 X C) was identified, with a similar yield to that reported for the control, which can be used as an open pollination variety since it has similar characteristics to the control “El Cid”, but with native tomato genes.

Identification of multiple abiotic stress tolerant donors for climate-resilient rice (Oryza sativa) development

The increasing occurrence of adverse weather events is continuously challenging agricultural production globally. The wide genetic base of rice (Oryza sativa L.) and the availability of a diverse set of germplasm can be explored to identify multiple abiotic stress-tolerant donors for rice improvement. Therefore, an experiment was conducted during 2018–21 at ICAR-National Rice Research Institute, Cuttack, Odisha to evaluate diverse rice germplasm (68 accessions) for vegetative stage drought and submergence stress and for their anaerobic germination potential. Under drought stress, 49 accessions showed a drought score (DS) of 1 indicating a tolerance response. The early vegetative score indicated that 58 accessions were highly vigorous, while the drought recovery score indicates that >90% of the genotypes showed good recovery after the drought cycle. The same genotypes showed a average survival rate (SR) of 48% under two weeks of complete submergence. Among them, 11 were found highly tolerant with >70% SR and 26 genotypes scored positive SUB1A locus by SNP-based functional marker AEX1. Nearly 50% of the genotypes scored positive for SUB1A, based on both AEX1 and Sub1A203 markers, which nearly matched the phenotyping result. Out of 68, only 4 accessions showed more than 50% germination under anaerobic conditions. A multivariate analysis showed that 11 genotypes had both drought and submergence tolerance, while 6 genotypes were having tolerance to drought and anaerobic germination. We found only 1 accession (IC516149) tolerant to all these 3 stresses which can be identified as a potential donor for multiple abiotic stresses.

Analysis of the results of studying the soft winter wheat collection by tolerance to powdery mildew

Topicality. Thanks to analysis and systematization of wheat collection, we will be able to obtain new sources of tolerance and create a trait collection for the developing tolerant varieties suitable for cultivation in different ecozones of Ukraine. Yield losses from pathogens can be reduced by introducing new varieties with a wide genetic base of group tolerance. Purpose. To characterize the soft winter wheat collection in terms of tolerance to powdery mildew in the conditions of the Southern Forest Steppe of Ukraine. Materials and Methods. During 2011–2019, the research was conducted at the Ustymivka Research Station of Plant Production Institute named after V. Ya. Yuriev NAAS of Ukraine. We studied 1406 samples of soft winter wheat (Triticum aestivum L.) from 33 countries, including 53.1 % – Ukrainian origin, 10.1 % – from Turkey, 8.6 % – from the United States, 6.9 % – from Russia, 17.0 % – from Europe. Research methods: field, dialectical, hypothesis, synthesis, induction, statistical, observation. Results. The manifestation of the main foliar diseases on collection samples of soft winter wheat was observed to determine field tolerance to diseases in the following organogenesis stages: autumn tillering, spring budding, stem elongation, beginning of heading, milk-dough maturity. In the early growth and development stages of wheat plants (seedlings – heading), plants were insignificantly damaged by powdery mildew. In the autumn tillering stage, 5 samples out of 234 were not affected by powdery mildew: 831/10, 853/10 (UKR), Pesma (YUG), Gruia, Gloria (ROU). During the period of stem elongation, there are 12 samples of soft winter wheat susceptible to this disease in this stage of organogenesis. Arid conditions in 2012 and 2013 were more favorable for distribution of the wheat collection for disease tolerance at the heading stage, in which the susceptible and weakly susceptible samples under study accounted for approximately 14 %. The maximum damage by this pathogen occurs in milky-wax ripeness of wheat. Distribution by the level of tolerance significantly depends on the conditions of a particular year. Thus, in 2011 (excessively humid conditions), the percentage of susceptible samples of wheat to the pathogen was 57.5 %; in 2012 and 2013, a larger group of samples was noted as weakly susceptible. The significant influence of the amount of precipitation and the level of hydrothermal coefficient (HTC) on the number of susceptible wheat samples to powdery mildew during heading (r = 0,83 and r = 0,91, respectively) was established. The average level of correlation between the indicators of the number of highly susceptible wheat samples to this disease and the level of HTC (r = 0,33) was noted. The method of distant hybridization using foreign genes helps to obtain lines more resistant to specific pathogens of soft winter wheat. Conclusions. Distribution of winter wheat samples by the level of tolerance to powdery mildew depended significantly on the conditions of a particular year. The special collection of samples resistant to the most common diseases of soft winter wheat allows you to systematize the selection of parental lines on specific traits, which will create more resistant lines. Key words: soft winter wheat, tolerance, powdery mildew, stage of organogenesis, hydrothermal coefficient, distant hybridization method

Unifying Principles of Cryopreservation Protocols for New Plant Materials Based on Alternative Cryoprotective Agents (CPAs) and a Systematic Approach

This review addresses a frequently encountered problem of designing an effective cryopreservation procedure for new (not previously cryopreserved) or difficult plant materials. This problem hinders worldwide efforts of applying cryopreservation across a wide genetic base of wild and a number of cultivated plants. We review recent advances in modifications of routinely applied cryoprotective solutions (CPAs) and suggest a practical approach to protocol development which embraces the physiological complexity of plant tissues as well as a wide spectrum of behaviours under CPA treatment. We suggest that vegetative plant materials are classified into four categories based on their size, structure, and the response to osmotic and chemical stresses provoked by CPA mixtures of varied composition and concentration, including alternative osmoprotection and vitrification solutions. A number of up to 15 preset protocols designed specifically for each category is then applied to the material. The protocols resulting in the best regrowth are then combined into the optimized procedure. The ma -andcryopreservation protocol is a minimal amount of starting materials required for the tests and a relatively accurate prediction of material behaviour under cryopreservation stress provided by the relatively few CPAs treatments. The unifying principles revealed by this approach could broaden a spectrum of wild species and materials which can be safely conserved by cryopreservation. Also anticipated is application of this approach to plant materials of biotechnological value as well as cultivars of agricultural and horticultural crops which do not respond well to standard protocols developed for their kind.

HISTORY AND EVALUATION OF EMMER WHEAT

Grains are the most important source of calories and protein in the world. It is known that 52% of the daily calorie intake per capita in the world is taken from proteins and 47% from grain products. Wheat grain, which is one of the most important cereal products, has been the main food source for most countries for many years due to its suitable nutritional value, transportation, storage, easy cultivation, and wide adaptation limits.
 Undoubtedly, wheat comes first among the cultivated plants that are of great importance in different aspects today. Wheat is an indispensable food item for human nutrition in Turkey as well as all over the world. Productive and high-quality wheat varieties developed with traditional plant breeding programs have met the nutritional needs of people so far, and studies continue rapidly today. However, world agriculture is facing serious problems due to changing biotic and abiotic environmental pressures. The cultivars have become more homogeneous in terms of their genetic structures and contain less genetic diversity than their village varieties, transitional forms, and wild relatives. Wild species, transitional forms, and village varieties are gene stores that have a wide genetic base and constitute an important resource for the elimination of future problems of cultivated plants or for the acquisition of new characteristics in plants.

Significance of sweet sorghum as a multi-purpose crop for sub-Saharan Africa

There is great interest in sweet sorghum (Sorghum bicolor L.) for promoting resilience in rural livelihoods in Sub- Saharan Africa (SSA). Unlike other crops, sweet sorghum is a multi-purpose crop for grain, feed, fodder, chewing, syrup and biofuel production. The objective of this paper is to analyse information on the diversity within the crop, its adaptation and plant breeding efforts in SSA. We also discuss opportunities that exist in SSA that make the crop an attractive alternative. It is clear from the review that the crop has a wide genetic base, hence significant improvements can be made on a number of preferred traits. The review further outlines four possible production models for the economic development of the sweet sorghum industry in Sub-Saharan Africa; which are (i) production for supply to urban chewing markets, (ii) syrup production, (iii) biofuel production and (iv) fodder production. Although current research focuses on production of ethanol for biofuel, other potential uses such as production for chewing, syrup and fodder cannot be overlooked for most SSA farmers. A lot has to be done on the research front before biofuel production from sweet sorghum can be profitable and technically feasible. Future plant breeding efforts can be tailor made to deliver cultivars with peculiar traits for various end-uses.

Multivariate Analysis and Its Application for Characterizing Cowpea Landraces

Background: Several major crops have been genetically eroded due to introduction of new material but cowpea have great potential and wide genetic base of novel significance. A new strategy of cowpea evaluation was adopted to investigate the potential of 71 landraces representing 31 districts of Pakistan through multivariate analysis to devise future plan for germplasm conservation. Methods: Cowpea 71 landraces collected from 31 districts were planted under field conditions in an augmented design. Plant descriptors qualitative traits (plant color, leaf shape, plant type, twining tendency, anthocynin pigment and fodder types) and agronomic traits (plant height, branches, pods, grain yield, biomass and harvest index) were recorded. Protein banding pattern was established. Similarity index, variance were calculated and phylogenetic trees were constructed by software “Statistica”.Result: Four cowpea landraces showed tremendous performance to phenotypic as well as protein banding pattern variation viz., Pk-27154 (Jhang), Pk-27047 (Vehari), Pk-27029 (Sialkot) and Pk-27107 (Bahawalpur). High inter and intra variation suggested further genotype x environmental interaction trials at multi-locations. Sampling from the neglected areas especially Sindh and Baluchistan parts are hereby recommended to gather unique landraces and accessions before the genetic resources might be depleted through various environmental stresses.

Recent Strategies for Detection and Improvement of Brown Planthopper Resistance Genes in Rice: A Review.

Brown planthopper (BPH; Nilaparvata lugens Stal) is considered the main rice insect pest in Asia. Several BPH-resistant varieties of rice have been bred previously and released for large-scale production in various rice-growing regions. However, the frequent surfacing of new BPH biotypes necessitates the evolution of new rice varieties that have a wide genetic base to overcome BPH attacks. Nowadays, with the introduction of molecular approaches in varietal development, it is possible to combine multiple genes from diverse sources into a single genetic background for durable resistance. At present, above 37 BPH-resistant genes/polygenes have been detected from wild species and indica varieties, which are situated on chromosomes 1, 3, 4, 6, 7, 8, 9, 10, 11 and 12. Five BPH gene clusters have been identified from chromosomes 3, 4, 6, and 12. In addition, eight BPH-resistant genes have been successfully cloned. It is hoped that many more resistance genes will be explored through screening of additional domesticated and undomesticated species in due course.

Analysis of genetic diversity and population structure in Asparagus species using SSR markers

BackgroundVarious Asparagus species constitute the significant vegetable and medicinal genetic resource throughout the world. Asparagus species serve as important commodity of food and pharmaceutical industries in India. A diverse collection of Asparagus species from different localities of Northwest India was investigated for its genetic diversity using simple sequence repeat (SSR) markers. ResultsPolymorphic SSR markers revealed high genetic diversity. Primer SSR-15 amplified maximum of 8 fragments while 3 primers, namely, SSR-43, SSR-63, and AGA1 amplified minimum of 3 fragments. Collectively, 122 alleles were amplified in a range between 3 and 8 with an average of 5 alleles per marker. The size of the amplified alleles ranged between 90 and 680 base pairs. Polymorphism information content (PIC) value varied from a highest value of 0.499 in primer AGA1 to a lowest value of 0.231 in primer SSR-63 with a mean value of 0.376 showing considerable SSR polymorphism. Dendrogram developed on the basis of Jaccard’s similarity coefficient and neighbor-joining tree segregated all the studied Asparagus species into two discrete groups. Structure analysis based on Bayesian clustering allocated different accessions to two independent clusters and exhibited low level of individual admixture. ConclusionsThe genetic diversity analysis showed a conservative genetic background for maximum species of asparagus. Only Accessions of Asparagus adscendens were split into two diverse clusters suggesting a wide genetic base of this species as compared to other species. Overall genetic diversity was high, and this germplasm of Asparagus can be used in future improvement programs. The findings of current research on Asparagus germplasm can make a momentous contribution to initiatives of interbreeding, conservation, and improvement of Asparagus in future.

Exploring the genetic base of the soybean germplasm from Africa, America and Asia as well as mining of beneficial allele for flowering and seed weight.

Genetic diversity is the foundation for any breeding program. The present study analyzed the genetic base of 163 soybean genotypes from three continents viz. Africa, America and Asia using 68 trait-linked simple sequence repeats (SSR) markers. The average number of alleles among the germplasmfrom the three continents followedthe trend as Asia (9) > America (8) > Africa (7). Similar trends were observed for gene diversity (0.76 > 0.74 > 0.71) and polymorphism information content (PIC) (0.73 > 0.71 > 0.68). Thesefindings revealed that soybean germplasm from Asia has wider genetic base followed by America, and least in Africa. The 163 genotypes were grouped into 4 clusters by phylogenetic analysis, whereas model-based population structure analysisalso divided them into 4 subpopulations comprising 80.61% pure lines and 19.39% admixtures. The genotypes from Africa were easily distinguished from those ofother two continents using phylogenetic analysis, indicatingimportant role of geographyical differentiation for this genetic variability. Our results indicated that soybean germplasm has moved from Asia to America, and from America to Africa. Analysis of molecular variance (AMOVA) showed 8.41% variation among the four subpopulations, whereas 63.12% and 28.47% variation existed among and within individuals in the four subpopulations, respectively. Based on the association mapping, a total of 21 SSR markers showed significant association with days to flowering (DoF) and 100-seed weight (HSW). Two markers Satt365 and Satt581 on chromosome 6 and 10, respectively, showed pleiotropic effect or linkage on both traits. Genotype A50 (Gakuran Daizu/PI 506679) from Japan has 8 out of the 13 beneficial alleles for increased HSW. The diverse genotypes, polymorphic SSR markers and desirable alleles identified for DoF and HSW will be used in future breeding programs to improve reproductive, yield and quality traits.

Field screening of RRISL recommended rubber clones against Corynespora Leaf Fall Disease

Identification of resistant clones is of vital importance in the management of Corynespora leaf fall disease (CLFD) of rubber. The recommended and potential clones were screened in a bud wood nursery which was especially designed for screening purposes at Ratnapura, Kalutara, Moneragala and Padiyatalawa. The lesion types agreed with the symptoms observed in the field plants and new symptoms have been identified from Padiyatalawa, in non-traditional rubber growing areas. Analysis of results from test methods showed that 81% of the recommended clones by the Rubber Research Institute of Sri Lanka (RRISL) can be ranked as resistant. Among the clones screened, no clones were found to be severely susceptible, yet moderately or mildly susceptible clones have been identified. This information should be used in future breeding programmes and also should be considered by the growers while selecting clones for their own plantations. The cultivation of resistant clones with a wide genetic base is considered as the most reliable long-term solution in the management of CLFD.

Assessment of genetic diversity in yardlong bean (Vigna unguiculata (L.) Walp subsp. sesquipedalis Verdc.) germplasm from India using RAPD markers

Germplasm characterization is essential to utilize and improve plant genetic resources in various breeding programs. The present study was aimed to characterize genetic variation in 28 accessions of yardlong bean (Vigna unguiculata (L.) Walp. subsp. sesquipedalis Verdc.) collected from different states of India. A total of 48 random amplified polymorphic DNA markers were examined to generate binary data profiles, out of these 31 markers were informative with scorable and reproducible banding patterns. 100% polymorphism was attained across the genotypes with total 2447 amplicons. Among these, OPC8 was highest with outcome of 160 amplicons, OPS7 and OPD5 followed with 149 and 144 amplicons. The polymorphic information content value among the genotypes varied from 0.23 to 0.93. Jaccard’s similarity coefficient ranged from 0.063 to 0.942 explaining wide genetic base. Dendrogram constructed by Unweighted Pair Group Method with Arithmetic Averages method classified 28 genotypes into 5 major clusters. Cultivar IC-582860 was found to be unique due to its least similarity with other genotypes. IC-582850 and IC-582875 showed highest similarity with (94%). Correlation study among morphological traits also revealed highly positive correlation between seed protein content with pod length; 100 seed weight with pod length and seed protein content; pod yield with number of pods per cluster and number of pods per plant. Thus the present study reveals discrimination, characterization and differentiation of yardlong bean by explaining genetic variation between and within the genotypes. This may further useful for genome mapping, crop improvement and to develop new plant varieties with high yield and pod quality in yardlong bean.

Evaluation of tomato genotypes for early blight disease resistance caused by Alternaria solani in Pakistan

Four hundred one tomato genotypes representing 11 species were screened against early blight (EB) disease caused by Alternaria solani in a net-house during 2013 to 2017. Considerable variation in resistance/susceptibility levels to EB was observed in the tested germplasm. Only one genotype ‘21396’ of Solanum lycopersicum was resistant and 56 were moderately resistant while the remaining were susceptible to highly susceptible. The pace of disease development was much slower in resistant genotype as symptoms were confined only to lower older leaves. The resistant genotype ‘21396’, most of the moderately resistant ones and a few susceptible and highly susceptible genotypes were rated resistant to stem and fruit infection. Resistant and moderately resistant S. lycopersicum genotypes and mutants with desirable characteristics could be grown in regions with high disease incidence, and can be used for the development of resistant/tolerant cultivars. The moderately resistant germplasm with very poor horticultural traits can nevertheless be used in resistance breeding programmes for developing superior cultivars and hybrids having new resistance genes to EB with a wider genetic base.

Evaluation on second generation progeny test of introduced Acacia crassicarpa species in Wonogiri, Central Java

Kartikaningtyas D, Surip, Setyaji T, Sunarti S, Nirsatmanto A. 2018. Evaluation on second generation progeny test of introduced Acacia crassicarpa species in Wonogiri, Central Java. Pros Sem Nas Masy Biodiv Indon 4: 52-57. Tree improvement of introduced species Acacia crassicarpa was implemented by establishing the second generation of progeny test using wide genetic base, and it was expected to produce superior individuals with good genetic quality. The purpose of this study is to determine the growth and genetic diversity of introduced A. crassicarpa derived from Papua New Guinea (PNG) provenance on a second generation progeny test. The progeny test was established in Wonogiri which was laid out in randomized completely block design / RCBD, 66 families, 6 replications, 4 tree-plot with a spacing of 4 x 2 meters. Measurement was conducted at 36 months after planting including height, diameter at breast height, bole length, stem straightness and stem volume. The results showed that the families were significantly different for all measured traits. The proportion of the family variance to the total phenotypic variance ranged from 3.55% to 7.45%. Individual heritability was moderate(0.14 to 0.30), while the family heritability was low to moderate (0.28 to 0.46). The genotype correlations ranged from 0.31 to 0.91, and the value is greater than the phenotype correlations, except in diameter for diameter-stem straightness correlations. Genetic gain of the traits were 1.72% to 4.64%, with the highest gain was found for bole length.

Variability and genetic diversity study in an advanced segregating population of rice with bacterial blight resistance genes introgressed

ABSTRACT Bacterial blight disease of rice caused by Xanthomonas oryzae pv. oryzae is one of the most important widespread disease around the globe and can cause severe yield reductions of up to 30% of the total yield. Genetic variability was studied in 54 families of CB 174 R × IRBB 60 rice with bacterial blight resistance genes introgressed at the Department of Rice, Tamil Nadu Agricultural University, Coimbatore, India. Traits such as plant height and the number of productive tillers per plant were found to have negative skewness in this study, indicating the duplication of gene effects. Panicle length and the number of grains per panicle were found to have positive kurtosis, indicating gene interactions. The phenotypic coefficient of variation was slightly higher than the genotypic coefficient of variation for all traits, indicating that the observed variation was not only due to genotypic but also due to the environmental effect on the expression of these traits. High heritability coupled with high genetic advance as a percent of the mean was observed for plant height. Moreover, moderate heritability coupled with high genetic advance as a percent of the mean was observed for the single plant yield of rice. Cluster and principal component analyses revealed that the 54 F2:3 families were grouped into three clusters based on six agro-morphological traits. Clusters III and II had higher mean values for most of the studied traits than cluster I. Intercrossing lines from distinct clusters can be identified and crossed to generate larger variability to produce desirable recombinants for higher yield with a wide genetic base.

Heterosis and combining ability studies for economic traits in garden pea (Pisum sativum L.)

A line × tester analysis comprising of 7 promising lines and three testers having wider genetic base was carried out for pod yield and related horticultural traits in garden pea (Pisum sativum L.) Among parents, line 17, line 14 and Palam Triloki were observed as best general combiners for pod yield and majority of component traits. Cross, line 17 x Arkel showed high heterosis and SCA effects for pod yield and related horticultural traits. The cross combination line 17 x Palam Triloki was most promising for early flowering and green pod picking. For most of the traits including pod yield per plant non-additive gene actions were of prime importance.

Genetic diversity and relationship assessment of tomato (Solanum lycopersicum L.) genotypes using molecular markers

Genetic variability and relationships among 21 genotypes of tomato were analyzed using PCR-based molecular markers. A total of 25 random decamer oligonucleotide primers were examined to generate RAPD profiles. Out of these, reproducible patterns were obtained with 15 primers. A total of 72 amplicons were obtained, out of which all were polymorphic and seven were unique bands. In case of SSR studies, however, nine primers were used and total number of amplicons obtained were 33 with three unique bands. The percentage of total polymorphism across genotypes was 100% in both RAPD and SSR studies. Genetic similarity matrix, based on Jaccard's coefficients, ranged from 3.85% to 73.17% indicating a wide genetic base. Dendrogram was constructed by using unweighted pair group method with arithmetic averages method. The study showed the importance of RAPD and SSR markers for genetic analysis and indicated a considerable amount of genetic diversity among the different studied genotypes of tomato.

Assessment of genetic diversity in lettuce (Lactuca sativa L.) germplasm using RAPD markers.

The importance of germplasm characterization is an important link between the conservation and utilization of plant genetic resources in various breeding programmes. In the present study, genetic variability and relationships among 25 Lactuca sativa L. genotypes were tested using random amplified polymorphic DNA (RAPD) molecular markers. A total of 45 random decamer oligonucleotide primers were examined to generate RAPD profiles, out of these reproducible patterns were obtained with 22 primers. A total of 87 amplicon were obtained, out of which all were polymorphic and 7 were unique bands. The level of polymorphism across genotypes was 100% as revealed by RAPD. Genetic similarity matrix, based on Jaccard's coefficients ranged from 13.7 to 84.10% indicating a wide genetic base. Dendrogram was constructed by unweighted pair group method with arithmetic averages method. RAPD technology could be useful for identification of different accessions as well as assessing the genetic similarity among different genotypes of lettuce. The study reveals the limited genetic base and the needs to diversify using new sources from the germplasm.

Genetic Diversity among Selected Elite CIMMYT Maize Hybrids in East and Southern Africa

Genetic gain within the CIMMYT Eastern and Southern Africa (ESA) hybrid maize (Zea mays L.) breeding program from 2000 to 2010 was recently estimated at 0.85 to 2.2% yr−1 under various environmental conditions. Over 100 varieties were disseminated from CIMMYT to farmers in ESA, hence the need to check genetic diversity and frequency of use of parents to avoid potential narrowing down of the genetic base. Fifty‐five parents from CIMMYT ESA used in the hybrids were fingerprinted using genotyping‐by‐sequencing. Data analysis in TASSEL and MEGA6 generated pairwise genetic distances between parents of 0.004 to 0.4005. Unweighted pair group method with arithmetic mean (UPGMA) analysis produced two clusters (I and II) with two subclusters each (A and B) and two sub‐subclusters (IAi and IAii). Principal coordinate analysis produced three clusters where IAi and IIA from the UPGMA analysis formed independent clusters while IAii, IB, and IIB clustered together. Lines were separated by pedigree and origin. Ninety‐five percent frequency of pairwise genetic distances ranged between 0.2001 and 0.4000. However, only four of the 55 parents (CML444, CML395, CML312, and CML442) were each used in 15 to 30 of the 52 hybrids evaluated in the genetic gain study. The remaining 51 were used in one to four hybrids. Frequent use of the four parents gave 29 to 58% of the hybrids a narrow genetic base, posing risk in case of pest or disease outbreaks. Parents evaluated do not represent the genetic base of CIMMYT ESA but parents of the best‐performing hybrids selected from 2000 to 2010. Breeders should ensure a wide genetic base for released varieties to avoid breakdown in case of pest or disease outbreaks.

Molecular characterization of African marigold (Tagetes erecta) genotypes using RAPD markers

The present investigation was carried out to characterize 22 genotypes of marigold (Tagetes erecta L.) with RAPD (randomly amplified polymorphic DNA) markers. A total of 26 RAPD markers were utilized for assessment of genetic divergence in marigold which amplified a total of 241 amplicons, out of which 238 (98.80%) were found polymorphic. The average number of amplicon per primer was 9.27. The Jaccard's similarity coefficient ranged from0.18 to 0.80. The mean values of polymorphic information content (PIC), resolving power (RP) and marker index (MI) of RAPD primers were 0.38, 8.36 and 3.44 respectively. Cluster analysis was done by unweighted pair group method for arithmetic average (UPGMA) and Principal Component analysis (PCA) was also done for the grouping of genotypes. The broad range of Jaccard's similarity coefficient observed for the genotypic data generated suggest the wide genetic base for marigold genotypes which will be effectively explored for future breeding programmes.