Utility of pearl millet landraces in breeding dual-purpose hybrids for arid zone environments of India

In pearl millet (Pennisetum glaucum (L.) R. Br.), single cross hybrids based largely on exotic germplasm, have found very limited adoption in drought-prone arid regions mainly due to their inadequate adaptation to prevalent extremely harsh agro-climatic conditions. This study tested the hypothesis that the use of restorer parents derived from adapted landrace germplasm could be an alternative strategy in developing suitable hybrids for arid regions. Forty inbred restorer lines developed from two phenotypically diverse landraces were used to develop hybrids evaluated in this study for their performance in five typical arid zone environments between 2003 and 2007. Inbred lines from both landrace populations differed significantly in their combining ability for biomass, harvest index and grain and stover yields. A larger proportion of experimental hybrids, based on selected inbred lines, significantly outperformed the commercial checks for grain and stover yields. Increase in grain and stover yields was achieved primarily due to their higher biomass productivity, with no decline in harvest index. Choice of landrace determined the relative grain and stover productivity of their hybrids. Phenotypic differences observed in parental landraces in tillering and panicle length were also visible in their respective hybrids, indicating that characteristics of landrace parental populations were transmitted in their hybrids.     

A 192bp allele at the <Emphasis Type="Italic">Xgwm261</Emphasis> locus is not always associated with the <Emphasis Type="Italic">Rht8</Emphasis> dwarfing gene in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

The height-reducing gene Rht8 was introduced into Italian wheats by breeder Nazareno Strampelli from the Japanese landrace Akakomugi, and has been widely used in wheats adapted to southern and eastern European conditions. Following identification of a close linkage to Rht8, microsatellite marker Gwm261 has been used extensively to screen large numbers of diverse international germplasm. A 192bp allele at this locus has been taken as “diagnostic” for Rht8 and used to infer the international distribution of Rht8. In this paper, we report several instances of cultivars and mapping populations that vary for the presence of the 192bp allele at the Xgwm261 locus (Xgwm261 ₁₉₂ ), but with no associated reduction in height, suggesting a lack of association with Rht8. For instance, in the population derived from a cross between Sunco (Rht-B1b, Xgwm261 ₁₆₅ ) and Tasman (Rht-D1b, Xgwm261 ₁₉₂ ), there were significant height differences associated with the segregation of Rht-B1b and Rht-D1b, but no height differences between Xgwm261 genotypes. Similar results were obtained in a population derived from the cross between Molineux (Rht-B1b, Xgwm261 ₁₉₂ ) and Trident (Rht-D1b Xgwm261 ₂₀₈ ). In contrast, the cross between Trident and Chuanmai 18 (Xgwm261 ₁₉₂ ) gave significant height effects at both the Rht-D1 and Xgwm261 loci, with no epistatic interaction between loci. Chuanmai 18 is closely related to the Strampelli wheat Mara (ancestrally derived from Akakomugi) and is therefore likely to carry Rht8. The old Japanese cultivar Norin 10, used by Norman Borlaug to introduce Rht-B1b and Rht-D1b into Mexican wheats, also has a 192bp allele at the Xgwm261 locus, and the sequence of the amplified product is identical to that of Akakomugi. We suggest that the widespread use of Norin 10-derived germplasm during and after the Green Revolution introduced a second haplotype into international germplasm, in which Xgwm261 ₁₉₂ has no association with Rht8. Therefore, the presence of Xgwm261 ₁₉₂ is only indicative of Rht8 in wheat cultivars that have inherited this allele from Akakomugi or a Strampelli wheat ancestor.     

Participatory crop improvement and formal release of <Emphasis Type="Italic">Jethobudho</Emphasis> rice landrace in Nepal

Jethobudho is an aromatic rice landrace of the Pokhara valley in middle hills of Nepal. Although local consumers are willing to pay a high price for its purchase, the landrace has a problem with quality variation. Decentralized participatory population improvement for specific market-identified traits was conducted on “Jethobudho” populations collected from farmers’ fields in seven geographic regions of the valley in Nepal. The preferred post harvest quality traits, field tolerance to blast and lodging, and superior post harvest quality traits of Jethobudho were established by a consumer market survey. These traits were used for screening the materials. 338 sub-populations of Jethobudho were evaluated for yield, disease, lodging resistance, and post harvest quality traits. Significant variation was found for culm strength, neck blast tolerance, awn characteristics, panicle length, number of grains per panicle, test grain weight and post harvest quality traits, whereas no significant variation was found in grain yield, plant height, tiller number, maturity period and leaf blast. Based on these identified traits and micro-milling evaluations, 183 populations were screened in on-farm and on-station nurseries, and in succeeding years populations were further screened by plant breeders and expert farmers in research trials, resulting in the selection of 46 populations for post harvest quality traits. Six accessions with similar agronomic traits, field tolerance to blast and lodging, and superior post harvest quality traits, were bulked and evaluated on-farm using participatory variety selection (PVS). The enhanced Jethobudho accessions were also evaluated for aroma using simple sequence repeat (SSR) and found to have unique aromatic genetic constitution. Community based seed production groups were formed, linked to the Nepal District Self Seed Sufficiency Programme (DISSPRO), and trained to produce basic seeds (truthfully labeled) of Jethobudho. The National Seed Board of Nepal released the enhanced landrace in the name of “Pokhareli Jethobudho” in 2006, as the first bulk variety of traditional high quality aromatic rice improved through participatory plant breeding to be formally released in Nepal for general cultivation under the national seed certification scheme. Landrace improvement is shown as an important option for supporting programmes for in situ conservation of landraces on-farm.     

Genetic diversity in landrace populations of Hordeum vulgare L. from Sardinia, Italy, as revealed by RAPDs, isozymes and morphophenological traits

Barley is the second most widely cultivated cereal on the island of Sardinia. It is grown for green fodder, grain and straw, all of which are used for animal feet. The cultivation of modem varieties is limited and many farmers grow local populations of the six-row landrace ‘S'orgiu sardu’. Twelve local populations (20 strains per population) were evaluated for 13 random amplified polymorphic DNA (RAPD) markers, sisisozyme loci and five morphophenological traits. Results showed that Sardinian barley is characterized by a lax six-row spike and is. in general, a spring type. Isozyme polymorphism was delected for only two esterase loci (Est and Est 4). The genetic variation for all types of murkers, was found located mostly within population (about 84%, for isozymes aud morphaphenological traits and 89%, for RAPDs). This finding appears to confirm the hypothesis that the populations studied belong to the same land race called ‘S'orgiu sardu’ by farmers. A geographical differential ion between southern and northern populations was foand in relation to distinct environmental characteristics. Taking into account all types of marker 209 (90.5%) different genotypes were identified out of 231 individuals. The overall results confirm the high variability that can be found within landrace populations, underlining the value of landraccs as a source of genetic variation.     

The cultivation revival of a landrace: pedigree and analytical breeding

This paper aims at improving the legume landrace Fava Santorinis (Lathyrus sp.) through the study of the existing variability, and an intra-landrace pedigree, combined with analytical selection, scheme. The experiments were conducted at the farm of Aristotle University of Thessaloniki during five growing seasons (2005–2009), and the selection was applied on a spaced plant conditions. In the first stage, single-plant frequency distributions of the source landrace for grain yield and pod number plant⁻¹ was studied, and a percentage of 60.80% of non productive plants was found. In the second stage, improvement of grain yield relied on direct pedigree selection, accomplished by analytical selection for the number of pods plant⁻¹, plant leaf color and vigor. This procedure was followed along the first generation progenies, and, later on, along two successive generations on the offsprings of two populations, one with purple and the other with white flower color. In the third stage, the evaluation of the fourth-generation progenies of each population for grain yield, showed superiority ranging from 42.48 to 107.89% compared to the source landrace. Furthermore, the breeding procedure succeeded in: (i) decreasing the coefficient of variability of grain yield and pods plant⁻¹, thus increasing the stability of performance, (ii) reducing by 56.41 and 39.67% the non productive plants for white and purple flower populations, respectively, and (iii) maintaining the mean and the variability for pod traits as in the original landrace. Realized heritability for grain yield was positive during all selection cycle.     

Characterizing the molecular and morphophysiological diversity of Italian red clover

Red clover (Trifolium pratense L.) is the third major forage species in Europe, but there is limited information on the biodiversity and the genetic structure of landraces and natural populations which evolved in this region. The objective of this study was producing such information for Italian germplasm on the ground of molecular and morphophysiological diversity. The study included 16 Italian natural populations from a wide range of environments, four landraces representing the four traditional commercial ecotypes, and two varieties. Eight morphophysiological traits were assessed in a replicated trial under field conditions, whereas two AFLPs primer combinations with 140 polymorphic markers were recorded on a random sample of 13 genotypes per population. Ordination and classification results based on morphophysiological data clearly kept track of the type of germplasm (i.e. landrace or natural population) and its geographic origin, unlike results based on molecular markers. Euclidean distances among populations based on morphophysiological traits were not correlated with Nei’s genetic distances based on molecular markers according to Mantel’s test. Geographical distances among landrace or natural population material was correlated with distances based on morphophysiological traits but not with those based on molecular markers. The average within-population variation estimated via molecular markers was about 2.6-fold higher than that among populations, preventing an acceptable discrimination among most populations. On average, natural populations tended to have within-population variation similar to varieties and somewhat lower than landraces. Our results have implications for collection, conservation, exploitation and registration in a sui generis system of red clover genetic resources.     

Variation of grain iron content in a local upland rice germplasm from the village of Huai Tee Cha in northern Thailand

Crown rust caused by Puccinia coronata Cda. f. sp. avenae Eriks., is a major fungal disease of cultivated oats (Avena sativa L.) in Tunisia. Six landrace oats (M_tK₂, JT₅, BJ₃₅, GT₁, ZN₃ and JT₀) locally collected and previously screened for their relative oat crown rust resistance were used in this experiment. These accessions were evaluated during a two cropping season in field plots under heavy natural oat crown rust infection. Assessment criteria to crown rust reactions were AUDPC, latent period, uredinia size and number of uredinia per cm² of infected leaf area. Principal components analysis showed that the variables were grouped in two components. These two principal components explained 83.56% of the total variance. The projection of the point-cloud representing the populations on the plan formed by the principal components ‘Fact 1’ (63.83%), in abscissa, and ‘Fact 2’ (19.73%) in ordinate, permitted to distribute the accessions in several groups. Three landrace oats (M_tK₂, JT₅, and JT₀) showed the lowest value of all the components used. These landrace oats might be good sources of effective and durable resistance to crown rust.     

Diversity, genetic structure, distinctness and agronomic value of Italian lucerne (Medicago sativaL.) landraces

Eleven landraces belonging to the seven commercial ecotypes of northern Italy, and seven elite varieties, were evaluated with the aims of: (i) comparing landrace and variety germplasm for dry weight (DW, recorded across three harvests spanning over two years) and morphophysiological characteristics; (ii) estimating among-population (s _A ²) and within-population (s _W ²) genetic variances of landrace and variety germplasms; (iii) investigating the interrelationships among traits at the plant and the population levels; (iv) exploring patterns of phenotypic diversity, and the relationships between diversity and environmental variables at landrace collecting sites; and (v) assessing the distinctness of ecotypes. Some 256 or 512 genotypes per landrace, and 128 genotypes per variety, were grown in dense stand in an unreplicated design together with a replicated clone. Compared with varieties, landrace material showed higher total DW (+9%) and DW at the last harvest (+43%), lower (2.5-fold) summer mortality and autumn dormancy (P< 0.01), and similar winter mortality. Landraces exhibited a greater s _W ²value than varieties for all traits except autumn dormancy and number of florets per inflorescence (P< 0.01), with s _W ²always exceeding s _A ²(P< 0.01). The ratio of s _W ²to s _A ²averaged 23.1 for landraces and 6.5 for varieties across eight traits. Frequency of mowing at collecting sites was associated with higher total DW, better persistence, lower summer and winter mortality, larger leaflets and more stems per plant (r≥ 0.66, P< 0.05). Cluster analysis showed that landraces geographically close or belonging to the same commercial ecotype tended to greater similarity. However, one landrace that evolved under very frequent mowing differed greatly from other landraces of the same ecotype. Based on discriminant analysis, two ecotypes may be sufficiently distinct for registration in a sui generissystem, even though they may not meet the criteria for registration under a homegenity requirement     

Outcrossing rates of barley landraces from Syria

Diversity levels in populations of barley landraces may be influenced by varying levels of natural outcrossing caused by environmental conditions. Outcrossing was studied in 10 accessions of the barley landrace Arabi Aswad from different environments in Syria. Electrophoretic variation at two codominant isoenzymes (Est1 and Est2) in six seeds of 50 families per population were analysed and multilocus outcrossing rates calculated. Results were correlated with interpolated environmental conditions. Outcrossing was, on average, 1.7% and not significantly different from the outcrossing rate of wild barley. A significant increase of outcrossing was observed with increasing inter‐annual variation in rainfall and decreasing minimum temperatures of the coldest month.     

Inheritance of seed resistance to bruchids in cultivated mungbean (Vigna radiata, L. Wilczek)

Bruchid beetles or seed weevils are the most devastating stored pests of grain legumes causing considerable loss to mungbean (Vigna radiata (L.) Wilczek). Breeding for bruchid resistance is a major goal in mungbean improvement. Few sources of resistance in cultivated genepool were identified and characterized, however, there has been no study on the genetic control of the resistance. In this study, we investigated the inheritance of seed resistance to Callosobruchus chinensis (L.) and C. maculatus (F.) in two landrace mungbean accessions, V2709BG and V2802BG. The F₁, F₂ and BC generations were developed from crosses between the resistant and susceptible accessions and evaluated for resistance to the insects. It was found that resistance to bruchids in seeds is controlled by maternal plant genotype. All F₁ plants derived from both direct and reciprocal crosses exhibited resistance to the bruchids. Segregation pattern of reaction to the beetles in the F₂ and backcross populations showed that the resistance is controlled by a major gene, with resistance is dominant at varying degrees of expressivity. Although the presence of modifiers was also observed. The gene is likely the same locus in both V2709BG and V2802BG. The resistant gene is considered very useful in breeding for seed resistance to bruchids in mungbean.     

Farmers' seed management practices open up new base populations for pearl millet breeding in a semi-arid zone of India

Farmers in western Rajasthan (north‐west India) produce and maintain their landrace populations of pearl millet through their own distinct seed management practices. The objective of this study was to characterize morphological and agronomic variability of different traits between and within three farmers' populations using quantitative‐genetic parameters. Populations examined were a typical landrace and two modified landraces, which were generated through farmer introgression of modern varieties with different levels of subsequent selection. From these three populations, 100 random full‐sib progenies were evaluated in field trials at two locations in western Rajasthan over two years. Significant genetic variation existed within the three populations. Estimates of heritability were moderate to high for all observed traits. Predicted selection response for grain yield across environments was 1.6% for the typical landrace and 2.2% for both the modified landraces. Results suggest that the introgression of modern varieties into landraces had increased the genetic diversity. Therefore, farmers' current breeding activities could open up new resources for plant breeding programmes aiming at plant improvement for the semiarid zones of India.     

Resistance to bacterial blight (Pseudomonas syringae pv. pisi) in Spanish pea (Pisum sativum) landraces

Pea bacterial blight (Pseudomonas syringae pv. pisi) has long been known to be present in pea growing areas of Spain and to cause serious crop losses, although there is no published record of its occurrence. A collection of 16 isolates from a winter pea trial in Valladolid in 1991 which were shown in this study to be P.s. pv. pisi races 4 and 6 would appear to be the first published record of the disease in Spain. This occurrence of races 4 and 6 is the same as reported for winter-sown peas in the South of France. Ten Pisum sativum landraces from different geographical areas of Spain and considered to be representative of the traditional pea crop, were tested for resistance to seven races of P.s. pv. pisi. Seedlings of each landrace were stem inoculated with the type strain of each race in a glasshouse. Resistance exhibited by the different landraces mainly conformed to those previously described in pea cultivars indicating various combinations of the main resistance genes: R3, R2+4, R3+4 and R2+3+4. R3 was the most frequent R gene, being present in all landraces. R4 was present in four and R2 in three of the landraces tested. Variation for resistance within landraces was limited except for landrace accessions ZP-0102, ZP-0109 and ZP-0137 which also showed variation for morphological traits. The resistance responses of landrace ZP-0109 were difficult to interpret, but suggested a genetic mixture with some evidence of less well documented R genes, R5 and/or R6, and possibly some unknown resistance to race 6. This revised version was published online in July 2006 with corrections to the Cover Date.     

Line selection for exploiting durum wheat (T. turgidum L. var. durum) local landraces in modern variety development program

Summary Pure line selection for grain yield applied within four durum wheat local landraces (Triticum turgidum L. var durum) was studied in an effort to determine: (i) the agronomic performance of selected line mixtures (bulks) and their value as potential new cultivars, (ii) the effectiveness of pure line selection for grain yield within local landraces and (iii) the correlated selection response of yield components and kernel quality traits. Four local durum wheat landraces were used. Two of them, Mytilini-1 and Mytilini-2 are still cropped in some rural areas of the island Mytilini whereas the other two, Limnos and Mavragani are maintained in the Greek Gene Bank. Following their preliminary evaluation for agronomic performance under current growing conditions, 100 individual plants from each landrace were randomly selected. Selected plants (pure lines) were field evaluated head to row during 1997–98 and 1998–99 growing seasons. Based on grain yield performance, bidirectional selection, high vs low, was practised within each landrace. Thus the five higher yielding lines and their corresponding lower ones from each landrace were identified. Selected lines, with no further progeny testing, were pooled using a balanced seed composite to form the high yielding five line bulk and its respective low counterpart. The resulting 16 bulks (eight high and eight low) along with their four source landraces and two commercial varieties, Mexicalli and Simmeto, used as checks, entered field testing for agronomic performance in two and one location during 1999–00 and 2000–01 growing seasons respectively. Data for grain yield and yield components (1000 kernel weight, number of kernels, and productive tillers) along with kernel quality data (protein content and vitreous) were recorded. Data for grain yield indicated that the landraces studied seemed to be line mixtures, as expected, since they responded to bidirectional phenotypic pure line selection. The high yielding bulks were of interesting agronomic performance, equivalent to or significantly better than that of the commercial checks and are worth further testing as potential cultivars. Selected high bulks of Mytilini 2 landrace significantly outyielded both the source landrace and the commercial checks maintaining the high protein content of the source landrace, which was significantly higher than checks. This performance provides evidence that the within landraces selection of lines combining high grain yield with high protein content seems to be feasible. In conclusion, evidence is presented that genetic variability seems to be available within the landraces studied which could be worth using in breeding programs. Furthermore the simple pure line selection breeding effort undertaken seemed to be effective in developing line bulks with promising performance and worth further testing as potential cultivars.     

Random amplified polymorphic DNA (RAPD) markers variability among cultivars and landraces of common beans (Phaseolus vulgaris L.) of south-Brazil

To evaluate the variability among cultivars and landraces of common bean(Phaseolus vulgaris L.), 15 cultivars and 18 landraces of common bean (Phaseolus vulgarisL.), a undefined species of Phaseolus,two landraces of Vigna angularis L., and a landrace of soybean (Glycine maxL.), were screened with fifteen oligonucleotide primers in PCR reactions. An average of 20.3 RAPD bands were scored per primer. A total of 304 amplification products were scored of which 88.8% were polymorphic among Phaseolus genotypes. Based on the RAPD markers, four major clusters were formed. Three clusters corresponded to the soybean, to the two Vigna angularis landraces, and to the Phaseolus sp. landrace, respectively. The fourth cluster include all the landraces and cultivars of Phaseolus vulgaris. This large group could be separated into three subgroups that were correlated with the phaseolin patterns and the average seed weight of the genotypes. The analysis shows that most of the landraces collected in South Brazil (17 out of 18) belong to the Andean gene pool, and most of the cultivars (13 out of 15) belong to the Middle American gene pool. This revised version was published online in July 2006 with corrections to the Cover Date.     

Identification of DNA probes that reveal polymorphisms among closely related Phaseolus vulgaris lines

Summary Analyses of genetic diversity within populations could be of great benefit to plant genetic resources conservation. In order to identify genetic markers that are variable within populations, the genome of Phaseolus vulgaris was screened with several DNA sequences in order to identify hypervariable sequences. Polymorphisms were observed between Middle American and Andean cultivars using the protein III tandem repeat of the M13 phase and the 33.15 human minisatellite. Extensive differences were observed when the DNA of two divergent lines—BAT93 and Jalo EEP558, of Middle American and Andean origin, respectively—were digested with HinfI, TaqI, HaeIII and hybridized with the 33.15 human minisatellite. Similarly, numerous polymorphisms were observed when the M13 protein III tandem repeat region was hybridized with TaqI digests of these cultivars. Polymorphism was also detected among sister lines of two F₆ backcross materials involving Middle American and Andean lines when genomic DNA was digested with TaqI and hybridized with M13 tandem repeat region. In addition, polymorphism was observed among Porrillo cultivars that resulted from selection within a single landrace population. Whereas only one isozyme difference had been observed previously among the Porrillo cultivars, eleven restriction fragments detected by the M13 protein III tandem repeat sequence differentiated these cultivars. Ribosomal DNA also hybridized to several polymorphic bands on TaqI and EcoRI genomic Southern blots of the F₆ backcross material. Only one polymorphism was observed with EcoRI-digested genomic DNA of BAT93 and Jalo EEP558 was hybridized with microsatellite (GACA)₄. This probe might be useful in ascertaining relationships at the species and subspecies level, and as a marker in mapping studies. Our results show that both the human 33.15 minisatellite and M13 should be useful probes to detect within-population variability in common bean.     

SSR-tagged breeding scheme for allogamous crops: a trial in bunching onion (<Emphasis Type="Italic">Allium fistulosum</Emphasis>)

In several autogamous and vegetatively propagated crops, DNA markers have been used for cultivar identification. However, allogamous crops such as bunching onion (Allium fistulosum L.) are recalcitrant to marker-aided cultivar identification, as well as hybrid seed purity tests, due to the high degree of genetic heterogeneity within each cultivar. To aid cultivar identification and ensure its accuracy in bunching onion, we proposed the “SSR-tagged breeding” scheme in our previous study. The feasibility of this scheme was investigated here using a landrace of bunching onion with two populations tagged with two or four selected SSR markers. Compared with a control population, no significant differences were detected in the agronomic traits of the SSR-tagged populations. The targeted SSR loci were genetically uniform within each population whereas other loci maintained high heterogeneity. These results demonstrate that the SSR-tagged breeding scheme, even with a very small number of markers, is efficient for the identification of newly bred cultivars, and consequently for F₁ purity tests, in allogamous crops in which inbreeding depression is as severe as in bunching onion.     

Seed Shattering of Cañahua (Chenopodium pallidicaule Aellen)

Cañahua (Chenopodium pallidicaule Aellen) is a semi‐domesticated relative of quinoa (Chenopodium quinoa Willd.) with high nutritious quality. It is tolerant to frost, drought, saline soils and pests. One seed yield limitation is seed loss during the maturity stages. Two greenhouse experiments in Denmark and field experiments in Bolivia were carried out to determine seed shattering in landraces and cultivars with different growth habits. 15–21 % of the seed shattering in the fields took place whilst the plants still were flowering and 25–35 % during physiological maturity. Seed shattering varied between locations on the Bolivian Altiplano. Cañahua types with the semi‐prostrate growth (‘lasta’) had the highest seed shattering rate in the greenhouse experiments. The Umacutama landrace had lower seed shattering (1 %) than the cultivar Kullaca (7.2 %) both of the ‘lasta’ type. Under field conditions, the cultivar Illimani with the erect growth (‘saihua’) had the highest seed shattering rate (6.4–33.7 %) at both locations and at four different sowing dates. The Umacutama had the lowest rate (0.5–1.5 %). There were no significant differences between plants of the ‘lasta’ and the ‘saihua’ types. The landrace had significantly less seed loss than the cultivars. However, in the greenhouse, the landrace yield was approximately 25 % lower than the yields of the cultivars. In general, cañahua cultivars had higher yield compared to landraces, but also a higher seed shattering rate. Landraces may be used in breeding programmes to develop high‐yielding cultivars with reduced seed shattering.     

Inheritance of ‘domestication’ traits in bambara groundnut (Vigna subterranea (L.) Verdc.)

Controlled crosses in bambara groundnut were attempted between a range of thirty-six bambara groundnut landraces (thirty domesticated (V. subterranea var. subterranea) and six wild (V. subterranea var. spontanea)). Ten F₁ seed were produced. Of these, eight germinated producing F₂ populations. On seed set, four populations could be unambiguously confirmed as true crosses by F₃ seed coat colour. A single F₂ population, derived from a domesticated landrace from Botswana (DipC; female parent) crossed with a wild accession collected in Cameroon (VSSP11; male parent) was used to study a range of agronomic and domestication traits. These included; days to emergence, days to flowering, internode (fourth) length at harvest, number of stems per plant, leaf area, Specific Leaf Area (SLA), Carbon Isotope Discrimination (CID), 100 seed weight, testa colour and eye pattern around the hilum. On the basis of variation for internode length and stems per plant, 14 small F₃ families were selected and grown under field conditions to further investigate the genetic basis of the ‘spreading’ versus ‘bunched’ plant character, a major difference between wild and cultivated bambara groundnut. Results presented suggest that traits including leaf area, SLA, CID and 100 seed weight are controlled by several genes. In contrast, the variation for traits such as internode length, stems per plant, days to emergence and seed eye pattern around the hilum are likely to be under largely monogenic control. The results of this work are discussed in relation to the domestication of bambara groundnut.     

Inheritance of heading time in spring barley evaluated in multiple environments

The inheritance of heading time of spring barley was studied in three extremely early genotypes IB, RL and ‘Mona’ (M), which is homozygous recessive for the early maturity ea8 (=ea_k) gene conferring extreme earliness under short daylengths and is relatively photoperiod insensitive, and five (GP, MA, PS, NU and BA) spring genotypes that are early to intermediate for heading time. Frequency distributions of F₂ generations grown at Ouled Gnaou, Morocco (32°15′ N), an environment which maximizes differences between photoperiod‐insensitive and photoperiod‐sensitive genotypes, indicated that across populations many loci were segregating in a complex Mendelian manner. IB and RL were both homozygous recessive for the ea8 gene, which conferred an early heading time. RL had partially dominant alleles at second locus (Enea8), which enhanced its earliness. Recovery of only progeny within the parental range of genotypes for heading time from the crosses of RL/M and IB/M suggests that numerous loci remained suppressed, perhaps latent, given their diverse parentage. The ea8 recessive homozygote in RL suppressed another unidentified locus which, when homozygous recessive in the absence of the ea8 recessive homozygote, conferred extreme earliness in one short daylength environment (Ouled Gnaou, Morocco) but was undetected in another environment (Davis, CA, USA). Epistatic gene action and genotype × environment effects strongly influenced heading time. In addition to a genetic system consisting of single‐locus recessive homozygotes conferring photoperiod insensitivity, a second genetic system, based on dominant alleles at one or a few loci, derived from the early heading Finnish landrace ‘Olli’, also confers extremely early heading time under short daylengths and relative photoperiod insensitivity in the genotype GP.