Research on the inheritance of seed dormancy in lettuce (Lactuca sativa L.) and selection for non-dormancy

Summary Inheritance of dormancy and the results of selection of non-dormant genotypes in segregating populations of lettuce were investigated. Diallel crosses were therefore carried out between two dormant (DOR) and two non-dormant (NDOR) cultivars. F₁, F₂ and F₃ populations were analysed.Environmental variation for dormancy usually was large. The mean germination time (GT) of F₁ seeds from the NDOR % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaciaacaqabeaadaqaaqaaaKaaafaafaqabeGaba% aajqgaa+FaaiaadIhaaeaacaWG4baaaaaa!3B90!\[\begin{array}{*{20}c}x \\x \\\end{array}\]DOR crosses was often intermediate to the GT of the NDOR and DOR parent. The mean GT of F₁ seeds from DOR % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaciaacaqabeaadaqaaqaaaKaaafaafaqabeGaba% aajqgaa+FaaiaadIhaaeaacaWG4baaaaaa!3B90!\[\begin{array}{*{20}c}x \\x \\\end{array}\]DOR crosses equalled the mean GT of the parents; the same applies for the NDOR % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaciaacaqabeaadaqaaqaaaKaaafaafaqabeGaba% aajqgaa+FaaiaadIhaaeaacaWG4baaaaaa!3B90!\[\begin{array}{*{20}c}x \\x \\\end{array}\]NDOR crosses. No differences between reciprocals were observed and neither were such differences found for F₂ populations. F₂ populations from DOR % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaciaacaqabeaadaqaaqaaaKaaafaafaqabeGaba% aajqgaa+FaaiaadIhaaeaacaWG4baaaaaa!3B90!\[\begin{array}{*{20}c}x \\x \\\end{array}\]DOR crosses showed no significant segregation of rapidly germinating seeds and in F₂ populations from NDOR % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaciaacaqabeaadaqaaqaaaKaaafaafaqabeGaba% aajqgaa+FaaiaadIhaaeaacaWG4baaaaaa!3B90!\[\begin{array}{*{20}c}x \\x \\\end{array}\]DOR crosses no accumulation of genes for long GT occurred. In F₂ populations from NDOR % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaciaacaqabeaadaqaaqaaaKaaafaafaqabeGaba% aajqgaa+FaaiaadIhaaeaacaWG4baaaaaa!3B90!\[\begin{array}{*{20}c}x \\x \\\end{array}\]DOR crosses usually 40–60% of the seeds germinated as rapidly as the seeds of the NDOR parents. Only one gene (D) could be responsible for the difference in dormancy behaviour of the DOR and NDOR cultivars. The behaviour of the F₃ lines from various NDOR % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaciaacaqabeaadaqaaqaaaKaaafaafaqabeGaba% aajqgaa+FaaiaadIhaaeaacaWG4baaaaaa!3B90!\[\begin{array}{*{20}c}x \\x \\\end{array}\]DOR crosses supports this hypothesis. A regression of F₃ means on the value of F₂ seeds for GT of various NDOR % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaciaacaqabeaadaqaaqaaaKaaafaafaqabeGaba% aajqgaa+FaaiaadIhaaeaacaWG4baaaaaa!3B90!\[\begin{array}{*{20}c}x \\x \\\end{array}\]DOR crosses showed that h²-narrow usually was rather high for most crosses implying that selection for non-dormancy can be carried out in F₂ populations.     

Analysis of quantitative variability for seed yield and related characters in Lotus corniculatus L. cv. Leo

Summary Quantitative variability for seed yield and six other characters was analysed in Lotus corniculatus L. cv. Leo. The material consisted of 144 polycross progenies and 100 parents.Wide variability existed for all characters. The characters with the greatest variability were seed yield, forage grading and plant height. The polycross progeny test was employed to study the general combining ability of the parents. Highly significant differences existed for all seven characters under study.Parent-offspring genotypic and phenotypic correlations were high and significant for all characters except genotypic correlations for seed yield and seeds per pod. High h² values (broad sense) were obtained for seed size and days to flowering. Traits with moderate to high h² were seed yield (71% in parents, 64% in progenies), plant height, forage grading, and seeds per pod. The character pods per inflorescence had the lowest h².Positive estimates of % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabiGaaiaacaqabeaadaqaaqaaaOqaaiqabo8agaqcaK% aaavaabeqaceaaaeaacaqGYaaabaGaaeiraaaaaaa!3A89!\[{\text{\hat \sigma }}\begin{array}{*{20}c} {\text{2}} \\ {\text{D}} \\ \end{array} \] were obtained only for seed size. The ratio of dominance variance to additive variance indicated partial dominance for this character. Except for seed yield, in all other cases these estimates had very high sampling errors. In all cases except pods per inflorescence and seeds per pod high positive estimates of % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabiGaaiaacaqabeaadaqaaqaaaOqaaiqbeo8aZzaaja% qbaeqabiqaaaqcaauaaiaaikdaaKaaGeaacaqGbbaaaaaa!3B30!\[\hat \sigma \begin{array}{*{20}c} 2 \\ {\text{A}} \\ \end{array} \] were obtained.The data indicated that it may be possible to simultaneously improve seed yield and maintain forage yield. Seed yield had positive and significant associations with seed size, seeds per pod and pods per inflorescence. The associations of days to flowering with forage grading (negative) and with pods per inflorescence (positive) were also significant.     

Heritability and predicted gain from selection in components of crop duration in divergent chickpea cross populations

Genetic analysis of ten quantitative traits related to crop duration in chickpea was carried out using three F ₂ sib-populations; 272-2 × CDC Anna, 298T-9 × CDC Anna and 298T-9 × CDC Frontier. F ₃ and F ₄ families from these populations were further evaluated for traits found important in the initial study. Also, 112 recombinant inbred lines (RILs) of chickpea cross ICCV 2 × JG 62 were evaluated for days to flowering, days to maturity and reproductive period. An analysis of the F ₂ population data using the mixed model approach revealed that the additive component of variance was significant for days to flowering, days to first podding and days to first pod maturity, while dominance genetic variance was significant for morphological components of crop duration such as height to first pod and height at flowering. Comparatively high heritability estimates (39–48%) were obtained for days to flowering, days to first pod maturity, percent pod maturity at four months after planting and days to maturity based on offspring-parent (F ₄ and F ₃ generations) regression and/or analysis of variance for the RIL population. The predicted gain from selection as a percentage of the population mean was low (5% or less) for these key components of crop duration owing to the low variability detected within the populations, the exception being percent pod maturity. To maximize gain from selection in these traits, it is therefore, essential to increase genetic variability among the progenies, potentially through multi-parent crosses that may involve gene introgression from across desi and kabuli types of chickpea and from wild progenitors.     

Effectiveness and relative discriminatory abilities of techniques measuring genotype × environment interaction and stability in okra (Abelmoschus esculentus (L) Moench)

Summary Twenty selected okra genotypes were evaluated in four different environments for stability of performance, measured by days to flowering, number of branches per plant, plant height, number of pods per plant, pod weight, and pod yield per plant. An analysis of the components of G × E interaction showed that it might not always be adequately explained by a linear function of the environment. The heritability estimates for the response of the characters showed that the number of branches per plant was under strong genotypic influence. The stability variance parameters, % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaaiaacaqabeaadaqaaqaaaOqaaiqbeo8aZzaaja% WaaWbaaSqabeaacaaIYaaaaaaa!3A18!\[\hat \sigma ^2\]and W-mean square and the deviation MS employed in the analyses of stability indicated that most of the genotypes were unstable in respect of the characters. The % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaaiaacaqabeaadaqaaqaaaOqaaiqbeo8aZzaaja% WaaWbaaSqabeaacaaIYaaaaaaa!3A18!\[\hat \sigma ^2\]and W-mean square produced similar results which were different from those of deviation MS; the two stability-variance techniques were more discriminatory than the regression technique.     

Agronomic performance and water-use efficiency of F3 soybean populations grown under contrasting base saturation

Most of the Brazilian soils, especially in Cerrado biome, have high acidity and toxic aluminium, making the application of limestone an indispensable technique to obtain high yield in soybean crop. The hypothesis of this study was that contrasting base saturation provides changes in water-use efficiency (WUE) and agronomic traits of soybean populations. Thus, we evaluated the WUE and agronomic performance of F₃ soybean populations under different base saturation levels. Each experiment was conducted in a randomized complete blocks design with three replicates and 10 F₃ populations (P1, P2, P3, P4, P5, P6, P7, P8, P9 and P10) for two crop seasons. Segregating populations were obtained by bulk method. In the first experiment, F₃ populations were evaluated without correction of base saturation (V = 30%), while in the second experiment, limestone was applied three months before sowing to increase base saturation to 60%. The traits evaluated were as follows: calcium, magnesium and potassium contents, water-use efficiency (WUE), plant height, first pod height, main stem diameter and grain yield. Our findings indicate that WUE and agronomic performance of F₃ soybean populations depends on the saturation condition. We identified the P4 and P9 populations as the most promising for use in breeding programmes aiming at higher tolerance to abiotic stress caused by low base saturation in soil.     

Combining ability of soybean (Glycine max) for low phosphorus tolerance on acidic soils of Western Ethiopia

Determining the gene actions governing the inheritance of traits of interest has paramount importance in designing a breeding approach to improve the progeny populations. This study was undertaken to determine the combining ability of nine selected parental lines in the F₂/F₃ segregating populations for low P tolerance. The experiment was laid out in an alpha lattice design in two locations, that is Mettu and Assossa of Western Ethiopia that are characterized by soils with low P and pH. General combining ability (GCA) effects were highly significant for grain yield, pod length, days to maturity and plant height, while specific combining ability (SCA) effects were highly significant for grain yield, 100-seed weight, pod length and plant height. The parent Hardee-1 was identified as the best general combiner for yield, number of seeds per pod, pod length, plant height and pod number. The results suggest that additive gene action was important for several of the studied traits, implied by significant GCA effect, which might indicate selection for these traits could be effective in later segregating generations.     

Micropropagation of intra and interspecific Lens hybrids

An intraspecific (Tetir × ILL 323) and an interspecific (Alpo × L. odemensis) lentil hybrid were multiplied in vitro in three consecutive micropropagation cycles to increase the production of F₂ seeds. Cloning efficiencies were slightly higher for Tetir × ILL323 (83%) compared to Alpo × L. odemensis (67%). A total of 982 F₂ seeds were produced in the experiment with Alpo × L. odemensis, consisting of the 334 F₂ seeds of the original hybrid and 648 F₂ seeds produced by the 12 plants cloned; consequently, F₂ seed production was increased three-fold over the original hybrid (194%). A total of 6050 F₂ seeds were produced in the experiment with Tetir × ILL 323, made up of the 483 F₂ seeds of the original hybrid and 5567 F₂ seeds produced by the 15 plants cloned; therefore, F₂ seed production was increased by more than twelve-fold over the original hybrid (1153%). In both hybrids the F₂ seed production of cloned plants diminished in the three consecutive multiplication cycles, with the plants having experienced less vegetative development. In lentil, F₂ seed production of cloned plants is related for the first time to the length of their period of vegetative development. In conclusion, micropropagation of hybrids is an interesting tool to construct from a single individual large F₁ populations that enable to increase by a manifold the production of F₂ seeds useful for genetic studies and breeding.     

Further evidence of polygenic inheritance of partial resistance in barley to leaf rust,Puccinia hordei

Summary The latent period (LP) is a crucial component of partial resistance. Five cultivars, L94, Sultan (Su), Volla (Vl), Julia (Ju) and Vada (Va), representing the known range in partial resistance and LP were crossed in a diallel, and the F₁, F₂ and F₃ tested. The LP effectuated by the five cultivars is about 9, 10^1/2, 10^1/2, 13 and 15^1/2 days, respectively. The crosses Su×L94, Vl×L94 and Ju×L94 had an F₂ positively skewed. Their F₂ means were similar or only slightly larger than the F₁ means. The F₂ frequency distributions in the crosses Vl×Su, Ju×Su and Ju×Vl were normal or nearly so with F₁ and F₂ means similar to each other and to the mid-parent value. The crosses involving Va as a parent again showed a positive skewness but with F₂ means considerably larger than the F₁ moans.Most F₂'s ranged from the low parent to the high parent values without transgression. In the crosses Va×L94 (reported earlier) and Ju×L94 the parental values were not recovered among 216 and 154 F₂ plants, respectively. The cross Ju×Va showed transgression beyond the low parent, Ju.From these data it is concluded, assuming no linkage, that seven loci are involved. The + alleles (governing a longer LP) are thought to be distributed over the parents as follows: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGceaqabeaacaqGmb% GaaeyoaiaabsdacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabcca% caqGGaGaaeiiaiaab2cacaqGTaGaaeiiaiaabccacaqGGaGaaeiiai% aabccacaqGGaGaaeiiaiaabccacaqGTaGaaeylaiaabccacaqGGaGa% aeiiaiaabccacaqGGaGaaeiiaiaabccacaqGGaGaaeylaiaab2caca% qGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaa% b2cacaqGTaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqGGaGaae% iiaiaabccacaqGTaGaaeylaiaabccacaqGGaGaaeiiaiaabccacaqG% GaGaaeiiaiaabccacaqGGaGaaeylaiaab2cacaqGGaGaaeiiaiaabc% cacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqGTaGaaeyl% aiaabccaaeaacaqGtbGaaeyDaiaabccacaqGGaGaaeiiaiaabccaca% qGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqGRaGaae4kaiaa% bccacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqGRaGaae% 4kaiaabccacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabUcacaqG% RaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaab2% cacaqGTaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqGGaGaaeii% aiaabccacaqGTaGaaeylaiaabccacaqGGaGaaeiiaiaabccacaqGGa% GaaeiiaiaabccacaqGGaGaaeylaiaab2cacaqGGaGaaeiiaiaabcca% caqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqGTaGaaeylaa% qaaiaabAfacaqGSbGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqG% GaGaaeiiaiaabccacaqGGaGaaeiiaiaabUcacaqGRaGaaeiiaiaabc% cacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabUcacaqGRaGaaeii% aiaabccacaqGGaGaaeiiaiaabccacaqGGaGaaeylaiaab2cacaqGGa% GaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabUca% caqGRaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqGGaGaaeiiai% aab2cacaqGTaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqGGaGa% aeiiaiaabccacaqGTaGaaeylaiaabccacaqGGaGaaeiiaiaabccaca% qGGaGaaeiiaiaabccacaqGGaGaaeiiaiaab2cacaqGTaaabaGaaeOs% aiaabwhacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqGGa% GaaeiiaiaabccacaqGGaGaae4kaiaabUcacaqGGaGaaeiiaiaabcca% caqGGaGaaeiiaiaabccacaqGGaGaae4kaiaabUcacaqGGaGaaeiiai% aabccacaqGGaGaaeiiaiaabccacaqGRaGaae4kaiaabccacaqGGaGa% aeiiaiaabccacaqGGaGaaeiiaiaabccacaqGRaGaae4kaiaabccaca% qGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqGRaGaae4kaiaa% bccacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaab2cacaqGTaGaae% iiaiaabccacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqG% GaGaaeylaiaab2caaeaacaqGwbGaaeyyaiaabccacaqGGaGaaeiiai% aabccacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabUcacaqGRaGa% aeiiaiaabccacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabUcaca% qGRaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqGGaGaae4kaiaa% bUcacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqGGaGaae% 4kaiaabUcacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqG% GaGaaeylaiaab2cacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabc% cacaqGGaGaae4kaiaabUcacaqGGaGaaeiiaiaabccacaqGGaGaaeii% aiaabccacaqGGaGaaeiiaiaabUcacaqGRaaaaaa!1BBA!\[\begin{gathered} {\text{L94 - - - - - - - - - - - - - - }} \hfill \\ {\text{Su + + + + + + - - - - - - - - }} \hfill \\ {\text{Vl + + + + - - + + - - - - - - }} \hfill \\ {\text{Ju + + + + + + + + + + - - - - }} \hfill \\ {\text{Va + + + + + + + + - - + + + + }} \hfill \\ \end{gathered} \]The genes are supposed to act additively (intermediate inheritance) with the exception of one locus (the 6th or 7th locus) which shows dominance for the shorter LP (for the-alleles). The effect of this locus on LP seems considerably larger than that of the other loci. There are indications of physiological barriers, which means that LP's shorter than the one of L94 or much longer than that of Va are not possible.The effect of + genes in genotypes governing LP's close to these barriers (with very few or very many + alleles respectively) is smaller than in genotypes governing intermediate LP's.     

Estimation of additive, dominance and digenic epistatic interaction effects for certain yield characters in Vigna sesquipedalis Fruw

Inheritance of yield and yield contributing characters were investigated using generation mean analysis, utilising the means of six basic populations viz., P₁, P₂, F₁, F₂, BC₁P₁ and BC₁P₂ in four crosses of Vigna sesquipedalis. The analysis reiterated that the importance of dominance (h) gene effects for pod yield/plant and pods/plant as compared to additive (d) gene effects. However, significant and positive additive effects were noticed for pod yield/plant, pods/plant, pod weight and seed weight in different crosses. The three types of gene interactions (additive, dominance and epistasis) were significantly involved for pods/plant in cross KU 7 ×KU 8. Among the digenic epistatic interactions, both additive ×additive (i) and dominance × dominance (l) contributed more for pod yield/plant and pods/plant, however, it varied among the crosses. Populations having earliness can be developed as indicated by reducing dominance effects. Pedigree selection and heterosis breeding is suggested to exploit the fixable and non fixable components of variation respectively in Vigna sesquipedalis. This revised version was published online in July 2006 with corrections to the Cover Date.     

Predicting transgressive segregants in early generation using single seed descent method-derived <Emphasis Type="Italic">micro-macrosperma</Emphasis> genepool of lentil (<Emphasis Type="Italic">Lens culinaris</Emphasis> Medikus)

In a self-fertilised crop like lentil, the identification of transgressive segregants for economically important trait such as seed yield is an important aspect of any practical breeding programme. The prediction of expected transgressive segregants in F₁ generation obtained as a ratio of additive genic effect [d] and additive variance (D) i.e. [d]/√D was studied in 28 crosses of lentil generated in a diallel fashion involving four parents each of macrosperma (exotic) and microsperma (Indian) types, respectively, resulting in three hybridization groups. The seed material advanced to F₂, F₃ and F₄ generations through single seed descent method was evaluated to determine the observed transgressive segregants for seed yield/plant. The observed frequency of crosses showing more than 20% transgressive segregants in F₂ to F₄ generations were exhibited in 9(32%) crosses, of which 7(77%) crosses were of macrosperma × microsperma type. Genotypes Precoz and HPL-5 of the exotic group (macrosperma) produced maximum number of transgressive segregants with the genotypes L-259, L-4145 and PL-406 of the Indian origin (microsperma). Goodness of fit (non-significant χ² value) in F₂ generation was observed for 19(68%) crosses of the total genepool, out of which 9(56%) crosses each in F₃ and F₄ generation belonged to the macrosperma × microsperma group, depicting it as the gene pool of paramount importance to obtain maximum transgressive segregants, therefore establishing the efficacy of the method used.     

Single plant selection for yield in lentil

Summary Individual plant selection for yield in lentil is problematic at a commercial crop density primarily because of inter-plant entanglement by tendrils. Visual plant selection for yield was compared with random selection in the F₅ at three plant densities (66, 133 and 200 seeds/m²) by an evaluation of F₇ progeny yields over two seasons in two populations of lentil. Random plant sampling was as effective as visual plant selection in isolating high-yielding F₇ lines. The plant density of the selection environment did not affect the response to selection. The correlations between the seed number of selected F₅ plants and the mean yield of their F₇ progenies were r=+–0.26 and –0.06 in two populations, indicating the lack of positive response to plant selection for seed number. The results show that 1) random sampling is the most economic of the methods tested of plant selection for yield and 2) the plant density of the environment for plant selection can be low enough to avoid inter-plant entanglement by tendrils, allowing a focus in plant selection on characters, other than yield, of importance to the breeding program and with a higher heritability than yield.     

Potential of wild germplasm for increasing yield of grain sorghum

Summary Sorghum [Sorghum bicolor (L.) Moench] backcross populations containing 3 to 50% wild germplasm were evaluated in south central India for grain yield and nine related traits. No individual BC₀F₂- to BC₂F₂-derived lines were high transgressive segregates for grain yield. Only 1.5% of all BC₃F₂- or BC₄F₂-derived lines were transgressive segragates, with 26% higher mean grain yield than their respective recurrent parents. The ten highest-yielding BC₂F₂- to BC₄F₂-derived lines per mating having parent CK60B yielded an average of 14% more than CK60B, which was, at the 5% level, a statistically significant difference. However, the increased yield was associated with increased plant height. The highest-yilding lines from RS/R/A2725 x virgatum and RS/R/A2725 x verticilliflorum were an average of 13.5% higher-yielding than RS/R/A2725 (a significant difference) and were equal in plant height. Selection increased BC₂ mean grain yields by 6 to 27%. Population mean yield, mean yield of selected lines, and frequency of high-yielding lines were highest in the BC₄.Journal paper no. 380, ICRISAT, Patancheru, India; Journal paper no. J-11114, Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, USA.     

Quantitative trait loci analysis in Theobroma cacao using molecular markers. Inheritance of polygenic resistance to Phytophthora palmivora in two related cacao populations

Two related segregating populations of Theobroma cacao L. were analysed for their resistance to Phytophthora palmivora. The first F₁ population was obtained by crossing two susceptible cacao clones of Catongo (a highly homozygous genotype) and Pound 12(a highly heterozygous genotype) and the second population was obtained by backcrossing a single F₁ tree with Catongo. The genetic maps obtained for each population were compared. The F₁ map includes 162 loci and the backcross has 140 loci. The two maps, F₁ and BC₁, exhibit high co-linear loci organization covering respectively, 772 and 944 cM.Phytophthora resistance was assessed by measuring the size increase of a lesion at five (DL5)and ten days (DL10) after pod inoculation. Six different QTL were detected in the F₁ and BC₁ populations. One QTL was found in both populations, and appeared to be a major component of disease resistance, and explaining nearly 48% of the phenotypic variance in the F₁ population. The absence of some yield QTL detection in the BC₁ in comparison with the F₁ population is due to the lack of transmission of the favouring alleles for these QTL from the single F₁ tree used for the backcross. The phenotypic variance explained by the action of the quantitative trait alleles indicated that genetic factors of both major and minor effects were involved in the control of the character studied. QTL conferring increased resistance to Phytophthorawere identified in both susceptible parents, suggesting the presence of transgressive traits and the possibility of selection in cacao. Pleiotropic and epistatic effects for the QTL were also detected. Finally, the use of marker assisted selection (MAS) in cacao breeding programs is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Comparison of pedigree selection and single seed descent for oil yield in linseed (Linum usitatissimum L.)

Summary Four populations of linseed derived from five parents were advanced from the F₂ to the F₆ generation by SSD and to the F₅ by pedigree selection. These populations were used to compare the efficiency of the two methods in order to provide superior genotypes with respect to grain yield and oil content, i.e. oil yield. The results showed minimum differences between pedigree and SSD lines for grain yield, where in only one cross the SSD lines were significantly superior to the pedigree lines. Since pedigree selection was carried out for both, seed yield and oil content, a positive response to selection was expected. However, early selection for yield, a character with low heritability, was not successful. On the contrary, significant differences for oil content were detected between the two groups of lines in three of the four crosses studied. In these cases the pedigree lines were superior to the SSD lines. These results demonstrate that strict selection in early generations for oil content, a character with comparatively high heritability, is feasible and successful in linseed. However, selection for seed yield should be postponed to later inbred generations. Consequently, in breeding for maximum oil yield of linseed a two-step selection procedure is recommended.Abbreviations PS pedigree selection - SSD single seed descent - TGW thousand grain weight     

Inheritance of resistance to Puccinia coronata var. avenae in six selections of Avena sterilis

Summary Six selections of Avena sterilis, introduced from Israel as sources of resistance to oat crown rust, were crossed with susceptible A. byzantina Frazier. The number of genes conditioning resistance to culture H-14 of race 326 of Puccinia coronata var. avenae in each of the six selections was determined from studies of F₁, F₂ and F₃ populations from the crosses. P.I. 287211, P.I. 295919 and P.I. 296244 each appeared to have a single dominant gene for resistance, and P.I. 296265 and P.I. 296266 each two dominant ones. C.I. 8295 had a single partially dominant gene for resistance. Crosses among the A. sterilis parents indicated that at least four different genes conditioned resistance to culture H-14.Association between F₂ reaction to crown rust and morphological characters of the spikelet was determined with the % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaaiaacaqabeaadaqaaqaaaOqaaiabeE8aJnaaCa% aaleqabaGaaGOmaaaaaaa!39FC!\[\chi ^2 \] test for independence. In four crosses, all spikelet characters appeared to be independent of rust reaction. In Frazier x P.I. 296244, basal pubescence of the lemma on the secondary floret appeared to be associated with reaction to crown rust. Strong association between reaction to crown rust and lemma pubescence on the primary floret was evident in Frazier x P.I. 296265.     

Genetic analyses of agronomic traits in Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.)

The consumption of products made from Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) has increased in recent years in Japan. Increased consumer demand has led to recognition of the need for early varieties of this crop with high and stable yields. In order to accomplish this, more information is needed on the genetic mechanisms affecting earliness and yield. We conducted genetic analysis of 3 agronomic traits (days to flowering, plant height and total seed weight per plant) to segregate F₂ and F₃ populations derived from a cross between Tartary buckwheat cultivars ‘Hokuriku No. 4’ and ‘Ishisoba’. Broad-sense heritability estimates for days to flowering, plant height and total seed weight were 0.70, 0.62 and 0.75, respectively, in F₃ population. Narrow-sense heritability for total seed weight (0.51) was highest, followed by heritability for days to flowering (0.37), with heritability for plant height (0.26) lowest. Later flowering was associated with increased plant height and higher yields. From the F₄ generation, we identified twelve candidate plants with earlier maturity and reduced plant height compared to ‘Hokuriku No. 4’, but almost the same total seed weight. These results suggest that hybridization breeding using the single seed descent (SSD) method is an effective approach for improving agronomic characteristics of Tartary buckwheat.     

Selecting superior spring wheat crosses in early generations

Summary Three methods were evaluated as potential aids in identifying superior crosses early in the breeding program: (1) F₁ yield, (2) F₂ yield, and (3) midparental yield. Two sets of spring wheat (Triticum aestivum L. em. Thell.) crosses and parents were evaluated in replicated single row plots in F₁ and in replicated multi-row plots in F₂ over a period of five years. On the basis of F₁ yields, two of the highest yielding and two of the lowest yielding crosses in each set were chosen for a more detailed selection study in subsequent generations.In Set 1, random F₂ head selections for each of the selected four crosses were evaluated in 3-row yield plots in F₄. In Set 2, F₂ plant selections were made on the basis of head weight and the highest yielding 10% evaluated for yield in F₄.Lines of crosses identified as high yielding in F₁ had significantly greater mean yields in F₄ than those of crosses that were low yielding in F₁. The high yielding crosses had three to four times as many lines yielding in the top 10% in F₄ than did the low yielding crosses.Correlations for yield were obtained between F₁ and F₂ in different years, F₂ and midparents in the same year, lower or no correlations between F₁ and midparents in the same year, and no correlations between F₁ and midparent and F₂ and midparent in different years. It is suggested that larger plot sizes rather than single rows be used to evaluate parents.Midparental yield, F₁ yield and F₂ yield tests are recommended as a progressive set of screening tests for a given set of crosses to effectively maintain the superior crosses in the breeding program.     

Evaluation of Pedigree and Single Seed Descent Selection Methods for Cultivar Development in Cowpea (Vigna unguiculata L. Walp)

Three crosses of cowpea (Vigna unguiculata [L.] Walp) were used to assess the effectiveness of two selection procedures in cowpea. The selection procedures were pedigree selection (PD) and single seed descent selection (SSD). Lines developed through each procedure were yield tested and selected at F₆ and F₇ for PD and SSD, respectively. The selected lines for both procedures were compared at F₈ for grain yield per plant (YLD), number of pods per plant (NPO), and pod development period (PDP), in two locations. Lines developed through both procedures differed more in their population means than in the performance of their top 10% or highest yielding lines. There was no consistent relationship between magnitude of genetic variability and percentage of superior lines obtained from each procedure. Both procedures have been effective in producing superior genotypes for yield and number of pods. The PD method produced superior transgressive segregants in two out of the three crosses for PDP. SSD allowed a more rapid generation than PD.     

Restoration of meiotic regularity and fertility among derivatives of Lens culinaris x L. Nigricans hybrids

Summary The wild lentil, L. nigricans is cross compatible with the cultivated species. Chromosome pairing in their F₁ hybrids is highly irregular due to a difference of three translocations between the parental species. However, the hybrids are partially fertile and in the F₂ populations there is a marked improvement in fertility. About 19% of the F₂ plants were meiotically stable, fully fertile and their chromosome arrangement was similar to that of the cultivated species. All these are clear indications for the possibility of rapid introgression between the two species and hence systematic screening of L. nigricans for traits of economic value is fully justifiable.     

Rapid generation cycling of an F2 population derived from a cross between Lens culinaris Medik. and Lens ervoides (Brign.) Grande after aphanomyces root rot selection

Cultivated lentil (Lens culinaris Medik.) is susceptible to aphanomyces root rot (ARR), whereas partial resistance is present in wild lentil including Lens ervoides (Brign.) Grande. Approximately six generations of selfing are required to fix a desired trait in a population, which usually requires 2 years in a breeding programme, so the primary objective was to develop a rapid generation cycling (RGC) technique that achieves this goal in 1 year. Rapid generation cycling was then tested on an F₂ population (LR‐59) derived from a L. culinaris × L. ervoides cross in combination with a reliable ARR screening technique, which generates a wide range of disease severities conducive to selection. Phenotyping of an F₂ population of more than 1,200 plants resulted in scores ranging from 2.4 to 4.0 on a scale from zero to five. Plants with scores lower than 4.0 were selected for advancement for five generations using a modified single‐seed descent method, optimum growing conditions, 20‐hr photoperiod and harvest of immature seeds. Seeds were germinated in a 100 μM gibberellin solution. Average generation length after phenotyping was 56 days resulting in five generations within approximately 300 days. Using a modified inoculation protocol, ARR phenotyping of the F₇ population resulted in scores ranging from 1.4 to 4.0. This inexpensive, nonsterile speed breeding protocol saves 1 year in the development of lentil varieties with improved ARR resistance.