Identification of heterotic groups and patterns among breeding populations provides fundamental information to help plant breeders more knowledgeably manipulate heterosis. A diallel analysis was conducted among nine alfalfa ( Medicago sativa L.) germplasms, commonly referred to as African, Chilean, Flemish, Indian, Ladak, M. falcata, M. varia, Peruvian, and Turkistan, which represent a significant proportion of the genetic diversity present in US cultivars. Heterotic responses were determined by evaluating forage yield of the germplasms and their 36 half-diallel hybrids in seeded plots that were harvested five times in each of 2 years. Commercially acceptable yields were obtained from some hybrids of unimproved parents, where at least one parent was adapted to the study environment. Variation among crosses was attributed primarily to general combining ability (GCA) effects; however, specific combining ability effects were also significant. GCA estimates for African, Chilean and Peruvian were positive, while those for Ladak, M. falcata, and M. varia were negative. Estimates for variety heterosis effects were positive for Peruvian and M. falcata and negative for Indian and M. varia. Significant mid-parent heterosis [(MPH) range of -21% to 55%] and high-parent heterosis [(HPH) range of -33% to 23%] was detected. M. falcata hybrids exhibited the highest MPH values. However, this likely reflects the poor yield of M. falcata per se in the study environment and consequently, low MPH values. Peruvian hybrids demonstrated the highest cross mean performance, significant positive MPH in all crosses, and positive HPH in five out of eight crosses. The results indicate that Peruvian should be recognized as a heterotic group. Alfalfa breeders may wish to explore opportunities for heterotic yield gains that are likely to exist in hybrids between the Peruvian germplasm and elite breeding populations, in particular, those adapted to the southwestern United States. MPH results suggest that alfalfa breeders may have capitalized on the heterotic response between Flemish and M. varia during past development of alfalfa synthetics adapted to the central and northern latitudes of the United States.

Improving commercial utilization of perennial Medicago collections requires developing approaches that can rapidly and accurately characterize genetic diversity among large numbers of populations. This study evaluated the potential of using amplified fragment length polymorphism (AFLP) DNA markers, in combination with DNA bulking over multiple genotypes, as a strategy for high-throughput characterization of genetic distances (D) among alfalfa (Medicago sativa L.) accessions. Bulked DNA templates from 30 genotypes within each of nine well-recognized germplasms (African, Chilean, Flemish, Indian, Ladak, Medicago sativa subsp. falcata, Medicago sativa subsp. varia, Peruvian, and Turkistan) were evaluated using 34 primer combinations. A total of 3754 fragments were identified, of which 1541 were polymorphic. The number of polymorphic fragments detected per primer combination ranged from 20 to 85. Pairwise D estimates among the nine germplasms ranged from 0.52 to 1.46 with M. sativa subsp. falcata being the most genetically dissimilar. Unweighted pair-group method arithmetic average (UPGMA) analysis of the marker data produced two main clusters, (i) M. sativa subsp. sativa and M. sativa subsp. varia, and (ii) M. sativa subsp. falcata. Cluster-analysis results and D estimates among the Chilean, Peruvian, Flemish, and M. sativa subsp. varia germplasms supported the hypothesis that Peruvian was more similar to original Spanish introductions into Central and South America than Chilean. Hierarchical arrangement of the nine germplasms was supported by their respective geographic, subspecific, and intersubspecific hybrid origins. Subsets of as few as seven highly informative primer pairs were identified that produced comparable D estimates and similar heirarchical arrangements compared with the complete dataset. The results indicate that use of primer-pair subsets for AFLP analysis of bulk DNA templates could serve as a high-throughput system for accurately characterizing genetic diversity among large numbers of alfalfa populations.

Plant breeders and geneticists often use diallel mating designs to obtain genetic information about a trait of interest from a fixed or randomly chosen set of parental lines. Diallel analyses of broad‐based populations have frequently been conducted by means of three analyses presented by Gardner and Eberhart in 1966. The original paper of Gardner and Eberhart used sequential model fitting to obtain estimates of effects and corresponding sums of squares. This approach, although having a long history, suffers from shortcomings which have led to confusion about what hypotheses the analyses actually test. The objectives of this paper were to delineate clearly all models implicitly required to perform Gardner and Eberhart Analyses II and III, and to present explicit formulas for effects in terms of the population means which are fundamental and unambiguous. While developing formulas of effects, we discovered a typographic error associated with variety effects in the original example of Analysis II. Our results also indicate that Analyses II and III effect formulas are rather nonintuitive both biologically and genetically, and incorporate multipliers that are functions of the number of parents. Another specific result shows that the varietal effects obtained in Gardner and Eberhart's Analysis III are “unconstrained” estimates, while those from the Analysis II are estimates constrained by the assumption of “no heterosis.” These results have implications for the use and interpretation of such effects. A SAS computer program for analyzing diallels among broad‐based populations according to Gardner and Eberhart's Analyses II and III is also reported.

subsp. sativa and nothosubsp. varia (Martyn) Arcang. (Johnson and Tieszen, 1994;Ray et al., 1998). A range Designing effective breeding strategies to integrate selection for of 0.8‰ was detected for ⌬ among 78 winterhardy North carbon isotope discrimination (⌬), as a means to improve alfalfa (Medicago sativa L.) water-use efficiency (WUE), will depend upon American cultivars (Johnson and Rumbaugh, 1995), and the association between ⌬ and forage yield. The current study was a range of 0.9‰ among half-sib families of an elite alfalfa conducted to determine responses in ⌬ affiliated with significant yield breeding population (Ray et al., 1999a(Ray et al., , 1999b. Evidence responses that were previously observed among 36 diallel hybrids of clearly indicates that ⌬ should be amenable to manipulanine alfalfa germplasms (commonly referred to as African, Chilean, tion by traditional alfalfa breeding techniques. Narrow-Flemish, Indian, Ladak, M. falcata, M. varia, Peruvian, and Turkissense heritabilities for ⌬ under both irrigated and watertan). The influence of additive and nonadditive gene action on ⌬, and stressed conditions were 0.56 (Ray et al., 1999a, 1999b), the behavior of ⌬ across harvests was also determined. Forage yield while broad sense heritabilities based on individual plants and ⌬ of the germplasms and their half-diallel hybrids were evaluated exceeded 0.80 in alfalfa (Johnson and Rumbaugh, 1995). near Las Cruces, NM, during May, June, and July in each of 2 yr in Johnson and Rumbaugh (1995) reported significant GCA seeded plots that were flood irrigated every 14 d. Values for ⌬ of hybrids did not significantly exceed those of the most extreme parents effects, but not specific combining ability (SCA), for ⌬ in in any harvest. Variation for ⌬ among crosses was attributed primarily a diallel among 14 clones from the NC-83-1 germplasm to general combining ability (GCA) effects. The magnitude of parental (Kehr et al., 1975). The lack of significance for SCA in per se and GCA effects, and their ability to predict hybrid ⌬ varied that study may reflect the fact that NC-83-1 traced to substantially between the first harvest and later harvests. Variety only winterhardy accessions that were randomly intereffects for ⌬ in Ladak, M. varia, and M. falcata became increasingly mated for two cycles. Opportunities to detect SCA and/ negative as the growing season progressed, while those for African, or heterosis effects for ⌬ may be greater in hybrids de-Chilean, Flemish, Indian, Peruvian, and Turkistan increased. Results rived from distinct populations adapted to a wider range suggest that fundamental differences in stomatal conductance exist of climatic conditions. between subspecies sativa and falcata.

En Cuauhtemoc, Chihuahua, el cultivo de manzano presenta, en ocasiones, un crecimiento de ramas y brotes excesivos, ocasionando competencia por luz y nutrientes. Los reguladores de crecimiento vegetal sintéticos son utilizados para reducir la longitud de brotes sin causar fitotóxicidad y no alterar los patrones de desarrollo. El objetivo del estudio fue evaluar tres tratamientos, dos de Prohexadione-Calcium, Apogee 27.5%, con dosis de 149.9 g y 206.3 g de ingrediente activo, ambas diluidas en 1000 l de agua y un testigo, para medir la respuesta en el crecimiento de ramas y brotes y su efecto colateral sobre Erwinia amilovora. El diseño experimental fue Bloques Completos al Azar con ocho repeticiones. Se realizaron tres aplicaciones foliares sobre el cultivar “Golden delicious”, el 22 de abril, 6 y 20 de mayo del 2005. La unidad experimental fue de 3 árboles mayores de 10 años, la parcela útil el del centro. Se hicieron cuatro muestreos, los tres primeros se realizaron previos a las aplicaciones correspondientes. En la primera medición todos los tratamientos se comportaron estadísticamente iguales entre si, lo que ayudo a reflejar el efecto de los tratamientos en las otras tres mediciones. En la segunda, las dosis de Apogee manifiestan diferencia estadística entre sí y con el testigo. En la tercera y cuarta medición, los dos tratamientos de Apogee tuvieron las mayores diferencias estadísticas entre sí y con el testigo. La dosis alta redujo el crecimiento de los brotes en un 48.5% en relación al testigo. No se observó efecto de fitotoxicidad. DOI: https://doi.org/10.54167/tecnociencia.v1i3.53