Univrsity of Tehran Press Iranian Journal of Field Crop Science 2008-4811 57 1 2026 03 21 The Assessment of General Combining Ability and Heterosis in Iranian Ecotypes of Alfalfa (Medicago sativa L.) to Produce Synthetic Varieties The Assessment of General Combining Ability and Heterosis in Iranian Ecotypes of Alfalfa (Medicago sativa L.) to Produce Synthetic Varieties 85 95 105730 10.22059/ijfcs.2025.390755.655128 FA Ali Moghaddam Maize and Forage Crops Research Department, Seed and Plant Improvement Inst. AREEO karaj Iran 0000-0001-7831-8914 Seyed Mohammad Ali Mofidian Maize and Forage Crops Research Dep. Seed and Plant Improvement Ins. AREEO karaj Iran 0000-0003-4540-5450 Journal Article 2025 02 22 Introduction. Alfalfa (Medicago sativa L.) is the most important forage crop in Iran. Iran is recognized as one of the primary centers of origin of alfalfa worldwide and possesses extensive genetic diversity associated with this species. In general, from both genetic and breeding perspectives, cultivars grown domestically and globally are predominantly open-pollinated populations with varying levels of genetic diversity or genetic base. Local and indigenous populations (ecotypes) account for the largest cultivated area in the country. Most alfalfa cultivars used in recent decades worldwide are synthetic or composite populations with diverse genetic backgrounds, developed through the intercrossing of selected clones or superior populations. A key step in the development of synthetic varieties in alfalfa is the estimation of parental combining ability, typically assessed through forage yield performance of progenies derived from polycrosses. Materials and Methods. With the objective of selecting superior parents with favorable general combining ability for the development of a synthetic population, the present study was conducted using 20 genotypes. These included 10 polycross progenies (half-sib families) along with 10 domestic parental alfalfa genotypes, comprising two cultivars (‘Ahang’ and ‘Mandegar’), two ecotypes from Bam and Yazd, and six ecotypes from cold and temperate regions identified by the codes KFA3, KFA4, KFA11, KFA13, KFA15, and KFA16. The experiment was carried out in a randomized complete block design (RCBD) with three replications at the research farm of the Seed and Plant Improvement Institute in Karaj over the years 2020 to 2022. Each genotype was planted in four double-row plots, each five meters in length, with 50 cm spacing between rows. The seeding rate was calculated at 25 kg per hectare. Irrigation was applied using the furrow method at intervals of 7-10 days. The first year (2020) was considered the establishment phase, and data collection was conducted over two years starting from spring 2021. The traits evaluated included plant height, stem density per square meter, regrowth rate, fall dormancy score, and dry and fresh forage yield. Mean comparisons over the two-year period were performed using the SNK test at the 5% probability level. Results and Discussion. Statistical analysis indicated significant differences among genotype means for all traits except fresh forage yield. Among the polycross progenies, Poly-KFA3 exhibited the highest dry forage yield with 22.91 tons per hectare, while Poly-KFA15 showed the lowest yield with 19.48 tons per hectare. The mean fresh and dry forage yields of the polycross progenies were 3.7 and 0.7 tons per hectare higher, respectively, than those of the parental genotypes. Among the evaluated materials, the polycross progenies Poly-KFA3 and Poly-Yazdi exhibited the greatest plant heights, with mean values of 78.6 and 77.4 cm, respectively, whereas the parental genotype KFA11 showed the lowest height at 66.1 cm. Overall, the polycross progenies showed an average increase of approximately 4 cm in plant height compared to the parental genotypes. Regarding regrowth rate, measured 14 days after harvest, the genotypes Poly-Yazdi, Yazdi, and Poly-KFA3 showed the highest regrowth rates, with mean values of 44.2, 43.6, and 42.4 cm, respectively. In contrast, KFA11, KFA3, and Ahang exhibited the lowest regrowth, with averages of 24.8, 27.0, and 27.4 cm, respectively. The polycross progenies displayed an average increase of 3.7 cm in regrowth rate relative to the parental genotypes over the 14-day period following harvest. For fall dormancy score, the polycross progenies Poly-Yazdi and Poly-KFA3 recorded the highest values, with means of 8.7 and 8.6, respectively, while the parental genotypes KFA11, KFA3, and Ahang showed the lowest scores, averaging 3.1, 3.4, and 3.4, respectively. The mean fall dormancy score of the polycross progenies (6.4) represented a 20% increase compared to that of the parental genotypes (5.1). A distinguishing characteristic of tropical or, more precisely, semi-dormant and non-dormant alfalfa types—such as the Bami—is their high regrowth rate and fall dormancy score. The polycrossing of Bami and Yazdi alfalfa with cold-region genotypes (dormant type), and the transfer of these traits into cold-adapted germplasm, resulted in substantial heterosis for these characteristics in the derived half-sib families. The highest heterosis percentages observed among the polycross progenies for plant height, stem number per square meter, regrowth rate, fall dormancy score, fresh forage yield, and dry forage yield were 13.25%, 7.94%, 57.03%, 150.49%, 10.92%, and 14.25%, respectively. With respect to forage yield traits, the highest general combining ability (GCA) was associated with the parent KFA3, with values of 6.33 and 1.99 tons per hectare for fresh and dry forage yield, respectively. In contrast, the lowest GCA was observed for KFA15, with values of −6.2 and −1.45 tons per hectare for fresh and dry forage yield, respectively. Conclusion. Based on the estimates of general combining ability of the parental genotypes, along with their origin and cultivation area, and with the aim of maximizing genetic diversity while minimizing inbreeding effects in subsequent seed production generations, five parents—Bami, Yazdi, KFA3, KFA13, and KFA16—were selected for intercrossing to develop a new synthetic variety. Introduction. Alfalfa (Medicago sativa L.) is the most important forage crop in Iran. Iran is recognized as one of the primary centers of origin of alfalfa worldwide and possesses extensive genetic diversity associated with this species. In general, from both genetic and breeding perspectives, cultivars grown domestically and globally are predominantly open-pollinated populations with varying levels of genetic diversity or genetic base. Local and indigenous populations (ecotypes) account for the largest cultivated area in the country. Most alfalfa cultivars used in recent decades worldwide are synthetic or composite populations with diverse genetic backgrounds, developed through the intercrossing of selected clones or superior populations. A key step in the development of synthetic varieties in alfalfa is the estimation of parental combining ability, typically assessed through forage yield performance of progenies derived from polycrosses. Materials and Methods. With the objective of selecting superior parents with favorable general combining ability for the development of a synthetic population, the present study was conducted using 20 genotypes. These included 10 polycross progenies (half-sib families) along with 10 domestic parental alfalfa genotypes, comprising two cultivars (‘Ahang’ and ‘Mandegar’), two ecotypes from Bam and Yazd, and six ecotypes from cold and temperate regions identified by the codes KFA3, KFA4, KFA11, KFA13, KFA15, and KFA16. The experiment was carried out in a randomized complete block design (RCBD) with three replications at the research farm of the Seed and Plant Improvement Institute in Karaj over the years 2020 to 2022. Each genotype was planted in four double-row plots, each five meters in length, with 50 cm spacing between rows. The seeding rate was calculated at 25 kg per hectare. Irrigation was applied using the furrow method at intervals of 7-10 days. The first year (2020) was considered the establishment phase, and data collection was conducted over two years starting from spring 2021. The traits evaluated included plant height, stem density per square meter, regrowth rate, fall dormancy score, and dry and fresh forage yield. Mean comparisons over the two-year period were performed using the SNK test at the 5% probability level. Results and Discussion. Statistical analysis indicated significant differences among genotype means for all traits except fresh forage yield. Among the polycross progenies, Poly-KFA3 exhibited the highest dry forage yield with 22.91 tons per hectare, while Poly-KFA15 showed the lowest yield with 19.48 tons per hectare. The mean fresh and dry forage yields of the polycross progenies were 3.7 and 0.7 tons per hectare higher, respectively, than those of the parental genotypes. Among the evaluated materials, the polycross progenies Poly-KFA3 and Poly-Yazdi exhibited the greatest plant heights, with mean values of 78.6 and 77.4 cm, respectively, whereas the parental genotype KFA11 showed the lowest height at 66.1 cm. Overall, the polycross progenies showed an average increase of approximately 4 cm in plant height compared to the parental genotypes. Regarding regrowth rate, measured 14 days after harvest, the genotypes Poly-Yazdi, Yazdi, and Poly-KFA3 showed the highest regrowth rates, with mean values of 44.2, 43.6, and 42.4 cm, respectively. In contrast, KFA11, KFA3, and Ahang exhibited the lowest regrowth, with averages of 24.8, 27.0, and 27.4 cm, respectively. The polycross progenies displayed an average increase of 3.7 cm in regrowth rate relative to the parental genotypes over the 14-day period following harvest. For fall dormancy score, the polycross progenies Poly-Yazdi and Poly-KFA3 recorded the highest values, with means of 8.7 and 8.6, respectively, while the parental genotypes KFA11, KFA3, and Ahang showed the lowest scores, averaging 3.1, 3.4, and 3.4, respectively. The mean fall dormancy score of the polycross progenies (6.4) represented a 20% increase compared to that of the parental genotypes (5.1). A distinguishing characteristic of tropical or, more precisely, semi-dormant and non-dormant alfalfa types—such as the Bami—is their high regrowth rate and fall dormancy score. The polycrossing of Bami and Yazdi alfalfa with cold-region genotypes (dormant type), and the transfer of these traits into cold-adapted germplasm, resulted in substantial heterosis for these characteristics in the derived half-sib families. The highest heterosis percentages observed among the polycross progenies for plant height, stem number per square meter, regrowth rate, fall dormancy score, fresh forage yield, and dry forage yield were 13.25%, 7.94%, 57.03%, 150.49%, 10.92%, and 14.25%, respectively. With respect to forage yield traits, the highest general combining ability (GCA) was associated with the parent KFA3, with values of 6.33 and 1.99 tons per hectare for fresh and dry forage yield, respectively. In contrast, the lowest GCA was observed for KFA15, with values of −6.2 and −1.45 tons per hectare for fresh and dry forage yield, respectively. Conclusion. Based on the estimates of general combining ability of the parental genotypes, along with their origin and cultivation area, and with the aim of maximizing genetic diversity while minimizing inbreeding effects in subsequent seed production generations, five parents—Bami, Yazdi, KFA3, KFA13, and KFA16—were selected for intercrossing to develop a new synthetic variety.

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