Population-based diallel analyses among nine historically recognized alfalfa germplasms

Area of Science:

• Plant breeding and genetics
• Agronomy
• Forage crop science

Background:

• Understanding heterosis, or hybrid vigor, is crucial for optimizing crop yields.
• Alfalfa (Medicago sativa L.) exhibits significant genetic diversity, impacting breeding strategies.
• Identifying distinct heterotic groups aids in predicting and exploiting hybrid performance.

Purpose of the Study:

• To identify heterotic groups and patterns within nine diverse alfalfa germplasms.
• To evaluate the combining ability and heterotic responses of alfalfa germplasms and their hybrids for forage yield.
• To provide insights for alfalfa breeders to enhance yield through strategic hybridization.

Main Methods:

• Conducted a diallel analysis involving nine alfalfa germplasms and their 36 half-diallel hybrids.
• Evaluated forage yield in seeded plots over 2 years with five harvests per year.
• Analyzed variation using general combining ability (GCA) and specific combining ability (SCA) effects, alongside mid-parent heterosis (MPH) and high-parent heterosis (HPH).

Main Results:

• General combining ability (GCA) effects were the primary source of variation among crosses.
• Peruvian germplasm exhibited positive GCA and variety heterosis effects, with high cross mean performance and significant positive MPH.
• Significant MPH (up to 55%) and HPH (up to 23%) were detected, with Peruvian hybrids showing the most promising results.

Conclusions:

• Peruvian germplasm should be recognized as a distinct heterotic group in alfalfa breeding.
• Alfalfa breeders can leverage Peruvian germplasm, especially when crossed with elite breeding populations adapted to the southwestern US, for yield gains.
• Past breeding efforts may have utilized heterotic responses between Flemish and M. varia for developing synthetics adapted to central and northern US latitudes.