Breeding Alfalfa (Medicago sativa L.) Adapted to Subtropical Agroecosystems

Abstract

Alfalfa is planted in more than 30 million hectares worldwide, but despite its popularity in temperate regions, it is not widely grown in subtropical agroecosystems. It is critical to improve alfalfa for such regions, considering current predictions of global warming and the increasing demands for animal-based products. In this study, we examined the diversity present in subtropical alfalfa germplasm and reported genetic parameters for forage production. An initial screening was performed from 2014 to 2016, evaluating 121 populations from different subtropical origins. Then, a breeding population was created by crossing selected plants, resulting in 145 full-sib and 36 half-sib families, which were planted in a row-column design with augmented representation of three controls (‘Bulldog805′, ‘FL99′ and ‘UF2015′). Dry matter yield (DMY), canopy height (AH), and percentage blooming (BLOOM) were measured across several harvests. Moderate narrow-sense heritability and high genetic correlations between consecutive harvests were estimated for all traits. The breeding line UF2015 produced higher DMY than FL99 and Bulldog805, and it could be a candidate cultivar release. Several families produced higher DMY than all checks, and they can be utilized to develop high yielding and adapted alfalfa cultivars for subtropical agroecosystems.

Phenomics-Assisted Selection for Herbage Accumulation in Alfalfa (Medicago sativa L.)

“…Most of the production is concentrated in the mid-east and west coast ( USDA-NASS, 2020 ). Despite its lower presence as a forage crop in the lower southeastern United States and other subtropical regions in the world, breeding efforts are underway to develop non-dormant alfalfa cultivars adapted to these environments ( De Assis et al, 2010 ; Vivela et al, 2018 ; Adhikari et al, 2019 ; Acharya et al, 2020 ).…”

“…Nevertheless, HA has become a target breeding trait among alfalfa breeders more recently ( Sakiroglu and Brummer, 2017 ; Dos Santos et al, 2018 ; Adhikari et al, 2019 ; Acharya et al, 2020 ; Benabderrahim et al, 2020 ; He et al, 2020 ; Ren et al, 2021 ; Tang et al, 2021 ). However, traditional field phenotyping for HA is based on the destructive sampling of experimental units at the ground level, weighing fresh samples, drying, and weighing dried samples to estimate dry matter content.…”

“…Genetic parameters for alfalfa yield are essential to define optimal selection schemes ( Casler and Brummer, 2008 ). Heritability estimates for HA in alfalfa ranged from 0.15 to 0.30 ( Bowley and Christie, 1981 ; Riday and Brummer, 2002 ; Annicchiarico, 2015 ; Acharya et al, 2020 ). These low to moderate estimates are expected in alfalfa and other perennial forage crops with long selection cycles, cross-pollinated breeding schemes, and traits with significant genotype × environment interaction ( Annicchiarico, 2015 ).…”

Comparison among nine alfalfa breeding schemes based on actual biomass yield gains

“…In addition, it is limited by a high extent of non‐additive genetic variance, which arises from complementary gene interactions among favorable dominant alleles at tightly linked loci in repulsion phase and, to a lesser extent, from intra‐locus allelic interactions allowed for by autotetraploidy (Bingham et al., 1994; Gallais, 1984; Woodfield & Bingham, 1995). Large non‐additive genetic variation contributes to reportedly severe inbreeding depression (Gallais, 1984; Kimbeng & Bingham, 1998) and narrow‐sense heritability ( h 2 ) as low as .20–.30 (Acharya et al., 2020; Annicchiarico, 2015; Riday & Brummer, 2005) for alfalfa biomass yield.…”

Triple full‐sibs: A method for estimating components of genetic variance and progeny selection in plants

“…One of the problems with estimating components of variance from progeny data is that, in general, it is not possible to separately estimate the additive and dominance components. Full‐sib recurrent selection is widely used in different alogamous species, such as maize (Berilli et al., 2013; Romay et al., 2011), sweet corn ( Zea mays ) (Moore & Tracy, 2019), alfalfa ( Medicago sativa L.) (Acharya et al., 2020), Eucalyptus (Lima et al., 2011), and Pinus (Li et al., 2020), among others. In the case of full‐sib progenies, although the expected gain per selection cycle is greater than that with half‐sibs, the additive and dominance variance components are confounded in the variance measured among progenies, which does not allow direct estimation of the expected gain from selection.…”