Fusarium oxysporum f. sp. medicaginis (Fom) and Rhizoctonia solani (Rs) are the major soil-borne fungal pathogens that pose severe threats to commercial alfalfa production in China. However, the effects of Fom and Rs co-infection on alfalfa and whether co-infection alters disease resistance responses among diverse varieties remain unknown. A collection of 80 alfalfa varieties (Medicago sativa) originated from seven countries were used to study the effects of Fom and Rs co-infection on alfalfa and host resistance responses. The co-infection resulted in more severe disease and reductions in growth and biomass allocation across varieties in comparison with either single infection by Fom or Rs; in addition, root morphology was much more strongly altered by the co-infection. Principal component analysis based on all plant traits showed that varieties under the co-infection were related to the single infection by Rs, being separated from Fom, and hierarchical clustering found differential response patterns among varieties upon co-infection compared with either single infection, with most varieties being highly susceptible to the co-infection. Furthermore, varieties that were most resistant to either single infection were not effective to co-infection, and there was no individual variety with resistance to both pathogens singly and co-infected. This study reveals for the first time that the co-infection by Fom and Rs alters disease resistance responses among diverse alfalfa varieties and provides useful information for developing alfalfa varieties with resistance to the co-occurrence of different soil-borne pathogens.

Transcription factors (TFs) are critical adaptor molecules that regulate many plant processes by controlling gene expression. The recent increase in the availability of TF data has made TFs a valuable resource for genic functional microsatellite marker development. In the present study, we developed TF gene-derived microsatellite (TFGM) markers for Medicago truncatula and assessed their cross-species transferability. A total of 203 SSRs were identified from 1467 M. truncatula TF coding sequences, 87.68% of which were trinucleotide repeats, followed by mono-(4.93%) and hexanucleotide repeats (1.48%). Further, 142 TFGM markers showed a high level of transferability to the leguminous (55.63%-85.21%) and non-leguminous (28.17%-50.00%) species. Polymorphisms of 27 TFGM markers were evaluated in 44 alfalfa accessions. The allele number per marker ranged from two to eight with an average of 4.41, and the PIC values ranged from 0.08 to 0.84 with an average of 0.60. Considering the high polymorphism, these TFGM markers developed in our study will be valuable for genetic relationship assessments, marker-assisted selection and comparative genomic studies in leguminous and non-leguminous species.

An increasing demand for new and improved livestock forage products is driving the development of forage systems in arid regions. Our study evaluated the productivity of 10 alfalfa (Medicago sativa L.) varieties and the relationship between forage yield and canopy structure traits, such as plant height, branch number, stem/leaf ratio, and leaf area index in the arid Hexi Corridor, north-west China. Here, plant height, primary branch number per plant, and stem/leaf ratio were positively correlated with forage yield. In terms of a two-year total yield, Gannong No. 5 produced the highest value (13,923 kg ha−1), followed by the WL342HQ (12,409 kg ha−1), Phabulous (11,928 kg ha−1), and Xinjiang Daye (11,416 kg ha−1) varieties. Therefore, these four alfalfa varieties are suitable for large-scale cultivation in the Hexi Corridor region and other arid areas where the effect of precipitation is even larger than that of temperature. These results provide valuable information for the selection and cultivation of alfalfa varieties, which could improve forage yield and the production of livestock in arid regions.