Occurrence of Anthracnose Caused by Colletotrichum fructicola on Ficus hirta in Southern China.

Ficus hirta Vahl. is a Moraceae plant, named for its palm-like leaves. It is a widely used traditional medicinal material with definite curative effect. At the same time, it is also a commonly used soup material among the folk in South China. In March 2022, a serious leaf spot disease with symptoms similar to anthracnose was observed on F. hirta in several plantations in Qinzhou and Zhanjiang City of China, with an incidence of 32~65%. The early symptoms of infected leaves were small, round, yellow spots that further expanded into larger, brown, irregular, necrotic lesions surrounded by dark brown edges, which eventually led to leaf wilt. Twenty symptomatic leaves were collected from three plantations with a total area of about 10 hm2. Fragments (2×2 mm) from the 20 infected leaves were surface sterilized, plated on potato dextrose agar (PDA) and incubated at 28°C. After 3 days, isolates with similar cultural morphology were obtained and three representative isolates (WZMT-1, WZMT-3 and WZMT-8) were randomly selected for following study. The colonies by single-spore purification on PDA were initially cottony, pale white and became grayish green with age. The conidia were hyaline, abundant, cylindrical, with rounded ends, 14.4~18.2 µm×4.6~6.0 µm (av. 16.2 µm×5.4 µm, n=100). Conidiogenous cells hyaline, cylindrical or ampulliform, 6.2~22.7 µm × 2.7~5.0 µm (av. 12.9 µm×3.8 µm, n=50). Appressoria were brown to dark brown, ovoid to clavate, elliptical or irregular, 7.9~13.4 µm × 5.6~9.2 µm (av. 10.6 µm×7.9 µm, n=50). The morphology of the fungus resembled Colletotrichum fructicola (Prihastuti et al. 2009). For molecular identification, the internal transcribed spacer (ITS) regions, glyceraldehyde-3-phosphatedehydrogenase (GAPDH), actin (ACT), beta-tubulin 2 (TUB2), calmodulin (CAL), partial manganese superoxide dismutase (sod2), partial Apn2-Mat1-2 intergenic spacer and partial mating type (Mat1-2) (ApMat) genes were amplified from genomic DNA for the isolates using the primers described by Silva et al. (2012) and Weir et al. (2012). The sequences of the above seven loci of the three isolates (accession nos. OQ121661 to OQ121663 and OQ133400 to OQ133417) were obtained and showed over 99% identity with the existing sequences of ex-type culture ICMP 18581 of Colletotrichum fructicola (Weir et al. 2012). A multilocus phylogenetic analysis of the seven loci concatenated sequences using the maximum likelihood method revealed that the isolates belong to C. fructicola. To confirm pathogenicity, five 3-month-old potted plants were used for inoculation with each representative isolate. Tested plants were sprayed with 10 ml of a conidial suspension (1 × 108 conidia/ml) , and the controls plants were sprayed with sterile water. All the plants were incubated in a growth chamber at 26 ± 2°C with 95% relative humidity. After 10 days, typical lesions like those observed on the field plants appeared on all inoculated plants, while the control remained healthy. The same fungal pathogen was reisolated and the identity was confirmed by morphological characterization and molecular analysis, confirming Koch's postulates. The pathogen has been reported as the causal agent of anthracnose on a wide range of plant hosts worldwide (Marquez-Zequera et al. 2018; Horfer et al. 2021; Jiang et al. 2022; Li et al. 2023). To our knowledge, this is the first report of anthracnose on F. hirta caused by C. fructicola in southern China.

Stenocarpella chrysopogonis, a New Species Causing Leaf Streak Disease of Chrysopogon zizanioides in Southern China.

Vetiver grass (Chrysopogon zizanioides) has been widely used in recent years for ecological environment management, restoration of degraded ecosystems, and essential oil extraction. In 2019, a leaf streak disease of C. zizanioides was observed in Zhanjiang, Guangdong Province, China. The disease appeared as large streak lesions on the leaves, on which conidiomata were formed. A pathogenicity test with the fungus isolated from these lesions confirmed Koch's postulates and thus the fungus as the causal agent of this disease. A morphological resemblance of the pathogen to Stenocarpella was noted upon microscopic examination. Phylogenetic trees inferred from both individual and combined ITS, LSU, and tef1 sequences confirmed the pathogen as a species of the Diaporthaceae and revealed it to be closely related to Phaeocytostroma and Stenocarpella species. As morphological characters clearly placed the pathogen in the genus Stenocarpella, it was described as S. chrysopogonis.

Forage Yield, Canopy Characteristics, and Radiation Interception of Ten Alfalfa Varieties in an Arid Environment.

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.

Co-infection by Soil-Borne Fungal Pathogens Alters Disease Responses Among Diverse Alfalfa Varieties.

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.

Development and Characterization of Transcription Factor Gene-Derived Microsatellite (TFGM) Markers in Medicago truncatula and Their Transferability in Leguminous and Non-Leguminous Species.

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.