Transcriptomic Analysis Reveals That Rho GTPases Regulate Trap Development and Lifestyle Transition of the Nematode-Trapping Fungus Arthrobotrys oligospora

Nematode-trapping (NT) fungi are widely distributed in terrestrial and aquatic ecosystems. Their broad adaptability and flexible lifestyles make them ideal agents for controlling pathogenic nematodes. Arthrobotrys oligospora is a model species employed for understanding the interaction between fungi and nematodes.

Fungistatic Mechanism of Ammonia against Nematode-Trapping Fungus Arthrobotrys oligospora, and Strategy for This Fungus To Survive Ammonia

Soil fungistasis is a phenomenon in which the germination and growth of fungal propagules is widely inhibited in soil. Although fungistatic compounds are known to play important roles in the formation of soil fungistasis, how such compounds act on soil fungi remains little studied.

Historical Differentiation and Recent Hybridization in Natural Populations of the Nematode-Trapping Fungus Arthrobotrys oligospora in China

Maintaining the effects of nematode-trapping fungi (NTF) agents in order to control plant-parasitic nematodes (PPNs) in different ecological environments has been a major challenge in biological control applications. To achieve such an objective, it is important to understand how populations of the biocontrol agent NTF are geographically and ecologically structured. A previous study reported evidence for ecological adaptation in the model NTF species Arthrobotrys oligospora. However, their large-scale geographic structure, patterns of gene flow, their potential phenotypic diversification, and host specialization remain largely unknown. In this study, we developed a new panel of 20 polymorphic short tandem repeat (STR) markers and analyzed 239 isolates of A. oligospora from 19 geographic populations in China. In addition, DNA sequences at six nuclear gene loci and strain mating types (MAT) were obtained for these strains. Our analyses suggest historical divergence within the A. oligospora population in China. The genetically differentiated populations also showed phenotypic differences that may be related to their ecological adaptations. Interestingly, our analyses identified evidence for recent dispersion and hybridization among the historically subdivided geographic populations in nature. Together, our results indicate a changing population structure of A. oligospora in China and that care must be taken in selecting the appropriate strains as biocontrol agents that can effectively reproduce in agriculture soil while maintaining their nematode-trapping ability.

اختبار التضاد الفطري بين الفطرين الاحيائيين Trichoderma harzianum وT.viride وبعض الفطريات الصائدة للنيماتود على الاوساط الصلبة

تم اختبار القدرة التضادية بين الفطرين الأحيائيين Trichoderma harzianum وT. viride مع سبعة أنواع من الفطريات الصائدة للنيماتود (Arthrobotrys oligospora و A.conoides و A.eudermata و A.thaumasia و A.microcaphoides و A.cookedichison و Clonostachys rosea) على الوسطين وسط بطاطا - دكستروز- أكار (PDA) ووسط أكار- خلاصة الذرة (CMA). أظهرت النتائج ان الفطرين T. harzianum و T. viride يمتلكان قدرة تضادية عالية ضد الفطريات الصائدة للنيماتود المختبرة ، ووجد ان الفطر T. harzianum له تضاد ضد الفطريات الصائدة المختبرة أفضل من الفطر T.viride ، وبينت الدراسة ان الفطرين T.harzianumو T.viride لهما درجة تضاد 1، 2، 3 حسب مقياس Bell et al., (1982). كانت أكثر درجة تضاد هي 2 للفطرين T. harzianum و T. viride مع أغلب الفطريات المدروسة على الوسطين CMA وPDA. أظهرت النتائج انه لا يوجد اختلاف واضح في درجة التضاد عند استخدام الوسطين الزرعيين CMA وPDA عدا بعض الفطريات التي كان تضادها اختلف بين الوسطين الزرعيين. ولوحظ ان الفطر T. harzianum كانت درجة تضاده 1 مع الفطر A. conoidesوعلى الوسطين CMA و PDA والفطر A.thaumasia على الوسط CMA، في حين ان الفطر T.viride اعطى نفس الدرجة مع الفطر A.eudermata على الوسط PDA

High Predatory Capacity of a Novel Arthrobotrys oligospora Variety on the Ovine Gastrointestinal Nematode Haemonchus contortus (Rhabditomorpha: Trichostrongylidae)

With the worldwide development of anthelmintic resistance, new alternative approaches for controlling gastrointestinal nematodes in sheep are urgently required. In this work, we identified and characterized native nematode-trapping fungi. We collected seven isolates of fungi with the capacity to form adhesive, three-dimensional networks as the main mechanism to capture, kill, and consume nematodes. The nematode-trapping fungi were classified into two groups; the first group includes the R2-13 strain, showing faster growth, abundant aerial hyphae, scarce conidia production, bigger conidia, and it formed a clade with Arthrobotrys oligospora sensu stricto. The second comprises the A6, A12, A13, R2-1, R2-6, and R2-14 strains, showing a growth adhering to the culture medium, forming little aerial hyphae, smaller conidia, and these formed a sister clade to A. oligospora. Except for the R2-6 strain, conidia production was induced by light. In all the strains, the predatory capacity against the sheep gastrointestinal nematode Haemonchus contortus was greater than 58% compared with the control group. The A6 and A13 strains were the most active against the infective H. contortus third instar (L3) larvae, with an average capture capacity of 91%. Altogether, our results support evidence for a novel A. oligospora variety with high nematode-trapping activity and promissory in helminthic control.