The Receptor-like Kinase TaCRK-7A Inhibits Fusarium pseudograminearum Growth and Mediates Resistance to Fusarium Crown Rot in Wheat

The fungus F. pseudograminearum can cause the destructive disease Fusarium crown rot (FCR) of wheat, an important staple crop. Functional roles of FCR resistance genes in wheat are largely unknown. In the current research, we characterized the antifungal activity and positive-regulatory function of the cysteine-rich repeat receptor-like kinase TaCRK-7A in the defense against F. pseudograminearum in wheat. Antifungal assays showed that the purified TaCRK-7A protein inhibited the growth of F. pseudograminearum. TaCRK-7A transcript abundance was elevated after F. pseudograminearum attack and was positively related to FCR-resistance levels of wheat cultivars. Intriguingly, knocking down of TaCRK-7A transcript increased susceptibility of wheat to FCR and decreased transcript levels of defense-marker genes in wheat. Furthermore, the transcript abundances of TaCRK-7A and its modulated-defense genes were responsive to exogenous jasmonate treatment. Taken together, these results suggest that TaCRK-7A can directly inhibit F. pseudograminearum growth and mediates FCR-resistance by promoting the expression of wheat defense genes in the jasmonate pathway. Thus, TaCRK-7A is a potential gene resource in FCR-resistant wheat breeding program.

Genetics of Resistance to Common Root Rot (Spot Blotch), Fusarium Crown Rot, and Sharp Eyespot in Wheat

Due to soil changes, high density planting, and the use of straw-returning methods, wheat common root rot (spot blotch), Fusarium crown rot (FCR), and sharp eyespot (sheath blight) have become severe threats to global wheat production. Only a few wheat genotypes show moderate resistance to these root and crown rot fungal diseases, and the genetic determinants of wheat resistance to these devastating diseases are poorly understood. This review summarizes recent results of genetic studies of wheat resistance to common root rot, Fusarium crown rot, and sharp eyespot. Wheat germplasm with relatively higher resistance are highlighted and genetic loci controlling the resistance to each disease are summarized.

Phosphorus supply does not affect Fusarium crown rot of winter wheat

Fusarium crown rot (FCR) is a major limitation to the wheat (Triticum aestivum L.) industry in the inland Pacific Northwest (PNW), USA. Genetic resistance to FCR is poorly understood and major-gene resistance is not available in adapted cultivars. Chemical control is ineffective and crop rotations, which disrupt cycles of the disease, are not feasible in the region’s precipitation-limited climate. Cultural control methods are the only realistic option for farmers who struggle to minimize the impact of this disease. It is well-established that FCR is favored by moisture-limited environments and an oversupply of plant-available nitrogen in soil. Effects of the supply of phosphorus in soil have not been clearly delineated. We conducted a two-year FCR experiment at two locations in the low precipitation (< 30 cm) zone of north-central Oregon. Phosphorus fertilizer was applied in-furrow, at rates of 0, 5, and 15 kg P ha-1, to plots planted with either a hard red or soft white winter wheat cultivar. The 15 kg P ha-1 application rate increased tissue phosphorus concentration, early season dry matter, and phosphorus uptake at both locations and both years of this study. Phosphorus treatment had no effect on grain yield, protein, or test weight. Phosphorus had no effect on the severity of FCR. This research improved our knowledge of cultural management boundaries as they relate to the control of FCR.

Contamination and translocation of deoxynivalenol and its derivatives associated with Fusarium crown rot of wheat in Northern China

Fusarium crown rot (FCR) is one of the most important wheat diseases in Northern China. The main causal agent of FCR, Fusarium pseudograminearum, can produce mycotoxins such as type B trichothecenes. Therefore, FCR could be an additional source of mycotoxin contamination during wheat production. Field inoculation experiments demonstrated that FCR disease severity strongly impacts the distribution pattern of trichothecenes in different wheat tissues. Mycotoxins were mainly observed in lower internodes and a low amount was detected in the upper parts above the 4th internode. However, high levels of trichothecene accumulation were detected in the upper segments of wheat plants under field conditions, which would threaten the feed production. The variation of mycotoxin content among sampling sites indicated that besides disease severity, other factors like climate, irrigation, and fungicide application may influence the mycotoxin accumulation in wheat. A comprehensive survey of DON and its derivatives in wheat heads with FCR symptoms in natural fields was conducted in 80 sites of seven provinces in Northern China. Much higher levels of mycotoxin were observed than those in inoculation experiments. The mycotoxin content varied greatly among sampling sites, but no significant differences were observed if compared at province level, which indicated that the variation is mainly due to local conditions. Trace amounts of mycotoxin appeared to be translocated to grains, indicating that FCR infection in natural fields poses a relatively small threat to contamination of grains, but a larger amount to plant parts that may be used as animal feed. To our knowledge, this is the first report of trichothecene accumulation in wheat stems, heads, and grains following FCR infection in natural field condition. These investigations provide novel insights into food and feed safety risk caused by FCR in Northern China.

Diagnostic Guide: Fusarium Crown Rot of Winter Wheat

Fusarium crown rot of winter wheat is an economically important disease in most regions where winter wheat is grown. Fusarium crown rot is caused by Fusarium culmorum and F. pseudograminearum. This diagnostic guide details information to aid in field, molecular, and morphological diagnosis of Fusarium crown rot.

Small “Nested” Introgressions from Wild Thinopyrum Species, Conferring Effective Resistance to Fusarium Diseases, Positively Impact Durum Wheat Yield Potential

Today wheat cultivation is facing rapidly changing climate scenarios and yield instability, aggravated by the spreading of severe diseases such as Fusarium head blight (FHB) and Fusarium crown rot (FCR). To obtain productive genotypes resilient to stress pressure, smart breeding approaches must be envisaged, including the exploitation of wild relatives. Here we report on the assessment of the breeding potential of six durum wheat-Thinopyrum spp. recombinant lines (RLs) obtained through chromosome engineering. They are characterized by having 23% or 28% of their 7AL chromosome arm replaced by a “nested” alien segment, composed of homoeologous group 7 chromosome fractions from Th. ponticum and Th. elongatum (=7el1L + 7EL) or from different Th. ponticum accessions (=7el1L + 7el2L). In addition to the 7el1L genes Lr19 + Yp (leaf rust resistance, and yellow pigment content, respectively), these recombinant lines (RLs) possess a highly effective QTL for resistance to FHB and FCR within their 7el2L or 7EL portion. The RLs, their null segregants and well-adapted and productive durum wheat cultivars were evaluated for 16 yield-related traits over two seasons under rainfed and irrigated conditions. The absence of yield penalties and excellent genetic stability of RLs was revealed in the presence of all the alien segment combinations. Both 7el2L and 7EL stacked introgressions had positive impacts on source and sink yield traits, as well as on the overall performance of RLs in conditions of reduced water availability. The four “nested” RLs tested in 2020 were among the top five yielders, overall representing good candidates to be employed in breeding programs to enhance crop security and safety.

Genetic variation for fusarium crown rot tolerance in durum wheat

Tolerance to the cereal disease Fusarium crown rot (FCR) was investigated in a set of 34 durum wheat genotypes, with Suntop, (bread wheat) and EGA Bellaroi (durum) as tolerant and intolerant controls, in a series of replicated field trials over four years with inoculated (FCR-i) and non-inoculated (FCR-n) plots of the genotypes. The genotypes included conventional durum lines and lines derived from crossing durum with 2–49, a bread wheat genotype with the highest level of partial resistance to FCR. A split plot trial design was chosen to optimize the efficiency for the prediction of FCR tolerance for each genotype. A multi-environment trial (MET) analysis was undertaken which indicated that there was good repeatability of FCR tolerance across years. Based on an FCR tolerance index, Suntop was the most tolerant genotype and EGA Bellaroi was very intolerant, but some durum wheats had FCR tolerance indices which were comparable to Suntop. These included some conventional durum genotypes, V101030, TD1702, V11TD013*3X-63 and DBA Bindaroi, as well as genotypes from crosses with 2–49 (V114916 and V114942). The correlation between FCR tolerance and FCR-n yield predictions was moderately negative indicating it could be somewhat difficult to develop FCR-tolerant genotypes that are high yielding under low disease pressure. However, FCR tolerance showed a positive correlation with FCR-i yield predictions in seasons of high disease expression indicating it could be possible to screen for FCR tolerance using only FCR-i treatments. These results are the first demonstration of genetic diversity in durum germplasm for FCR tolerance and they provide a basis for breeding for this trait.