Inoculation methods and agressiveness of Macrophomina phaseolina isolates in cowpea

ABSTRACT: The fungi Macrophomina phaseolina is the charcoal rot causal agent, one of the most important cowpea crop disease in semiarid regions can causes 100% yield losses. The search for resistant genotypes requires efficient phenotyping. In addition, there is the problem of great variation in aggressiveness between isolates. This study aimed to 1) test three methods of inoculation in semiarid conditions, and 2) to evaluate the aggressiveness of isolates of M. phaseolina. In the first experiment carried out in greenhouse, the inoculations methods were evaluated, using two cowpea lines, three inoculation methods and three pathogen isolates. On the second experiment, fifteen M. phaseolina isolates were inoculated in one cultivar to evaluate their aggressiveness. By assessing the length of the lesions and the severity of the disease using an index, we identified the toothpick inoculation method as the most efficient. Toothpick method allowed to discriminate the genotypes and the aggressiveness of the pathogen.

Fungivory: a new and complex ecological function of Doru luteipes (Scudder) (Dermaptera: Forficulidae)

We report the discovery that the earwig predator Doru luteipes (Scudder, 1876) (Dermaptera: Forficulidae) feed on Puccinia polysora Underw uredospore, the causal agent of Southern Rust of Corn (SRC), which is a primary disease affecting the maize crop in Brazil. We performed experiments in laboratory and greenhouse to test the effect of D. luteipes (1st/2nd and 3rd/4th instars, and adults) fungivory on the P. polysora uredospore concentration. All trials showed a significant reduction of the initial concentration of uredospore. There was a reduction in uredospore concentration with increase in number of D. luteipes feeding on them. We also tested the uredospore consumption by quantifying its percentage in the feces of D. luteipes. Nymphs of the 2nd, 4th instar and adults fed 88%, 85%, and 83.8% of the uredospore, respectively. For nymphs of the 3rd instar, the percentage of uredospore consumption (75.6%) was statistically significant compared with the other groups. In greenhouse experiment, at twenty-eight days after plant inoculation with 9.9 x 104 uredospores, the percentage of uredospore consumption was 81.7%. Our results confirmed the fungivory of D. luteipes on P. polysora uredospore. This is the first report of D. luteipes fungivory, which may play an important role in the biological control of P. polysora in corn.

ARTIFICIAL FIELD INOCULATION OFBREAD WHEAT ADVANCED LINES WITH TILLETIAINDICA, CAUSAL AGENT OF KARNAL BUNT

The reaction to Tilletiaindica of one thousand and ninety twobread wheat advanced lines were evaluated in the field during the crop season 2016-2017. Sowing in beds with two rows was carried out on November 11 and 24, 2016, using 8 g of seed. Five spikes per line were inoculated by injection with 1 mL of an allantoidsporidial suspension (10,000/mL) during the boot stage, and at maturity the percentage of infection was determined by counting healthy and infected grains. The range of infection in the first date was 0-88.83 with a mean of 31.81%, while in the second date it was 0-82.65% with a mean of 24.44%.The range of infection of the two dates was 0.46-83.71% with a mean of 28.12%.Sixteenlines showed a percentage of infection equal or below 5.0% in both dates, and out of those lines, the following five showed less than 2.5%: two sister lines of MUNAL#1/FRANCOLIN#1*2/3/ATTILA*2/PBW65//MURGA(CMSS12Y00701T-099TOPM-099Y-099M-0SY-13M-0WGY), MUNAL#1/FRANCOLIN#1*2/3/ATTILA*2/PBW65//MURGA (CMSS12Y00701T-099TOPM-099Y-099M-0SY-17M-0WGY), BAJ#1/3/KIRITATI//ATTILA*2/PASTOR*2/4/MUTUS*2/TECUE#1, VILLAJUAREZF2009/6/ATTILA/3*BCN//BAV92/3/PASTOR/4/TACUPETOF2001*2/BRAMBLING/5/PAURAQ, and KACHU/BECARD//WBLL1*2/BRAMBLING/4/FRET2/TUKURU//FRET2/3/MUNAL#1. Lines with the highest percentage of infection were: BABAX/LR42//BABAX*2/3/KUKUNA/4/CROSBILL#1/5/BECARD/6/KSW/SAUAL//SAUAL/7/BABAX/LR42//BABAX*2/3/KUKUNA/4/CROSBILL#1/5/BECARD with 88.83 in the first date,MUU/KBIRD//2*KACHU/KIRITATIwith 84.77 and 82.65%in the first and second date, respectively, and TACUPETOF2001*2/BRAMBLING//WBLL1*2/BRAMBLING/6/WBLL1*2/KURUKU*2/5/REH/HARE//2*BCN/3/CROC_1/AE.SQUARROSA(213)//PGO/4/HUITES/7/BAV92//IRENA/KAUZ/3/HUITES/4/2*ROLF07 with 81.67% in the first date. The average of the three highest levels of infection of the susceptible checkwas99.7%.

RNA-seq analysis of Rhizoctonia solani AG-4HGI strain BJ-1H infected by a new viral strain of Rhizoctonia solani partitivirus 2 reveals a potential mechanism for hypovirulence

Rhizoctonia solani partitivirus 2 (RsPV2), in the genus Alphapartitivirus, confers hypovirulence on Rhizoctonia solani AG-1-IA, the causal agent of rice sheath blight. In this study, a new strain of RsPV2 obtained from R. solani AG-4HGI strain BJ-1H, the causal agent of black scurf on potato, was identified and designated as Rhizoctonia solani partitivirus 2 strain BJ-1H (RsPV2-BJ). An RNA sequencing analysis of strain BJ-1H and the virus RsPV2-BJ-free strain BJ-1H-VF derived from strain BJ-1H was conducted to investigate the potential molecular mechanism of hypovirulence induced by RsPV2-BJ. In total, 14319 unigenes were obtained, and 1341 unigenes were identified as differentially expressed genes (DEGs), with 570 DEGs being down-regulated and 771 being up-regulated. Notably, several up-regulated DEGs were annotated to cell-wall-degrading enzymes, including β-1,3-glucanases. Strain BJ-1H exhibited increased expression of β-1,3-glucanase following RsPV2-BJ infection, suggesting that cell wall autolysis activity in R. solani AG-4HGI strain BJ-1H might be promoted by RsPV2-BJ, inducing hypovirulence in its host fungus R. solani AG-4HGI. To the best of our knowledge, this is the first report on the potential mechanism of hypovirulence induced by a mycovirus in R. solani.

Aqueous extracts from Acalypha gaumeri and Bonellia flammea for leaf blight control in chrysanthemum (Chrysanthemum morifolium)

The chrysanthemum is the second most important cut flower in the world, however, its quality and commercial value is affected by the leaf blight produced by <em>Alternaria </em>spp. The objective of this work was to evaluate the causal agent of leaf blight in Chrysanthemum, and its control with aqueous extracts of <em>Acalypha gaumeri </em>and <em>Bonellia flammea</em>. The fungus was collected and identified from leaves and stems of chrysanthemum plants. Subsequently, molecular identification and pathogenicity tests were performed on chrysanthemum plants. In the field, treatments were evaluated with weekly applications of: T1: <em>B. flammea </em>bark extract, T2: <em>A. gaumeri </em>root extract, T3: negative control (water) and T4: Captan® fungicide. Prior to the application of the treatments, plants were inoculated with the isolated fungus (2.5 × 106 spores mL-1) and severity was evaluated. <em>Alternaria chrysanthemi </em>was identified as the causal agent. Based on the severity percentage, the lowest averages of the area under the disease progress curve, the lowest rates of apparent infection, the lowest intensity of the disease and the greater effectiveness in controlling the disease were observed for T2 (165, 0.017, 8 and 67%, respectively) followed by T1 (186, 0.022, 13 y 50 %, respectively) and T4 (179, 0.023, 14 y 45%, respectively), observing a significantly different than negative control T3 (369, 0.025, 25 and 0%, respectively). Plant extracts have potential to be used as an alternative in the management of <em>Alternaria </em>leaf blight in chrysanthemum.

Identification and Characterization of Nectria pseudotrichia Associated with Camellia Canker Disease in China

Camellia japonica is a native tree species with high economic value that is widely cultivated in southern China. In recent years, canker disease has been observed in camellia plantations in Zhejiang Province, China, with the disease incidence rate in some plantations exceeding 20%. Canker disease severely affects the trunks and branches of C. japonica in China, but the causal agent has not yet been identified. In this study, the pathogen was isolated from infected C. japonica tissues through a conventional tissue isolation approach. Species identification was conducted using morphological methods combined with multilocus phylogenetic analysis. Pathogenicity was tested based on Koch’s postulates. The results showed that the pathogen could be isolated from the diseased bark of C. japonica ‘Hongluzhen’. The pathogen was identified as Nectria pseudotrichia based on morphological, cultural, and molecular traits. The inoculation of the pathogen into C. japonica ‘Hongluzhen’ caused necrotic lesions on healthy seedlings, and the fungus N. pseudotrichia could be re-isolated from such lesions. Therefore, N. pseudotrichia is the causal agent of canker disease affecting C. japonica in China.

Fusarium sp., causal agent of vascular wilt in citrus and its sensitivity to fungicides

<p>Citrus wilt is a disease of recent appearance in the northern area of Veracruz that causes economic losses to producers in the region. The present work aimed to identify the causative agent of this disease and evaluate different fungicides to determine its<em> in vitro</em> sensitivity. A fungus was consistently isolated in plants with wilt symptoms; it was morphologically identified indifferent culture media and molecularly identified by PCR using the EF1-728F/EF1-986R primers. The fungus was inoculated in three varieties of citrus under greenhouse conditions. The sensitivity test was carried out with the fungicides chlorothalonil, benomyl thiabendazole, prochloraz, and a biological agent (<em>Bacillus subtilis</em>) at different concentrations, plus a negative control. <em>Fusarium</em> sp. (Accession No. MW438335) was morphologically and molecularly identified as the causal agent of vascular wilt in citrus fruits, causing growth retardation, decreased number of roots, wilting of the apical bud, and necrosis in the vascular system of the three varieties inoculated. The most effective fungicides in inhibiting mycelial growth were thiabendazole, prochloraz, and the biological agent <em>Bacillus subtilis</em>.</p>