Effect of Irrigation Regimes on Disease Expression in Melon Plants Infected with Monosporascus cannonballus

The effect of irrigation regimes on disease expression in melon plants infected with Monosporascus cannonballuswas studied during two summer growing seasons (1998 and 1999) in the Arava region of southern Israel. Less frequent and reduced irrigation postponed the onset of plant collapse and lowered disease incidence. Delaying disease development in infested fields by reducing irrigation frequency allowed crop harvest before plant collapse. However, reduced irrigation regimes reduced yields, as shown in methyl bromide fumigated plots. Fruits from melon plants grown under reduced irrigation in the infested plots were also of lower quality due to water shortage. The delay in plant collapse under the reduced irrigation treatments was attributed to a combined effect of reduced fruit load and the development of a deeper root system, which could support the increased water demand of the mature, fruiting plant.     

Potential of indigenous antagonistic rhizobacteria in the biological control of Monosporascus root rot and vine decline disease of muskmelon

ABSTRACT

Monosporascus root rot and vine decline (MRVD) of muskmelon, caused by Monosporascus cannonballus, is an economically important disease worldwide. The objectives of this study were to isolate native rhizobacterial strains and to evaluate their ability to promote plant growth and to provide protection against M. cannonballus. Thirty eight native bacterial isolates from the rhizosphere soil of muskmelon and cucumber were screened for their antagonism against M. cannonballus in a dual culture assay. Among them, five isolates viz., Bacillus amyloliquefaciens (B4), Pseudomonas mendocina (B7), Bacillus endophyticus (B10), Pseudomonas resinovorans B11 and P. aeruginosa AT3, identified based on the 16S rRNA gene sequence analysis, showed a significant level of antagonism and the inhibition zone ranged from 5.6 mm to 25.9 mm. Scanning electron microscopic observation of the hyphae of M. cannonballus at the inhibition zone revealed morphological abnormalities including shrinkage, loss of turgidity, pit formation and deformation. These bacterial isolates showed compatibility with one another and with Trichoderma viride. Greenhouse experiments revealed that P. resinovorans B11 was the most effective among the bacterial antagonists in controlling MRVD in melon. When applied as seed treatment and soil application, P. resinovorans B11 reduced the incidence of MRVD by 93.1%, relative to the infected control.     

甜瓜黑点根腐病及其研究进展

甜瓜黑点根腐病是一种重要的根部真菌病害,造成严重的经济损失,危及甜瓜产业的健康发展。文章综述了黑点根腐病病害症状、病原特性、病害循环、发生规律与防治方法,并对今后的研究作了展望。     

甘肃酒泉发现坎诺单孢菌引起的甜瓜倒秧

2018年7月中旬在甘肃省酒泉市金塔县, 甜瓜成熟前10~20 d, 一些田块出现了严重的倒秧, 从罹病植株的褐腐根上分离到坎诺单孢菌Monosporascus cannonballus, 病株分出率达76.9%。致病性测定结果显示:在试验条件下(25℃±3℃), 菌株TG-84对甜瓜(品种:‘86-1’)的致病性强, 出苗后13 d, 倒苗率达80%。     

Resistance to melon vine decline derived from Cucumis melo ssp. agrestis: genetic analysis of root structure and root response

Melon vine decline is a major soilborne disease that causes severe economic losses around the world. The fungal pathogens Monosporascus cannonballus Pollack et Uecker and Acremonium cucurbitacearum Alfaro‐García, W. Gams et J. García‐Jiménez have been reported as the main causal agents of this disease. A relatively high level of resistance has been reported in Cucumis melo L. ssp. agrestis (Naud.) Pangalo in the Asiatic accession Pat 81. Although specific resistance mechanisms controlling pathogen‐induced root lesions have been characterized in Pat 81, the development of a vigorous and branched root system can also appreciably increase its tolerance to vine collapse. The genetics of root traits related to root vigour and structure were studied in the progeny derived from a cross between Pat 81 and the highly susceptible cultivar ‘Piñonet’ market class ‘Piel de Sapo’(C. melo L. ssp. melo). The inheritance of specific resistance to soilborne fungi was also studied by analysing root response to inoculation employing naturally infested soil. Estimates of the broad‐(H) and narrow‐sense (h²) heritabilities indicated that the majority of the variation for lesion resistance in lateral and fine roots, in the root weight, root length, and the root surface area could be explained by additive effects, whereas dominance is important in plant biomass and resistance to lesions in hypocotyls. Selection for improved root systems conferring resistance and tolerance to vine decline was successfully conducted in BC₁ progeny derived from a Pat 81 בPiñonet’ mating. Moderate values of heritabilities (0.03–0.76) suggest that breeding strategies that combine family and individual selection could enhance genetic progress. As some of the traits analysed exhibited heterosis, breeding methods directed towards recovering hybrid vigour may increase gain from selection.     

A temporal genetic analysis of disease resistance genes: resistance to melon vine decline derived from Cucumis melo var. agrestis

Melon vine decline causes severe economic losses to melon crops all over the world. Two fungi. Acremonium cucurbitacearum and Monosporascus cannonballus, have been reported as the main causal agents of root damage, responsible for the decrease in root water and nutrient uptake capacity. However, melon vine decline aetiology is not completely understood, so screening assays must be conducted under natural infestation conditions. In field assays, the erratic effect of uncontrolled environmental factors makes the study of the trait's genetics difficult. The percentage of asymptomatic plants scored at individual moments during the infection process in the field is an imprecise indicator of the resistance level of each genotype. The analysis of disease progress curves does allow for the minimization of the stochastic fluctuations caused by environmental factors at various moments in time. Using this analysis the mode of inheritance of the partial resistance to melon vine decline derived from the accession Pat 81 of Cucumis melo var. agrestis was further studied. Data from the six generations assayed (susceptible and resistant parents. F₁, F₂, and backcrosses BC₁ and BC₂ were fitted to an additive/dominance model without epistatic effects using a scaling test. Monogenic control was proposed as the simplest model to explain the data. Assuming this simple model, the method of analysis also allowed for the characterization of the incomplete penetrance of resistance, which varies as a log probit function of the time. Simple genetic control would simplify the use of Pat 81 in breeding programmes aimed at developing commercial melon varieties with resistance to vine decline.     

甜瓜黑点根腐病菌Monosporascus cannonballus在中国大陆的首次报道

2005年夏季,在甘肃省中部的半干旱种植区的一块甜瓜品种试验田中,一些甜瓜植株在收获前2周突然凋萎,从病根上分离得到3株生长速度快的高温型子囊菌,对其中2个菌株进行了形态特征、生物学特性及致病性研究,根据其独特的、每个子囊内仅产生一个黑色子囊孢子的主要形态特征和对甜瓜及西瓜的致病性,将其鉴定为Monosporascus cannonballus PollackUecker。这是该菌在我国大陆的首次报道。