Quantitative assessment of the interaction between the antagonistic fungus Talaromyces flavus and the wilt pathogen Verticillium dahliae on eggplant roots

Quantitative aspects of the interaction between the antagonist Talaromyces flavus, the pathogen Verticillium dahliae and eggplant roots, were studied. When eggplant roots were inoculated with T. flavus, prior to the infection with the pathogen, the population density of T. flavus on V. dahliae-infected roots was at least 3 times higher than on healthy uninfected roots, and the proliferation of T. flavus on diseased eggplant roots was related to the severity of wilt symptoms, in the two levels of application of T. flavus studied. However, in all classes of disease severity tested (disease index, 0–3), the population density of T. Flavus on eggplant roots treated with 10⁶ ascospores g^–1 rooting mixture was significantly (p=0.05) higher than with 10⁵ ascospores g^–1. In roots treated with 10⁵ and 10⁶ T. flavus ascospores g^–1 rooting mixture, the population density of V. dahliae was reduced by 51% and 69%, respectively. When testing the relationships between the population density of V. dahliae in the roots and disease severity, no significant (p=0.05) difference was found between disease indexes 2 and 3. However, the density of V. dahliae on roots of plants with disease index 1 was significantly (p=0.05) lower than disease indexes 2 and 3. The positive relationship between the inoculum concentration of V. dahliae and the population density of T. flavus developed on eggplant roots was significant (p=0.001), linear, and highly correlated (r=0.945) on a logarithmic scale. In addition, the analysis of these data revealed a significant (p=0.05), high, negative and linear correlation (r=–0.985) between the log concentration of V. dahliae inoculum and the disease reduction achieved by T. flavus.     

茄子根系分泌物中香草醛和肉桂酸对黄萎菌的化感效应

采用室内培养和生物测定的试验方法,研究了不同浓度的香草醛和肉桂酸对黄萎菌（Verticillium dahliae）及茄子种子萌发、幼苗生长的化感效应.结果表明,香草醛和肉桂酸对茄子黄萎菌的化感效应存在差异,表现为所有浓度的肉桂酸都抑制了黄萎菌孢子萌发,当浓度为0.5mmol/L时抑制作用最大;香草醛在浓度为0.1mmol/L时抑制孢子萌发,其余浓度则表现出促进作用.对香草醛和肉桂酸的生物测定结果显示,当浓度为0.1mmol/L时,肉桂酸促进茄子种子萌发和幼苗生长,其余浓度则表现为抑制作用,并且随着浓度的加大抑制作用增强;香草醛在各浓度水平下都促进了茄子种子萌发和幼苗生长,当浓度为0.5mmol/L时促进作用最大.     

不同温度和光照度下以及收集时间内茄子根系分泌物量

在温度为25℃、光照度为300μmol·m-2·s-1的条件下,收集时间为5 h的茄子根系分泌物的量最大.     

黄萎病菌粗毒素接种对感病和抗病茄子品种的一些酶类活性和光合特性的影响

以黄萎病菌粗毒素接种不同茄子品种的结果表明:接种后抗病品种比感病品种的过氧化物酶(POD)、超氧化物歧化酶(SOD)活性高,而多酚氧化酶(PPO)和苯丙氨酸解氨酶(PAL)活性则相对稳定;前者叶的净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)和细胞间CO2浓度(Ci)的变化幅度比后者小,但72 h后二者的叶片Pn、Gs、Tr都明显呈下降趋势.     

Fusarium Species Isolated from Common Weeds in Eggplant Fields and Symptomless Hosts of Fusarium oxysporum f. sp. melongenae in Turkey

Thirteen species of weed plants were collected between May and September in 2010 and 2011 from eggplant fields representing 11 distinct locations covering a wide geographical area of Turkey. Weeds are potential hosts of many plant pathogens and may not exhibit disease symptoms when colonized. Fusarium spp. were isolated from five monocotyledonous species and eight dicotyledonous species. A total of 212 isolates recovered from weeds were assigned to eight Fusarium species on the basis of morphological characteristics. F. oxysporum was the most frequently isolated species (29.7%), followed by F. solani (19.8%), F. graminearum (13.7%), F. verticillioides (12.7%), F.equiseti (9.9%), F. avenacearum (8.0%), F. proliferatum (3.8%) and F. subglutinans (2.4%). The F. oxysporum isolates from different weed hosts were characterized by means of pathogenicity and vegetative compatibility grouping (VCG) tests. Among these, 29 isolates were found to be pathogenic to eggplant cv. Kemer and re‐isolated as Fusarium oxysporum Schlecht. f. sp. melongenae (Fomg) as evidenced. These isolates from weed hosts were assigned to VCG 0320. This study is the first report of Fomg isolated from weeds in eggplant fields in Turkey. None of the weed species tested showed symptoms of wilting in pot experiments, and F. oxysporum was isolated with greater frequency from all inoculated weeds. The results of this study indicate that several weed plants may serve as alternative sources of inoculum for Fomg, during the growing season.     

Threshold‐based spraying decision programmes for the red spider mite Tetranychus marianae on eggplant

The red spider mite, Tetranychus marianae McGregor (Acari: Tetranychidae), has been an important pest of eggplant Solanum melongena L. (Solanaceae) and other vegetables in the Mariana Islands. The damage due to T. marianae has been severe and caused huge economic losses. Because no threshold levels are available for T. marianae, many growers are applying up to 12 chemical applications per eggplant cropping period. This is not only expensive, but also results in lower yields because of extensive foliar damage and development of resistance in mites to chemicals. To diminish the calendar‐based chemical applications and to preclude damage to foliage and fruit quality, this study was undertaken for the development of a threshold level for optimum timing of chemical applications for T. marianae. In the direction of this aim, an attempt was made to generate different threshold levels by applying chemical spray (Sun‐spray 6E, 5 ml/l) within 12 h after reaching the threshold levels at 2, 4, 6, 8 and 10 mites/leaf, as well as current recommended calendar‐based sprays and non‐sprayed control in a replicated block design for the dry and wet seasons of 2010 at two locations (Yigo and Inaranjan) in Guam (USA). Based on T. marianae‐infested leaves, incidence of T. marianae and yield levels, the plots sprayed at 2 or 4 mites/leaf in the dry season and 2–8 mites/leaf during the wet season had significantly lower leaf damage and incidence of T. marianae compared with a greater number of mites/leaf in calendar‐based sprays and control plots. At the greater threshold levels, the mean yield was significantly reduced in comparison with the mean yield obtained when plots were sprayed at a threshold of 2–8 mites/leaf. Therefore, it is concluded that the optimum threshold chemical spray for T. marianae on eggplant is 4 mites/leaf during the dry season and 8 mites/leaf in the wet season.     

Evaluation of three aqueous plant extracts and Lamdacot in controlling eggplant fruit borer (Daraba laisalis Wlk.) (Lepidoptera: Pyralidae) in north-eastern Nigeria

Field experiments carried out in Dadinkowa, Gombe State, Nigeria, during 2007 and 2008 cropping seasons evaluated the efficacy of three aqueous plant extracts namely neem (Azadirachta indica A.H.L. Juss.), bitter melon (Momordica balsamina Linn.) and siam weed (Chromolaena odorota (L.) King and Robinson) compared to a conventional insecticide, Lamdacot 500EC, in managing fruit borer (Daraba laisalis Wlk.) attack of eggplants in north-eastern Nigeria. The experiments were laid out in a randomised complete block design replicated four times including controls. The results showed that the application of aqueous extracts (5% w/v concentration) of A. indica and M. balsamina at one-week interval during the fruiting stage was effective and at par with the conventional insecticide, Lamdacot, in reducing eggplant fruit borer infestation and fruit damage, as well as the resulting increase in fruit yield. Farmers can therefore adopt the practice of applying 5% w/v concentration of the above aqueous plant extracts at weekly intervals to control fruit borer attack of eggplants in the north-eastern region of Nigeria.     

Comparison between Solanum torvum Sw. and S. melongena L. after Ralstonia solanacearum inoculation

Bacterial wilt, caused by Ralstonia solanacearum, is one of the most devastating plant diseases, affecting some economically important Solanaceae crops. In contrast, Solanum torvum, also known as wild eggplant, does not wilt when infested with R. solanacearum. In order to describe the mechanism underlying the response of S. torvum, it was compared with the cultivated eggplant, S. melongena, when both were infected with the same R. solanacearum strain. No wilting occurred in S. torvum, although the bacteria colonised roots and stems in both species within the first 24 h. There were marked differences beyond 24 h, consisting of high bacterial mortality in S. torvum. Using the calli model, our investigations revealed an increase in cell wall monoamine oxidase activity in S. torvum after R. solanacearum inoculation, which did not occur in S. melongena.