Effectiveness of local isolates of Trichoderma spp. in imparting drought tolerance in rice, Oryza sativa.

Rice is a crop that requires high amount of water, and the drought is a major constraint in paddy cultivation. Water stress condition frequently prevails due to shortage of rain which results in significantly reduced plant growth and yield of rice. In the present study capability of Trichoderma spp. in imparting drought tolerance to rice, Oryza sativa was explored. Eleven local strains of Trichoderma spp. were applied to rice cv. Swarna Sub-1 through soil application (2 g/kg soil) and seed treatment (20 g/kg seed) under 0, 25, 50 and 75% less watering of the recommended amount. The soil application of T. harzianum AMUTHZ84 significantly promoted the shoot and root length (23.6 and 21.3%) followed by seed treatment (19.7 and 18.2%) under recommended level of irrigation condition (100% irrigation). Next in effectiveness was T. viride AMUTVR73 (21.5 and 18.1%) over untreated control. However, under 75% water availability, soil application with T. harzianum AMUTHZ82 was found superior over other isolates in enhancing shoot and root length (17.7 and 16.4%). The same isolate was also recorded to be superior under 50% (12.4 and 10.1%) and 25% water availability (9.3 and 8.1%) in enhancing the plant growth and biomass of rice cv. Swarna Sub-1. The isolate also significantly enhanced the leaf pigments, and photosynthesis in the rice plants grown under 25-75% water stress condition. In general, soil application of Trichoderma isolates was found more effective than seed treatment, and the T. harzianum AMUTHZ82 provided 8-17% enhancement in the plant growth, biomass, leaf pigments and photosynthesis of rice cv. Swarna Sub-1 grown under 25-75% water stress condition.

Incidence of Sheath Blight in Irrigated Rice and Associated Yield Losses in Northern India.

Rice-growing districts in Uttar Pradesh, India, were surveyed during the months of July and October to record the frequency of occurrence and disease incidence of sheath blight caused by Rhizoctonia solani in paddy. A total of 180 paddy fields were surveyed at the block level of 21 districts, where almost all the rice varieties were found highly susceptible to R. solani and exhibited severe yield loss compared with low-infested fields. The district Muzaffarnagar had the highest rate of disease occurrence, while maximum disease severity was recorded in the district Saharanpur. This district also had the highest soil population of R. solani, followed by Mathura, Muzaffarnagar, Barabanki, Aligarh, Sultanpur, Mainpuri, and Rampur. The greatest relative yield loss attributed to sheath blight infestation was recorded in Mathura (40%). The yield loss was linearly correlated with soil population of R. solani and disease incidence. Disease occurrence, incidence, severity, and yield loss to paddy were all significantly greater in the area which experienced relatively higher temperatures (25 to 38°C) and relative humidity (49 to 100%) during the months of June to August. Furthermore, the fields applied with a total dose of 250 to 280 kg nitrogen/ha exhibited higher disease severity (2.9 to 3.3 score) compared with fields that received a moderate dose of 140 to 180 kg N/ha (0.9 to 1.8 disease severity score). The rice nursery fields were found almost free from the sheath blight, but the disease was quite prevalent in the paddy fields with 7.2 to 38.9% disease incidence which resulted in 14.3 to 39.7% yield loss to rice.

Biological and Physiological Responses of Root-knot Disease Development on Five Cucurbits Exposed to Different Concentrations of Sulfur Dioxide.

A study was undertaken in order to investigate the effects of SO2 (25, 50, and 75 ppb) exposure for five hours on alternate days for three months on the susceptibility of five cucurbits to the infection of Meloidogyne incognita, causing root-knot disease. Four-week-old cucurbit plants were inoculated with 2000 J2 of M. incognita. SO2 levels of 50 and 75 ppb caused noticeable injury to foliage and reduced the plant growth parameters and biomass production of cucurbits (p ≤ 0.05). Nematode-inoculated plants caused characteristic oval, fleshy and large galls. The galls were formed closely, and as a result they coalesced, giving bead-like impressions especially in pumpkin and sponge gourds. Disease severity became aggravated on plants exposed to SO2 at 50 or 75 ppb concentrations. The nematode and SO2 interaction varied with the levels of SO2 and the response of the plant to M. incognita. SO2 at 50 or 75 ppb concentrations stimulated the pathogenesis of M. incognita on cucurbit species. The combined effect of 75 ppb SO2 and M. incognita suppressed plant length by 34% against the sum of decreases observed by M. incognita and SO2 individually (14-18%). At 50 ppb SO2, the fecundity of M. incognita was decreased and combined effect of SO2 and M. incognita was more than the sum of their singular effects. The study has proven that root-knot disease might become aggravated in the regions contaminated with elevated levels of SO2.

Effect of elevated levels of CO2 on powdery mildew development in five cucurbit species.

The environment is the key factor that influences the host-parasite relationship. Elevated CO2 levels resulting from various anthropogenic sources may directly affect the surroundings around pathogens and plants. It is hypothesized that plants may respond differently to pathogens in the environment containing an elevated concentration of CO2. To test the hypothesis an experiment was conducted to examine the effects of intermittent exposures of elevated levels of CO2 viz., 400, 500 and 600 ppm (5 hr/day on alternate days) on the development of Sphaerotheca fuliginea causing powdery mildew disease on five cucurbits species using open-top chambers. The elevated levels of CO2 acted as a growth promoter and significantly enhanced the plant growth of all five cucurbit species. Inoculation with the fungus incited specific mildew symptoms on the leaves and decreased the plant growth and biomass production of the cucurbits tested except bitter gourd. The intermittent exposures with elevated levels of CO2 aggravated the disease development. As a result, severe mildew developed on all five cucurbits, including bitter gourd, which expressed tolerance to the pathogen. Fungus colonization in terms of the number of conidia/cm2 leaf surface was significantly greater on the plants exposed to 500 or 600 ppm CO2. The stomata and trichome density and stomatal pore width were increased in the leaves of CO2 exposed plants. The CO2 exposures also accelerated the photosynthesis rate, but transpiration, stomatal conductance, salicylic acid and total phenols were decreased; fungus inoculation caused the effects just reverse of CO2. Interaction between S. fuliginea and CO2 was found synergistic at 500 ppm, whereas with rest of the concentrations it was near to additive.

Incidence of Root-Knot Nematode (Meloidogyne graminicola) and Resulting Crop Losses in Paddy Rice in Northern India.

Surveys of major rice growing districts in the state of Uttar Pradesh in Northern India were conducted for 3 consecutive years during 2013 to 2015 under a government-funded major research project to determine the frequency of occurrence and disease incidence of the rice root-knot nematode, Meloidogyne graminicola, in rice paddy fields. More than 800 paddy fields from 88 Tehsils (divisions within a district) in 18 major rice growing districts in Uttar Pradesh were surveyed, where M. graminicola was associated with root-knot disease in rice paddy fields based on morphological and molecular characterization of juveniles and adults. The highest frequency of disease in rice fields was observed in Aligarh (44.6%), followed by Muzaffarnagar, Shahjahanpur, and Kheri Lakhimpur (29.3, 28.0, and 27.4%, respectively). Maximum disease incidence was also recorded in Aligarh (44.6%), followed by Sultanpur, Mainpuri, and Muzaffarnagar (5.7, 5.2, and 4.5, respectively). Gall index and egg mass index values (on a 0 to 10 scale) were highest in Aligarh (3.5 and 2.1, respectively), followed by Muzaffarnagar (2.6 and 2.0) and Mainpuri (2.3 and 1.8). The average soil population of M. graminicola was highest in Aligarh (3,851 ± 297 second-stage juveniles [J2]/kg of soil), followed by Muzaffarnagar (2,855 ± 602 J2/kg of soil), whereas the lowest population was recorded in Barabanki (695 ± 400 J2/kg of soil) at the time of harvesting. Relative yield losses were also determined, and the highest yield loss attributed to M. graminicola infestation was recorded in Aligarh (47%). The yield loss was linearly correlated with the soil population density of M. graminicola and disease incidence.

Nanoparticle-Plant Interactions: Two-Way Traffic.

In this Review, an effort is made to discuss the most recent progress and future trend in the two-way traffic of the interactions between plants and nanoparticles (NPs). One way is the use of plants to synthesize NPs in an environmentally benign manner with a focus on the mechanism and optimization of the synthesis. Another way is the effects of synthetic NPs on plant fate with a focus on the transport mechanisms of NPs within plants as well as NP-mediated seed germination and plant development. When NPs are in soil, they can be adsorbed at the root surface, followed by their uptake and inter/intracellular movement in the plant tissues. NPs may also be taken up by foliage under aerial deposition, largely through stomata, trichomes, and cuticles, but the exact mode of NP entry into plants is not well documented. The NP-plant interactions may lead to inhibitory or stimulatory effects on seed germination and plant development, depending on NP compositions, concentrations, and plant species. In numerous cases, radiation-absorbing efficiency, CO2 assimilation capacity, and delay of chloroplast aging have been reported in the plant response to NP treatments, although the mechanisms involved in these processes remain to be studied.

Root-knot Nematode Problem of Some Winter Ornamental Plants and Its Biomanagement.

A microplot study under field conditions was carried out during 2 consecutive years to assess the effect of root-knot nematode infection (2,000 Meloidogyne incognita eggs/kg soil) on three winter ornamental plants: hollyhock (Althea rosea), petunia (Petunia hybrida), and poppy (Papaver rhoeas). Effects of root-dip treatment with the biocontrol agents Pochonia chlamydosporia, Bacillus subtilis, and Pseudomonas fluorescens and the nematicide fenamiphos were tested. The three ornamental species were highly susceptible to M. incognita, developing 397 and 285 (hollyhock), 191 and 149 (petunia), and 155 and 131 (poppy) galls and egg masses per root system, respectively, and exhibited 37% (petunia), 29% (poppy), and 23% (hollyhock) (P = 0.05) decrease in the flower production. Application of fenamiphos, P. chlamydosporia, P. fluorescens, and B. subtilis suppressed nematode pathogenesis (galls + egg masses) by 64%, 37%, 27%, and 24%, respectively, leading to 14% to 29%, 7% to 15%, 14% to 36%, and 7% to 33% increase in the flower production of the ornamental plants, respectively. Treatment with P. fluorescens also increased the flowering of uninfected plants by 11% to 19%. Soil population of M. incognita was decreased (P = 0.05) due to various treatments from 2 months onward, being greatest with fenamiphos, followed by P. chlamydosporia, B. subtilis, and P. fluorescens. Frequency of colonization of eggs, egg masses, and females by the bioagents was greatest by P. chlamydosporia, i.e., 25% to 29%, 47% to 60%, and 36% to 41%, respectively. Colonization of egg masses by B. subtilis and P. fluorescens was 28% to 31% and 11% to 13%, respectively, but the frequency was 0.3% to 1.3% in eggs. Rhizosphere population of the bioagents was increased (P = 0.05) over time, being usually greater in the presence of nematode.

Effects of root-dip treatment with certain phosphate solubilizing microorganisms on the fusarial wilt of tomato.

Root-dip application of Bacillus subtilis, Pseudomonas fluorescens, Aspergillus awamori, Aspergillus niger and Penicillium digitatum resulted in significant decline in the rhizosphere population of Fusarium oxysporum f. sp. lycopersici. A significant decrease in the severity of wilt occurred with A. awamori (37.1%) and P. digitatum (21.3%) compared to the control. Root-dip treatment with the phosphate solubilizing microorganisms tested resulted in significant increase in the yield of tomato, being greatest with A. awamori and P. digitatum in pathogen inoculated (36% and 33%) and uninoculated plants (19% and 23%). A chemical fungicide gave 24% better yield.