Biology and biocontrol of Sclerotinia sclerotiorum (Lib.) de Bary in oilseed Brassicas

Sclerotinia sclerotiorum (Lib.) de Bary is a necrotrophic plant pathogen infecting over 500 host species including oilseed Brassicas. The fungus forms sclerotia which are the asexual resting structures that can survive in the soil for several years and infect host plants by producing ascospores or mycelium. Therefore, disease management is difficult due to the long term survivability of sclerotia. Biological control with antagonistic fungi, including Coniothyrium minitans and Trichoderma spp, has been reported, however, efficacy of these mycoparasites is not consistent in the field. In contrast, a number of bacterial species, such as Pseudomonas and Bacillus display potential antagonism against S. sclerotiorum. More recently, the sclerotia-inhabiting strain Bacillus cereus SC-1, demonstrated potential in reducing stem rot disease incidence of canola both in controlled and natural field conditions via antibiosis. Therefore, biocontrol agents based on bacteria could pave the way for sustainable management of S. sclerotiorum in oilseed cropping systems

Rapid marker-assisted selection of antifungal Bacillus species from the canola rhizosphere

A marker-assisted approach was adopted to search for Bacillus spp. with potential as biocontrol agents against stem rot disease of canola caused by Sclerotinia sclerotiorum. Bacterial strains were isolated from the rhizosphere of canola and screened using multiplex PCR for the presence of surfactin, iturin A and bacillomycin D peptide synthetase biosynthetic genes. Among the 96 isolates screened, only CS-42 harbored all three genes and was subsequently identified as Bacillus cereus using 16S rRNA gene sequencing. This strain was found to be effective in significantly inhibiting the growth of S. sclerotiorum in vitro and in planta. Scanning electron microscopy studies at the dual culture interaction region revealed that mycelial growth was curtailed in the vicinity of bacterial metabolites. Complete destruction of the outmost melanised rind layer of sclerotia was observed when treated with the bacterium. Transmission electron microscopy of ultrathin sections challenged with CS-42 showed partially vacuolated hyphae as well as degradation of organelles in the sclerotial cells. These findings suggested that genetic marker-assisted selection may provide opportunities for rapid and efficient selection of pathogen-suppressing. Bacillus strains for the development of microbial biopesticides

Assessing impact of thermal units on growth and development of mustard varieties grown under optimum sown conditions

Thermal unit indices have a strong correlation with the phenology, growth and yield of crops and can be effectively used to select suitable crop cultivars for specific environmental conditions especially temperature. In this study, four mustard varieties (viz., 'BARI Sharisha-14', 'BARI Sharisha-15', 'BARI Sharisha-16' and 'Tori-7') were grown in two consecutive growing to assess the impact of thermal unit indices on crop growth and development, and to select the suitable variety for better yield under optimum sowing condition. Thermal unit indices viz., growing degree-day (GDD), helio-thermal units (HTU), phenothermal index (PTI) and heat use efficiency (HUE) were estimated from daily temperature and sunshine hours. Role of GDD on different growth indicators and seed yield (SY) were estimated through association and dependence of the traits. Significant variations in studied genotypes were observed for different traits. Among the studied varieties, 'BARI Sharisha-16' produced higher dry matter and seed yields (1.82 t ha-1) while accumulated maximum GDD at different growth stages. A strong positive association was obtained between GDD and the studied traits. Thermal unit indices had a strong influence in attaining different phenophases and other growth indicators. Therefore, results suggest that those indices could be used for growth prediction; further 'BARI Sharisha-16' is expected to use heat energy more efficiently for increasing the seed yields which indicated that the crop can perform better under global warming scenarios

Physiochemical Changes of Mung Bean [<i>Vigna radiata</i> (L.) R. Wilczek] in Responses to Varying Irrigation Regimes

Mungbean is one of the most powerful pulses providing substantial protein for human diets and fixing N to the soil, improving nutritional food security and agricultural sustainability. The production of summer mungbean in the tropics and subtropics is adversely affected by drought due to water scarcity caused by various factors as well as lack of rainfall. Irrigation at different growth phases is not a suitable solution. An environmentally friendly and economically viable answer is a convenient irrigation management option that will be available to farmers together with drought-tolerant genotypes. The study considered to determine the effect of differences between drought-tolerant and drought susceptible genotypes on water productivity response and physiological traits in mung beans. To quantify seed yield-related to irrigation at different growth stages eventually to quickly determine the most appropriate irrigation stage. One water stress tolerant mung bean genotype (BMX-08010-2) and one sensitive genotype (BARI Mung-1) were grown in the field with four different irrigation schedules along with water stress conditions (no irrigation) under rain shelter at Regional Agricultural Research Station, BARI, Ishwardi, Pabna, Bangladesh. The experiment was laid out in split plots with three replications, with irrigation schedules assigned in the main plot and mung bean genotypes assigned in the side plots. Water use efficiency ranged from 3.79 to 4.68 kg ha−1 mm−1 depending on irrigation regime, and mung bean seed yield of mung bean Water stress decreased plant water status, photosynthetic pigment and membrane stability index, and increased proline soluble sugar content. Treatments that received irrigation during two or three phases (I3 or I4) gave significantly higher yields than those that received irrigation during only one stage (I1 and I2) with the lowest yield. While the yield obtained ranged between 1145.44 kg ha−1 with seasonal irrigation of 277 mm (I4) and 555.14 kg ha−1 without irrigation (I0). The flowering stage (I3) was recorded as the most sensitive growth stage with an 18.15% yield reduction compared to the treatment with triple irrigation (I4). Also, depending on the irrigation sources, at least two irrigation phases should be provided at the triple leaf stage (I2, i.e., 20 DAS) and at the flowering stage (I3, i.e., 35 DAS) to achieve the highest yield. Genotypes that maintained the higher performance of physicochemical traits under water stress provided higher seed yield and promoted drought tolerance. Therefore, these parameters can be used as physiological and biochemical markers to identify and develop superior genotypes suitable for drought-prone environments