Search

Rice blast disease stands as one of the world’s most devastating afflictions, stemming from the ascomycete fungus Pyricularia oryzae. This malevolent force significantly diminishes rice yields in countries reliant on rice cultivation. Unraveling effective strategies to manage this perilous disease hinges upon a profound understanding of the morphological traits and genetic diversity exhibited by the pathogenic isolates. This study aimed to traverse the rice-growing zones of Bangladesh, gathering, identifying, and characterizing the rice blast pathogen P. oryzae. Nineteen isolates underwent scrutiny based on various criteria such as colony color (ranging from dark brownish with a black border to blackish grey with a white edge, ashy with a concentric ring, and grey), colony form (irregular and regular), growth rate, conidia morphology, and sporulation rate. To delve deeper into the genetic makeup, 9 SSR primers were employed to analyze the 19 isolates. The resulting fragment numbers spanned from six to fourteen. Remarkably, the population’s highest genetic variability surfaced with RM589 (0.9194), while RM5961 exhibited the least (0.759). The PIC (Polymorphism Information Content) values, indicating diversity among alleles and their frequency, ranged from 0.7216 to 0.9139. These findings underscored the dual diversity-both morphological and genetic-within the blast fungus population in Bangladesh. This research serves as a pivotal step towards fortifying our arsenal against blast disease. Identifying virulent genes, deciphering the intricate interactions between isolates and their hosts, and cultivating blast-resistant rice varieties all stand as crucial outcomes of this endeavor.

The study was conducted to evaluate the responses of rice and rice weed seedlings (barnyardgrass and weedy rice) at the three-leaf stage to Tinospora tuberculataleaf methanol extract (3.12, 6.25 and 12.5 g L−1) under hydroponic culture. It shows that the leaf methanol extract had various degrees effects depending on target plant species and each tested index (biomass, root length, shoot length, transpiration volume, chlorophyll a, chlorophyll band carotenoid contents). The effective concentration of the leaf extract capable of reducing 50% of rice growth was higher than those of target weed species. Moreover, the root length was more tolerant to leaf methanol extract in comparison to the other plant parameters measured. A greater reduction was observed in chlorophyll acontent compared to chlorophyll band carotenoid. The results revealed that the reduction of transpiration volume closely coincided with the magnitude of growth inhibition of tested plants. Ultra-fast liquid chromatography analysis revealed 11 of 32 peaks in chemical profile, including benzoic acid, caffeic acid, chlorogenic acid, isoorientin, isovitexin, orientin, p-anisic acid, syringic acid, trans-cinnamic acid, trans-ferulic acid, and vitexin have the same retention time with those peaks of the extract. The amount of compounds was present in the range of between 4 817 and 115.5 mg kg−1dry weight (DW). The concentration-response bioassay of all 11 individual compounds and their equimolar mixture against the seeds of barnyardgrass revealed their contribution in the allelopahic activity of T. tuberculataleaf extract. The examined compounds and their combination exhibited various degrees of growth inhibitory effects on the early growth of barnyardgrass. Therefore, the specific number, concentration, combination and inhibitory activity of bioactive compounds leads to allelopathy activity of T. tuberculataleaves which could be employable directly as a natural herbicide and its growth inhibitor compounds can be used as a template for producing new herbicides.

The world's population is increasing very rapidly, reducing the cultivable land of rice, decreasing table water, emerging new diseases and pests, and the climate changes are major issues that must be addressed to researchers to develop sustainable crop varieties with resistance to biotic and abiotic stresses. However, recent scientific discoveries and advances particularly in genetics, genomics and crop physiology have opened up new opportunities to reduce the impact of these stresses which would have been difficult if not impossible as recently as the turn of the century. Marker assisted backcrossing (MABC) is one of the most promising approaches is the use of molecular markers to identify and select genes controlling resistance to those factors. Regarding this, MABC can contribute to develop resistant or high-yielding or quality rice varieties by incorporating a gene of interest into an elite variety which is already well adapted by the farmers. MABC is newly developed efficient tool by which using large population sizes (400 or more plants) for the backcross F1generations, it is possible to recover the recurrent parent genotype using only two or three backcrosses. So far, many high yielding, biotic and abiotic stresses tolerance, quality and fragrance rice varieties have been developed in rice growing countries through MABC within the shortest timeframe. Nowadays, MABC is being used widely in plant breeding programmes to develop new variety/lines especially in rice. This paper reviews recent literature on some examples of variety/ line development using MABC strategy.

This study was undertaken to determine the effects of varied salinity regimes on the morphological traits (plant height, number of leaves, number of flowers, fresh and dry weight) and major mineral composition of 13 selected purslane accessions. Most of the morphological traits measured were reduced at varied salinity levels (0.0, 8, 16, 24 and 32 dS m−1), but plant height was found to increase in Ac1 at 16 dS m−1salinity, and Ac13 was the most affected accession. The highest reductions in the number of leaves and number of flowers were recorded in Ac13 at 32 dS m−1salinity compared to the control. The highest fresh and dry weight reductions were noted in Ac8 and Ac6, respectively, at 32 dS m−1salinity, whereas the highest increase in both fresh and dry weight was recorded in Ac9 at 24 dS m−1salinity compared to the control. In contrast, at lower salinity levels, all of the measured mineral levels were found to increase and later decrease with increasing salinity, but the performance of different accessions was different depending on the salinity level. A dendrogram was also constructed by UPGMA based on the morphological traits and mineral compositions, in which the 13 accessions were grouped into 5 clusters, indicating greater diversity among them. A three-dimensional principal component analysis also confirmed the output of grouping from cluster analysis.