Rice (Oryza sativa L) is a most important staple food crop of the world because more than half of the World’s population is dependent on it for their livelihood. Global rice production must be doubled by 2050 to cope up with the situation of population growth. Narrow genetic base in the released varieties has made the improvement in plateaus. Widening the genetic base is necessary to overcome the yield barrier. Hybridization and pre-breeding has been carried out to broaden the genetic base. Heritability and genetic advances were measured in the F5 lines (Tulaipanji × IR64), F3 lines (Tulaipanji × IR64 × PB1460), and F3 lines (Badshabhog × Swarna sub1). Some of the breeding lines were showing promising field performance with high yield potentiality. Wide crosses were performed to widen the genetic base between (Ranjit × O. rufipogon) and (Badshabhog × O. rufipogon) and the heritability pattern of the morphological characteristics in the progeny lines was evaluated. Nutritional quality of the rice grain is totally dependent on the morphology and histological characteristics of the caryopsis which are genetically determined. Caryopses ultrastructural analyses were carried out in seventeen different rice breeding lines through SEM. SEM analysis showed distinguishing ultrastructure in respect to pericarp, testa, aleurone layer, protein bodies and starchy endosperm in the breeding lines with distinctive inheritance pattern. This study provides information about the cross compatibility of the wide hybridization and heritability measures of the morphological traits which may supplement the breeding program to break the yield plateaus.

Rice (Oryza sativa L.) is a most important staple food grain consumed by more than half of the world’s population. Wild rice (O. rufipogon Griff.) is considered as the immediate ancestral progenitor of cultivated rice O. sativa, evolved through the process of domestication. Most of the cultivated rice produced grains with white pericarp, but can also produce grains with brown, red and black (or purple rice) pericarp. Red rice pericarp accumulates proanthocyanidin whereas black rice contains anthocyanin, both have antioxidant activity and health benefits. Black pericarp is predicted to be regulated by alleles of three genetic loci- Kala1, Kala3, and Kala4. Recombinational and insertional genetic rearrangement in the promoter region of Kala4 is crucial for the development of black pericarp in rice grain. In the present study, we report first time in the breeding history that aromatic black rice lines were developed through interspecific hybridization and introgression in the genetic background of O. sativacv. Badshabhog, Chenga and Ranjit. Badshabhog and Ranjit is white grain rice but Chenga is red rice category. Common Asian wild rice O. rufipogon is used as donor parent (red grain) and source of black rice gene. Several possible genetic explanations have come up for the creation of black rice pericarp in the progeny lines. Possible reason may be the rearrangement and insertion of LINE1 in the promoter region of Kala4 allele through recombination mechanism leading to ectopic expression of Kala4 gene for the accumulation of anthocyanin and resulted in black rice formation. Other genes and regulatory factors may be induced and become functional to produce black pericarp. Black pericarp colour appeared in F2 populations in the wide crosses (Badshabhog x O. rufipogon and Chenga x O. rufipogon) but not in the cross with (Ranjit x O. rufipogon). Black pericarp trait inherited in F4 and F5 population with segregation phenotypes.This is a first report in the history of rice genetics and pre-breeding research, that black rice has been created through wide crossing and introgression by combining wild rice O. rufipogon in the genetic background of O. sativa. Present experimental evidence provides a new model of black rice origin. Thus, black rice (indica type) of Indian subcontinent originated independently through natural out crossing and artificial selection in the course of domestication.

Yield and yield components of wet season rice are highly depends on age and storage duration of seedling. Sometimes, farmers are compelled to transplant aged and stored seedlings due to natural calamities like flash flood, flood, drought etc. An experiment was conducted in Agronomy Field, Bangladesh Agricultural University, Mymensingh during July to December 2013 to determine the effect of age and storage duration of seedling on yield and yield components of transplant aman rice. BRRI dhan 52 was used in the experiment. Four seedling age (25, 30, 35 and 40-d old) and four storage durations of uprooted seedlings (0, 1, 2 and 3-d) were laid out in split-plot design with 3 replications. Seedling age, storage duration and their interaction were significant on yield and yield contributing characters such as panicles m-2 , grains panicle-1 , panicle length, plant height, tillers hill-1 and harvest index. Grain yield gradually decreased along with increased seedling age and storage duration. Seedlings of 25-d-old with 0-d storage duration produced the highest grain yield (6.35 t ha-1) that was at par with 1-d storage seedling (6.15 t ha-1) and thereafter yield reduced dramatically. The highest harvest index (47.1%) was found when 25-d-old seedlings were transplanted and the lowest harvest index (46.5%) was obtained in 40-d-old seedlings. Therefore, 25-d-old seedlings stored up to 1-d after uprooting would be suggested for transplanting to obtain better performance of wet season rice.

The experiment was conducted at the Agronomy research field of Bangladesh Agricultural University, Mymensingh from July to December 2013 to find out the effect of seedling age and storage duration on growth and yield of wet season rice. The experiment comprised of four ages of seedling (25, 30, 35 and 40-d-old) and four storage durations (0, 1, 2 and 3-days) of uprooted seedlings. Rice var. BRRI dhan52 was used as a test variety. The experiment was laid out in a split-plot design with 3 replications placing seedling age in the main plot and storage duration in the sub- plot. The effect of age and storage -duration of seedling, and their interaction were significant on growth parameters (shoot height, root length, number of tillers hill-1, leaf area index and crop growth rate), grain yield and straw yield. The growth parameters and yield exhibited a trend of decrease with the increase in seedling age and storage duration. All the growth parameters and yield showed highest value in the younger seedlings of 25-d-old with 0-day storage duration of uprooted seedlings while the lowest in the older seedlings of 40-d-old with 3-days of storage duration. The var.BRRI dhan52 produced the highest LAI (8.23), CGR (7.33 mg day-1 hill-1) and biomass (26.87 g) at 60, 45 and 60 days after transplanting. Grain yield reduced by 13, 19 and 37% of 30, 35 and 40-d-old seedlings, respectively compared to 25-d-old seedlings. In case of seedling storage, grain yield reduced by 5, 14 and 31% of 1, 2 and 3-d storage, respectively compared to 0-d storage. For optimum growth and yield of wet season rice, 25-d-old seedlings may be stored up to 1-day after uprooting taking into account the possible delay in transporting seedlings to the flood affected area from the nearby districts.Bangladesh Agron. J. 2017, 20(1): 45-56