Marker-assisted introgression of QTLs for yield under moisture stress into elite varieties of rice (Oryza sativa)

Rice production is severely constrained by the moisture stress. The present study was undertaken to transfer two important QTLs viz., (qDTY2.2 and qDTY4.1), which controls yield under moisture stress (DTY) into two elite varieties, that is, MTU1010 and NLR34449 through marker-assisted breeding. Foreground and background selections of backcross generations, that is, BC₁F₁, BC₂F₁ and BC₂F₂ identified several promising introgression lines (ILs) with two QTLs and single QTLs with an appreciable level of recovery of recipient parent genome. In ILs, the recovery of MTU1010 genome content was estimated to be 83%–93% while the recovery of NLR34449 was 84%–92%. The two-QTL ILs of MTU1010 and NLR34449 backgrounds (qDTY2.2 and qDTY4.1) have shown substantial yield advantage (32 to 84%) over the single-QTL ILs (either qDTY2.2 or qDTY4.1) under moisture stress conditions. Among all, two ILs, MBC-124 and NBC-127 are the best high yielding lines under moisture stress conditions. These outyielded ILs have the potential to be released as varieties in rainfed ecosystem and also can be used as donors in the existing breeding programme in rice.     

EFFECT OF SOIL WATER AND NUTRIENTS ON PRODUCTIVITY OF KENTUCKY BLUEGRASS SYSTEM IN ACIDIC SOILS

The grasslands of the Appalachian region spread over undulating terrain with high annual precipitation rate which causes a large variation in soil and nutrient factors like water potential (WP), pH, nitrogen (N) and phosphorus (P) levels. There is a need to understand these factors and their interactive effects to design precise agronomic practices for acidic grasslands to maximize production. A pot experiment was conducted with an objective to quantify the effects of WP, pH, N and P rates on herbage accumulation and nutrient recovery of Kentucky bluegrass (Poa pratensis L.) cropping system. Centrally rotatable composite design was applied to study the effects of two levels of WP and five levels each of pH, N, and P fertilizer additions in order to optimize bluegrass herbage mass (yield). WP, pH, and N were significant main effects, as were the interactions WP × pH, WP × N, and pH × N. The yield response function was derived from these four factors. The order of importance for these model parameters based on their effect on herbage accumulation was WP > N > WP × pH > pH >WP × N > pH × N. The optimum levels of WP, soil pH, N, and P rates were predicted for Kentucky bluegrass by using the response surface yield model of this pot study i.e., WP of ?422 kPa to ?166 kPa, 5.5–6.1 soil pH, 50–68 N mg kg^?1, 36–40 P mg kg^?1. Concentration (%) of nutrients like N, P, potassium (K), calcium (Ca), and magnesium (Mg) were determined to study the impact of WP, pH, N, and P factors and their interactions on plant nutrient recovery. Main effects like WP, pH, and N levels had significant influence on N and P concentration in plant tissue. K, Ca, and Mg concentrations in plant tissue were significantly affected by WP, pH and their interaction. The results of this greenhouse study imply the necessity to incorporate the information about the variation of soil and nutrient factors in designing precise agronomic practices to low productive acid reclaimed grasslands with undulating topography and high annual precipitation rate.