Breeding rice for nitrogen use efficiency

Abstract

The aim of present investigation was to study the gross morphology and incidence of canine mammary tumors (CMTs) based on age, sex, breed, reproductive status and location along with histopathological classification and immunohistochemical characteristics. A total of 56 CMTs samples were collected from 49 cases of dogs. Gross morphology was studied in 26 cases of canine mammary tumors. For histopathological classification, samples were fixed in 10% formalin, embedded in paraffin and sections (5 μm thick) obtained from each was stained with HandE stain. Immuno-histochemistry was carried out by using p63 antibody to confirm the histopathological types of CMTs. Malignant tumors and benign tumors were mostly observed in older dogs. Among 9 breeds affected, the highest incidence was recorded in a German shepherd. Caudal abdominal pair was most commonly affected. Most of the cases were observed in intact female dogs, except for one male dog. The tumors were oval and round in shape with 30–2000 g weight, soft to hard in consistency and grayish white cut surface. Out of 56 CMTs, the highest incidence was found of malignant neoplasms (36/56, 64.28%), followed by benign neoplasms (10/56, 17.85%) and non-neoplastic proliferation hyperplasia/dysplasia (10/56, 17.85%). Complex carcinoma, carcinoma, and malignant myoepithelioma and malignant myoepithelioma were confirmed by p63 antibody. In these neoplasms, myoepithelial cells showed strong immunoreactivity with p63.Development of nitrogen use efficient (NUE) rice varieties is inevitable for sustainability of environmental friendly and economical agricultural practices. Several management practices are being studied for increasing efficiency of spatial and temporal inputs of N under National Innovations for Climate Resilient Agriculture (NICRA). Attempts are being made to develop NUE rice varieties with multidisciplinary approach and conventional selection along with mapping and next generation sequencing strategies. Around 800 rice genotypes were characterized under low and recommended nitrogen for two consecutive seasons and the promising donors further evaluated to identify consistent NUE rice genotypes. Several mapping populations were developed using the NUE donors and popular rice varieties. QTL/genomic regions were identified for yield under low N using biparental and association mapping. Using minimum marker set of 50 rice SSR markers, 12 genomic regions were identified for yield and yield associated traits under low nitrogen. Several promising recombinants of yield and NUE were identified and these breeding lines were evaluated under multi-locations and stable performers were identified under AICRIP Trial - Evaluation of Radiation and Nitrogen use efficient promising rice genotypes -Plant Physiology during Kharif 2016, 2017 and 2018. As nitrogen is the building block of biomass, an optimum N is required for realizing the yield. The strategy should be to maximise uptake and improve utilization, so that remobilization of N to yield is achieved under low N.