A series of experiments was set up to examine the effects of nitrogen on rice (Oryza sativa L.) resistance against Nilaparvata lugens (Stål) and Sogatella furcifera (Horváth). Egg laying by N. lugens was reduced on the indica variety IR60. Nymph biomass (N. lugens and S. furcifera) was also lower on IR60: this was associated with low honeydew production and a high proportion of xylem-derived honeydew in N. lugens but not in S. furcifera. Nitrogen increased egg-laying by S. furcifera and increased N. lugens nymph biomass on all varieties tested. Oviposition and egg mortality in both planthopper species were examined on plants at 15, 30 and 45 days after sowing (DAS). Sogatella furcifera laid more eggs on plants at 15 DAS, but laid few eggs during darkness; N. lugens continued to lay eggs on older rice plants (30 DAS) and during darkness. Egg mortality was high on cv. Asiminori, highest at 45 DAS, and higher for S. furcifera than for N. lugens. Mortality of S. furcifera eggs was associated with lesions around the egg clusters. These were more common around clusters laid during the day and suggested induction by Asiminori of an ovicidal response. Egg mortality declined under higher soil nitrogen levels. Results are discussed in the light of improving rice resistance against planthoppers and reducing rates of planthopper adaptation to resistance genes.

This study examines the nature of intraspecific interactions among Nilaparvata lugens (St al) (Hemiptera: Delphacidae) planthoppers feeding on resistant and susceptible rice varieties. Planthopper nymphs produced less honeydew and gained less weight when feeding on rice variety IR62 (resistant) compared to susceptible rice varieties. A series of bioassays was conducted that varied N. lugens nymph densities on IR62 and IR22 (susceptible). Increasing nymph density facilitated feeding by conspecifics; however, intraspecific competition increased mortality of nymphs on IR62 (but rarely on IR22). Furthermore, nymph weights declined with increasing conspecific density on IR22, and the effects were weak on IR62. More female nymphs than males survived on IR62 but this was not affected by density. Nitrogenous fertilizer increased competition among N. lugens on young plants of IR22, but not on IR62. Results indicate that nymphs have a low efficiency in accessing resources when feeding on IR62, even where the plants have received fertilizer. Female-biased survival and biomass compensation for mortality may promote population recovery after development on the resistant plant and accelerate adaptation to the resistant variety.

We report here tagging and fine-mapping of gm3 gene, development of a functional marker for it and its use in marker-assisted selection. The recessive rice gall midge resistance gene, gm3 identified in the rice breeding line RP2068-18-3-5 confers resistance against five of the seven Indian biotypes of the Asian rice gall midge Orseolia oryzae. We report here tagging and fine-mapping of gm3 gene, development of a functional marker for it and demonstrated its use in marker-assisted selection (MAS). A mapping population consisting of 302 F10 recombinant inbred lines derived from the cross TN1 (susceptible)/RP2068-18-3-5, was screened against gall midge biotype 4 (GMB4) and analyzed with a set of 89 polymorphic SSR markers distributed uniformly across the rice genome. Two SSR markers, RM17480 and gm3SSR4, located on chromosome 4L displayed high degree of co-segregation with the trait phenotype and flanked the gene. In silico analysis of the genomic region spanning these two markers contained 62 putatively expressed genes, including a gene encoding an NB-ARC (NBS-LRR) domain containing protein. A fragment of this gene was amplified with the designed marker, NBcloning 0.9 Kb from the two susceptible TN1, Improved Samba Mahsuri (B95-1) and two resistant cultivars, RP 2068-18-3-5 and Phalguna (with Gm2 gene). The amplicons were observed to be polymorphic between the susceptible and resistant genotypes and hence were cloned and sequenced. A new primer, gm3del3, which was designed based on sequence polymorphism, amplified fragments with distinct size polymorphism among RP2068-18-3-5, Phalguna and TN1 and B95-1 and displayed no recombination in the entire mapping population. Expression of the candidate NB-ARC gene in the susceptible TN1 and the resistant RP2068-18-3-5 plants following infestation with GMB4 was analyzed, through real-time reverse transcription PCR. Results showed twofold enhanced expression in RP2068-18-3-5 plants, but not in TN1 plants, 120 h after infestation. Amino acid sequence and structure analysis of the proteins coded by different alleles of gm3 gene showed deletion of eight amino acids due to an early stop codon in RP2068-18-3-5 resulting in a change in the functional domain of the protein. The gm3del3 was used as a functional marker for introgression of gm3 gene into the genetic background of the elite bacterial blight resistant cultivar Improved Samba Mahsuri (B95-1) through MAS.

30Bacterial blight (BB) disease reduces the yield of rice varieties and hybrids considerably in many 31 tropical rice growing countries like India. The present study highlights the development of durable BB 32 resistance into the background of an elite maintainer of rice, DRR17B, by incorporating two major 33 dominant genes, Xa21 and Xa33 through marker-assisted backcross breeding (MABB). Through two sets 34 of backcrosses, the two BB resistance genes were transferred separately to DRR17B. In this process, at 35 each stage of backcrossing, foreground selection was carried out for the target resistance genes and for 36 non-fertility restorer alleles concerning the major fertility restorer genes Rf3 and Rf4, using gene-specific 37 PCR-based markers, while background selection was done using a set of 61 and 64 parental polymorphic

Intensive tillage coupled with imbalanced nutrient management in maize–wheat systems in low-carbon calcareous soils often results in poor productivity vis-à-vis degradation in soil health. Conservation tillage viz. permanent bed planting (PB) and zero tillage (ZT)/ direct seeding with residue retention coupled with precision nutrient management might improve soil properties and yield of crops. Concerning this, a long-term experiment was conducted from 2014–2015 to 2020–2021 with a maize–wheat cropping system at TCA, Dholi farm of RPCAU, Pusa. Treatments consisted of three main plots of different tillage practices, viz. PB, ZT, and conventional tillage (CT) and three sub-plots of nutrient management options, viz. farmers’ fertilization practice (FFP), site-specific nutrient management with Nutrient Expert® (NE) software, and GreenSeeker (GS) based nitrogen-management. From this study, it was observed that both the PB and ZT resulted in about 31–33% and 43–45% improvement in SOC and water-soluble aggregates (WSA), respectively, comparing them under CT. These two conservation tillage practices also improved the other soil bio-chemical properties. Better soil properties under PB and ZT helped in the improvement of system yield by about 13–18% comparing yield under CT. Moreover, both these tillage practices showed an additional net return of USD 330–USD 400 over CT. PB was found a bit better over ZT concerning soil properties, yield, and economics. Comparing nutrient management options, precision nutrition using NE and GS showed significant improvement in the soil bio-chemical parameters, yield, and economics of the cropping system over FFP. SSNM using NE showed slightly better results than GS. Thus, from this long-term study, it can be concluded that the permanent bed system with residue retention and precision nutrition using Nutrient Expert® software are the best options concerning tillage and nutrient management, respectively, for improvement of the soil properties of problematic calcareous soils, thereby, enhancing the yield and economics of the maize–wheat cropping system.

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Area under organic cultivation of wheat (Triticum aestivum L.) is increasing in India. The present two-year study was carried out during 2017–18 and 2018–19 to observe the yield performance of wheat with application of silicon solution (amorphous silica SiO2) under sub-humid conditions of southern plains and Aravalli Hills of Rajasthan. Factorial RBD with five levels of silicon concentration and three growth stages, viz. CRI, tillering and jointing stages were replicated thrice during rabi season of 2017–18 and 2018–19 at Udaipur, Rajasthan, India. Results revealed that application of silicon 8 g/litre water at tillering stage proved significantly superior in enhancing growth characteristics, yield attributes, yield and also gave maximum net returns of 110281/ha and B:C ratio of 2.32