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Recent predictions on climate change indicate that high temperature episodes are expected to impact rice production and productivity worldwide. The present investigation was undertaken to assess the yield stability of 72 rice hybrids and their parental lines across three temperature regimes over two consecutive dry seasons using the additive main effect and multiplicative interaction (AMMI), genotype and genotype × environment interaction (GGE) stability model analysis. The combined ANOVA revealed that genotype × environment interaction (GEI) were significant due to the linear component for most of the traits studied. The AMMI and GGE biplot explained 57.2% and 69% of the observed genotypic variation for grain yield, respectively. Spikelet fertility was the most affected yield contributing trait and in contrast, plant height and tiller numbers were the least affected traits. In case of spikelet fertility, grain yield and other yield contributing traits, male parent contributed towards heat tolerance of the hybrids compared to the female parent. The parental lines G74 (IR58025B), G83 (IR40750R), G85 (C20R) and hybrids [G21 (IR58025A × KMR3); G3 (APMS6A × KMR3); G57 (IR68897A × KMR3) and G41 (IR79156A × RPHR1005)] were the most stable across the environments for grain yield. They can be considered as potential genotypes for cultivation under high temperature stress after evaluating under multi location trials.

Genetic improvement of rice for grain micronutrients, viz ., iron (Fe) and zinc (Zn) content is one of the important breeding objectives, in addition to yield improvement under the irrigated and aerobic ecosystems. In view of developing genetic resources for aerobic conditions, line (L) × tester (T) analysis was conducted with four restorers, four CMS lines and 16 hybrids. Both hybrids and parental lines were evaluated in irrigated and aerobic field conditions for grain yield, grain Fe and Zn content. General Combining Ability (GCA) effects of parents and Specific Combining Ability (SCA) effects of hybrids were observed to be contrasting for the micronutrient content in both the growing environments. The grain Fe and Zn content for parental lines were negatively correlated with grain yield in both the contrasting growing conditions. However, hybrids exhibited positive correlation for grain Fe and Zn with grain yield under limited water conditions. The magnitude of SCA mean squares was much higher than GCA mean squares implying preponderance of dominance gene action and also role of complementary non-allelic gene(s) interaction of parents and suitability of hybrids to the aerobic system. The testers HHZ12-SAL8-Y1-SAL1 (T1) and HHZ17-Y16-Y3-Y2 (T2) were identified as good combiners for grain Zn content under irrigated and aerobic conditions respectively.

The harvested plant products, specifically, the grains of cereals are major drivers of soil phosphorus (P) depletion. However, the breeding or biotechnology efforts to develop low P seeds have not been attempted because of possible adverse effects on seedling vigour and crop establishment. Several studies have contradictory observations on influence of seed P on seedling vigour. Lack of appropriate genetic material has been the major bottleneck in reaching the consensus. In this study, we used 30 EMS induced mutants of rice cultivar Nagina22 to understand the role of seed P on seedling vigour and associated physiological processes. Seedling vigour, morpho-physiological characteristics, acid phosphatases, alpha-amylase, and expression of P transporter genes were analyzed in seedlings obtained from seeds of high and low grain P mutants. The study suggests that seed P has a significant role on seedling vigour, chlorophyll content and photosynthesis process of young seedlings, and P transport from roots. Notably, we identified few mutants such as NH4791 , NH4785 , NH4714 , NH4663 , NH4614 , and NH4618 which showed least influence of low seed P on seedling vigour and other metabolic processes. Therefore, these mutants can be used in breeding programs aiming for development of low P grains. Also, these and other identified mutants can be used to decipher the genetic and molecular mechanisms regulating the differential response of seed P on germination, seedling vigour and several other physiological processes influencing the crop growth and establishment.

Background Drought stress is considered as one of the major production constraints in rice. RPHR-1005R is a restorer line (R-Line) with a popular, medium-slender grain type, and is the male parent of the popular Indian rice hybrid, DRR-H3. However, both the hybrid and its restorer are highly vulnerable to the drought stress, which limits the adoption of the hybrid. Therefore, the selection of the restorer line RPHR-1005R has been made with the objective of enhancing drought tolerance. Methods and results In this study, we have introgressed a major QTL for grain yield under drought ( qDTY 1.1 ) from Nagina22 through a marker-assisted backcross breeding (MABB) strategy. PCR based SSR markers linked to grain yield under drought ( qDTY1.1 - RM431, RM11943), fertility restorer genes ( Rf3- DRRM -Rf3 -10 , Rf4- RM6100) and wide compatibility ( S5 n allele) were deployed for foreground selection. At BC 2 F 1 , a single plant (RPHR6339-4-16-14) with target QTL in heterozygous condition and with the highest recurrent parent genome recovery (85.41%) and phenotypically like RPHR-1005R was identified and selfed to generate BC 2 F 2 . Fifty-eight homozygous lines were advanced to BC 2 F 4 and six promising restorer lines and a hybrid combination (APMS6A/RPHR6339-4-16-14-3) were identified. Conclusions In summary, the six improved restorer lines could be employed for developing heterotic hybrids possessing reproductive stage drought tolerance. The hybrid combination (APMS6A/RPHR6339-4-16-14-3) was estimated to ensure stable yields in drought-prone irrigated lowlands as well as in directly seeded aerobic and upland areas of India.

Phosphorus (P) is an essential macro-nutrient required for growth and development of all crop plants including rice. Low availability of P in the soils manifests in terms of impeding crop growth leading to yield losses in rice. Adequate genetic variability for low soil P tolerance and also P use efficiency has been documented in rice and a major QTL called Pup1, conferring tolerance to low soil P has been identified, characterized and cloned from an Indian landrace, Kasalath. In the present study, a set of 98 germplasm lines collected from North-Eastern part of India were characterized for low soil P tolerance by screening them in a plot with low soil P (with available P < 2.0 kg ha−1) and also a plot with normal soil P (available P > 20 kg ha−1). The rice lines showed significantly high genetic variability for low soil P tolerance associated traits. Stress indices were estimated based on yield under normal and low soil P conditions and cluster analysis based on the stress indices; yield under normal and low soil P condition grouped the genotypes into highly tolerant, tolerant and sensitive to low soil P. Among the rice lines, 18 showed tolerance to low soil P (i.e. yield reduction < 70% in low soil P condition). The genotypic analysis based on Pup1 associated molecular markers revealed the presence of complete or partial Pup1 genomic region in most of the germplasm lines. Interestingly, a landrace called Wazuhophek was observed to be completely devoid of Pup1 and hence it can serve as novel source for low P tolerance.

With an objective of mapping novel low soil P (Phosphorus) tolerance loci in the non- Pup1 type donor rice line, Wazuhophek, we screened a recombinant inbred line (RIL) mapping population consisting of 330 lines derived from the cross Wazuhophek x Improved Samba Mahsuri (which is highly sensitive to low soil P) in a plot with low soil P for tolerance associated traits. Molecular mapping with SSR markers revealed a total of 16 QTLs (seven major and nine minor QTLs), which are associated with low soil P tolerance related traits. Interestingly, a QTL hotspot, harbouring 10 out of 16 QTLs were identified on the short arm of chromosome 8 (flanked by the makers RM22554 and RM80005). Five major QTLs explaining phenotypic variance to an extent of 15.28%, 17.25%, 21.84%, 20.23%, and 18.50%, associated with the traits, plant height, shoot length, the number of productive tillers, panicle length and yield, respectively, were located in the hotspot. Two major QTLs located on chromosome 1, associated with the traits, total biomass and root to shoot ratio, explaining 15.44% and 15.44% phenotypic variance, respectively were also identified. Complex epistatic interactions were observed among the traits, grain yield per plant, days to 50% flowering, dry shoot weight, and P content of the seed. In-silico analysis of genomic regions flanking the major QTLs revealed the presence of key putative candidate genes, possibly associated with tolerance.

Phosphorus (P) is one of the macronutrients essential for plant growth and development. Rice (Oryza sativa L.) is sensitive to P starvation and its deficiency influences many key plant functions, resulting in crop yield penalties. Although the hybrid rice segment is well-known for its yield heterosis, P deficiency and bacterial leaf blight diseases are evident limitations. APMS6B, the female parent of DRRH-3 is susceptible to low P and bacterial blight disease. In the present study, the improvement of APMS6B to P starvation and resistance to bacterial leaf blight (BB) was carried out using the marker-assisted backcross breeding approach. Kasalath (+Pup1 QTL) was used as a donor, and a promising IL (ATR 594-1) at BC1F4 generation was identified with 81.15% of recurrent parent genome recovery. Concurrently, this IL was intercrossed with GU-2 (+Xa21 and Xa38). Intercross F1s (ICF1) hybridity was confirmed through foreground selection having maximum RPGR (88.29%) and was selfed to produce ICF2. The resultant progenies were phenotyped for BB using Xoo inoculum (IX-020), simultaneously genotyped with gene-specific functional SSR markers forXa21 and Xa38. The identified BB-resistant plants were subjected to foreground selection for Pup1. Four promising ICF3 plants (BP-10-1, BP-10-3, BP-10-5, and BP-10-15 with Xa21, Xa38, and Pup1) along with parents and checks were screened both in low P plot (< 2 kg P2O5 ha−1) as well as in normal plot (> 25 kg P2O5 ha−1) during dry and wet seasons 2018. The field evaluation identified four promising intercrossed lines with better root growth in the primary root length of extracted zone and root volume. In addition, fewer reductions in grain yield (39.10%) under P starvation and less susceptibility indices values (< 1) for BB were observed. These lines may be exploited in the CMS conversion and development of climate-resilient, biotic and abiotic stress-tolerant rice hybrids.

Improved-Samba-Mahsuri (ISM), a high-yielding, popular bacterial blight resistant (possessing Xa21, xa13 , and xa5 ), fine-grain type, low glycemic index rice variety is highly sensitive to low soil phosphorus (P). We have deployed marker-assisted backcross breeding (MABB) approach for targeted transfer of  Pup1,  a major QTL associated with low soil P tolerance, using Swarna as a donor. A new co-dominant marker, K20-1-1, which is specific for  Pup1  was designed and used for foreground selection along with functional markers specific for the bacterial blight resistance genes,  Xa21, xa13 , and  xa5 . A set of 66 polymorphic SSR marker were used for the background selection along with a pair of flanking markers for the recombination selection in backcross derived progenies and in BC 2 F 2 generation, 12 plants, which are homozygous for  Pup1 , all the three bacterial blight resistance genes and possessing agro-morphological traits equivalent to or better than ISM were selected and selfed to produce BC 2 F 3 s. They were evaluated in plots with low soil P and normal soil P at ICAR-IIRR, Hyderabad for their low soil P tolerance, and bacterial blight resistance and superior lines were advanced to BC 2 F 6 . One of the lines, when tested at multiple locations in India was found promising under both normal as well as low soil P conditions.

Increasing yield is of major importance for Asian and African food security. Knock out mutants in the rice cytokinin oxidase gene CKX2 had shown potential for yield improvement. Here we explored whether subtle changes in CKX2 activity by editing FAD and cytokinin binding site sequences could improve the Indian mega-variety Samba Mahsuri. Knock out and single mutants in FAD and cytokinin binding sites induced by CRISPR/Cas12a caused moderate yield increases. Among 80 CKX2 alleles, five lines with in-frame mutations in both FAD and cytokinin binding domains produced even higher yield. One line, KAMALA, showed superior agronomic performance in 18 field locations (irrigated and rainfed ecologies) over three seasons in trials conducted by AICRPR (All India Coordinated Research Project on Rice), with an average 19% grain yield increase, early maturity, complete panicle emergence, and unaltered grain quality. KAMALA was registered as the first genome-edited variety ready for cultivation by Indian farmers.Competing Interest StatementThe authors have declared no competing interest.Funder Information DeclaredICAR-NASF, NASF/CRISPR-Cas-7003/2017-18, NASF/ BGAM-9021/2022-23

This study aims to develop biodegradable films by combining hemicellulose B (HB) with methylcellulose (MC) and carboxymethyl cellulose (CMC) at two mass ratios, HB/MC 90/10 and HB/CMC 60/40. The effect of plasticizers, glycerol (GLY) and polyethylene glycol (PEG), on these films’ mechanical and physicochemical properties was also investigated. Results showed that the film thickness increased with the addition of GLY and PEG. Moisture content was lower in plasticized films, possibly contributing to better storage. Plasticizers also induced more pronounced color changes, intensifying the lightness and yellowness. Physical attributes such as peel ability, foldability, and transparency were also noticeably improved, particularly in films with higher GLY and PEG concentrations. Additionally, plasticizers enhanced the mechanical properties more significantly in the HB/CMC films, as evidenced by improved tensile stress, elongation at break, elastic modulus, and toughness. However, oxygen and water vapor permeabilities, two of the most critical factors in food packaging, were reduced in the HB/MC films with plasticizers compared to the HB/CMC counterparts. The findings of this study bear significant implications for developing sustainable packaging solutions using hemicellulose B isolated from agricultural material processing waste. These biopolymer-based films, in conjunction with biobased plasticizers, such as glycerol biopolymer, can help curtail our reliance on conventional plastics and alleviate the environmental impact of plastic waste.