Rice production is severely limited by drought stress, which causes significant monetary losses. The global climate change is turning into a more significant problem. Enhancing agricultural yield in the drought-prone rainfed areas has become critical in light of the current and projected global food demand. There is a need for rice varieties with drought tolerance in order to achieve the production objective from rainfed areas, and genetic improvement for drought tolerant should be a high priority issue of study in the future. The intricate structure of breeding for drought-tolerant rice varieties makes it a challenging endeavour, and multigenic regulation of drought-tolerant features would be a significant roadblock for the ongoing study. In this chapter, we discussed on the recent crop improvement program for the development of drought-tolerant rice varieties and highlighted the most recent advancements through conventional to molecular breeding level for adaption of cultivars against drought tolerance in rice under different agro-climatic conditions.

Rice is a vital staple food, especially in Asia, but it is highly susceptible to drought, leading to significant yield losses. To ensure food sustainability, drought-tolerant rice varieties are essential. Conventional breeding methods improve drought tolerance by focusing on biometric traits like root depth, avoidance, escape, and tolerance. This involves screening and crossing drought-tolerant varieties with high-yielding ones, followed by selection and evaluation. Techniques such as pedigree selection, recurrent selection, and backcrossing introduce desirable genes to enhance drought tolerance. Induced mutation through radiation exposure is also used. The molecular basis of drought tolerance involves identifying and manipulating genes responsible for rice's response to water stress. Techniques like QTL analysis, transcriptomics, genomics, and proteomics identify genes and QTLs associated with drought tolerance. Important genes involved in drought response include DREB, LEA, and ROS scavenging genes. Identifying QTLs enables the development of molecular markers for efficient screening of drought-tolerant rice genotypes. In conclusion, conventional breeding and molecular approaches are employed to develop drought-tolerant rice varieties. Conventional breeding improves biometric traits, while molecular techniques identify and manipulate specific genes associated with drought tolerance. This combination holds promise for high-yielding and drought-tolerant rice cultivars, contributing to global food security. However, further research is needed to understand the complex genetic mechanisms underlying drought tolerance in rice and enhance breeding precision and efficiency.

The need for mechanical harvesting in cotton production has become paramount as labor costs continue to rise. Efficient machine harvesting requires short and compact cotton plants. This study developed ten F1 populations by crossing five Indian-origin cotton genotypes using a half-diallel mating design. Field trials were conducted in two seasons, Kharif 2022 and summer 2023, at Coimbatore, India. Significant genetic variability was observed across all plant architecture traits, with strong G × E interactions (P ≤ 0.01), highlighting clear opportunities for breeding compact high-yielding cotton types. A consistent negative correlation between plant height and seed cotton yield in both environments suggested that shorter plants provided greater yield stability. An ideal plant height of 75-110 cm was identified as the most suitable for mechanized harvesting. Within this ideal range, architecture traits such as zero monopodia, internode and branch lengths showed a consistent negative association with yield, while plant density, sympodial branch origin and number were positively linked to higher yield. Stepwise regression identified the groups of mainstem internode (1st-4th nodes) and sympodial branch lengths (lower, middle, upper) as key yield-influencing traits, offering targets for breeding compact, high-performing cotton types. Pooled values indicated an ideal mean mainstem internodes lengths (MIL) of approximately 5.2 cm and sympodial branches lengths (SBL) of approximately 19.9 cm, with shorter internodes enhancing plant sturdiness and uniformity, while reduced sympodial length improved canopy openness, light penetration and harvest efficiency with minimal trash intake. The findings provide practical recommendations on compact plant architecture traits, particularly ideal internode and branch lengths, to enhance yield potential and facilitate mechanical harvesting in cotton.

Improving nitrogen use efficiency (NUE) while sustaining crop productivity is a major challenge for sustainable maize production. Plasma-activated water (PAW), enriched with reactive oxygen and nitrogen species, has emerged as a promising biostimulant for enhancing nutrient acquisition and plant performance. This study evaluated the effects of PAW on root architecture, rhizosphere metabolism, nitrogen acquisition, agronomic nitrogen use efficiency (ANUE), and grain yield (GY) under four nitrogen application rates (0, 50, 75, and 100% of the recommended dose) in maize grown under controlled polyhouse conditions. PAW significantly increased root surface area (RSA), root hair density (RHD), root hair length (RHL), total organic carbon (TOC), organic acid secretion (OAS), free amino acid (FAA) accumulation, nitrogen uptake, GY, harvest index (HI), and ANUE compared with normal water irrigation (P ≤ 0.001). Field Emission Scanning Electron Microscopy (FESEM) revealed pronounced root hair proliferation and elongation under PAW, particularly at 75% nitrogen, while High-Performance Liquid Chromatography (HPLC) demonstrated greater accumulation of citric, malic, succinic, and oxalic acids, indicating enhanced rhizosphere carbon metabolism and nutrient mobilization. Multivariate analyses identified coordinated regulation of root and rhizosphere traits as the principal driver of productivity. Principal component analysis explained 95.2% of the total variation and clearly separated PAW + 75% N and PAW + 100% N from the remaining treatments. Pearson correlation and hierarchical clustering analyses demonstrated strong positive associations among RSA, rhizosphere metabolites, nitrogen uptake, GY, and HI, confirming an integrated root–rhizosphere functional network. Piecewise latent path analysis revealed that improved root architecture enhanced rhizosphere activity (β = 0.631), leading to improved nitrogen acquisition (β = 0.697), and ultimately higher grain productivity (β = 1.043). Random Forest analysis identified nitrogen uptake (27.99%), HI (22.95%), FAA (19.27%), TOC, and RSA as the strongest predictors of GY. PAW + 75% N achieved the highest Treatment Performance Index, outperforming PAW + 100% N and sustaining superior productivity with 25% lower fertilizer nitrogen application. These findings demonstrate that PAW reprograms the root–rhizosphere–nitrogen acquisition continuum to maximize NUE, providing a mechanistic framework for improving nitrogen acquisition under controlled polyhouse conditions; field validation is required before broad agronomic application.

Warangal Samba (WGL-14) is a widely known medium slender-grain rice variety that matures within 135-140 days. This variety has been extensively cultivated in Telangana, India, due to its high yield potential of 7-7.5 t/ha and its favourable cooking qualities. However, it is highly susceptible to rice blast disease caused by the fungus Magnaporthe oryzae. This research sought to improve the blast resistance of WGL-14 by incorporating the Pi54 gene, a widely recognized blast resistance gene, using (MABB) along with selection based on phenotypic traits. NLR-145, a high-yielding rice variety containing the Pi54 gene, was used as the donor parent and crossed with WGL-14 to produce F1 plants. The Pi54MAS marker, which is specific to the Pi54 gene, was employed for foreground selection in F1, BC1F1, BC2F1 and BC3F1 generations, while background selection involved 80 parentals polymorphic SSR markers and phenotypic traits observed in each backcross generation. At BC3F5 generation, 28 lines were selected for their strong resistance to blast, high yields, plant type, grain characteristics and other traits comparable to the recurrent parent. These 28 lines were tested in yield trials during the wet seasons from 2018 to 2020 at the Regional Agricultural Research Station (RARS) in Warangal. At Advanced Varietal Trials (AVT), 3 lines namely WGL-1467, WGL-1472 and WGL-1473 were identified as having strong blast resistance and superior agronomic traits, closely resembling the original WGL-14.