Genotypic and morphological diversity analysis in high altitude maize (Zea mays L.) inbreds under Himalayan temperate ecologies

The present investigation was carried out to generate information on genetic divergence of maize (Zea mays L.) inbreds and to identify elite lines to develop potential hybrids for high altitude ecologies. Data were recorded for thirteen (13) quantitative traits viz. germination (%), root depth, shoot length, days to 50 % pollen shed, days to 50% silking, plant height, ear height, ear length, ear girth, number of kernels per row, 100 seed weight, grain yield per plant. The tested genotypes expressed significant variability with high estimates of heritability (broad sense) for all the traits revealing that these traits are amenable to genetic improvement. Grain yield per plant exhibited positive and significant correlation with plant height, ear height, ear width, number of kernels per row, number of kernel rows and 100 seed weight at both the levels which exhibit a strong possibility for improvement of grain yield per plant by selection for these traits. Genetic divergence based on thirteen quantitative traits grouped thirty maize inbred lines into four clusters as per Mahalanobis D2 analysis employing Tocher’s method which revealed wide diversity in elite genotypes owing to the involvement of diverse parental lines in the hybridization programme. Grain yield per hectare was the main factor contributing to total divergence (41.16%) which needs to be considered for highlighting clusters to be chosen for the purpose of further selection

Harnessing Genome Editing Techniques to Engineer Disease Resistance in Plants

Modern genome editing (GE) techniques, which include clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 9 (CRISPR/Cas9) system, transcription activator-like effector nucleases (TALENs), zinc-finger nucleases (ZFNs) and LAGLIDADG homing endonucleases (meganucleases), have so far been used for engineering disease resistance in crops. The use of GE technologies has grown very rapidly in recent years with numerous examples of targeted mutagenesis in crop plants, including gene knockouts, knockdowns, modifications, and the repression and activation of target genes. CRISPR/Cas9 supersedes all other GE techniques including TALENs and ZFNs for editing genes owing to its unprecedented efficiency, relative simplicity and low risk of off-target effects. Broad-spectrum disease resistance has been engineered in crops by GE of either specific host-susceptibility genes (S gene approach), or cleaving DNA of phytopathogens (bacteria, virus or fungi) to inhibit their proliferation. This review focuses on different GE techniques that can potentially be used to boost molecular immunity and resistance against different phytopathogens in crops, ultimately leading to the development of promising disease-resistant crop varieties

Comparison of selection indices for screening maize (Zea mays L.) germplasm for cold tolerance

The comparisons among the 6 selection indices S 1 , S 2 , S 3 (simultaneous selection indices comprising of X 1 only; X 1 +X 5 and X 1 +X 2 +X 3 +X 4 respectively as their component traits), S 4 (Rank summation index), S 5 (Baker’s standard deviation index) and S 6 (Elston’s weight free index) were made involving 4 primary cold tolerance traits namely field emergence per cent (X 1 ), fresh seedling root mass (X 2 ), seedling dry weight (X 3 ), days to 50% silk emergence (X 5 ) along with grain yield ha −1 (X 4 ). Highly significant rank correlations of proposed selection indices conferred the suitability in use of one index if substituted for other, to score the genotypes for selection. Selection differentials for all the indices were generally positive with respect to the traits X 1 , X 2 , X 3 and X 4 except S 2 which, was accompanied with negative differentials for X 2 , X 3 and X 4 . S 1 was found to be an important cold tolerance trait depicting not so less differentials compared to other traits and had positive differentials under each selection criteria. Index S 6 was efficient in selecting early silking varieties with high yield and tolerance to cold. The populations NDSM 8 WN, NDSAB (MER), NDSLC and land races GL20W and Dawar-2 showed high degree of cold tolerance among 67 genotypes evaluated and showed at par results with the C 15 check which was top ranking under 5 out of 6 selection used

The resilience of rice under water stress will be driven by better roots: Evidence from root phenotyping, physiological, and yield experiments

Rice is the principal food grain crop of the world, grown on over 164 million hectares. Water is an important production constraint in food crops. Till recently, crop breeding efforts have mainly focused on the shoot, whereas most of the major drivers of the yield gap directly influence the root system, thereby implicating the plant's resource acquisition efficiency. Despite the substantial experimental evidence for the importance of root traits in drought tolerance, lesser efforts have been directed towards drought-adaptive root traits based on the selection index in rice. The above-ground components are easy to phenotype, and lesser efforts towards root traits stem mainly from the phenotyping bottlenecks of reliable recovery and evaluation of root traits. Moreover, greater phenotypic plasticity of root traits in response to changes in soil resource status, and lack of less costly screening techniques for roots is still a challenge, leading to comparatively lesser information about the potential role of roots in developing drought-resilient rice varieties. Root phenes are not as high in number as is the huge shopping list of above-ground traits and exploring the natural variation of root traits could assist rice improvement programs in developing varieties with desired root phenes for target environments. More importantly, elucidation of the relationship of root traits with the physiological and biochemical responses contributing to grain yield is also imperative. In this paper, we discuss the potential role of roots in determining the resilience of rice varieties for future farming systems based on evidence from root phenotyping, the relationship of root phenes with physiological efficiency and yield under water stress in rice

Improved protocol for efficacious in vitro androgenesis and development of doubled haploids in temperate japonica rice.

DH (Doubled haploid) is the immortal mapping population and an outcome of single meiotic cycle, contributed from male partner. An improved procedure was developed for high frequency androgenesis in japonica genotypes, K-332 and GS-88 and their F1s. A total of 207 fertile, green, di-haploid plants were generated from K-332 × GS-88 hybrids using the improved anther culture protocol. The investigation was carried out to evaluate callus induction potential and regeneration response for the genotypes and the derived F1s on N6 media and modified N6 media (N6M). Whereas, N6 failed to induce callusing, agarose solidified N6M media supplemented with 4% maltose, growth regulators; NAA (2 mg/l), 2, 4-D (0.5 mg/l), Kinetin (0.5 mg/l), and silver nitrate induced high calli percentage of 27.6% in F1s, 9.5% and 6.7% in GS-88 and K-332 respectively. Murashige and Skoog (MS) media supplemented with 3% sucrose, and the hormonal combination BAP (2 mg/l), Kinetin (1 mg/l) and NAA (1 mg/l) induced high green shoot regeneration rates (0-60.0%). The effect of cold pre-treatment at 4°C and the stage of anther collection and their interaction was studied. The effect of cold pre-treatment (CP) of collected boots at 4°C (for CP2: 2, CP4: 4, CP6: 6 and CP8: 8 days) at different stages of panicle emergence (BES4-6: 4-6, BES7-10: 7-10, BES11-13: 11-13, BES>13: more than 13 inches was worked out in relation to the effect on response of calli induction, albino regeneration, green plant regeneration and number of shoots/green calli. CP referred to the number of days for which the collected boots were incubated before they were inoculated. BES was the length (inches) between flag leaf and penultimate leaf at the time of boot collection. We concluded that CP6 and BES7-10 showed better response to callus proliferation and regeneration of plantlets across genotypes. The appropriate pre-treatment, stage of anther collection and favourable media composition resulted in high calli induction and green plant regeneration rates in recalcitrant japonica genotypes. The modified N6 media resulted into efficient callus induction and is expected to be useful for studies which aim at rapid generation of mapping populations for genetic studies

Abiotic Stress Tolerance-Progress and Pathways of Sustainable Rice Production

Rice is globally a major food crop and its production has progressively been affected by various types of abiotic stresses especially drought, flooding, salinity, heat and cold in most of the cultivable rice ecosystems. The incidence, intensity and duration of these stresses are anticipated to aggravate due to climate change consequences, demanding resilient yields in these situations to be essential. Present paper deals with reviewing various types of abiotic stresses and their mitigation strategies for enhancing and stabilizing rice production in stress prone areas. Review of available literature pertaining to the study area has been used as research methodology for this paper. The available literature suggests that stress-tolerant varieties can serve as the most viable strategy to contribute in coping with the problem of abiotic stresses. Although, good progress has been made in the development of stress-tolerant rice varieties (STRVs) and incessant efforts are being made to spread these varieties in target areas, adoption by farmers is yet to meet expectations. Advantage, affordability, awareness and availability are the main factors responsible for adopting of any technology. The adoption of stress-tolerant varieties has not reached its potential, predominantly due to the lack of awareness and non-availability of seeds amongst farmers. Strategic and intentional collaborations should be ensured for scaling the sustainable delivery and diffusion of STRVs. A promotional roadmap that ensures the linkages between private and public seed sectors remains the key factor for its successful adoption. Similarly, strengthening of formal, informal and semi-formal seed systems is crucial to accelerate the dissemination of these varieties. There is an imperative need to create strategic plans for the development of varieties possessing multiple stress tolerance. Significant investments for sustainability of rice production in stress prone areas form the essential component of long-term agricultural development. The sooner these investments and strategies are accomplished, the greater the gains are expected

Characterization of Pre-Breeding Wheat (<i>Triticum aestivum</i> L.) Germplasm for Stripe Rust Resistance Using Field Phenotyping and Genotyping

Wheat is highly affected by stripe rust disease, particularly under cooler environments, and the losses can reach up to 100 percent depending on the intensity of infection and the susceptibility of the genotype. The most effective method to manage this disease is the use of resistant varieties. In the present study, 192 wheat genotypes were evaluated for stripe rust resistance under field conditions and also in a laboratory using molecular markers. These lines included pre-breeding germplasm developed for rust resistance and some high-yielding commercially grown wheat varieties. Out of 192 genotypes, 53 were found to be resistant, and 29 showed moderate resistance reaction under field conditions, whereas the remaining genotypes were all either moderately susceptible or susceptible. Under controlled conditions, out of 109 genotypes, only 12 were found to be resistant to all the six virulent/pathogenic pathotypes. Additionally, a selection of 97 genotypes were found resistant in field screening and were subjected to molecular validation using the markers linked to major R-genes, viz., Yr5, Yr10, Yr15 and Yr17. Nine genotypes possessed the Yr5 gene, twelve had the Yr10 gene, fourteen had the Yr15 gene and thirty-two had the Yr17 gene. The resistance genes studied in the current study are effective in conferring resistance against stripe rust disease. The genotypes identified as resistant under both field and controlled conditions can be used as sources in stripe rust resistance breeding programs

Combination of Strobilurin and Triazole Chemicals for the Management of Blast Disease in Mushk Budji -Aromatic Rice

Rice blast is considered one of the most important fungal diseases of rice. Although diseases can be managed by using resistant cultivars, the blast pathogen has successfully overcome the single gene resistance in a short period and rendered several varieties susceptible to blast which were otherwise intended to be resistant. As such, chemical control is still the most efficient method of disease control for reducing the losses caused due to diseases. Field experiments were conducted over two successive years, 2018 and 2019, in temperate rice growing areas in northern India. All the fungicides effectively reduced leaf blast incidence and intensity, and neck blast incidence under field conditions. Tricyclazole proved most effective against rice blast and recorded a leaf blast incidence of only 8.41%. Among the combinations of fungicides, azoxystrobin + difenoconazole and azoxystrobin + tebuconazole were highly effective, recording a leaf blast incidence of 9.19 and 10.40%, respectively. The chemical combination mancozeb + carbendazim proved less effective in controlling the blast and it recorded a disease incidence of 27.61%. A similar trend was followed in neck blast incidence with tricyclazole, azoxystrobin + difenoconazole, and azoxystrobin + tebuconazole showing the highest levels of blast reductions. It is evident from the current study that the tested fungicide combinations can be used as alternatives to tricyclazole which is facing the challenges of fungicide resistance development and other environmental concerns and has been banned from use in India and other countries. The manuscript may provide a guideline of fungicide application to farmers cultivating susceptible varieties of rice

Explicating genetic architecture governing nutritional quality in pigmented rice

Rice is one of the most important staple plant foods that provide a major source of calories and nutrients for tackling the global hunger index especially in developing countries. In terms of nutritional profile, pigmented rice grains are favoured for their nutritional and health benefits. The pigmented rice varieties are rich sources of flavonoids, anthocyanin and proanthocyanidin that can be readily incorporated into diets to help address various lifestyle diseases. However, the cultivation of pigmented rice is limited due to low productivity and unfavourable cooking qualities. With the advances in genome sequencing, molecular breeding, gene expression analysis and multi-omics approaches, various attempts have been made to explore the genetic architecture of rice grain pigmentation. In this review, we have compiled the current state of knowledge of the genetic architecture and nutritional value of pigmentation in rice based upon the available experimental evidence. Future research areas that can help to deepen our understanding and help in harnessing the economic and health benefits of pigmented rice are also explored