Heiplanmi Rymbai

Seed weight is a critical factor influencing germination, seedling establishment, and subsequent crop development. Khasi Mandarin exhibits considerable variation in seed weight, and limited information is available on the effect of seed weight on germination and seedling performance. This study assesses the effects of seed grades on seed germination, seedling growth and vigour in Khasi Mandarin. Based on seed weight (SW), the individual seeds were categorised into three groups: Large Seed Weight (LSW), Medium Seed Weight (MSW), and Small Seed Weight (SSW). Seedling characteristics were assessed at 60, 90, and 120 days after sowing (DAS) through destructive sampling. Results showed that large seed weight reduced the days to germination (36.4 ± 2.29 DAS) compared to SSW and MSW. Similarly, LSW increased germination percentage (88.89 ± 2.11%), and pairwise comparisons showed that LSW had greater odds of germination than MSW (1.78-fold) and SSW (3.11-fold). Seedling characteristics were highest in LSW at 120 DAS, producing substantial increases in root characteristics, including root weight (fresh and dry) and number, and in plant growth (plant height, diameter, and dry weight). Chlorophyll index, leaf-specific weight, and seedling vigour index were also higher in seedlings raised from LSW at 120 DAS. Seed grading with large seed weight (≥ 0.81 g) is a critical determinant of germination, seedling growth, and vigour; therefore, it represents promising seed source for raising vigorous nursery seedlings of Khasi Mandarin.

Citrus greening disease, also known as Huanglongbing (HLB), caused by the bacterium Candidatus Liberibacter asiaticus (CLas), has a detrimental effect on plants and can be a factor in citrus decline, a major threat worldwide to the citrus industry. The reactions of different Citrus species to post-HLB infection are still enigmatic. Therefore, nine prominent Citrus species (Citrus reticulata, C. sinensis, C. limonia, C. karna, C. trifoliata, C. jambhiri, C. volkameriana, C. maxima, and C. latipes) were studied in the field experiment to understand their physiological, biochemical, nutritional, and enzymatic responses to HLB infection. Based on the morphological appearance of the plants, the incidence of CLas was confirmed using gene-based DNA markers OI1/OI2c (1160 bp) and A2/J5 (703 bp). The result showed that HLB incidence ranged from 0 to 100% across different Citrus species (PCR-based). Interestingly, C. latipes showed no typical symptoms and tested negative by PCR. Contrastingly, the incidence in other species was 91.7% in C. maxima, 80.0% in C. trifoliata, and 100% in the remaining cCitrus species. The severity of the symptoms ranged from 61.08 ± 7.5% (C. sinensis) to 0.69 ± 0.2% (C. latipes). In the infected species, C. trifoliata and C. maxima recorded the least reduction in chlorophyll (Chl), net photosynthetic rate (Pn), stomatal conductance (gs), nutrients, and enzyme activities. Comparative analysis revealed that the HLB-infected species exhibited lower Chl, Pn, gs, nutrient levels, and antioxidant enzyme activities. In contrast, potassium, protein, stress biomarkers (proline, H₂O₂, MDA), and starch content were higher in the HLB-infected plants. Therefore, C. latipes and C. trifoliata are immune to HLB and can be utilised in breeding and as rootstocks for commercial citrus cultivars.

Introduction: The multiple nutritional disorders producing the early decline of citrus productivity are commonly observed across the citrus belts of northeast India. This situation is further compounded by a mismatch between annual addition and consumption of fertilizers, in the backdrop of an erroneous diagnosis of nutrient imbalance. In this background, we attempted to diagnose nutrient balance in Khasi mandarin ( Citrus reticulata Blanco) orchards using several diagnostic tools comprising machine learning (ML) tools. Methods: A database of soil available nutrients (KMn0 ₄ -N, Brays-P, NH ₄ 0Ac-K, DTPA-Fe, DTPA-Mn, DTPA-Cu, DTPA-Zn) and fruit yield documenting 180 Khasi mandarin orchards of seedling origin (10–30 years old with row-to-row distance of 4 m and trees 6 m apart) raised under rainfed conditions in the Meghalaya state of northeast India. Diagnosis methods were compared: the sufficiency level of available nutrients (SLAN), the basic cation saturation ratio (BCSR), the compositional nutrient diagnosis (CND), the diagnosis and recommendation integrated system (DRIS) and ML tools like random forest and xgboost. Results: Soil test interpretation of a low-yielding and nutritionally imbalanced orchard differed among diagnostic methods. DRIS predicted deficient-to-low concentrations of Zn, Ca, P, N, and K; other nutrients like Fe, Cu, Mn, and Mg were at optimum-to-high concentrations. CND standards diagnosed Zn deficiency and Cu excess with potential agronomic manifestations for early decline in productivity. SLAN interpretation was highly skewed for Ca; moderately skewed for Mg, Cu and Zn, and unskewed for N, P, K, Fe and Mn. The accuracy of ML regression models relating nutrient expressions to fruit yield was invariably high, followed by SLAN. The ML xgboost regression model exhibited the highest accuracy in predicting fruit yield from soil test. Conversely, the BCSR, which considers only three cationic dual ratios, was inaccurate. There were distortions when relating concentration values to DRIS indices to determine ‘optimum’ concentration ranges. The ML classification models showed that concentration values were also less accurate than clr to classify data as true negative (TN) or true positive (TP). The xgboost classification model showed optimum ranges for N, P, Ca, Mg, Mn, and Cu; whereas K, Fe, and Zn fell below the lower limits. Conclusion: ML, hence, as a classification approach, aided in discarding cases of poor yields and high yields showing luxury nutrient consumption or suboptimal nutrient levels. The soil test standards and site-by-site comparisons can further support site-specific nutrient management and precision fertilization. Considering Zn as the most deficient nutrient, Zn biofortification interventions are recommended to increase fruit yield and quality in Khasi mandarin.

Kiwifruit is a potential commercial fruit crop in the northeastern hill region of India due to congenial agro-climatic conditions. Among soft fruits, kiwifruit is arguably the best-known due to its flavour and nutritional value. A ripe fruit has a pleasant aroma, a refreshing, exquisite flavour, and a high nutritional content. Kiwifruit is gaining importance in the foothill tracts of the Himalayas due to its wide adaptability, precocity, high economic returns, marketability, and potential for diversification in sustainable horticulture. Despite the potential for kiwifruit cultivation, several constraints must be addressed for successful cultivation. The aspects to be carefully observed are flowering, pollination, pollenisers, training and pruning. The lack of genetically superior planting material, the high cost of establishment of kiwifruit orchards, and the lack of standardised techniques for pruning-cum-training and other operations. In addition, all the cultivars of kiwifruit except Hayward bear heavily. Therefore, regulation is necessary to produce a high-quality and well-sized crop. Commercial cultivation of kiwifruit has great potential in the hilly areas of the country. Strategies and approaches include identification of suitable agro-climatic conditions, selection of cultivars, placement of pollenisers and pollinators, quality planting materials, training and pruning, and integrated management of water and nutrients for sustainable production to enhance the yield and quality of fruits, as well as the livelihood and economics of the farmers.

The present study was conducted to assess the genetic diversity, association ship and identify stable lines of king chilli (Capsicum chinense Jacq.) at Horticulture Research Farm, ICAR Research Complex for NEH Region for three consecutive years (2021, 2022 and 2023) keeping in view the vast genetic diversity of king chilli present in the North Eastern Hill Region of India which are yet to explore to its fullest potential. The results of the study reveal that for the economic trait fruit yield per plant, the highest value was recorded in RCML5 (1003.40g) followed by RCML1 (949.85g) and RCNL4 (898.46g). Similarly, for quality parameters the highest dry matter (%), ascorbic acid content (mg/100g), total flavonoid (mg QE/g) and capsaicin (%) was recorded in RCML6 (19.78 %), RCMP6 (693.41 mg/100g), RCNL-1 (5.12 mg QE/g) and RCML16 (5.90 %), respectively. High heritability (˃60 %) coupled with high GA (˃20 %) was observed for desirable traits such as fruit yield per plant, no. of fruits per plant, no. of fruits per cluster and average fruit weight. Among the quality traits, ascorbic acid content exhibits high heritability (˃60 %) and high GA (˃20 %). This indicates the presence of additive gene action and the potential response of these traits towards selection. Cluster analysis revealed that cluster 6th, comprising of 9 accessions, was the largest, while the largest inter-cluster distance based on the Mahalnobis Euclidean Distance was recorded between cluster 8th and 6th (77.28). The Principal Component Analysis revealed that 7 PCs with eigenvalues more than 1 contribute 84.53 % of the total variability. Plant spread (E to W), no. of fruits per plant, ascorbic acid content and capsaicin content were depicted as the major predictors of total variability. The present study identifies accessions RCML5, RCML1 and RCNL4 as the best performers for fruit yield and most of its related traits. It exhibits the potential of giving higher yield in future improvement programmes, while accessions viz., RCML16, RCML5 and RCML10 are promising for capsaicin content. Based on stability analysis accession RCNL1, a moderate yielder and mid-maturity with average capsaicin content, was stable across environments. These identified accessions can served as a gene bank for future crop improvement programme in king chilli.

Maize is a staple food grain in the eastern Himalayas of India, traditionally grown only during the Kharif seasons using local cultivars. The cultivation of Rabi maize is a relatively new concept in the hills; however, favourable agro-climatic conditions offer potential for higher economic returns and proper utilisation of paddy fallow. A study was conducted in the adopted cluster villages (05 villages), Ri-Bhoi district, Meghalaya, covering a 15-hectare area, using a participatory approach to investigate the adoption of improved maize cultivars during the Rabi season. The results showed that DA 61 A and RCM 75 had promising growth and yield performances (5.2-5.8 green cob MT/ha). Prior to intervention, all the respondents grew only local varieties, and the growing seasons were mainly Kharif (76.67 %) and Zaid (23.33 %), with none cultivating during the Rabi season. In the post-intervention period, most respondents partially adopted Rabi maize cultivation technology, with a 60.0 % overall adoption level. Partial adoption was mainly due to a preference for high-value vegetables (ranked first at 100 %) and non-availability of varieties (96.67 %). The highest gross return, net return and benefit-cost ratio were recorded in improved cultivars (DA 61A and RCM 76). A negative correlation (r = -0.547*) was observed between disease incidence and Rabi maize yield. Adoption of Rabi maize cultivars shows promise for enhancing the socio-economic status and livelihoods of participating farmers.

Sohshang (Elaeagnus latifolia L.) is an important underutilised fruit crop in the eastern Himalayas, India. The whole fruit is edible and possesses several health-beneficial bioactive ingredients. Several value-added and processing products have developed from this fruit. However, the commercial orchards of this crop are very limited due to the non-availability of quality planting materials. Therefore, different propagation strategies were adopted to understand the propagation behaviours of this crop. Three grafting methods (wedge, tongue, and shoot tip grafting), four cuttings (shoot tip, softwood, hardwood, and semi-hardwood), and seed germination (large, medium and small seeds) were used as propagation strategies. Results found that no sprouts and growth were observed in different grafting techniques. Among different cuttings, hardwood and semi-hardwood produced sprouts and growth; however, the growth showed wilting and died from 20 days onwards. In seed propagation, the days taken to germinate were reduced by 21.4-25.8% in large seeds as compared to medium and small seeds. Similarly, the large seeds increased the number of leaves by 10-18%, the germination percentage (16-28%), and the survival percentage (12-13%) more than other seeds. Correlation studies revealed that large seeds showed a significant positive association with germination (r=0.80**), survival (0.68*), and growth traits but were negatively correlated with days to germination (r=-0.95**). Therefore, this species is difficult to propagate through grafting (wedge, tongue, and shoot tip) and is considered difficult to root through cuttings. However, seed propagation, particularly large seeds (>3.5 g), could be used effectively for rapid multiplication of this crop.

Irrigation scheduling plays a vital role in the efficient utilization of water to obtain optimum yield, particularly for high value crops grown under protected conditions. The present experiment was conducted during 2020–22 at Horticulture Experimental Farm, ICAR-Research Complex for North Eastern Hill Region, Umiam, Meghalaya to standardize the irrigation scheduling (IS) (5, 7, and 10-days interval) in high-value vegetable crops [tomato (Solanum lycopersicum L.), capsicum (Capsicum annuum L.) and king-chilli (Capsicum chinense Jacq.)] grown under naturally ventilated low-cost polyhouse in the mid-hill conditions of Meghalaya. The results revealed a significant effect of IS on plant growth (reduction in plant height, leaf area) and yield attributes (fruit setting, fruit size, fruit weight and total yield) of the crops with an increase in level of moisture stress. The highest yield of tomato (82.7 t/ha), capsicum (40.8 t/ha) and king-chilli (11.8 t/ha) was recorded in the 5-day interval of IS and on increasing the IS interval to 7-days, the yield decreased by 28.7, 36.1 and 35.7%, respectively. Among the crops, capsicum was found to be more sensitive to water stress, followed by king-chilli and tomato. Among the crops, water productivity with respect to irrigation water was maximum in tomato (60.0 g/kg) followed by capsicum (17.2 g/kg) and king-chilli (10.0 g/kg). Among the varieties grown, Megha Tomato-3 of tomato, hybrid Mahabharat of capsicum and landrace Red Long of king-chilli were found superior for growth and yield attributes at different levels of moisture regime. The farmers of the region can get higher yield using identified varieties with irrigation at 5-days intervals.