Relationship between Wheat Yield and Yield Attributing Character at Late Sowing Condition

Correlation coefficient and path analysis were computed between yield and yield attributing trait among twenty genotypes of wheat. The research was conducted during winter season of 2020/2021 in the agronomic field of the Institute of Agriculture and Animal Science (IAAS), Bhairahawa, Nepal to identify the traits which influence the positive and negative relation to grain yield. Twenty genotypes of wheat were sown on 24th December 2020 on alpha lattice design with two replications. It has been found that under heat stress, DTB, DTH, DTM, CLC, PH, NGPS show a non-significant positive correlation with GY. Similarly ET shows a highly significant positive correlation to GY. However, SL, SW, TKW have a non-significant negative correlation with GY. In path analysis, DTM and ET have a positive direct effect on GY and DTH, SL, CLC and NGPS have an indirect effect on GY. Hence, the ET and DTM can be used to select wheat genotype for breeding purpose and studies to improve yield of genotypes under heat stress condition

Evaluation of Yield Attributing Trait of Spring Wheat Genotypes Under Normal and Late Sowing Condition

Wheat (Triticum aestivum) is the third most important cereal crop in Nepal after rice and maize. The research is carried out during the winter season in agronomic field of the Institute of Agriculture and Animal Science (IAAS), Bhairahawa, Nepal. Sowing is carried out 28th November 2020 and 24th December 2020 on alpha lattice design with two replication of twenty wheat genotype under normal and late sowing respectively. In the late sowing condition, all genotype's performance is reduced as compared to normal sowing. Under late sown condition, high temperatures reduced the days to booting (15.64%), days to heading (14.97%), days to maturity (14.16%), chlorophyll content (15.99%), plant height (8.59%), spike length (7.03%), number of spikelet per spike (9.21%), number of grain per spike (10.6%), spike weight (15.32%), effective tiller/m2 (9.92%), thousand kernel weight (10.3%) and grain yield (22.5%). NL 1420 presented higher 4118 kg/ha and 3310.5 kg/ha yield respectively and BL 4407 presented early maturity 119.2 DAS and 100.6 DAS respectively in normal sowing and late sowing condition. In a combined environment, maximum grain yield is recorded in NL1420. The result suggested that the tolerant line against the late sowing condition can be used as genetic resource for crop improvement and promote for grain yield

Correlation coefficient and path analysis of yield and yield attributing characters of rice (Oryza sativa L.) genotypes under reproductive drought stress in the Terai region of Nepal

An experimental trial of nine rice genotypes was conducted in the Agronomy field of the Institute of Agriculture and Animal Science (IAAS) Paklihawa Campus under a randomized block design layout with three replications from July to November of 2022. The aim was to study genetic variability and analyze the character association of yield and yield-attributing components in rice genotypes and their direct and indirect effect on grain yield under reproductive drought stress conditions. Observations on days to flowering (50%), plant height, panicle length, panicle weight, number of grains/panicles, effective panicle/m², grain yield, and 1000 kernel weight were recorded. Grain yield showed a highly positive significant correlation with effective panicle/m² (0.713**), followed by plant height (0.347) and panicle length (0.289). The path coefficient analysis of different traits revealed the highest positive direct effect of the effective panicle per m² (0.748963), followed by panicle length (0.24145) and plant height (0.227505). The highest negative direct effect was shown by the number of grains per panicle (-0.31218). The experimental results revealed that the selection of trait-effective panicle per square meter would be most beneficial for the improvement of yield in rice genotypes facilitating selection and plant breeding programs

AMMI and GGE biplot analysis of yield of different elite wheat line under terminal heat stress and irrigated environments

Wheat crop contributes to a major portion of the agriculture economy of Nepal. It is ranked as the third major cereal crop of the country even though, it faces terminal heat stress which speeds up the grain filling rate and shortens the filling period, causing reduction in grain weight, size, number and quality losses. We can minimize this loss through a genotypic selection of high-yielding lines by understanding the genotype-environment interaction. The objective of this research is to obtain a high yielding line with a stable performance across the environments. In order to do so, we conducted an experiment using eighteen elite wheat lines and two check varieties in alpha-lattice design with two replications in different environments viz. irrigated and terminal heat stress environment from November 2019 to April 2020. The analysis of variance revealed that genotype, environment and their interaction had a highly significant effect on the yield. Furthermore, the which-won–where model indicated specific adaptation of elite lines NL 1179, NL 1420, BL 4407, NL 1368 to the irrigated environment and Bhirkuti to the terminal heat-stressed environment. Similarly, the mean-versus-stability study indicated that elite lines BL 4407, NL 1368, BL 4919, NL 1350, and NL 1420 had above-average yield and higher stability whereas elite lines Gautam, NL 1412, NL 1376, NL 1387, NL 1404, and NL 1381 had below-average yield and lower stability. The ranking of elite lines biplot, PC1 explaining 73.6% and PC2 explaining 26.4% of the interaction effect, showed the rank of elite line, NL 1420 > NL 1368> NL 1350 > other lines, close to the ideal line. On the basis of the obtained results, we recommend NL 1420 with both the high yield and stability is suited across both the environments, while NL 1179 and Bhirkuti is adapted specifically for irrigated and terminal heat stress environment, respectively

Drought stress effect, tolerance, and management in wheat – a review

AbstractWheat is the most important cereal crop in the world. It contributes as a major source of protein and calories in the daily human diet. Drought has become a major abiotic stress that severely affects wheat production globally. Changing rainfall patterns, increased atmospheric CO2 levels, rises in atmospheric temperature and hot and dry winds are the major causes of drought stress. It has morphological, physiological, and biochemical consequences such as reduced yield performance, yield attributing parameters, germination, and seed vigor, early leaf senescence, early maturity, decreased chlorophyll content, decreased Rubisco activity, decreased photosynthesis, and decreased starch accumulation. Drought produces reactive oxygen species that cause oxidative damage to the plants leading to programmed cell death. Wheat plant has developed various tolerance mechanisms such as drought escape, avoidance, and tolerance to protect them from drought. Increasing trichome density and leaf waxiness, root: shoot ratio, stay green, accumulation of proline, production of various enzymes viz; superoxide dismutase (SOD), ascorbate (APX), peroxidase (POD), catalase (CAT), osmotic adjustment, ABA accumulation, and formation of dehydrins leads to drought tolerance. Screening of the various genotypes for the identification of novel trait combinations, genetic engineering, and transgenic approaches (incorporates, transfer, and introduces the desirable gene into the desired plants) and thereby the adaptable varieties can be selected and induced to develop new varieties with desired characteristics would be a major genetic management strategies to overcome drought, increase production, and ensure the food and nutritional security of the world

Molecular basis of heat stress tolerance in wheat

The rise in Earth’s temperature is one of the most alarming climatic issues in the field of agriculture and food production, in the present context. The increase in temperature leads to heat stress, major abiotic stress responsible for a huge decline in the production of crops. Wheat (Triticum aestivum), among many crops, also experiences a significant decline in yield and overall productivity due to extreme heat stress. But Wheat has also developed natural tolerance mechanisms to defend itself from heat damage. The selection of cultivars with a higher degree of tolerance mechanism protects against thermal stress, which minimizes the risk of poor productivity to a greater extent. In this review, we discuss the current works of literature concerning the heat stress tolerance mechanism in wheat plants and also highlight the strategic approaches that improve their heat stress tolerance at the molecular level. The success of these approaches depends on a better understanding of heat tolerance traits, their genomic composition, and molecular responses

AMMI and GGE biplot analysis of yield performance of wheat genotypes under irrigated, heat stress and heat drought environments

Wheat is the third most important cereal crop in Nepal. The impact of global warming is threatening global wheat production and food security. The terminal heat stress reduces the grain quality of wheat. However, the drought is affecting more than 15% of global wheat productivity. To find out the stable and high- yielding wheat genotype the experiment was carried out in Rupandehi, Nepal with twenty genotypes under three different environmental conditions namely heat drought, heat stress and irrigated in an alpha lattice design with two replications in each environment. The AMMI (Additive mean effect multiplicative interaction) biplot analysis shows differences in 20 different genotypes in terms of yield and stability. The analysis of variance model showed the share of GE (genotype and environment) interaction in the variation in grain yield of twenty wheat genotypes. The grain yield of genotype varied significantly with environmental impact (p ). The AMMI stability value (ASV) examined NL1387 as the most stable line. The tested environments were discriminative for genotype and showed negative correlation between them. The GGE biplot analysis was conducted to find out the best performing line under different environments and the stable line in diverse environments. The NL1420 was found stable genotype in all three tested environment. The NL1376 line is most ideal ranking first in the ranking biplot. The mean versus stability model indicated NL1369 and NL1376 as elite genotypes and NL 1404, BL4919 and NL1387 can be recommended as new cultivars