Drought stress and pathogen infection simultaneously occur in the field. In this study, the interaction of these two stresses with chickpea, their individual and combined effect and the net impact on plant growth and yield traits were systematically assessed under field and confined pot experiments. The field experiments were conducted for four consecutive years from 2014–15 to 2017–18 at different locations of India. Different irrigation regimes were maintained to impose mild to severe drought stress, and natural incidence of the pathogen was considered as pathogen stress. We observed an increased incidence of fungal diseases namely, dry root rot (DRR) caused by Rhizoctonia bataticola , black root rot (BRR) caused by Fusarium solani under severe drought stress compared to well-irrigated field condition. Similar to field experiments, pot experiments also showed severe disease symptoms of DRR and BRR in the presence of drought compared to pathogen only stress. Overall, the results from this study not only showed the impact of combined drought and DRR stress but also provided systematic data, first of its kind, for the use of researchers.

In nature plants are often simultaneously challenged by different biotic and abiotic stresses. Although the mechanisms underlying plant responses against single stress have been studied considerably, plant tolerance mechanisms under combined stress is not understood. Also, the mechanism used to combat independently and sequentially occurring many number of biotic and abiotic stresses has also not systematically studied. From this context, in this study, we attempted to explore the shared response of sunflower plants to many independent stresses by using meta-analysis of publically available transcriptome data and transcript profiling by quantitative PCR. Further, we have also analyzed the possible role of the genes so identified in contributing to combined stress tolerance. Meta-analysis of transcriptomic data from many abiotic and biotic stresses indicated the common representation of oxidative stress responsive genes. Further, menadione-mediated oxidative stress in sunflower seedlings showed similar pattern of changes in the oxidative stress related genes. Based on this a large scale screening of 55 sunflower genotypes was performed under menadione stress and those contrasting in oxidative stress tolerance were identified. Further to confirm the role of genes identified in individual and combined stress tolerance the contrasting genotypes were individually and simultaneously challenged with few abiotic and biotic stresses. The tolerant hybrid showed reduced levels of stress damage both under combined stress and few independent stresses. Transcript profiling of the genes identified from meta-analysis in the tolerant hybrid also indicated that the selected genes were up-regulated under individual and combined stresses. Our results indicate that menadione-based screening can identify genotypes not only tolerant to multiple number of individual biotic and abiotic stresses, but also the combined stresses.

Reduced spikelet fertility appears to be one of the major factors responsible for the decreased rice grain yield when cultivated under semi irrigated aerobic condition. We demonstrate that genotypes with better root systems coupled with higher cellular level tolerance (CLT) can significantly improve spikelet fertility under semi-irrigated aerobic condition in the field. A set of 20 contrasting rice accessions differing in root traits and CLT with significant molecular diversity were subjected to specific soil moisture regimes during a period between five days before and 10 days after anthesis. Lowest spikelet fertility was observed among the plants grown under water limited (WL) conditions followed by the plants grown aerobically in field conditions (AF). Deep rooted genotypes generally maintained higher spikelet fertility under both WL and AF conditions. Furthermore, genotypes that had high roots biomass as well as high CLT recorded the lowest reduction in spikelet fertility under WL and AF compared with the low root and low CLT genotype. This study emphasised the relevance of combining water acquisition and CLT for improving field level tolerance of rice to water limitation. Such genotypes recorded significantly higher grain yield under stress as well as well watered conditions. The study led to the identification of promising trait donor genotypes which can be exploited in breeding to develop superior trait pyramided cultivars suitable for semi irrigated aerobic cultivation.

Rhizoctonia bataticola causes dry root rot (DRR), a devastating disease in chickpea (Cicer arietinum). DRR incidence increases under water deficit stress and high temperature. However, the roles of other edaphic and environmental factors remain unclear. Here, we performed an artificial neural network (ANN)-based prediction of DRR incidence considering DRR incidence data from previous reports and weather factors. ANN-based prediction using the backpropagation algorithm showed that the combination of total rainfall from November to January of the chickpea-growing season and average maximum temperature of the months October and November is crucial in determining DRR occurrence in chickpea fields. The prediction accuracy of DRR incidence was 84.6% with the validation dataset. Field trials at seven different locations in India with combination of low soil moisture and pathogen stress treatments confirmed the impact of low soil moisture on DRR incidence under different agroclimatic zones and helped in determining the correlation of soil factors with DRR incidence. Soil phosphorus, potassium, organic carbon, and clay content were positively correlated with DRR incidence, while soil silt content was negatively correlated. Our results establish the role of edaphic and other weather factors in chickpea DRR disease incidence. Our ANN-based model will allow the location-specific prediction of DRR incidence, enabling efficient decision-making in chickpea cultivation to minimize yield loss.

Abiotic stressors such as drought and heat predispose chickpea plants to pathogens of key importance leading to significant crop loss under field conditions. In this study, we have investigated the influence of drought and high temperature on the incidence and severity of dry root rot disease (caused by Macrophomina phaseolina) in chickpea, under extensive on- and off-season field trials and greenhouse conditions. We explored the association between drought tolerance and dry root rot resistance in two chickpea genotypes, ICC 4958 and JG 62, with contrasting resistance to dry root rot. In addition, we extensively analyzed various patho-morphological and root architecture traits altered by combined stresses under field and greenhouse conditions in these genotypes. We further observed the role of edaphic factors in dry root rot incidence under field conditions. Altogether, our results suggest a strong negative correlation between the plant water relations and dry root rot severity in chickpeas, indicating an association between drought tolerance and dry root rot resistance. Additionally, the significant role of heat stress in altering the dynamics of dry root rot and the importance of combinatorial screening of chickpea germplasm for dry root rot resistance, drought, and heat stress have been revealed.

:The simultaneous delivery of water and fertilizers to the active root zone through subsurface drip fertigation system ensures optimum growth of sugarcane. Field experiment was conducted at ZARS, V.C. Farm, Mandya during 2014-15 and 2015-16 seasons comprising of plant and ratoon cane, respectively. The investigation was conducted to know the performance of sugarcane as influenced by duration and levels of subsurface drip fertigation. Results revealed that fertigation duration upto 9.5 months recorded significantly higher growth parameters of plant and ratoon cane at harvest viz., plant height (330.6 and 296.2 cm), number of tillers m -1 (34.66 and 43.33), leaf area dm 2 m -1 (87.32 and 118.69), total dry matter production g plant -1 (652.57 and 466.91) and SPAD reading (34.67 and 37.72), respectively. Growth parameters significantly not influenced by fertigation levels. Whereas, the interaction between fertigation duration and levels were significant. Fertigation upto 9.5 months with 125 per cent RDF recorded significantly higher growth parameters viz., plant height (332.5 and 299.5 cm), number of tillers m -1 (34.97 and 43.98), leaf area dm 2 m -1 (89.27 and 121.63), total dry matter production g plant -1 (658.70 and 473.37) and SPAD reading (34.92 and 37.82) in plant and ratoon cane, respectively at harvest. Stastically, at par results were observed with fertigation upto 9.5 months with 100 per cent of RDF and fertigation upto 9.5 months with 75 per cent of RDF. Normal method of sugarcane cultivation with surface irrigation with 100 per cent RDF soil application recorded lower plant height (281.4 and 259.1 cm), number of tillers m -1 (29.2 and 38.15), leaf area dm 2 m -1 (57.34 and 84.38), total dry matter production g plant -1 (519.69 and 340.36) and SPAD reading (23.39 and 26.47). Thus, results clearly indicated that 25 per cent of the recommended dose of fertilizer could be saved with higher cane growth through sub surface drip fertigation (SSDF) over normal practice of sugarcane cultivation.Key Words : Sub surface drip fertigation, Fertigation duration, Fertigation levels, SPAD reading View Point Article : Padmanabhan, M., Nagaraju, Mohanraju, B. and Thimmegowda, M.N. (2017). Influence of subsurface drip fertigation duration and levels on growth parameters of plant and ratoon sugarcane. Internat. J. agric. Sci., 13 (2) : 315-320,

No abstract

: An experiment studying the effects of various levels of fertigation duration and fertigation levels on jaggery quality parameters of sugarcane using the variety CO86032 over two crop seasons (2014-15 and 2015-16) was conducted at ZARS, V.C. Farm, Mandya. Results revealed that jaggery quality parameters like juice extraction per cent, net rendament value, reducing sugars in jaggery and jaggery hardness did not differ significantly due to fertigation duration, fertigation levels and their interaction. Whereas, significantly higher jaggery recovery (13.82 and 13.45 %) and jaggery yield (31.92 and 28.19 t ha -1 ) was recorded with fertigation duration upto 9.5 months in plant and ratoon cane at harvest, respectively. Jaggery recovery and jaggery yield significantly not influenced by fertigation levels. The interaction between fertigation duration and levels were significant. Fertigation upto 9.5 months with 125 per cent RDF recorded significantly higher jaggery recovery(13.96 and 13.55 %) and jaggery yield (32.21 and 28.91 t ha -1 ) in plant and ratoon cane at harvest, respectively. Stastically, at par results were observed with fertigation upto 9.5 months with 100 per cent of RDF and fertigation upto 9.5 months with 75 per cent of RDF. Normal method of sugarcane cultivation with surface irrigation with 100 per cent of RDF soil application recorded lower jaggery recovery (11.87 and 11.10 %) and jaggery yield (16.70 and 13.70 t ha -1 ) of plant and ratoon cane at harvest, respectively. Experimental results clearly indicated that sub surface drip fertigation (SSDF) helps to increase the jaggery quality parameters over normal practice of sugarcane cultivation.Key Words : Sub surface drip fertigation, Fertigation duration, Fertigation levels, Jaggery recovery View Point Article : Padmanabhan, M., Nagaraju, Mohanraju, B. and Thimmegowda, M.N. (2017). Effect of subsurface drip fertigation on jaggery quality parameters of sugarcane. Internat. J. agric. Sci., 13 (2) : 385-389,