Choudhary Muhammad Ayyub

Morpho-physiological evaluation of tomato genotypes under high temperature stress conditions

BACKGROUND Tomato (Solanum lycopersicum L.) is an important but heat-sensitive vegetable crop. The losses in tomato production associated with heat stress are aggravating further under a global warming scenario. The present study was designed to investigate the comparative performance of tomato genotypes under high temperature stress. Tomato genotypes (191) were exposed to the controlled conditions of high temperature (40/32 °C day/night temperature). Different morphological (shoot length, root length, shoot fresh weight, root fresh weight, shoot dry weight, root dry weight and number of leaves), physiological (photosynthetic rate, transpiration rate, water use efficiency, stomatal conductance to water, sub-stomatal CO2 and leaf temperature) and SPAD value (chlorophyll content) were recorded to check the diversity among genotypes against heat stress. RESULTS All the genotypes showed a significantly variable response in almost all the attributes under high-temperature conditions. Correlation among the variables provided a clear understanding of the phenomena involved. Based on all the attributes studied, genotypes L00090 and L00091 were found to be the most heat tolerant compared to other genotypes, whereas CLN1462A and CLN 1466E were found to be comparatively sensitive. CONCLUSION It was concluded that the studied attributes were genotype dependent, and significant diverse performance was noted. The findings of this study pave the way towards the selection of tolerant genotypes, not only for use under high-temperature conditions but also to employ them in breeding programs to produce heat-tolerant hybrids.

METHYL JASMONATE BRINGS ABOUT RESISTANCE AGAINST SALINITY STRESSED TOMATO PLANTS BY ALTERING BIOCHEMICAL AND PHYSIOLOGICAL PROCESSES

This manuscript mainly defines about the effect of foliar application of methyl jasmonate (C13H20O3) (MeJA) on physiological and biochemical processes in tomato under both saline and non-saline conditions. Two tomato genotypes Rio Grande (tolerant) and Savera (sensitive) were grown in pots having sand as growth medium. The salinity substantially decreased the physiological and biochemical parameters. Different doses of MeJA (0.0, 10, 20, 30, 40, 50, 60 µM) were applied on both control and salt stressed tomato plants. Methyl Jasmonate MeJA significantly ameliorated the deleterious effects of salinity on tomato plants by inducing the physiological and biochemical resistance. Different parameters responded to MeJA at various extents. Our findings illustrate that all the parameters responded to foliar application of MeJA and it is quite helpful creating physiological and biochemical resistance in salinity stressed tomato plants.

Proline application enhances growth of chilli by improving physiological and biochemical attributes under salt stress.

Salinity is one of the most alarming abiotic stress affecting crop productivity and significant crop loss globally. It impedes plant performance by inducing deleterious effects on germination and plant vigor. Moreover, 6% of total land area and 30% in irrigated lands are affected by salinity (Fahad et al., 2014). This leads to massive loss in terms of productivity and arable land, as most of the economically important particularly horticultural crops are sensitive to salinity. Chilli is an important cash crop due to its high economical and nutritional value of its fruit (Howard et al., 2000). It is generally categorized as salt sensitive crop. Salt stress reduces chilli production (Navarro et al., 2002). Salinity stress cause changes in physiological processes that cause reduction in plant growth and productivity. Salt stress, increased osmotic potential, generates water deficit conditions in the soil (Navarro et al., 2003), ionic toxicity, because of high concentration of toxic ions (Na and Cl) that accumulate within the plant, ionic imbalance due to the accumulation of ions in the plant cells, which cause the deficiency of the others nutrients (Lycoskoufis et al., 2005). Under salinity stress increased level of reactive oxygen species (ROS) in cells causes K efflux from the cells. Increased ROS concentrations weakens the defense mechanism which leads to oxidative stress. ROS are very destructive to plants at higher concentrations. Under salinity stress ROS increases and can pose a threat to plant cells by causing lipids peroxidation, proteins oxidation, impairment of nucleic acids, inhibit activation of enzymes, activates programmed cell death and ultimately leading to death of the cells (Sharma et al., 2012). There are different approaches used to combat salt stress like conventional breeding, genetic manipulation and foliar application of osmoprotectants. The complexity and polygenic nature of salt tolerance in crops are important factors contributing to the difficulties in breeding salt tolerant crop varieties. Breeding efforts have been hampered by a lack of understanding to salt tolerance mechanisms as well as a lack of field and laboratory screening tests (Zhu, 2000). Genetic screening technique includes diverse plant genetic resources that provides opportunity to develop improved and resistant cultivars with desirable features, that are beneficial for farmers (yield potential and large seed) as well as for breeders (abiotic stress tolerance potential, disease and pest resistance and photosynthesis) (Govindaraj et al., 2015). Proline which is usually considered as an osmoprotection agent is also known to be involved in reducing the oxidative damage by scavenging the free radicals. Proline may also play a role as protein compatible hydrotrope (Ashraf and Foolad, 2007). It supports cytoplasmic acidosis and maintain Pak. J. Agri. Sci., Vol. 53(1), 43-49; 2016 ISSN (Print) 0552-9034, ISSN (Online) 2076-0906 DOI: 10.21162/PAKJAS/16.4623 http://www.pakjas.com.pk

SALINITY IMPAIRS IONIC, PHYSIOLOGICAL AND BIOCHEMICAL ATTRIBUTES IN POTATO

Agriculture is one of the most exposed sectors to vagaries of climate change (Malik, 2012). Around 20-25% of the world (Munns and Tester, 2008) and 26% of Pakistan’s agricultural (Anonymous, 2010) irrigated lands are affected by salinity. Saline area is increasing day by day due to higher evapotranspiration that demand more irrigation and consequently, more salt accumulation in the root zone especially in arid and semiarid regions of the world (Iqbal et al., 2009; Mou, 2011). Predominately, salinization (50–80%) is caused by NaCl salt (Kaouther, 2012). Primary toxic ion is Na as it not only impairs K uptake but also interrupts regulation of stomata which eventually causes water loss. Na enters in leaf apoplast through xylem stream and left behind as water evaporates. Na mainly compete and occupies cations binding sites by reducing uptake and transport of Ca and K (Munns and Tester, 2008; Horie et al., 2012; Hasanuzzaman et al., 2013). Hyperosmotic accompanied with hyper ionic conditions enhance generation of reactive oxygen species (ROS) damaging the proteins, lipids, DNA and carbohydrates molecules, which weakens the plant defense mechanism and modifies membrane structures and its composition (Tuteja, 2007; Ismail, 2014; Jbir-Koubaa, 2014; Gao et al., 2015). Moreover, ROS intensifies MDA contents, deactivates enzymes, disrupts ions of normal cellular metabolism and enhances electrolyte leakage that causes programmed cell death (necroptosis) and reduced photosynthetic activity (Gao et al., 2015). Therefore, plants manifest various scavenging machineries like enzymatic antioxidant system (SOD, CAT, POD), the level of which is elevated during abiotic stresses (Gill and Tuteja, 2010; Choudhury, 2013; Ismail, 2014). It also affects plant water relations and gas exchange attributes together with metabolic toxicity, reduction in green pigments and thereby intervening photosynthetic activity (Ashraf and Harris, 2013; Gupta and Huang, 2014; Li et al., 2014). Potato (Solanum tuberosum L.) is a staple food for about 50% world’s population and third largest crop in human consumption. It is fourth major crop with respect to area and production in the world. It provides high energy per unit land, water and time along-with valuable source of vitamins and minerals (Abhayapala et al., 2014; Gao et al., 2015). It is moderately salt-sensitive (Mitsuya et al., 2000) with 50% growth and yield reduction at 5 dSm salt stress (Hmida-Sayari et al., 2005). However, tolerance level varies from cultivar to cultivar (Bruns and HechtBuchholz, 1990). Increasing saline area demands salt tolerant cultivars for sustainable potato production (Mou, 2011). Hence, it is necessary to understand salinity tolerance mechanism in potato, helpful in developing stress tolerant potato cultivars by using various modern techniques (Gururani et al., 2013). Considering this scenario, present experiment was conducted to assess adverse effects of salinity stress on ionic Pak. J. Agri. Sci., Vol. 53(1), 17-25; 2016 ISSN (Print) 0552-9034, ISSN (Online) 2076-0906 DOI: 10.21162/PAKJAS/16.4766 http://www.pakjas.com.pk

Study of Efficacy of Various Split Applications of Inorganic Nitrogen on Potato Crop

Series of experiments have been conducted to find the optimized dose and efficacy of nitrogen to fulfill the requirements of plant at each level by making split doses. Being most important macro nutrient, afield trial was conducted to study the effect of without applying nitrogen (control) single nitrogen (N) application at planting time on yield and nitrogen uptake of potato in comparison to various split applications. Data were collected about plants vegetative growth, total yield and qualitative factors (TSS, nitrogen, phosphorus, potassium and protein percentage in tuber). Experimental design used was Randomized Complete Block Design (RCBD) having seven treatments with three replications. Data were analyzed by using standard statistical techniques. Overall, qualitative characters of tubers and yield enhanced with split nitrogen application as compared to all nitrogen applied once at planting time whereas, there was no significant difference between tuber nitrogen, potassium, phosphorus and protein contents.

Exploring the better genetic options from indigenous material to cultivate tomato under high temperature regime

Screening test was conducted on 54genotypes of tomato to analyze the effect of heat stress and categorize them as heat tolerant or heat susceptible ones. Seedlings were grown at temperatures of 28/22oC day/night. Four weeks after sowing, plants were exposed to high temperatures of 40/32oC day/night for one week. Data for various morphological (root and shoot length, root and shoot fresh and dry weight, number of leaves) and physiological parameters (chlorophyll contents, sub-stomatal CO2, transpiration rate, stomatal conductance, photosynthetic rate, water use efficiency and leaf temperature) were recorded. Heat stress had a negative effect on all physiological and morphological processes of the genotypes. However, “Parter Improved”, “Legend” and “Roma” were the most tolerant genotypes whereas “Grus Chovka”, “Nepoli”, “Tima France”, “Kaldera” and “Cold Set” were susceptible to heat stress.