ФИЗИОЛОГИЯ РАСТЕНИЙ, 2011, том 58, № 1, с. 126-132
ПРИКЛАДНЫЕ АСПЕКТЫ
УДК 581.1
PHYSIOLOGICAL AND MORPHOLOGICAL CHARACTERISTICS OF CHICKPEA ACCESSIONS UNDER LOW TEMPERATURE STRESS
© 2011 Leila Heidarvand*, Reza Maali Amiri*, Mohammad Reza Naghavi*, Yadollah Farayedi**,
Behzad Sadeghzadeh**, Khoshnood Alizadeh**
*Department of Agronomy and Plant Breeding, University College of Agriculture and Natural Resources
of the University of Tehran, Karaj, Iran **Dryland Agricultural Research Institute, Ministry of Jihad-e-Agriculture Research and Education Organization,
Maradheh, Iran Received October 19, 2009
Economically important crop chickpea (Cicer arientinum L.) is sensitive to chilling stress, and breeding for chilling tolerance is the economic option even in countries with a high risk for drought and heat stresses. In this study, we have analyzed chilling-induced responses of ten chickpea accessions under field and growth-chamber conditions in order to screen, using phenotypic and physiological methods, for chilling tolerance. The field data analysis revealed that there were significant differences between accessions in their cold tolerance. The percent survival and cold-tolerance scores were the most important indices describing genotype tolerance to low temperature under field conditions; they can be used to assess chickpea cold tolerance. During environmentally controlled testing, the effects of low temperature regimes (—10°C for 15 and 30 min) were studied and cold tolerance was measured by electrolyte leakage from damaged leaves. The analysis of field data and cold treatments showed that two accessions, Sel 95Th1716 and Sel 96Th11439, grouped in one cluster, are good cold-tolerant genotypes (showing low scores for cold tolerance and electrolyte leakage). In comparison with ILC 8262, released as cold-tolerant, these genotypes showed more tolerance. Flip 00-6C, ILC 533, and Jam were less tolerant to cold stress. Thus, we have shown that as well as field studies, short-term cold treatment and electrolyte leakage assay can be used to evaluate low temperature tolerance of chickpea profitably in a short time.
Key words: Cicer arietinum — genetic variation — electrolyte leakage — cold tolerance
INTRODUCTION
Plants are sessile and are exposed to considerable fluctuations in temperature during the day—night cycle and at changes in weather conditions and seasons [1]. Many plant species are injured or killed by exposure to low temperatures in the range of 0—15°C. These species are classified as chilling-sensitive [2]. Chickpea (Cicer arietinum L.), an economically important crop and cool-season grain legume, is sensitive to chilling stress, and its adaptability and productivity directly and/or indirectly (due to susceptibility to weeds, insects, and diseases) are limited by low temperatures [3].
Chilling stress induces oxidative processes in plant cells. These processes are initiated by reactive oxygen species, which arise from disturbed operation of electron transport chains and bring about various manifestations of chilling damage [4, 5]. These stresses affect
Abbreviations'. EL — electrolyte leakage; ELI — electrolyte leakage index; PCA — principal component analysis; UPGMA — unweighted pair group method using arithmetic averages. Corresponding author. Reza Maali Amiri. Department of Agronomy and Plant Breeding, University College of Agriculture and Natural Resources of the University of Tehran, Karaj, 3158777871, Iran. Fax. 98-261-222-7605; e-mail. rmamiri@ut.ac.ir
the functions of cell membranes as the primary site of freezing injury, elevate membrane viscosity, and promote lipid transition from a liquid crystalline to a gel phase [6]. As a result, the cells either adapt to these changes or perish. The fluidity of membranes is important for maintaining the barrier properties and for the activation and functioning of certain membrane-bound enzymes [7].
Plants (including chickpea) acclimate to environmental low temperature primarily due to the shifts in cell metabolism determined by differential gene expression, which results in changes in the membrane composition and accumulation of cryoprotectants and antioxidants [8—13].
Breeding for tolerance to chilling stress is the most economic and environmentally acceptable option to improve chickpea production in our country and most Asian countries, where winter-sown chickpea is advised to escape drought and high temperature stresses after spring-sowing that causes significant losses. An important component of breeding could be screening the common cultivated species or their wild relatives to identify chilling-tolerant accessions. Because of the inherent sensitivity of chickpea to low temperatures, there has been a great interest in new varieties that are
0 5 10 15 20 25
_l______________I______________I______________I_____________1_____________L
Flip 99-48C —| ILV 8262 —
Flip 97-211C--
Flip 00-6C — -
Flip 98-108C —I _
Jam -
Sel 95Th1716 —,-
Sel 96Th11439—'
Sel 95Th1745 -
Fig. 1. Dendrogram generated by the cluster analysis of morphological traits.
The scales portray a dissimilarity index calculated using Euclidean distance coefficient, and the dendrogram was developed using UPGMA clustering procedures.
tolerant to chilling. Like for other crops, classical breeding and physiological and genetic approaches are main strategies applied for chickpea genetic improvement. The severity of various stresses is unpredictable under field experiments; therefore, field trials are increasingly supplemented with controlled environment testing and physiological screening. However, understanding the mechanisms underlying a specific stress is essential for the later strategies to be applied. Therefore, in this study chickpea seedlings were subjected to subzero temperatures under field conditions and also to short-time leaf exposure under growth-chamber conditions to study physiological responses (as indicators of chilling injury). The comparison of these responses could be useful in identifying differences associated with the relative capabilities of each accession to cope with chilling.
MATERIALS AND METHODS
Field conditions. A total of 10 chickpea (Cicer arien-tinum L.) accessions (Flip 97-211C, Flip 00-6C, Flip 99-48C, Sel 95Th1716, Sel 96Th11439, ILC 8262, Sel 95Th1745, ILC 533 (cold-sensitive check), Jam (check local cultivar), and Flip 98-108C) were used for cold tolerance screening. In order to evaluate the Kabuli accessions more precisely, Sel 95Th1745 was used as a desi type. The accessions were sown in November in a randomized complete block design with three replications at the Dryland Agriculture Research Institute (DARI) of Iran (46.15° E, 37.15° N, and 1720 m above sea level) in Maragheh city ofAzerbaijan province in the north west of Iran. During cropping season, cold stress was severe in January and February. Seedlings passed the lowest temperature of —25°C with snow covering and —11°C without snow. The accessions were grown in two rows of 3 m in length with
inter- and intra-row spacing of 25 and 10 cm, respectively. For best comparisons, we used selected accessions from previous experiments and cold-sensitive check ILC 533 [14]. Because this accession is sensitive to low temperature and cannot pass winter in Ma-ragheh, we used check local cultivar (Jam) for analysis. After sowing and germination in autumn, the following indices were recorded: percent survival (seedlings remained after winter), yield (g/4 m2), weight of 100 seeds (g), plant height (cm), days from sowing to the appearance of 50% flowers, days from sowing to 90% maturity. Accession cold tolerance was evaluated in scores. To this end, we used a scale from 1 to 9, where 1 — plants free from any damage, 2 — highly tolerant, 3 — tolerant, 4 — moderately tolerant, 5 — intermediate, 6 — moderately sensitive, 7 — sensitive, 8 — highly sensitive, and 9 — all plants are killed [15]. Recorded data were analyzed for simple statistics, i.e., mean and standard deviation. The analysis of variance (ANOVA), as a confirmatory analysis, was performed, and then the means of results were compared by Duncan's multiple range tests. All chickpea accessions were subjected to procedure of principal component analysis (PCA) using a computer software SPSS 10.0. Principal component analysis of data was performed to investigate the importance of different characters in explaining multivariate polymorphism [16], and then the accessions were plotted according to their first two principal component scores. Genotypes were clustered based on morphological traits by the UPGMA (unweighted pair group method using arithmetic averages) clustering method.
Greenhouse conditions. Seeds of ten chickpea accessions were sterilized with 10% sodium hypochlorite for 5 min, soaked in distilled water, and then germinated in Petri dishes on filter paper for 72 h at 25°C in a thermostat. Subsequently the seedlings were planted
Table 1. Simple correlation (r) between values of the chickpea accessions for different traits
Trait Yield, g/4 m2 Yield, 100 seed wt, g Days to 50% flowering Days to maturity Height, cm Percent survival
Yield, g/4 m2
Yield, 100 seed wt, g -0.516
Days to 50% flowering -0.823* 0.484
Days to maturity -0.409 0.607 0.730*
Height, cm -0.850** 0.486 0.620 0.285
Percent survival 0.047 -0.091 -0.332 -0.712** -0.037
Cold tolerance score 0.184 0.039 0.121 0.578 -0.179 -0.800**
Notes: * Significant at 5%. ** Significant at 1%.
in pots containing soil, sand, and farmyard manure. Plants were grown in a growth chamber at 25°C, an ir-radiance of200 ^mol/(m2 s) from white light luminescent lamps, a 16-h photoperiod, and 75% relative humidity for 14 days. Experimental seedlings were subjected to chilling as described below. Control seedlings were grown at 25°C.
Chickpea winter-sowing in Iran, where temperatures rarely fall below —10°C even in short-term periods, has advantages over trad
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