INTRODUCTION
Lentil is an important component of the rain fed farming
system of West Asia and Africa and source of high-quality protein for
humans (Hamdi et al., 1992). Research indicated lentil seed yield
increased with irrigation frequency and total water use (Salehi et
al., 2006). There are strong linear relationships (r2>0.90)
between yield and moisture supply in lentil (Silim et al., 1993a).
Supply sufficient water in irrigated and rainfed pea increased seed size,
seed yield, biomass yield and harvest index (Singh and Saxena, 1990).
Salehi et al. (2006) reported that the seedling and flowering stages
were most sensitive to water availability and drought stress. However
a deficiency of water during of any growth stages in legume species often
result in a loss of seed yield. Captipon et al. (1988) reported
intensive drought stress in dry season and strong wind in humid season
reduced Mung bean seed yield. They suggested high seed yield has related
pods size and number and resistance to pests and disease.
Drought tolerance or resistance in native plant species
is often defined as survival, but in crop species it must be define in
terms of productivity (Passioura, 1983). The general term `drought tolerance`
can be used to refer to several type of drought resistance, such as drought
escape and dehydration tolerance or avoidance (Turner, 1979; Jones, 1993).
In contrast to the cultivated germplasm, drought escape was relatively
unimportant in wild lentil (Hamdi and Erskine, 1996). Levitt (1972) noted
that drought resistance can be defined as: the water stress necessary
to produce a specific plastic strain. The choice of parameters used to
quantify the level of stress and the intensity of strain are some what
arbitrary.
Hamdi (1996) reported genotypes 293, 234, ILL 6025, ILL
3715 and ILL 5821 were the most tolerant to dry conditions. In addition,
the genotypes 270, 91, 273, 316, 300 and ILL 3693, 6025, 3715, 5782, 3490
showed general adaptability. Khattab (1995) found Heritability estimates
were high for 100 seed weight, moderate for days to maturity and low for
the remaining characters. He suggests, 100 seed weight, seeds per plant
and pods per plant could be considered as selection criteria in lentil
improvement if these traits proved to be highly correlated with yield.
Salam and Islam (1994) reported M1-30, M1-52 and M1-563 had greater values
for filled pods, yield per plant and harvest index under stress than L112.
M1-596 had the greatest biomass production but the lowest seed yield in
all conditions.
Hamdi et al. (1992) reported that the variation in
mean seed yield per plant was largely explained (r2 = 0.833)
by the variation in water supply. Supplementary irrigations (50 mm each)
resulted in a 20% increase in seed yield per plant. They suggested Genotypes
ILL241, ILL5523 and ILL5527 were promising under irrigated conditions,
ILL1983, ILL2501 and ILL2526 in dry conditions and ILL5737 was stable
across a range of environments. Dantuma and Grashoff (1984) emphasized
that selection should increase the harvest index and reduce excessive
vegetative growth in favorable conditions.
Breeding for resistance to extremes of temperature and moisture
in cool season food legumes is limited by the lack of adequate screening
techniques. Development of new screening tests designed to select for
specific adaptive traits require a better knowledge of the mechanisms
of resistance in these crops, especially to drought (Wery et al.,
1994). The aim of this investigation was to study of seed yield and yield
component traits of Lentil (Lens culinaris Medik) under normal
and drought stress and found out the most sensitive yield component of
lentil in rainfed condition.
MATERIALS AND METHODS
Genotypes and environment: Twenty diverse genotypes, collected
from 3 countries selected randomly from the ICARDA lentil germplasm collection
(Table 1), were grown in Zanjan University Research Farm,
Iran (latitude 31°37´ N, longitude 48°49.5´, elevation 1633 m, EC of soil
water by the equation in EC = 2.33) in 2004. Monthly rainfall and minimum
air temperature during the growing seasons are shown in Table
2.
Experimental procedure: We used a split-plot design with three replications which
the main plots were lentil planted under drought stress and non stress
condition (irrigation
Table 1: |
Name and source of the 20 lentil
tested |
 |
ICARDA germplasm
accession number; ILL International Legume Lentil |
in three times: before flowering, flowering and pod filling
stage). The subplot factor were twenty genotypes of lentil (Table
1).
Lentil seed were sown at a depth of 4 to 6 cm and a density
of 200 seed m-2 in 4 m long rows, four rows per plot, with
25 cm between rows. Fertilizer at 22 kg p (50 kg P2O5)
and 30 kg N ha-1 was added to the soil prior to sowing.
For data collection twenty lentil plants from each plot
were picked out randomly and removed and then the plants height, pods
number per plant, seed yield per plant, 100 seed weight, biomass yield
and seed yield were noted. Harvest index calculated with Eq.
1:
Where: |
|
|
HI |
: |
Harvest Index |
SY |
: |
Seed Yield |
BY |
: |
Biomass Yield |
Coefficient of variance of the mentioned characters was
calculated as Eq.
2:
Where: |
|
|
Cv |
: |
Properties variation percent |
CP |
: |
Mean treats in non-stressed condition |
Cd |
: |
Mean treats in drought stressed condition |
Stress intensity was calculated according to Fisher and Maurer (1978)
(Eq. 3)
Where: |
|
|
 |
= |
Mean of yield under normal condition |
 |
= |
Mean of yield under drought stressed condition |
Statistical procedures: SAS program used for analysis of variance and SPSS program
for correlation parameter.
Table 2: |
Monthly rainfall,
minimum and maximum air temperature at 2004-2005 seasons |
 |
RESULTS AND DISCUSSION
There were significant differences among genotype for all
characters. Also, there were significant differences among stress for
all characters except for harvest index. Other studies have also indicated
the existence of variation for drought response among the genotypes under
study (Salehi, 2005). There were also significant differences amongst
the genotypexstress interaction for all characters except for seed yield,
100 seed weight (Table 3). Also, stress intensity (SI)
was estimated 0.235 as Fisher and Maurer (1978).
Mean values and variation of traits: The mean value of seed yield in drought stress environment
and normal condition was 20.2725 and 26.5161 g, respectively. CV% of seed
yield was 23.5466% (Table 4). Silim et al. (1993b)
and Grzesiak et al. (1996) reported seed yield reduced under drought
stress. In Table 4, the seed yield per plant was most
sensitive to drought stress but 100 seed weight was more tolerant trait
as CV percent. Also Table 4, showed that maximum and
minimum coefficient of variance percentage was in seed yield per plant
and 100 weight seed, respectively. The coefficient variance percentage
of harvest index obtained (%CV = -13.7425).
Results showed that seed yield per plant and number pod
per plant was reduced by water deficient (Table 4). Thus
the decrease in seed yield was mainly attributed to reduced seed yield
per plant and pod number. This result agrees with Richards (1983) and
Siddique et al. (1990). Total drought stress decreased all traits
except harvest index.
Improvement in adaptation of lentil to drought stress environments
requires improved tolerance to water deficient during flowering and poding.
Correlation between seed yield and other traits in normal
condition: Harvest index was highly correlated with seed yield (r =
0.739 p< 0.01) which is agree with Dutta and Mondal (1998). This character
could be a good index for selecting high yield genotypes in normal condition.
However, among number pod per plant and seed yield per plant have strongly
correlation (r = 0.777 p< 0.01). The correlation coefficient of seed yield
per plant and number pod per plant with seed yield was significant and
positive (Table 5). Esmail et al. (1994) showed
that characters such
Table 3: |
Mean squares of yield and seed yield
components of lentil under drought and normal condition |
 |
* and **: Significant at the 5% and
1% levels of probability, respectively |
Table 4: |
Mean values and variation of traits
in lentil under normal and drought stresses conditions |
 |
Table 5: |
Correlation between traits of lentil
cultivars in normal condition |
 |
* and **: Significant at the 5% and
1% levels of probability, respectively |
Table 6: |
Correlation between traits of lentil
cultivars under drought stress condition |
 |
* and **: Significant at the 5% and
1% levels of probability, respectively |
as number pod per plant and seed yield per plant were efficient
to be used in selecting genotypes with high yield capacity. Harvest index
showed a highly significant negative correlation with biomass yield and
plant height (r = -0.708; r = -0.444; respectively p< 0.01 and p< 0.05).
The negative association between harvest index and biomass yield is illustrated
by plant height which had non significant negative correlation with seed
yield and produced low seed yield. Thus, as shown here and in other studies
(Eissa et al., 1986; Singh et al., 1994). In conclusion,
based on present study studies it seemed that harvest index, number pod
per plant and seed yield per plant were useful characters to select for
high yield for normal condition in plant breeding programs.
Correlation between seed yield and other traits in drought
stress condition: The coefficients of correlation between grain yield and
other traits studied in drought stress condition are shown in Table
6. Grain yield was significantly correlated with biomass yield (r
= 0.524; p< 0.05). This is expected to occur where more assimilates available
to seed development ate associated with more vegetative growth. This result
agreed with those of Migdadi and Duwayri (1994). Grain yield was correlated
significantly and positively with number pod per plant, seed yield per
plant and harvest index (r = 0.353, 0.351 and 0.472, respectively; p<
0.05 in all cases). This result agreed with those of Luthra and Sharma
(1990). Also, a positive but insignificant correlation was found between
grain yield and plant height (r = 0.029). The correlation amongst number
pod per plant and seed yield per plant were strongly significant and positive
(r = 0.721; p< 0.01) which is agree with Manora and Manara (1988). We
suggest that the traits of pod number per plant, seed yield per plant,
biomass yield and harvest index are important characters under drought
stress conditions, as found by other researcher (Rajput and Sarwear, 1989).
|
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