| dc.description.abstract | Chili is one of the most notable horticultural commodities which have high
economic value. However, the national chili production is still low and unstable.
This instability in production is due to changes in chili agricultural land area
which resulted from land conversion and low plant productivity which caused by
changing growing environment conditions. Utilization of dry land for cultivation
of chili plants is an alternative that can be chosen to increase chili production.
Indonesia has enormous dry land potential, however, annual crop farming and
horticulture on dry land, especially outside Java, has low production due to
biophysical constraints on land and water deficit. Water deficit is one of the
limitations on chili production. An effort can be done to increase chili productivity
in dry land is the cultivation of superior varieties which are tolerant to less
irrigation. Evaluation of less irrigation tolerance of chili plants to identify the
response differences need to be conducted to obtain chili plants that are tolerant to
water deficit.
Breeding of less irrigation tolerance varieties requires donor parents that
have less irrigation tolerance and known information on genetic control of the
trait. Understanding the genetic basis of limited water tolerance of plants is a
prerequisite for developing superior genotypes. Lack of water generally affects
physiological, biochemical, and molecular processes in the form of disruption of
metabolite homeostasis and causes significant changes in the chemical
composition of plants that require temporal adjustment in the metabolic pathways.
Metabolomic analysis of chili genotypes with different tolerance levels can be
conducted to investigate important metabolite compounds in chili plants related to
limited water. The metabolic profile of chilies, especially in determining the level
of limited water tolerance to limited irrigation stress, is essential information in
developing limited water tolerant chili plant breeding program.
This study is entitled “genetic analysis and metabolomic study of less
irrigation tolerance of chili plants”. The study aimed to evaluate the selection
environment, select chili plants that are tolerant to less irrigation stress and
determine the genetic parameters, the general combining ability (GCA) and the
specific combining ability (SCA) of the genotypes used in relation to less
irrigation tolerance.
An irrigation interval of 7 days or equivalent to 52-58% media water
content of field capacity were used to identify differences in response between 23
genotypes of chili to less irrigation in pots. A polietylen glicol (PEG)
concentration of 15% or equivalent to osmotic potential of -4.1 Bar were used to
identify differences in response between 22 chili genotypes to drought stress
during the germination phase. The root shoot ratio character was determined as
selection character for less irrigation tolerance during the vegetative phase.
Meanwhile, selection characters to estimate the less irrigation tolerance of chili
genotypes in the germination phase were the hypocotyl length, root length, ratio
of root length to hypocotyl length, sprout length, hypocotyl dry weight, and
percentage of germination. The study results showed that there were differences in
the level of drought tolerance from the chili genotypes tested. Based on evaluation
at vegetative phase showed that IPB C-5, IPB C-7, IPB C-8, IPB C-12, IPB C-20,
IPB C-37, IPB C-145, SSP, Gada MK F1, and Yuni were categorized as very
tolerant genotypes and IPB C-10, IPB C-19, IPB C-51, IPB C-120, IPB C-142,
IPB C-143, IPB C-160, Seloka, Anies, Bonita, and Jalapeno were categorized as
sensitive, and IPB C-18 was categorized as tolerant. Based on evaluation at
germination stage showed that IPB C7, IPB C120, and Jalapeno genotypes were
very tolerant to water shortage and IPB C8, IPB C12, IPB C18, IPB C19, IPB
C37, IPB C145, and SSP were tolerant, then IPB C51, IPB C142, IPB C143,
Gada, Syakira, Yuni, Bonita, and Anies were categorized as moderate tolerant
genotypes, while IPB C10, IPB C20, and Seloka genotypes were sensitive to
water shortages.
Analysis of genetic parameters based on drought sensitivity index (DSI),
showed a significant effect of additive variance from the character of the lateral
roots number, and a significant effect of the dominant variance on the number of
fruit. In less irrigation conditions, the significant effect of additive variance was
also observed in the lateral roots number, while the significant effect of the
dominant variance was found in the root dry weight, number of fruits and fruit
weight.
General Combining Ability (GCA) analysis according to the DSI displayed
significant effect only in the number of fruit. Genotype with the best GCA based
on the DSI in the number of fruit was IPB C7. Analysis of GCA in less irrigation
conditions exhibited a significant effect in the character of root length, root shoot
ratio, number of fruits and fruit weight. IPB C7 were the genotype with the best
GCA values on the characters of root length, root to shoot ratio and number of
fruits under less irrigation conditions, while Seloka was the genotype with the best
GCA value for fruit weight under less irrigation conditions.
The analysis results of combining ability in half diallel cross based on the
DSI value showed that the specific combining ability (SCA) had a significant
effect on root to shoot ratio and number of fruits. The best SCA based on the DSI
value for the root to shoot ratio was observed in combination of IPB C-10 x
Seloka crosses, while the best SCA value for the number of fruit according to DSI
was shown in the combination of IPB C-10 x IPB C-8 crosses. The significant
effect of SCA in less irrigation conditions was found in root dry weight, number
of branches, root to shoot ratio, number of fruit and fruit weight. The best SCA
value for the root dry weight was shown in the crossing combination of IPB C-10
x IPB C-7, the best SCA value for the number of branches was found in crossing
combination of IPB C-18 x SSP, the utmost SCA value for the root to shoot ratio
and number of fruit was observed in the crossing combination of IPB C-8 x
Seloka, and the best SCA value for fruit weight was noted in crossing
combination of IPB C-10 x Seloka.
Eighty three volatile compounds were identified based on the results of the
metabolomic evaluation of three chili genotypes with different tolerance levels
that grew under normal and less-irrigation conditions. Only 10 metabolites,
namely: neophytadiene, ester-ethyl linolenic acid, linolenic acid, gammasitosterol,
phytol, Alpha-tocopherol, squalene, i-Propyl 7,10,13,16,19-
docosapentaenoate, Ergost-5-en-3-ol and Bicyclo [10.1.0] tridec-1-ene which can
distinguish genotypes based on watering treatment applied. From the ten
metabolites, there are only four which showed significant different concentration
between normal and less-irrigation conditions, namely linolenic acid, alphatocopherol,
gamma sitosterol and squalene. Alpha-tocopherol and squalene were
significant and positively correlated with the percentage of germination and fruit
weight characters. These results indicate that selection for tolerance to limited
irrigation can use these two metabolites as selection characters. | id |
