iecab2010 held on 1-15 june 2010 genome variability and plant age influence susceptibility to...

IeCAB2010 held on 1-15 June 20IeCAB2010 held on 1-15 June 201010

Genome Variability and Plant Age Influence Genome Variability and Plant Age Influence Susceptibility to Moisture Stress in the Susceptibility to Moisture Stress in the Cultivated Bananas (Cultivated Bananas (MusaMusa species) species)

11Baiyeri, K. P. and Baiyeri, K. P. and 22Ortese, E.Ortese, E. 11Dept. of Crop Science, University of Nigeria, Nsukka, Dept. of Crop Science, University of Nigeria, Nsukka,

Nigeria.Nigeria.22Akperan Orshi College of Agriculture, Yandev, Benue Akperan Orshi College of Agriculture, Yandev, Benue

State, Nigeria.State, Nigeria.


INTRODUCTIONINTRODUCTION Water stress is one of the major environmental Water stress is one of the major environmental

constraints that limit crop productivity worldwide.constraints that limit crop productivity worldwide. Consequent on climatic change, moisture Consequent on climatic change, moisture

availability (in terms of quantity, quality and availability (in terms of quantity, quality and duration) has become very unpredictable in most duration) has become very unpredictable in most places. places.

Moisture availability has been identified as one of Moisture availability has been identified as one of the most critical productivity determining factors in the most critical productivity determining factors in Musa Musa species (Robinson and Bower, 1986;species (Robinson and Bower, 1986; Turner Turner et alet al., 2007., 2007))..


Introduction…Introduction… Water deficit imposes huge reductions in crop yield through Water deficit imposes huge reductions in crop yield through

diminished leaf carbon fixation and general growth inhibition. diminished leaf carbon fixation and general growth inhibition.

However, the degree of plant susceptibility to transient or However, the degree of plant susceptibility to transient or prolonged moisture deficits is somewhat dependent on the prolonged moisture deficits is somewhat dependent on the plant’s physiological growth stage during the time of water stress plant’s physiological growth stage during the time of water stress (Hall (Hall et al.et al., 1981, 1981 ). ).

The deleterious effects of moisture stress in most species are The deleterious effects of moisture stress in most species are more disastrous during the reproductive growth phase (Evans, more disastrous during the reproductive growth phase (Evans, 1993); another precarious stage is the juvenile seedling stage.1993); another precarious stage is the juvenile seedling stage.


Introduction …Introduction …

Existing information suggests that hardiness in Existing information suggests that hardiness in MusaMusa species is influenced by genomic grouping. species is influenced by genomic grouping.

The cultivated bananas (The cultivated bananas (MusaMusa species) comprise of species) comprise of

three main genomic groups (AAA, AAB, ABB), but three main genomic groups (AAA, AAB, ABB), but with the array of emerging improved genotypes, with the array of emerging improved genotypes, tthere is need to evaluate genomic responses to here is need to evaluate genomic responses to moisture stress with a view to identifying putative moisture stress with a view to identifying putative tolerant or less susceptible genotype(s).tolerant or less susceptible genotype(s).


To study the influence of plant age and To study the influence of plant age and genome composition on the susceptibility genome composition on the susceptibility of of Musa Musa plants to transient drought plants to transient drought condition. condition.

ObjectiveObjective


Materials and Materials and MethodsMethods

Experimental Site:Experimental Site: The study was conducted in a glasshouse of The study was conducted in a glasshouse of the Department of Crop Science, University of Nigeria, Nsukkathe Department of Crop Science, University of Nigeria, Nsukka. . Nsukka is located 6Nsukka is located 6oo 52′N, 7 52′N, 7oo 24′E and 447.2 m above sea level, 24′E and 447.2 m above sea level, in the derived savanna agro-ecology of Nigeria.in the derived savanna agro-ecology of Nigeria.

Design of Experiment: Design of Experiment: A six-week moisture stress period was imposed on six A six-week moisture stress period was imposed on six MusaMusa genotypes comprising of two dessert bananas (AAA), two plantains genotypes comprising of two dessert bananas (AAA), two plantains (AAB) and two ABB cooking bananas at varying growth ages of 8, 12 or 16 (AAB) and two ABB cooking bananas at varying growth ages of 8, 12 or 16 weeks after planting. These were evaluated alongside the control (unstressed) weeks after planting. These were evaluated alongside the control (unstressed) plants in a 6 x 4 factorial in completely randomized design (CRD)plants in a 6 x 4 factorial in completely randomized design (CRD) of five of five replications. Each genomic group consisted of one landrace triploid (3x) and a replications. Each genomic group consisted of one landrace triploid (3x) and a hybrid tetraploid (4x) genotype.hybrid tetraploid (4x) genotype.


Materials and Methods …Materials and Methods …

Treatment application: Treatment application:

Fairly uniform early sword suckers were used in Fairly uniform early sword suckers were used in the study; these were raised in 17 kg of topsoil. the study; these were raised in 17 kg of topsoil.

At the specific age of introducing water stress, At the specific age of introducing water stress, watering was withdrawn for six weeks and watering was withdrawn for six weeks and thereafter re-introduced for another six weeks.thereafter re-introduced for another six weeks.


Data Collection and Data Collection and AnalysisAnalysis

Growth changes in:Growth changes in:

Plant height Plant height Plant girth Plant girth Number of live leaves, andNumber of live leaves, and Leaf area were evaluated after the six-week Leaf area were evaluated after the six-week

drought and rehydration cycles.drought and rehydration cycles.

All data collected were subjected to analysis All data collected were subjected to analysis of variance for factorials in CRD using of variance for factorials in CRD using GENSTAT Release 7.2 DE (GENSTAT, GENSTAT Release 7.2 DE (GENSTAT, 2007). The separation of treatment means 2007). The separation of treatment means for significant effects was by least for significant effects was by least significant difference (LSD) at 5 percent significant difference (LSD) at 5 percent probability level as described in Steel and probability level as described in Steel and Torrie (1980).Torrie (1980).


ResultsResults Susceptibility to moisture stress varied with plant age, genome group and Susceptibility to moisture stress varied with plant age, genome group and

ploidy levels.ploidy levels.

The effects of moisture stress were found to be most severe in the 16-week The effects of moisture stress were found to be most severe in the 16-week plants, whereas the 8- and 12-week-old plants had a fair tolerance. plants, whereas the 8- and 12-week-old plants had a fair tolerance. Considering the mean values across the six genotypes (Table 1), stress effects Considering the mean values across the six genotypes (Table 1), stress effects on leaf area, plant girth and number of live leaves were more severe on the on leaf area, plant girth and number of live leaves were more severe on the 16-week-old plants.16-week-old plants.

The negative values observed in leaf area, plant height and girth in the 16-The negative values observed in leaf area, plant height and girth in the 16-weeks plants after the stress (Table 1) and rehydration cycle (Table 2) are weeks plants after the stress (Table 1) and rehydration cycle (Table 2) are indications of shrinkage or outright loss of plant parts due to tissue indications of shrinkage or outright loss of plant parts due to tissue desiccation.desiccation.

The percentage survival values on Table 2 showed clearly that the 16-week-The percentage survival values on Table 2 showed clearly that the 16-week-

old plants were more susceptible to the transient drought.old plants were more susceptible to the transient drought.


Results …Results … The cooking bananas (ABB) and plantains (AAB) were more The cooking bananas (ABB) and plantains (AAB) were more

drought-tolerant than the AAA-dessert bananas.drought-tolerant than the AAA-dessert bananas.

The cooking bananas (‘Fougamou’ & ‘BITA 7’) and plantains The cooking bananas (‘Fougamou’ & ‘BITA 7’) and plantains (‘Agbagba’ & ‘PITA 22’) had a better growth recovery (Table 2) as (‘Agbagba’ & ‘PITA 22’) had a better growth recovery (Table 2) as evident from the higher values recorded in plant height, girth and evident from the higher values recorded in plant height, girth and number of leaves per plant after the rehydration period. number of leaves per plant after the rehydration period.

Besides, the dessert bananas had a very poor survival percentage, Besides, the dessert bananas had a very poor survival percentage, although the landrace genotypes ‘Agbagba’ and ‘Fougamou’ were although the landrace genotypes ‘Agbagba’ and ‘Fougamou’ were equally affected.equally affected.

Similarly, the landrace triploid genotypes were relatively more Similarly, the landrace triploid genotypes were relatively more

susceptible than the tetraploid hybrids. The mean values for number of susceptible than the tetraploid hybrids. The mean values for number of leaves, leaf area and plant girth (Table 1) showed the landrace genotypes leaves, leaf area and plant girth (Table 1) showed the landrace genotypes in plantains and dessert bananas to be more sensitive to moisture stress in plantains and dessert bananas to be more sensitive to moisture stress than the tetraploid counterparts.than the tetraploid counterparts.

Table 1: Changes in growth parameters of six Table 1: Changes in growth parameters of six MusaMusa genotypes exposed to moisture stress genotypes exposed to moisture stress

at 8, 12 & 16 weeks after planting.at 8, 12 & 16 weeks after planting. Plantains Dessert Bananas Cooking Bananas

Component of Growth

Plant Age at onset of stress

(weeks)

Agbagba

[3x] PITA

22 [4x]

Nsukka Local [3x]

FHIA 17 [4x]

Fougamou

[3x] BITA 7 [4x]

Mean

8 8.8 -11.5 -86.2 7.8 -20.7 -366.8 -78.1

12 8.6 2.7 7.0 8.0 1.7 7.3 5.9 16 -1446.4 -4.0 11.5 8.0 3.9 13.0 -235.7

Leaf Area (cm2)

Mean -476.3 -4.3 -22.6 7.9 -5.6 -115.5 -

8 -5.4 -2.7 -3.4 -2.8 -2.2 -3.7 -3.4 12 -5.0 -3.3 -6.4 -4.0 -3.0 -2.7 -4.1

16 -6.0 -5.2 -7.5 -5.5 -4.0 -5.0 -5.5 Number of

Leaves

Mean -5.5 -3.8 -5.8 -4.1 -3.1 -3.8 -

8 -0.6 -0.4 -0.4 0.2 -0.7 -0.4 -0.4 12 0.0 0.0 0.0 0.0 0.0 0.0 0.0 16 -2.0 -0.8 -1.2 -0.5 -2.5 -3.0 -1.7

Girth (cm)

Mean -0.9 -0.4 -0.5 -0.1 -1.1 -1.1 -

8 0.0 -0.3 0.2 0.2 -0.4 0.0 -0.1 12 0.6 0.5 0.4 0.7 0.3 0.8 0.5 16 3.0 2.3 4.0 3.5 1.0 1.0 2.5 Height (cm)

Mean 1.2 0.8 1.5 1.5 0.3 0.6 -

LSD (0.05)

Leaf Area Number of Leaves Girth Height Genotype (G) 134.8 1.0 0.5 0.6 Age (A) 95.3 0.7 0.3 0.4 G x A 233.5 ns 0.8 1.0

ns = non-significant at 5% probability level

Table 2: The recovery pattern and changes in growth components of six Table 2: The recovery pattern and changes in growth components of six MusaMusa genotypes genotypes

exposed to moisture stress at varying ages estimated after a 6-week rehydration cycle. exposed to moisture stress at varying ages estimated after a 6-week rehydration cycle. Plantains Dessert Bananas Cooking Bananas

Component of Growth

Plant Age at onset of stress

(weeks)

Agbagba

[3x] PITA

22 [4x]

Nsukka Local [3x]

FHIA 17 [4x]

Fougamou

[3x] BITA 7 [4x]

Mean

8 38.8 87.8 42.0 143.6 45.8 29.3 64.5 12 12.2 16.3 22.8 18.2 14.5 32.3 19.4 16 -1166.4 83.2 -329.0 -2028.0 -1449.0 -145.0 -839.0

Leaf Area (cm2)

Mean -371.8 62.4 -88.1 -622.1 -462.9 -27.8 -

8 2.2 3.2 1.6 3.0 2.0 3.3 2.6 12 1.8 2.7 1.6 2.6 2.0 2.3 2.2 16 3.0 3.3 2.0 2.0 3.0 3.5 2.8

Number of Leaves

Mean 2.3 3.1 1.7 2.5 2.3 3.0 -

8 1.4 1.5 2.2 1.2 3.2 1.3 1.8 12 1.0 1.7 0.8 1.8 1.0 1.0 1.2 16 3.0 1.8 2.5 -5.0 -2.0 10.5 1.8

Girth (cm)

Mean 1.8 1.6 1.8 -0.7 0.7 4.2 -

8 6.8 7.2 6.4 7.0 7.3 6.8 6.9 12 2.4 2.7 2.8 3.4 4.0 3.0 3.1 16 -16.8 5.7 -11.0 -45.0 -11.0 36.7 -6.9 Height (cm)

Mean -2.5 5.2 -0.6 -11.5 0.1 15.5 -

8 100 100 100 100 100 100 100

12 100 100 100 100 100 100 100

16 33 80 40 40 50 100 57.2 Percentage

survival (%)

Control 100 100 100 100 100 100 100

LSD (0.05)

Leaf Area Number of Leaves Girth Height Genotype (G) 107.2 0.4 1.9 6.3 Age (A) 75.8 0.3 ns 4.4 G x A 185.7 0.6 3.2 10.8

ns = non-significant at 5% probability level


This study suggests that This study suggests that MusaMusa crops at their early crops at their early vegetative growth stage are more likely to vegetative growth stage are more likely to withstand moisture stress than the older plants. withstand moisture stress than the older plants. Field planting and other cultural practices (like Field planting and other cultural practices (like mulching and irrigation) should be conscientiously mulching and irrigation) should be conscientiously planned to avoid prolonged exposure of plants to planned to avoid prolonged exposure of plants to drought, particularly at the reproductive transition drought, particularly at the reproductive transition phase.phase.

The differential sensitivities of the genomic groups The differential sensitivities of the genomic groups to the induced moisture stress makes breeding a to the induced moisture stress makes breeding a viable option for upgrading drought viable option for upgrading drought resistance/tolerance in bananas in readiness for the resistance/tolerance in bananas in readiness for the apparent change in global climate.apparent change in global climate.

Conclusion and application of findingsConclusion and application of findings

iecab2010 held on 1-15 june 2010 genome variability and plant age influence susceptibility to...

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