Inheritance of Type I Glandular Trichomes in Cucumis melo L.
F.J. Palomares-Rius, Sarria, E., Alba, J.M. and M.L. Gómez-Guillamón
Experimental Station ‘La Mayora’, CSIC, 29760, Algarrobo-Costa (Málaga- Spain)
INTRODUCTION: Glandular trichomes Type I (Picture 1 and 2), firstly described in Cucumis melo by Gómez-Guillamón et
al. (2006), are involved in the early rejection of melon plants as hosts by Aphis gossypii Glover, and, in high density, they
could be considered as an additional factor to the aphid resistance conferred by Vat gene (Sarria et al., 2007). The knowledge
of the inheritance mode of their density would enhance their utilization in melon breeding.
Head
MATERIALS AND METHODS:
• Trichome density was evaluated in a six-generation family,
obtained from the cross TGR-1551 x ‘Bola de oro’. Plants were
grown until 8-10 true leaf stage in pots (500 cm3) filled with soil
substrate placed in a growth chamber at 25 ºC (light) and 20 ºC
(dark) with a 16:8 h (L:D) photoperiod.
Basal cell
Stalk cells
• Two disks (5.9 mm diameter) from the second leaf from apex
were taken per plant. Leaf disks were decolorated by heating to
80ºC for three minutes in 100% ethanol and then stained with an
aqueous solution containing 0.05% toluidine blue O (O’Brien et al.
1964).
Picture 1. Glandular trichome Type I distribution (trichomes Type I marked by blue arrow).(right) and trichome
morphology (left) showing head, two stalk cells and one basal cell. Scale bar 100 µm.
• The average of the number of trichomes in the two leaf disks was
considered as the phenotypic value of each plant. Trichome density
data were transformed by log (x+1) prior to data analysis.
Picture 2. Glandular trichome Type I distribution on leaves of ‘Bola de Oro’ (right) and TGR-1551 (left) (glandular
trichomes Type I marked by blue arrow). Scale bar 500 µm.
• The midparent value (m), together with gene effects of additive
(d), dominance (h), and digenic epistatic interaction components of
means for Type I trichome density were estimated following
methods by Mather and Jinks (1982).
• The minimum number of genetic factors involved was estimated
by Wright‘s formula using the F2 segregation and with the
modifications described by Bjarko and Line (1988).
40
Bola de Oro
F1
TGR-1551
No. of plants
• The values for broad sense heritability (H2 ) and narrow sense
heritability (h2 ) were calculated in a single plant basis following
Rodríguez-Herrera et al. (2000) and Warner (1952), respectively.
30
20
n = 33
m = 91.6
s = 26.3
n = 32
m = 396.2
s = 83.2
n = 31
m = 437.0
s = 107 .4
10
RESULTS:
0
• Type I glandular trichome density distributions of both
parents did not overlap; the F1 performed like TGR-1551 and
F2 and backcrosses showed wide segregations (Figure 1).
40
F1 x Bola de Oro
F2
F1 x TGR-1551
No. of plants
30
n = 68
m = 200.9
s = 125.6
20
n = 177
m = 328.6
s = 198.5
n = 71
m = 387.6
s = 136.9
10
0
0
250
500
750
1000
No. trichomes.cm-2
0
250
500
750
1000
0
No. trichomes.cm-2
250
500
750
1000
No. trichomes.cm-2
Figure 1. Frequency distributions of Type I glandular trichome density in the six generations of
Cucumis melo from the cross TGR-1551 x ‘Bola de oro’. Number of plants (n), mean (m), and
standard deviation (s).
Table 1. Joint-scaling estimates (± S.E.) of components of generation means of log-transformed Type I
glandular trichome densities in a genetic family of six generations of Cucumis melo from the cross TGR-1551
x ‘Bola de oro’ and chi-square testing of adequacy of several models.
Parameter
mdh
mdhi
mdhj
mdhl
mdhij
mdhil
mdhjl
m
2.28*
±0.01
2.24*
±0.04
2.28*
±0.12
2.29*
±0.01
2.25*
±0.04
2.48*
±0.11
2.29*
±0.01
[d]
0.34*
±0.01
0.34*
±0.01
0.34*
±0.01
0.34*
±0.01
0.34*
±0.01
0.34*
±0.01
0.34*
±0.01
[h]
0.29*
±0.02
0.34*
±0.05
0.30*
±0.02
0.17*
±0.07
0.33*
±0.05
-0.30
±0.28
0.18
±0.07
0.04
±0.05
0.19
±0.11
[i]
0.05
±0.04
[j]
-0.08
±0.08
[l]
-0.07
±0.08
-0.04
±0.08
0.40*
0.13
±0.07
±0.18
0.12
±0.07
χ2
6.26
(3 df)
5.23
(2 df)
5.33
(2 df)
2.87
(2 df)
4.54
(1 df)
0.00
(1 df)
2.64
(1 df)
P
0.100
0.073
0.070
0.238
0.033
0.973
0.104
* Parameter different from 0 according to t-distribution test (P ≤ 0.05); df, degrees of freedom.
m = midpoint between parent; [d] = additive component; [h] = dominance component; [i] = additive x additive interaction component; [j]
= additive x dominance interaction component; [l] = dominance x dominance interaction component.
• Quantitative data analysis by joint-scaling tests fitted with
some of the genetic models assayed (Tab. 1). The values of
additive component in all models were very similar, [d] = 0.34.
Nevertheless, the models with maximum likelyhood were those
where epistatic dominance x dominance effect [l] was included,
especially mdhil (Table 1).
•In this model, the dominance component [h] was not
significant and the model could explain the similar performance
of F1 towards TGR-1551,by a positive, strong epistatic effect of
heterozygous loci.
• Although the minimum number of genetic factors (ne)
estimated according to Wright’s formula pointed to a
monogenic control (ne = 0.844 ± 0.125), estimations following
Bjarko and Line (1988), suggested an olygogenic character (ne
= 2.840 ± 0.375).
• High value of broad sense heritability (H2 = 0.861) and
moderate value for narrow sense heritability (h2 = 0.505) were
estimated for the character.
CONCLUSIONS:
Additive component is an important factor, but epistatic
dominat x dominant component is involved in the
inheritance of glandular trichome Type I density. These
results anticipate success in introgression of the
character.
AKNOWLEDGEMENTS: The authors thank the valuable contribution of Dr. R. Fernández-Muñoz to improve statistical analysis and the collaboration of
R. Tobar and R. Camero in all the experiments. This work has been financed by the CICYT Research Project: AGL2005-03850-C02-01.
Cited literature:
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- Gómez-Guillamón ML, Sarria E, Heredia A (2006). Epicuticular wax morphology and trichome types in relation to host plant selection by Aphis gossypii in melons. In Proceedings of
Cucurbitaceae 2006, (Holmes GJ, ed), Ed. Universal Press, Raleigh (NC, US) pp 108-115
-Kolb D, Müller M (2004) Light, conventional and environmental scanning electron microscopy of the trichomes of Cucurbita pepo ssp. pepo var. styriaca and histochemistry of glandular
secretory products. Ann Bot 94: 515-26
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- Sarria E, López-Sesé AI, Gómez-Guillamón ML (2007) Antixenosis frente a Aphis gossypii Glover en melón basada en la presencia de tricomas glandulares. In Proceedings of V Congreso
Nacional de Entomología Aplicada, Cartagena (SP) pp. 96