Waxy maizes from Argentina. I. Potential yield and endosperm protein content
--Corcuera, VR; Naranjo, CA

During 1990 at the IFSC-CIGEN and CITIM, a maize breeding plan was initiated. The purpose is to obtain waxy endosperm commercial hybrids. Four foundational populations were used: SCV1, SCV2, WEM and FW. To obtain inbreds from these populations, the ear-to-row method proposed by Shull is being used. Simultaneously, a divergent selection procedure is being done. This is based on Illinois Selections, as individuals with high protein content in their endosperm are separated from those with a low value for the same trait in each generation of inbreeding. Selfings are practised to obtain new generations.

In this article, the results obtained through the characterization of the foundational materials, as well as from their S1 progenies, are presented. With this purpose some plant, prolificity, ear and evolutive cycle traits were measured according to maize descriptors recommended by IBPGR.

1. PLANT TRAITS: plant height (PH) in meters; upper ear insertion height (UEIH)in meters; stalk diameter (SD) in cm; stalk number (SN); total leaf number (TLN).
2. PROLIFICITY TRAITS: number of productive nodes per tiller (PN); ears in the uppermost node (EUN); ears per tiller (ET) and ears per plant (EP).
3. EAR TRAITS: ear length in cm (EL); ear diameter in cm (ED); number of rows (RN); number of kernels per row (NKR); ear weight in grams (EW); kernel weight per ear in grams (KWE) and cob percentage (%C).
4. EVOLUTIVE CYCLE TRAITS: days from plant emergence to silking (DS); heat units from plant emergence to silking (HUS) in degrees C and F.

Tables 1 to 3 show the average values found for plant, prolificity and ear traits in the foundational materials and their S1 progenies.

SCV1 and SCV2 are two similar populations from the IFSC. They segregate for the gene wx in a 3:1 ratio. Both populations show short plants, with a low number of total leaves and slender stalks. Nevertheless, there are differences between them when prolificity traits are considered: SCV1 has high prolificity values whilst SCV2 shows low prolificity. SCV1 and SCV2 have small ears, but SCV1 has a high cob percentage.

WEM is another population from the IFSC. It carries the segment c c sh sh wx wx in the short arm of chromosome 9. The plants are short, with slender stalks, low number of total leaves, high prolificity, small and light ears with a high cob percentage.

FW was sent by CIMMYT in 1990. These are medium height plants, with approximately 13 leaves, low prolificity values, normal size ears but with high cob percentage.

Table 4 summarizes evolutive cycle trait values for the materials studied. All of them, present short evolutive cycle (measured from emergence to silking). Heat units in the period vary from 783.68 F to 988.16 F. Because of this, we recommend the sowing at a density of 70,000 to 80,000 plants/ha (35,000 to 40,000 plants/acre) in locations with a good water disposal. In Table 5, the potential yields are shown. In the estimations, prolificity values, yield/plant (grams of kernels/ear) and recommended sowing density were considered. The highest yielding inbred is FW followed in decreased order by SCV2, WEM and SCV1.

Considering the potential yields and average endosperm protein content, the amount of protein per hectare produced by each population and their S1 progenies can be estimated. Taking into account the semola extraction percentage during the milling process (approximately 45% of the field yield), the amount of protein in semolas produced per hectare was also calculated (see Table 6). It must be pointed out that the S1 inbred derived from the population FW has 10.74% protein in its endosperm. This value is superior to the average shown by most commercial hybrids in Argentina.

Finally, the authors insist that beyond the selection of high protein content ears, it is more interesting to select through the amount of protein produced per hectare by the inbred. Then it is necessary to select jointly by high yields and high protein content. In most cases, protein content is negatively related to yield, but in some genotypes such as FW, such negative correlation does not seem to exist, and then it is possible to carry out a selection process that contemplates both traits with certain success.

 Table 1. Plant traits measured in the populations (So) and their S1 progenies.
 
Material Gn PH* (m) UEIH1 (m) SD (cm) SN TLN
SW1 So 1.23a 0.37a 1.67a 1.13a 9.75a
S1 1.49b 0.48a 1.60a 1.60b 9.75a
SW2 So 1.40a 0.43a 1.58a 1.07a 10.00a
S1 1.53a 0.54a 1.65a 1.24a 10.04a
WEM So 1.33a 0.33a 1.44a 1.23a 9.56a
S1 1.31a 0.37a 1.48a 1.04a 9.74a
FW So 1.86a 0.68a 1.93a 1.12a 13.03a
S1 2.01a 0.65a 1.96a 1.13a 12.11b
* see abbreviations in the text.
1Average values followed by the same letter do not differ significantly at 0.05% within the same population.
Gn = generation

Table 2. Prolificity traits measured in the populations (So) and their S1 progenies.
 
Material
Gn
Pn*
EUN1
ET
EP
SCV1
So
1.50a
1.10a
1.50a
1.50a
 
S1
1.18
1.10a
1.18a
1.90a
SCV2
So
1.14a
1.05a
1.15a
1.14a
 
S1
1.46a
1.12a
1.58b
1.84b
WEM
So
1.40a
1.07a
1.37a
1.62a
 
S1
1.29a
1.07a
1.35a
1.41a
FW
So
1.14a
1.07a
1.04a
1.11a
 
S1
1.50a
1.11a
1.32a
1.43b
*see abbreviations in the text
1Average values followed by the same letter do not differ significantly at 0.05% within the same population.
Gn= generation

Table 3. Ear traits measured in the populations (So) and their S1 progenies.
 
Material Gn EL* (cm) ED1 (cm) RN NKR EW g WE g % C
SCV1 So 12.65 a 2.95a 13.60 a 21.16 a 36.90a 29.61 a 21.25 a
S1 12.30 a 3.12a 15.00 a 22.25 a 54.50b 44.00 b 19.24 a
SCV2 So 13.96 a 3.62a 14.40 a 27.00 a 70.80a 75.40 a 18.87 a
S1 13.78 a 3.60a 14.81 a 23.07 a 62.78a 48.70 a 24.00 b
WEM So 13.70 a 3.57a 14.34 a 20.67 a 52.50a 37.50 a 29.13 a
S1 14.85 a 3.77a 14.61 a 25.52 b 79.13b 60.43 b 25.00 a
FW So 16.49 a 3.89a 14.75 a 29.00 a 107.75 a 85.25 a 21.02 a
S1 18.62 b 4.17a 15.34 a 29.34 a 102.50 a 80.00 a 24.64 a
*see abbreviations in the text.
1Average values followed by the same letter do not differ significantly at 0.05% within the same population.
Gn= generation.

Table 4. Average days to silking and Heat Units measured in the populations (So) and their S1 progenies.
 
Material
Gn
Days
Heat Units
     
C
F
SCV1
So
54.50
459.6
859.3
 
S1
55.12
470.3
878.5
SCV2
So
53.89
459.6
859.3
 
S1
48.77
417.6
783.7
WEM
So
54.79
470.3
878.5
 
S1
58.07
506.3
943.3
FW
So
58.82
518.2
964.8
 
S1
59.64
531.2
988.2

Table 5. Potential yield (kg/ha) of the populations (So) and their S1 progenies according to sowing density (70,000-80,000 plants/ha), EP and KWE.
 
Material
Gn
EP
No. ears/ha
Potential yield (kg/ha)
SCV1
So
1.5
105,000-120,000
3,109-3,553
 
S1
1.9
133,000-152,000
5,852-6,688
SCV2
So
1.14
79,800-91,200
4,580-5,235
 
S1
1.84
128,800-147,200
6,273-7,169
WEM
So
1.62
113,400-129,600
4,252-4,860
 
S1
1.41
98,700-112,800
5,964-6,816
FW
So
1.11
77,700-88,800
6,624-7,570
 
S1
1.43
100,100-114,400
8,008-9,152

Table 6. Protein yields per hectare considering semola production (kg/ha) in the populations (So) and their S1 progenies.
 
Material
Gn
Endosperm protein content (%)
Semola yield (kg/ha)
Protein yield (kg protein/semola yield)
SCV1
So
10.80
1,399-1,599
151-173
 
S1
8.76
2,633-3,010
231-264
SCV2
So
8.14
2,061-2,356
168-192
 
S1
8.12
2,823-3,226
229-262
WEM
So
8.73
1,913-2,187
167-191
 
S1
9.21
2,684-3,067
247-282
FW
So
11.38
2,981-3,906
339-388
 
S1
10.74
3,603-4,118
387-442

 
 
 
 


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