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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