Forage Morphology and Productivity of Different Species of Tripsacum under Sub-Humid Tropical Conditions ^†

Abstract

Morphology and forage productivity of 25 Tripsacum spp. materials were characterized under tropical conditions in Nayarit, Mexico. Treatments included: Tripsacum latifolium, T. australe var. Australe, Tripsacum spp., T. dactyloides (cv. Meridionale and Hispidum), T. bravum, T. manisuroides, T. zopilotense, T. andersonii, T. lanceolatum, T. floridanum, T. laxum, T. cundinamarceae, T. intermedium, T. maizar, and T. peruvianum. Five in row equidistant plants (1.5 m) and three rows (replicates) per species, were evaluated and fertilized using 100-60-00 (N-P-K units) per hectare per year. Variables included: plant mean height, leading flowered stem’s height, plant crown circumference, basal cover, tillers per crown, forage yield and growth rates. Data was analyzed through a completely randomized design including 25 treatments (species, varieties, and/or ecotypes) and LSD tests for mean separation. Differences (p < 0.01) were observed among morphological, productive variables, and species. Outstanding material included T. latifolium and T. australe (8.3 and 5.6 kg DM per plant). Forage production ranged (p < 0.01) from 22% to 1405%, in comparison with the local ecotype T. dactyloides. Morphology and forage productivity within Tripsacum is highly variable, according to the genetic diversity available within this native to Mexico genus, suggesting that Tripsacum agamic complex presents enormous forage production potential for its promotion under grazing for rain-fed systems.

1. Introduction

Tripsacum spp. is a monoic, mainly diplosporic apomictic genus exclusive to the American continent [1,2]; because of its resemblance to corn “maiz” it is also known as “Maicillo” or “Guatemala grass”, it is considered close related to Zea and together with Teosintle Zea mays sub-species Parviglumis, close related to corn [3]. Tripsacum includes nearly 20 taxas distributed from USA to Paraguay [4], 12 of those concentrated in Guatemala and Mexico, considered as centers of origin of the genus [5], showing practically all the genus’ variability as well as several endemic species [6,7,8,9]. Tripsacum spp. agamic complex represents a source of important traits (genes) to generate, through selection or breeding, new plant materials showing outstanding traits for plant fitness and productivity: adaptation to harsh environments, higher production levels, better forage quality, better growing rates, both for wild life and domestic herds [10]. For tropical Mexico and because of Tripsacum spp. native condition (adaptation), it conforms a low-cost viable alternative to support animal production [11]. To date, Tripsacum spp. genus forage attributes have not been well established for productivity; however, it has been used as a forage source, under empirical strategies, for cattle production, for many years. Experimental results on Tripsacum spp. forage potential are scarce and restricted to T. dactyloides, mainly in the United States [12,13,14,15]. Studies in Mexico have shown it is possible to obtain from 8.9 to 16.4 tons DM ha⁻¹ in T. dactyloides and T. andersonii populations, respectively [16]. These productivity levels may be increased up to 40 tons DM ha⁻¹ in dense, well-established prairies and fertilized under optimal management conditions [17].

Under tropical conditions the observed growth rates for five Tripsacum species fluctuated from 1g in T. dactyloides (dry season) to 136 g DM plant per day for T. maizar (rainy season), respectively. Forage production fluctuated from 1.2 to 14.8 tons DM ha⁻¹ during the dry season and from 11.0 to 55.3 tons DM ha⁻¹ during the summer rainy season [11].

On this basis, the present study was developed to characterize forage morphology and productivity for 25 plant materials of Tripsacum spp. under tropical sub-humid conditions in Nayarit, Mexico.

2. Experiments

Experimental evaluation was developed at the National to Mexico Institute for Agriculture, Forestry, and Animal Research’s (INIFAP) “El Verdineño” research station at central Nayarit at 40 m above sea level, tropical sub-humid climate conditions (Aw₂), with a mean annual rain level of 1200 mm per year and mean temperature of 24 °C, and a dry season with seven to eight months of duration [18].

Treatments included 25 plant materials among ecotypes, varieties, and species of the Tripsacum genus: T. latifolium, T. australe cv. Australe, Tripsacum spp. (10A, 11A, and 19A), T. dactyloides (cv. Meridionale, Hispidum, JJ-CH, 3B (local placebo), and 98B), T. bravum (4A and 6A), T. manisuroides (14A and 16A), T. zopilotense, T. andersonii, T. lanceolatum (18A and 68B), T. floridanum, T. laxum 36B, T. cundinamarca, T. intermedium (2A and 21A), T. maizar 7B, and T. peruvianum, both from the International Center for Corn and Wheat Improvement (CIMMyT; A) and local collections (B). Individual five plants rows (1.5 × 1.5 m between plants and rows) that had been established for at least five years, were evaluated applying 100-60-00 (N-P-K) unique fertilization during the rainy season. Both forage morphology and production were evaluated at the end of the drought season (June 2017) with plants showing vegetative stage (mature due to drought) under a cutting interval of 210 days (end of the resting period imposed by drought). Forage samples were dried to 55 °C up to constant weight. Morphology measured variables included: plant height and leader stem (cm), plant crown circumference (m²), basal coverture (cm²), number of tillers per plant, including forage production (DM plant⁻¹; DM ha⁻¹), and rates of growth (DM g plant⁻¹ day⁻¹), as production variables. Data was analyzed using a completely randomized design with 25 treatments (plant species, ecotype, and varieties) with three replicates (row) and least significant difference for mean separation [19].

3. Results

Forage morphology showed differences (p < 0.01) among treatments for all studied variables (

Table 1. Morphology and productive traits of different Tripsacum species, ecotypes and varieties, under sub-humid tropics in Nayarit.

Species	Height (cm)		Plant Crown	Basal Coverture	Tillers per Plant	Forage Production		Growth Rate
Variety	Plant	Leading Stem	Circumference (m2)	(cm2)	(Number)	DM (kg Plant−1)	DM (Tons ha−1)	DM (g Plant−1 Day−1)
T. latifolium	148 a	200 a	4.02 a	1294 a	10 efgh	8.3 a	55.2 a	39.4 a
T. australe	155 a	188 a	3.1 bcd	789 bcd	79 fghi	5.6 b	35 b	25 b
Tripsacum spp. 11A	59 ijk	86 def	1.4 m	164 k	551 a	1.0 fgh	6.7 fgh	4.8 fgh
T. dactyloides, meridionale	120 b	126 bcd	3.37 abc	906 bc	74 ghi	2.3 cdefg	15.5 cdef	11.1 cdef
T. bravum 6A	119 b	165 ab	1.81 jklm	264 ijk	136 def	3.0 cde	20.2 cde	14.5 cde
T. dactyloides JJ-Ch	116 bc	166 ab	2.71 cdefg	592 defg	42 i	3.1 cd	20.6 cd	14.7 cd
T. manisuroides 14A	110 bcd	168 ab	2.43 defgh	475 efghij	56 hi	1.7 defg	11.1 defg	7.9 def
T. bravum 4A	103 bcd	161 ab	2.69 cdefg	576 defg	86 fghi	2.8 cdef	18.7 cdef	13.4 cde
T. zopilotense	99 bcde	136abcd	2.18 ghijkl	380 fghij	202 c	1.9 cdefg	12.7 cdef	9.1 cde
T. andersonii	95 bcde	139 abcd	2.55 defgh	521 defg	29 i	1.2 defg	8.1 defg	5.8 def
T. dactyloides 98B	93 cdef	144 abcd	3.53 ab	998 ab	125 defg	2.9 cde	19.6 cde	14.0 cde
T. lanceolatum 68B	85 defg	133 abcd	2.11 hijklm	356 ghijk	65 hi	0.9 gh	5.8 gh	4.1 gh
T. floridanum	83 efghi	133 abcd	2.11 hijklm	356 ghijk	167 cd	1.3 defg	8.5 defg	6.1 def
T. laxum 36B	81 efghi	128 bcde	2.97 bcde	704 bcde	42 i	0.7 gh	4.6 gh	3.3 gh
T. cundinamarceae	79 efghi	130 abcd	2.86 bcdef	669 cdefg	132 defg	2.4 cdefg	15.8 cdef	11.3 cde
T. lanceolatum 18A	79 efghi	128 bcde	2.23 fghijkl	406 efghij	152 cde	2.9 cde	19.8 cde	14.1 cde
T. manisuroides 16A	79 efghi	115 bcde	2.65 defgh	560 defg	159 cde	3.6 bc	24.2 bc	17.2 bc
Tripsacum spp. 10A	79 efghi	134 abcd	1.69 klm	232 jk	428 b	0.8 gh	5.1 gh	3.6 gh
T. intermedium 2A	71 fghij	95 cdef	1.55l m	195 k	182cd	0.4 h	2.9 h	2.0 h
T. maizar 7B	67 ghijk	116 bcde	2.59 defgh	536 defg	65 hi	0.7 gh	4.5 gh	3.2 gh
T. peruvianum	61 hijk	154 abc	1.71 klm	233 jk	83 fghi	1.2 efgh	7.9 efgh	5.6 efg
T. dactyloides 3B	60 hijk	114 bcde	2.92 bcdef	679 cdef	31 i	0.6 gh	3.6 gh	2.62 gh
T. dactyloides,Hispidum	49 jkl	93 def	1.46 m	169 k	75 ghi	0.7 gh	4.8 gh	3.4 gh
T. intermedium 21A	44 kl	71 ef	2.34 efghij	438 efghij	149 cde	1.5 defg	10.3 defg	7.3 def
Tripsacum spp. 19A	31 l	61 f	1.96 ijklm	313 hijk	37 i	0.3 h	1.9 h	1.4 h

Different letters within columns indicate differences (p ˂ 0.01) among species, ecotypes, and varieties.

). Higher plant height (p < 0.01) was observed for T. australe and T. latifolium with 155 and 148 cm, respectively; leader stem height was observed for T. australe and T. latifolium with 188 and 200 cm, respectively, and similar among the rest of treatments with a height higher to 130 cm. The plant’s crown circumference was superior (p < 0.01) for T. latifolium (400 cm), similar between T. dactyloides 98B and Meridionale with 350 and 340 cm, respectively. Regarding CB T. latifolium and T. dactyloides 98B were superior with 1294 and 998 cm², respectively. For tiller number per crown Tripsacum spp. 11A was different (p < 0.01) with 551 tillers per plant crown. Similarly, variables associated with forage production showed statistical differences (p < 0.01) among Tripsacum plant material and T. latifolium with 8.3 kg DM plant⁻¹ and 55.2 tons DM ha⁻¹ and growth rates of 39.43 DM g plant⁻¹ day⁻¹.

4. Discussion

Plant genetic resources have been important basis as source of genetic diversity for forage species. Plant collection within the center of species origin represents the first important step toward plant improvement [20] and its evaluation promises important technical advancements. Mexico represents an important center of diversity for several important crops such as corn, avocado, squash, cocoa, tomato, etc.; however, few grass (Poaceae) tropical forage species have evolved there [21]. Tropical genera such as Hymenachne spp., Paspalum spp., Echynochloa spp., and Tripsacum represent native to Mexico grass valuable genera to study [22]. Independently of forage morphological traits T. latifolium manifested superiority (p < 0.01) for productive variables. Forage production was different (p < 0.01) ranging from 22 to 1405% higher when compared to the local T. dactyloides 3B ecotype. The local ecotype was superior in 22 y 47% in comparison to the less productive material T. intermedium 2A and Tripsacum spp. 19A, respectively. These results are informative on the wide variability for forage production. Forage production obtained within the present study were similar or even higher to those reported [11,16,17], for native Tripsacum spp. populations. On the other hand, the observed growth rate is similar to those reported for five native to western Mexico ecotypes [11]. Under grazing, forage production should be measured on plant competition conditions, applying technology for efficient harvesting, avoiding both self-shadowing (senescence) and harvesting too young plant regrowth, that may endanger the crop because of mismanagement [20]. Evaluating commercial diploid varieties (Pete, Iuka) in the central plateau of Mexico (2240 masl) in comparison with native to Mexico ecotypes, the superiority of polyploid native ecotypes was confirmed for dry matter production [23]. Then, the next step is to validate the valuable detected plant material under plant competition conditions in order to define the promising plant materials for its solid promotion among cattlemen.

5. Conclusions

Both morphology and productive traits are highly variable in concordance with the wide diversity of Tripsacum genus in Mexico. Highest forage production levels as well as growing rates were observed for T. latifolium. Twenty-two of the evaluated plant materials showed superior forage production performance (from 22 to 1.405%) in comparison to the local ecotype. Tripsacum agamic complex is an important forage resource and it must be promoted as important for rain-fed prairies establishment to achieve its productive potential under grazing conditions.