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a D'Arrigo Bros., Salinas, CA
b Plant Genome Mapping Lab., Univ. of Georgia, Athens, GA
c USDA-ARS, National Arid Land Plant Genetic Resource Unit (NALPGRU), Parlier, CA
* Corresponding author (mjenderek{at}fresno.ars.usda.gov)
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONHISTORY AND CURRENT USEGENETICS OF FORAGE VARIETIESCONCLUSIONSREFERENCES |
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Abbreviations: CAM, crassulacean acid metabolism
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONHISTORY AND CURRENT USEGENETICS OF FORAGE VARIETIESCONCLUSIONSREFERENCES |
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HISTORY AND CURRENT USE |
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TOPABSTRACTINTRODUCTIONHISTORY AND CURRENT USEGENETICS OF FORAGE VARIETIESCONCLUSIONSREFERENCES |
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Flores and Aranda (1997) reported that 18 Opuntia species in Mexico were used as forage on the more than 3 million ha of rangeland in northern Mexico, and that 150000 ha of cactus were planted by ranchers and small producers with government support. Lopez et al. (1996) reported the use of 25 species and 12 varieties of Opuntia for forage in the state of Coahuila. Flores and Aranda (1997) reported that due to the extended drought from 1993 to 1996, more than 650000 cattle died. However, ranchers with cactus did not suffer as great a loss as those whose cactus ran out. Furthermore, reproduction rates and production levels were greater for animals that received cactus supplements.
In Brazil (Domingues, 1963, Dos Santos and de Albuquerque, 2001) more than 400000 ha of cactus are used for forage, and in northern Africa (Tunisa, Algeria, and Morocco) (Monjauze and LeHouerou, 1965, Nefzaoui and Salem, 2001) from 700000 to 1 million ha have been estimated to be used for livestock feed. Extensive spiny Opuntia stands in Tigray, Ethiopia have also been used for livestock food after the spines have been removed (Brutsch, 1997).
Major Opuntia germplasm introductions have been made to the Central Institute for Arid Horticulture, Bikaner, India (Singh and Singh, 2003) and to the Central Soil Salinity Research Institute in Karnal, India (Singh, 2003). They are being evaluated there for forage, fruit and vegetable uses in India's extensive arid lands.
In 2002, the USDA established an Opuntia germplasm collection with 203 accessions of 17 species at the National Arid Land Plant Genetic Resource Unit (NALPGRU) in Parlier, California. It included accessions collected and evaluated over an 18 yr period by the senior author as well as many other accessions. This collection included spineless accessions used as forage in South Africa and Brazil, spiny varieties used by Texas ranchers and spineless accessions that have greater freeze hardiness than Opuntia ficus-indica varieties. This paper reviews data on environmental adaptability and nutritional characteristics of Opuntia major forage clones. We have focused on accessions that have been reported as being important for forage internationally, or for which our 18 yr of evaluations suggest important forage characteristics. Some management techniques to fully utilize their forage potential are also described.
Characteristics of Major Forage Types
Data for the major forage types (Table 1) are confounded with years, investigators, and sites and thus are not directly comparable. However, it is possible to arrive at some general conclusions. The USDA germplasm contains the most important forage types in the USA and internationally. These include 5 wild Opuntia engelmannii var. lindheimeri selections (Texas A&M University Kingsville (TAMUK) #1503–1507) made by Texas rancher W.A. Maltsberger that vary considerably in spininess, 3 major forage types grown on several hundred thousand hectares of forage plantations in Brazil known as ‘Palma doce’/‘P. miuda’ (O. cochinilifera; TAMUK #1269), ‘Palma redonda’ (O. ficus-indica; TAMUK#1270) and ‘Palma gigante’ (O. ficus-indica; TAMUK # 1271), and 3 O. robusta selections (O. robusta var. chico; TAMUK #1240; O. robusta var. Monterrey, TAMUK #1241; and O. robusta var. robusta, TAMUK #1242) made by Burbank (De Kock, 1980) and used for forage in South Africa. The robusta types are preferred for forage as they are more resistant to the major insect pest cochineal (Dactylopius coccus) than ficus-indica and cochinilifera species (De Kock, 2001). The USDA collection in Parlier, CA also includes clones of the 33 seedlings (TAMUK# 1413–1441, PARL351–378 respectively) out of 300000 seedlings planted that survived a minus 16°C freeze in Saltillo, Mexico without damage (Martinez, 1968). However since this observation has not verified, these accessions require further testing.
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Cold Hardiness
Various publications have reported the cold tolerance of these clones after freezing weather in 1984/1985, 1989/1990, 1990/1991 and 1996/1997(Gregory et al., 1993; Nobel, 1990, Russell and Felker, 1987: Wang et al., 1997). Regarding adaptation to specific climatic zones, we believe recommendation for a specific USDA cold hardiness zone (www.usna.usda.gov/Hardzone/hzm-sm1.html; verified 11 July 2006) is more appropriate than listing the absolute minimum temperatures, since duration of below freezing temperature and prior conditioning are critical to survival and very difficult to quantify. From 1983 to 1998, more than 130 Opuntia clones were evaluated in Kingsville, Texas (USDA cold hardiness zone 8) for a variety of purposes, but not all were included in the same replicated trials. During this period severe freezes occurred in 1984/1985, 1989/1990, 1990/1991 and 1996/1997 in which the number of hours below freezing ranged from 40 to 129 and the absolute minimum temperatures ranged from –7°C to –12°C (Wang et al., 1997). In the first freeze, the South African O. robusta clones 1240, 1241, and 1242 had only 12 to 13% freeze damage, but the Brazilian forage clones Palma miuda (O. cochinilifera 1269) and Palma gigante (O. ficus-indica 1270) suffered 100% frost damage (Russell and Felker, 1987). In the 1984/1985 freeze the other O. ficus-indica and similar species also had 99 to 100% frost damage. In the worst freeze, December 1989 (62 consecutive hours below freezing, 16 h below –6.7°C, and an absolute minimum of –12°C), all O. ficus-indica, O. streptacantha, O. cochinilifera, and O. robusta type clones died and had no recovery from the roots. The cladodes on Opuntia sp clone 1233 changed from an erect to a drooping form for about 3 d but later recovered with no apparent damage. In contrast 1233 was killed by freezing weather in 1997 at the Texas A&M Research Station in San Angelo, Texas (cold hardiness zone 7) when O. ellisiana was not damaged (D. Ueckert, personal communication, 1998). The 1989 freeze had no apparent effect on any O. ellisiana cladodes (Wang et al., 1997; Parish and Felker, 1997). Later in the winter of 1989/1990 an undamaged ornamental plant of O. ellisiana (clone 1364) was located in San Angelo, Texas which is 450 km north of Kingsville in USDA cold hardiness zone 7. Since then we have frequently observed undamaged O. ellisiana clones in Austin, Alpine, and El Paso, TX. Cactus collector David Eppele in Deming, NM reports that O. ellisiana never freezes at that location which is in USDA cold hardiness zone 7. In Mendoza, Argentina, O. ellisiana was found to be the only spineless variety that withstood –16°C in December 2000. (Guevara et al., 2003). The 1989 freeze had no effect on the wild spiny O. engelmannii var. lindheimeri clones in Kingsville, TX.
To summarize with respect to cold hardiness, Opuntia ficus-indica clone 1270 is marginally acceptable in cold hardiness zone 8 in Kingsville, TX where it froze to the ground twice, between 1984 and 1998. The clone would be well adaptable to the more tropical cold hardiness zone 9, such as the Texas Rio Grande Valley where grapefruits are grown commercially. Clone 1233 "wilted" during the most extreme freezing period from 1983 to 1998 in Kingsville, TX, but it recovered without any damage. The clone is adaptable to cold hardiness zone 8. Since it froze in San Angelo in cold hardiness zone 7, it cannot be recommended for this zone. As O. ellisiana 1364 was not damaged by the worst freeze in San Angelo, TX over 15 yr it can be recommended for cold hardiness zone 7. The spiny O. engelmannii var. lindheimeri was not damaged by any of these freezes in Kingsville or San Angelo and could be recommended for either USDA zone 7 or 8.
Possible Areas of Adaptability
The adaptability of O. ellisiana to USDA cold hardiness zone 7 has important ramifications internationally. In North America, USDA cold hardiness zone 7 extends from the high elevation Chihuahua Desert of Mexico in the south, westward to southern Nevada and eastward through southern New Mexico, northern Texas, the states along the Gulf of Mexico and as far north as North Carolina www.usna.usda.gov/Hardzone/hzm-sm1.html; verified 11 July 2006). This species has recently been found to be the only spineless selection capable of withstanding winter temperatures in the Mendoza plains of Argentina (Guevara et al., 2003). Tunisian researchers have obtained clones for testing in the foothills of the Atlas Mountains. Climates with USDA zone 7 are also located in the arid regions of southern Asia such as the foothills of the Himalayas in India and Pakistan.
Spine Characters
While spiny varieties are readily consumed by livestock after the spines are singed off, usually with portable burners, and while palatable spiny varieties exist, it is our experience that the majority of growers prefer spineless varieties. This is even though significant effort has to be invested in fencing to eliminate access from wildlife and domestic stock because of the high palatability of the spineless varieties. Our experience with solar powered fencing of spineless Opuntias in Argentina was very favorable because of the much lower cost of fencing than burning or chopping the cactus. Furthermore the solar fence greatly reduced annual maintenance labor requirements for solid brush or hybrid brush/wire fences.
All of the spineless species possess nearly microscopic (150 µm diameter) hairlike barbed spines known as glochids. O. ellisiana and O. robusta have fewer glochids than the others. Of the clones in Table 1, only the wild Opuntia engelmannii var. lindheimeri has spines. W.A. Maltsberger used the clones of Opuntia engelmannii var. lindheimeri to establish a 120 ha plantation for cattle feed. To prepare the cactus for feeding, the spines were either burnt off with a propane torch, or burnt and chopped (Model 12, John Deere, Moline, IL) with an older style forage chopper that had a lower chopping speed than current models of forage choppers. While not much difference existed for spine length among the Maltsberger clones, the percentage of areoles with spines varied greatly (from 3.3–47.7% Chavez-Ramirez et al., 1997). A cross made between a spineless female parent O. ficus-indica 1281 and a spiny male O. engelmannii var. lindheimeri 1250 resulted in a considerable number of apomicts, but also progeny with small spineless cladodes the same size as the male parent. (Felker and Paterson, unpub obs). Currently, these progeny are being evaluated in various cold hardiness zones of the Argentina central arid zone at 33° S latitude by Juan Carlos Guevara of Instituto Argentino de Investigaciones de las Zonas Áridas (IADIZA).
The genetic control of spine production appears to be relatively simple. In hybridization studies among octaploid Opuntia with "commercial fruit," a cross between a spineless female and a spiny male resulted in 57% of spineless progenies (n = 84). In a cross between a spiny female and a spineless male, 63% of the progeny (n = 84) were spineless, and when both parents were without spines, 92% of the progeny (n = 155) were spineless (Felker, unpublished data, 2003). Collectively, these data suggest that spinelessness is relatively simply inherited. The recovery of spiny genotypes from spineless parents suggests that this sampling of parental genotypes each contained alleles for both spinelessness and spininess. Thus it should be possible to obtain spineless individuals if the parents yield fertile progeny and if one of the parents were spineless.
Fruit Quality
Inglese et al. (1995) and Felker et al. (2005) have suggested that the characteristics for internationally most desired fruit quality in Opuntia are: fruit size > 120 g, pulp percentage > 55%, Brix > 13%, pulp firmness > 1 kg, mature yield > 20 000 kg ha–1, post harvest shelf life at 2°C > 4 wk, and seediness < 3.5 g seeds per 100 g pulp. None of the clones in Table 1 meet all of these criteria. The fruit of the wild-types, clone 1233 and O. ellisiana, are only a fourth the minimum size for commercial varieties, and the "robusta" types have sub-standard Brix. While the Brazilian accessions 1270 and 1271 have fruits large enough to be used for human consumption, their Brix (12%) is generally below that found in commercially acceptable varieties. In spite of the low values of fruit quality for human use, the fruits of all these varieties are attractive to wildlife and domestic stock (Chavez-Ramirez et al., 1997).
Nutritional Value
The nutritional values for Opuntia cladodes arises from disparate papers on use of cactus by wildlife (Everitt and Gonzalez, 1981; Meyer and Brown, 1985), human food uses of the tender resprouts known as nopalitos (Retamal et al., 1987, Rodriguez-Felix and Cantwell, 1988), fertility studies to enhance fruit production for human food use (Karim et al., 1998, Nerd et al., 1993, Nobel, 1983), and a few papers on domestic livestock needs (Gregory and Felker, 1992, Shoop et al., 1977, Woodward et al., 1915).
In normal forage contexts, the high water content would be a serious disadvantage due to the high cost of transporting such forage. However, during droughts in arid regions, the high moisture content of cactus is a valuable asset because it greatly reduces animal drinking water requirements. Using Texas rancher W.A. Maltsberger's (1996) guidelines of 40 kg of Opuntia as a daily ration for an adult cow, and a 90% moisture content, cactus would contribute 36 L of water per day toward the animal's drinking requirements. As watering points in arid regions are often widely scattered, cactus helps to fulfill critical needs.
While cactus as normally consumed in unfertilized range situations is low in protein, i.e., about 5 to 6% (Everitt and Gonzalez, 1981, Meyer and Brown, 1985), with N fertilization these levels can be increased to the 10% level that is normally felt to be necessary for a lactating beef cow (Gonzalez, 1989). The highest crude protein values of 15%, reported by Nobel (1983) for fertilized fruit plantations in California, are well above the requirements for domestic livestock. The in vitro and in vivo digestibility measurements confirm the high digestibility of protein, dry matter, and organic matter and are on par with the better grass type forages (Woodward et al., 1915; Guevara et al., 2003). This high digestibility also leads to a relatively high energy content of 2.6 Mcal kg–1(Shoop et al., 1977; Retamal et al., 1987). The mineral composition is very low in Na, low in P, moderate in Mg, but high in both K and Ca (Retamal et al., 1987; Karim et al., 1998; Galizzi et al., 2004). This high level of calcium presumably would be of benefit to lactating ruminants during drought periods. For example, one kg fresh weight of cactus at 90% water contains 3.1 and 1.1 times as much calcium and potassium respectively as 1 L of goat milk (www.saanendoah.com/compare.html; verified 5 July 2006). The vitamin C levels are moderate with respect to other forages (Rodriguez-Felix and Cantwell, 1988). While the carotenoid concentrations are not outstanding with respect to other forages, in drought periods when all other herbaceous forages are brown, cactus often provides the only source of vitamin A precursors (Rodriguez-Felix and Cantwell, 1988). A protein and mineral supplement has been developed by W. A. Maltsberger to correct for mineral deficiencies in the livers of cattle that have been principally fed with cactus for up to a1 yr period (Felker, 1995).
The protein concentration in Opuntia is quite sensitive to nutrient supply. Gonzalez (1989) conducted a fertilizer trial with N and P fertilizers on yield and tissue concentration of the Texas spiny wild O. engelmannii var. lindheimeri and found that the crude protein increased from 4.5% for the zero fertility treatment to 10.5% protein for the 224 kg N and 112 kg P per hectare treatment. Since the protein requirements for a non-lactating and lactating cow are 6 and 9.25%, respectively, the fertilizer raised the protein level above the requirements for a lactating cow. It is also possible to increase the protein content of Opuntia via symbiotic relationships with Azospirillum (Rao and Venkateswarlu, 1982). Caballero-Mellado (1990) and Mascarua-Esparza et al. (1988) have shown that Azospirillum resulted in a 34% increase in Opuntia dry weight and a 63% increase in N content of the roots. They did not measure the influence of Azospirillum on the N content of the cladodes.
Productivity
The voluminous works of Nobel (1991, and 1994) have shown the high productivity of Opuntia and have confirmed the high water use efficiency in numerous gas exchange studies. However, there were only 2 replicated trials in the USA which included border rows and direct harvest to measure productivity. One trial used the only spineless cold hardy variety O. ellisiana to avoid potential damage from freezing weather (Han and Felker, 1997), and one trial measured the biomass productivity of the spiny Texas native O. engelmannii var. lindheimeri as a function of N and P fertilizer treatments (Gonzalez, 1989). The mean dry matter biomass productivity of the wild O. engelmannii var. lindheimeri variety in a zone with 430 mm annual rainfall was 52 Mg/ha after 4 yr.
In the trial with the slowest growing but most cold hardy of the spineless cacti, the absolute productivity the first 2 yr was low (1.8 and 4.9 Mg/ha dry matter) but after the plants reached a leaf area index of 2.0, the productivity increased to 14.2 and 17.7 Mg/ha dry matter in years 3 and 4. A water balance study that captured runoff, estimated soil evaporation with microlysimeters and measured drainage with neutron probes reported that the 17.7 Mg/ha productivity was obtained with 662 mm rainfall and 285 mm water transpired for a transpiration water use efficiency of 162 kg water/kg dry matter (Han and Felker, 1997). This is the highest water use efficiency we are aware of that is based on field dry matter accumulation. The stored water in the plants was 170 000 kg/ha which constituted a significant source of water for animals in the dry season. While O. ellisiana (Fig. 1 ) rarely produces more than 6 pads from the planted cladode in the first year, a large (50 cm long) cladode of O. sp. clone 1233 produced 115 cladodes the first year (Fig. 2 ) and we believe this species will prove to be much more productive than O. ellisiana, although 1233 is not adapted to USDA zone 7.
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GENETICS OF FORAGE VARIETIES |
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TOPABSTRACTINTRODUCTIONHISTORY AND CURRENT USEGENETICS OF FORAGE VARIETIESCONCLUSIONSREFERENCES |
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Some of the segregants in the O. ficus-indica x O. engelmanniii var. lindheimeri cross appear to have many of the characteristics of the cold hardy spiny parent (small fruit and bluish cladodes) but without spines. We are hopeful that these progeny will possess increased cold tolerance over the spineless O. ficus-indica and possibly the other spineless Opuntia types. Even if these segregants do not have greater frost hardiness than the currently available spineless O. sp. 1233 and O. ellisiana, at least a genetic route is now available to produce cold hardy spineless types. Possibly additional backcrossing to the cold hardy O. engelmannii var. lindheimeri parent may lead to both increased biomass production and increased cold hardiness of spineless individuals.
While all of the bagged, non-manipulated (selfed) flowers of the 1233 clone developed into fruits, these fruits abscised, indicating that this clone may be sterile (Wang et al., 1996). As spiny and spineless seedlings emerged from the feces of wildlife that had eaten the fruit of spineless types in South Africa and later spread over vast areas as a weed, sterility in forage types would be a significant advantage in introduction to new areas.
RAPD data comparing several O. ficus-indica types, an O. hyptiacantha fruit type (1287), O. ellisiana, O. sp. 1233, and the vegetable (nopalito) producing clone O. cochinilifera 1308 indicated that one O. ficus-indica clone 1281 was more closely related to the O. hyptiacantha clone than the other O. ficus indica clones (Wang et al., 1998). As the only major morphological difference between the O. ficus-indica clone and the O. hyptiacantha clone was the presence of spines on O. hyptiacantha, doubt was raised on the utility of spine characters in the assignment of species designation.
Sources of the Genetic Materials Outside North America
In addition to the USDA NPGS germplasm base, some of these promising clones (1270, 1233, and 1364) are available (as unrooted cladodes weighing about 1 kg each) from Dr. Ali Nefzaoui at the Institut National de la Recherché Agronomique de Tunisie, rue Hedi Karray, Ariana 2049, Tunisia, from Dr. Gurbachan Singh, Head, Central Soil Salinity Research Institute, Karnal, India, Dr. R.S. Singh, Central Institute for Arid Horticulture, Bikaner 334006, India, and from Juan Carlos Guevara, Instituto Argentino de Investigaciones de las Zonas Áridas (IADIZA), CC 507 (5500), Mendoza, Argentina.
Propagation and Planting Methods
Opuntia species are clonally propagated by placing an unrooted cladode (technically, a stem segment) in the soil which then roots and establishes a new plant. The major problem in establishing new plantations is loss of plants to rot. Thus treatment of the planting stock is the opposite of what is recommended for seedlings and shrubs. Typically 1 yr old cladodes are harvested, the cut ends dipped in a lime/copper fungicide mixture and placed vertically with the cut ends up for several weeks. This allows the cut ends to "heal over" preventing infection. The cladodes are planted in dry soil and not watered until resprouts appear or for several weeks. The growth of young cladodes is susceptible to competition from grasses and forbs. With the exception of picloram, Opuntias are resistant to virtually all herbicides including hexazinone, bromacil, diuron, etc. (Felker and Russell, 1987). One year old cladodes with a thick cuticle are also not damaged by glyphosate sprays. In Argentina for 5 yr we have used a combination of diuron at 4 kg a.i. per hectare per year, and glyphosate without cultivation. Snyman (2005) has found that the roots of 1 yr old cladodes extend horizontally to 1.5 m the first year, with 50% of them being in the top 5 cm, and thus no-till cultivation with herbicides is an interesting option. For maximum production for "cut and carry" systems, close spacing of about 1.2 x 1.2 m is useful, but where direct grazing is desirable, in-row spacing ranging from 1.0 to 1.5 m, and between row spacing of 3 to 5 m is desirable. For O. ellisiana with slow height growth, grazing could not begin before about the third year, while for the faster growing clones 1233 and 1270, under favorable conditions, grazing might begin about 2 yr after establishment. Grazing needs to be controlled so that only one and 2 yr old cladodes are consumed with the "woody" base not being damaged. Subsequent grazing is possible at 1 to 2 yr intervals depending on the rainfall and weed control.
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CONCLUSIONS |
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TOPABSTRACTINTRODUCTIONHISTORY AND CURRENT USEGENETICS OF FORAGE VARIETIESCONCLUSIONSREFERENCES |
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ACKNOWLEDGMENTS |
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Received for publication March 24, 2006.
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TOPABSTRACTINTRODUCTIONHISTORY AND CURRENT USEGENETICS OF FORAGE VARIETIESCONCLUSIONSREFERENCES |
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