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López Benitez, A., F. Ramirez, S. Kuruvadi, and F. Borrego. 1993. Interspecific hybridization between Parthenium argentatum Gray and Parthenium lozanianum Bartlett. p. 347-348. In: J. Janick and J.E. Simon (eds.), New crops. Wiley, New York.

Interspecific Hybridization Between Parthenium argentatum Gray and Parthenium lozanianum Bartlett

A. López Benitez, F. Ramirez, S. Kuruvadi, and F. Borrego


  1. METHODOLOGY
  2. RESULTS AND DISCUSSION
  3. REFERENCES
  4. Table 1

The genus Parthenium has been classified into 16 different species (Rollins 1950) from which only guayule (P. argentatum) contains substantial amounts of good quality rubber. Interspecific hybridization in guayule as a means of introducing desirable traits, requires basic information on the breeding behavior of the interspecific hybrids with regard to fertility and type of inheritance of the traits studied. In F1 hybrids between P. argentatum and P. hispidum var. auriculatum, Hashemi et al. (1987), reported that meiotic behavior was irregular as indicated by a low pollen stainability and the limited number of viable BC1 seeds. In contrast, Estilai et al. (1985), showed that guayule and P. schottii are readily crossed and the F1 hybrids produced showed a partial fertility and high degree of chromosome pairing. The inheritance of rubber content and morphological characters in interspecific hybrids have been described by Naqvi et al. (1984), as due to multiple gene action. A similar type of gene action has also been described by Naqvi et al. (1987) for growth habit, morphological traits, rubber, and resin contents of hybrids between guayule and P. fruticosum. In this paper, we report the morphological characters, rubber content and molecular weight, and resin content for hybrids between guayule and P. lozanianum, and compare the hybrids to their progenitors.

METHODOLOGY

Seed of diploid guayule and P. lozanianum were grown in the greenhouse. Chromosome counts on P. lozanianum at meiosis indicated 2n = 108. Diploid guayule proved to be self-incompatible, and was utilized as the female without emasculation. Crosses were made in one direction transferring pollen from P. lozanianum directly to the stigmas of guayule. Seed of parental species and hybrids were collected when ripe, seeded separately in the greenhouse and allowed to grow for 20 months. Plants were then sampled for plant growth characteristics; and for rubber and resin analysis. Plant height, plant spread, leaf length, leaf width, and peduncle length were determined from 10 individual plants of each parent and F1 hybrids. Rubber and resin analysis were performed on the same 10 plants according to Holmes and Robbin (1974). Rubber quality as estimated by molecular weight was determined for both parents and F1 hybrids according to Campos Lopez and Angulo Sanchez (1975).

RESULTS AND DISCUSSION

Table 1 presents morphological data, rubber content, rubber molecular weight, and resin content of P. argentatum, P. lozanianum, and their interspecific F1 hybrids. Plant height and spread, and leaf shape, length and width were the most conspicuous morphological differences between P. argentatum and P. lozanianum. Average leaf length of P. argentatum and F1 hybrids was about 30% lower than P. lozanianum. Leaf widths of P. lozanianum were 30% of guayule and hybrids. Peduncle length of the hybrids was larger than either parent. Hybrids were easy to recognize because of the intermediate nature of many morphological and agronomic traits as compared to the two parental species. The intermediate nature of the morphological characteristics of interspecific F1 hybrids in the genus Parthenium has been pointed out by Naqvi et al. (1984, 1987) who suggested a polygenic type of gene action for these traits. Rubber content in guayule (6.82%) was about 12 times greater than P. lozanianum (0.56%) but F1 hybrids had an average of 4.6% which is about 67% of that in guayule. Although P. lozanianum did not improve the rubber percentage of the hybrids, the total rubber production could be improved if biomass increased as indicated by Tysdale (1950).

The small traces of rubber found in P. lozanianum showed higher molecular weight than guayule. This trait was found in the hybrids indicating a dominant type of gene action. Campos Lopez and Angulo Sanchez (1975) indicated that the rubber from either Hevea or guayule should have a molecular weight of at least 2 million to be considered of good quality. Our results suggest that P. lozanianum could be utilized to improve rubber quality of guayule.

REFERENCES


Table 1. Morphological traits and rubber content of P. argentatum, P. lozanianum and their F1 hybrids grown in the greenhouse for 20 months.

Mean±SD
Variable P. argentatum P. lozanianum F1 hybrid
Plant
Height (cm) 46.7±3.0 110.6±6.9 64.7±9.2
Width (cm) 42.0±3.1 84.5±5.2 47.0±10.7
Leaf
Length (cm) 6.0±0.8 8.3±3.0 5.6±0.4
Width (cm) 1.7±0.3 5.4±2.9 1.7±0.2
Inflorescence
Peduncle length (cm) 12.2±1.7 10.6±2.2 17.6±4.5
Head width (cm) 5.3±0.3 5.1±0.3 5.3±0.4
Rubber
Content (%) 6.8±0.7 0.6±0.1 4.6±0.7
M.W. 1.95x106 2.27x106 2.21x106
Resin (%) 8.3±0.9 5.3±0.9 7.8±1.2


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