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Volume 84, 1956-57
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Agropyron × wallii a Natural Hybrid in New Zealand

H. E. Connor
Botany Division
Department of Scientific and Industrial Research Christchurch.

[Received by the Editor, October 4, 1956.]

Abstract

Agropyron × wallii (2n = 35) a natural hybrid between A. enysii (2n = 28) and A. scabrum (2n = 42) is formally described. Distribution, variation in floret characters, sterility, and possible future of the hybrid are discussed.

Introduction

Plants apparently morphologically intermediate between Agropyron enysii and A. scabrum were found in significant numbers at Porters Pass, inland Canterbury, in one area where the two species A. enysii and A. scabrum are found in extensive populations. The purpose of this paper is to describe and name the intermediate plants, now identified as hybrids, to record their sterility and to consider their possible future.

Formal Description
Agropyron × wallii hybr. nov.

Planta inter A. enysii T. Kirk et A. scabrum (R. Br.) Beauv. Gramen perenne, laxum, glaucum, stoloniferum. Culmi circa 1 m longi, ascendentes vel nutantes, fistulati. Laminae ad 2 mm latae, villosae; vaginae inferiores villosae, superiores glabrae. Ligulae breves, truncatae; auriculae villosae, culmos innovationesque amplectentes. Spicae (3)–5–(7) spiculis, (50)–85–(120) mm longae. Spiculae (2)–5–(7) floribus, appressae, cum aristis 25–40 mm longae, internodis longiores. Glumae subaequales aristiferae, 3–5–nerves. Lemma lanceolatum, dorso rotundatum, apice carinatum et scabrum, basi transverse sulcatum, (7.5)–10–(11.5) mm longum, apice integrum vel 1–2–dentibus lateralibus, 5-nerve; arista (10)–16–(23) mm longa, scabra, purpurascens sicut lemmatis apex. Palea lemma vix aequans, carinis scabra. Callus barbatus, obtusus, 0.5 mm longus. Rhachilla (1.5)–2.0–(2.5) mm longa, setulosa. Antherae (1.5)–2.2–(3.0) mm longae, luteae vel purpurascentes vel purpureae.

Perennial, stoloniferous. Culms lax, ascending to drooping, leafy, hollow, smooth, glaucous, about 1 m long. Branching intra- and extra-vaginal. Leaves up to 2 mm wide, blue-green, glaucous, villous; sheaths of basal leaves villous of culm leaves glabrous. Ligule short, truncate; collar flat; auricles clasping, villous. Spike of (3)–5–(7) spikelets, (50)–85–(120) mm long. Spikelets of (2)–5–(7) florets, appressed, straight, 25–40 mm long including awns, longer than the internodes. Glumes subequal, awn-tipped, 3–5-nerved, longer glume about ⅔ up the lemmas above. Lemma lanceolate, rounded on back, sharply indented at base, keeled and scabrid at apex (7.5)–10–(11.5) mm long, apex entire or with 1–2 lateral teeth, 5-nerved; awn (10)–16–(23) mm long; apex of lemma and the awn frequently purple. Palea sharply keeled, scabrid on the keels, almost as long as the lemma. Callus bearded, obtuse, 0.5 mm long. Rachilla (1.5)–2 0–(2.5) mm long, finely setulose. Anthers yellow through to purple (1.5)–2.2–(3.0) mm long.

Chromosome Number. 2n = 35 (determined by Dr. J. B. Hair).

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Distribution. Porters Pass, inland Canterbury, 2,700ft to 3,000ft.

Holotype. Porters Pass, Canterbury, 3,000ft, coll. H. E. Connor, 5/1/56, in Herb. Botany Division, No. 91921.

Paratypes. Porters Pass, H. E. C., Herbarium Botany Division Nos. 82737, 82738, 82739, 82740, 91920, 91922, 91923, 91925, 91926, 91927, 91928, 91929, 91930, 91931, 91932.

This plant is named in honour of Arnold Wall, Emeritus Professor of English, Canterbury University College, Christchurch, a well known botanist, and an extensive collector of grasses.

Some of the chief morphological features for A. enysii, A. scabrum, and A. × wallii are listed in Table 1, Group Tawera of A. scabrum (Connor, 1954) is used for comparison as it is one of the parents of the hybrid. It will be seen that A. × walli is, for the greater part, intermediate between the parent species.

Hybrids were found at five separate and distinct localities on the eastern side of the Torlesse Range, all in the vicinity of Porters Pass and always near to plants of A. enysii. A. enysii is found in seepages, damp places and on stream banks, while A. scabrum is found chiefly in dry sites, but also in or near the sites for A. enysii.

Table I.—Morphological features for A. enysii, A. scabrum and A. × wallii.
Character A. enysii A. × wallii A scabrum Group Tawera
Habit Stoloniferous perennial Stoloniferous perennial Caespitose perennial
Culms Decumbent to nodding. Decumbent to nodding Erect to erect-ascending
Leaf colour Bronze Blue-green Blue-green
Collar Flat or lopsided Flat Flat
Auricles Small, sometimes clasping, glabrous Long, clasping, villous Long, clasping, villous
Spikelets/spike Up to 18, appressed, close 3–6 appressed, ± distant 3–6 appressed, distant
Florets/spikelet 2–4 2–7 5–12
Apex of lemma 2-toothed Entire or 1–2-toothed Entire, very rarely 1-toothed
Base of lemma Indented Indented Not indented
Callus Short, blunt, with very short barbs Long, obtuse, with long barbs Long, obtuse, with long barbs
Lemma length* 6.0–9.5 mm 7.5–11.5 mm 7–12.0 mm
Palea length 6.5–9.0 mm 7.0–11.5 mm 7–12.0 mm
Awn length* 1.0–3.5 mm 10–23 mm 30–53 mm
Rachilla length 1 −2 mm 1.5–2.5 mm 2–3 mm
Anther length 2 −2.5 mm 1.5–3.0 mm 3–5 mm
Anther colour Yellow Yellow-purple Yellow-purple
Chromosome number 2n = 28 2n = 35 2n = 42

[Footnote] * Lemma length and awn length are difficult to determine accurately as the main nerve of the lemma is continuous with the awn, and there is often no definite point where the lemma ends and the awn begins. In A. enysii the apex of the lemma is 2-toothed and the awn definitely begins at the base of the sinus. When the lemma is entire, as in most florets of A. scabrum and some florets of A. × wallii the convention has been adopted of measuring as awn that which projects above the level of the top of the palea, leaving lemma length equal to palea length.

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The hybrid has not been found out in the open dry areas where A. scabrum is common. To judge from the distribution of the hybrids it is, I think, a reasonable assumption that A. enysii is the female parent in the cross.

The hybrid is stoloniferous and an individual plant once established can form a colony in some cases up to 3 feet in diameter. Such a colony looks like many individual plants, and probably develops into a clone of many members.

Variation In Floret Characters

From the 16 specimens collected, 30 penultimate spikelets were removed. On the three lowest florets in each spikelet lengths of floret, palea, lemma, awn, and rachilla were measured: results are presented in Table 2, where the specimens are grouped according to the separate localities from which they were collected. Of the 92 florets examined 39 had lemmas toothed at the apex, and all showed the indented base of the lemma which is a prominent character in A. enysii. The range for anther length was 1.5–3.0 mm, with a mean of 2.2 ± 0.05 and a standard deviation of 0.34. Another colour varied from yellow, to purple flecking on a yellow background, to total purple.

Table II.—Variation in Floret Measurements in A. × wallii. All measuremnts in mm.
Herbarium Specimens Total Length Lemma Length Awn Length Palea Length Rachilla Length No.
82737*, 82738,
82739, 82740, 25.64 ± 0.32 9.52 ± 0.12 16.12 ± 0.29 9.06 ± 0.13 2.01 ± 0.03
91920, 91921, 46
91922 s.d ‡ 2.19 sd 0.81 sd 1.99 s.d. 0.87 sd. 0.2
91923, 91925, 26 82 ± 0.32 10.74 ± 0.1 16.15 ± 0.35 10 76 ± 0.1 2 12 ± 0.05
91926, 91927 s.d 1.34 sd 0.45 sd. 1.45 sd 0.42 sd. 0.2 17
91928, 91929 22.82 ± 0.37 10.26 ± 01 12 56 ± 0.35 10.26 ± 0.1 1.97 ± 0.03
91930 s.d. 1.52 s.d 0.43 sd. 1.43 s.d. 0.43 s.d. 0.12 17
91931 29.83 ± 1.35 10.25 ± 0.42 19.58 ± 1.01 1033 ± 0.4 1.83 ± 0.1
s.d 3.31 s.d. 1.04 sd. 2.48 s.d 0.98 s.d. 0.26 6
91932 28.50 ± 0.67 10.58 ± 0.3 17.92 ± 0.54 10.67 ± 0.3 2.0 −
sd 1.64 s.d. 0.74 s.d. 1.32 sd 0.75 6
All Samples 25 81 ± 0.31 10.0 ± 0.09 16.0 ± 0.13 9.78 ± 0.11 2.01 ± 0.02 92
sd 2.97 sd 0.9 sd 1.3 s.d. 1.07 s.d. 0.19
Range 20–34 7.5–11.5 100–23.0 7.0–11 5 1.5–2.5

Sterility and Future of A. × wallii

When observed on January 12, 1955, the hybrids were at anthesis, with anthers and stigmas exserted. It was not noted whether or not the anthers had dehisced. A fortnight later, January 25, some plants were still flowering, and on the majority the spikes had reached the ripened colour. On January 5, 1956, there were some plants at anthesis, but for the greater part flowering was over. Both A. enysii and A. scabrum had set seed, and the seed was at either the “milk” or the “dough” stage. On both visits in 1955 pollen samples were taken from several plants, stained, and mounted. Of the 969 grains examined none was filled, and all were classified as sterile. No seed was set on any of the hybrids examined. That this hybrid with 2n = 35 should be sterile is not unexpected.

It seems likely that A. × wallii will exist only in the F1; backcrossing to either parent is not held to be likely, and gene exchange in the present state of A. × wallii to be impossible. The hybrid could possibly double its chromosome number and arrive at a state of chromosome balance. Should amphiploidy occur, the then new

[Footnote] *Serial numbers of specimens in Botany Division, D. S.I. R. Herbarium.

[Footnote] ‡ s d = Standard deviation of sample.

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species would resemble in many characters the F1. Although apomixis has been recorded in A. scabrum (Hair, 1956), it does not occur in A. scabrum Group Tawera. Any advantages that may have been derived from effective genes for apomixis are denied A. × wallii. At present A. × wallii seems of little evolutionary consequence in the flora of New Zealand.

The final proof that it is a hybrid would be its synthesis. Even without such experimental evidence there seems little doubt about its parentage and hybrid status for the following reasons:

  • i. A. enysii and A. scabrum are the only species of the genus found to date where the hybrids occur, despite purposeful searching in two successive seasons.

  • ii. The plants are for the greater part morphologically intermediate between A. enysii and A. scabrum.

  • iii. The plants totally failed to produce viable pollen in one season, and seed-set failed in two seasons.

  • iv. The chromosome number of A. enysii is 2n = 28 (tetraploid) and that for A. scabrum 2n = 42 (hexaploid); the hybrid is pentaploid, 2n = 35.

Acknowledgments

I wish to express my thanks to J. B. Hair, of the Botany Division, for making a chromosome count on the hybrid, and for permission to publish it, and to R. M. Williams, Applied Mathematics Laboratory, for arranging the analyses of the floret measurements.

References

Connor, H. E., 1954. Studies in New Zealand Agropyron. N.Z.J. Sci. Tech. B 34: 315–43.

Hair, J. B., 1956. Subsexual Reproduction in Agropyron. Heredity 10: 129–60.

H. E. Connor

,
M.Sc., Botany Division,
Department of Scientific and Industrial Research,
P.O. Box 2015, Christchurch.

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