The
              Report

No. 70: Lathyrus – a new grain legume


The full report
This is a summary of a published RIRDCreport titled Lathyrus - A New Grain Legume(Pub no. 99/150) by Philip Cocks, Universityof WA. Phone: (08) 9380 2555, Fax: (08) 9380 1108, 
Email: <pcocks@agric.uwa.edu.au>.The report is available in hardcopy or downloadable from this site (under New Plant Products ).
 
 

An early maturing, high yielding variety of the grain legume Lathyrus cicera, known as Chalus, has been developed through research funded by the Rural Industries Research and Development Corporation (RIRDC).

The new germplasm has a potential large domestic market as a high protein feed and could provide human food exports of up to 500,000 tonnes annually. It has also good potential as a food source for grazing stock.

Research into Lathyrus sativus (grasspea) and Lathyrus cicera (commonly known as chickling) was carried out by Philip Cocks, Kadambot Siddique and Colin Hanbury, of the Faculty of Agriculture at the University of Western Australia.

It was aimed at improving these valuable arid condition pulse crops which contain a dangerous water soluble neurotoxin called called called ß-N-oxalyl-L-a- ß -diaminopropionic
acid (ODAP).

In humans, the ODAP neurotoxin can cause a permanent paralysis of the lower limbs, (referred to as lathyrism), if consumed as a major part of the diet over a prolonged period of time.

But the newly developed Chalus has low ODAP neurotoxin concentrations under most conditions.

The Study

The research began in Western Australia in 1993 when 17 varieties of grasspea were tested, showing a good adaptation to medium 400mm annual rainfall environments. The project continued with further studies of grasspea and chickling vetch.

Evaluation of various types of both varieties subsequently were carried out.

Much of the preliminary research was undertaken by the International Centre for Agricultural Research in the Dry Areas (ICARDA) and special assistance was provided by its forage plant breeder, Dr Ali Abd El Moneim.

ICARDA also supplied the Australian team with germplasm.

Because of grasspea's and chickling's resistance to drought, together with their ability to grow on the fi ne textured, neutral to alkaline soils, they seemed attractive alternatives to the narrow-leafed lupin (Lupinus angustifolius) for large parts of the southern and south-western Australian cereal belt.

The grasspea showed particular promise to grow well on the fi ne-textured, neutral to alkaline soils occupying some 6.5 million hectares of this cereal belt where narrow-leafed lupin was unsuitable.

Another major advantage grasspea has over current grain legume varieties is that it is very resistant to both abiotic and biotic stress. For instance, it does not suffer from black spot and can, therefore, grow in areas where farmers are no longer able to grow the field pea. It is also resistant to foliar diseases, broomrape (Orobanche crenata) parasitism and does not suffer greatly from insect attack.

The fi rst part of the project aimed to investigate environmental causes of high neurotoxin concentration in seeds. It formed part of the thesis of Mr Steven Herwig.

Water stress effects on concentration of the ODAP neurotoxin also were investigated.

The Results

Before Chalus could be developed, the researchers had to look at ways of reducing the neurotoxins in the plant varieties. The timing of sowing was found to have a marked infl uence on neurotoxin concentration, with levels dropping as the season progressed.

Signifi cant environmental effects were also noted with three different Lathyrus species grown at three different sites in the West Australian wheatbelt.

The greatest influence on neurotoxin levels, however, resulted from water stress. While such a stress during pre-anthesis growth did not lead to an increase, post-anthesis water stress did.

Signifi cant increases in neurotoxin levels were noted (a doubling in one case), with the stress applied at the most vulnerable stage of early post-anthesis.

A negative relationship between neurotoxin concentration in seeds and the total amount of ODAP in the plant (total seed weight x ODAP concentration) also was established.

This suggested the effect of environment on neurotoxin levels in the seed was a secondary one. The primary effect of the environment was on the growth of the plant, which determined the number of pods, number of seeds and seed weight produced.

Under good conditions, the plant produces more pods and seeds than under poor conditions and reduced neurotoxin concentrations results from toxin dilution.

An experiment was undertaken to alter the ODAP concentration of plants grown under similar environmentally stress-free conditions, by increasing the number of pods, and subsequently the number of seeds developing on the plants.

It showed that under identical unstressed conditions, plants with only 10 pods produced 59 per cent more neurotoxin than plants with 100 pods.

But the possible infl uence of another, unknown factor was not discounted as ODAP concentration in seeds was found to vary across the five podding density treatments, being higher at the lower densities.

Further research is required to clarify this, involving new podding density experiments, but with a larger number of replications and genotypes.

Summary

The research has resulted in the development of Chalus as a high quality Lathyrus cicera variety for low and medium rainfall areas of Australia.

It shows good tolerance to a wide range of herbicides. Weed management packages are now being developed.

Bean yellow Mosaic Virus has been observed to infect Chalus but no other diseases have been recorded. Chalus is not susceptible to fi eld pea black spot, so it can be sown early. It can also be used as another crop legume to widen rotations where blackspot is a serious problem in fi eld pea. Chalus is a high yielding variety. It has consistently performed well over 15 trial sites across southern Australia, yielding on average fi ve per cent more than the grain legume variety, Lath-BC. At dry sites in Western Australia, the average yield of Chalus has been equivalent to or greater than Dundale fi eld pea.

The ODAP neurotoxin concentration in the seed of Chalus is considerably lower (44%) than Lath-BC and average seed quality is slightly greater. Protein levels are good, around 27 per cent, which is slightly lower than narrow-leafed lupins but greater than fi eld peas or faba bean. Chalus' lysine content is high, 5.8 g/16 g nitrogen compared with 4.7 g/16 g nitrogen in narrow-leafed lupins. Fat and fi bre contents are less than narrow-leafed lupins.

The In sacco protein degradability of Chalus is 93per cent, approximately twice the maintenance level for cows. This compares with 94 per cent for chick peas, faba beans and fi eld peas and 90 per cent in narrow-leafed lupins.

Chalus has a quickly soluble fraction of 53 per cent compared with 35 per cent for narrow-leafed lupins. This suggests that Chalus is a source of readily available protein in the rumen and presumably the rest of the animal.
 
 
 

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