With the central Queensland chickpea harvest looming, growers are being encouraged to familiarise themselves with the different seed defects prior to delivery and ensure marked or weather damaged grain is not retained for next year’s plant.
Seed coat markings are defined as dark marks on the seed coat which are not caused by disease and do not blemish the underlying cotyledons.
Some of the most common markings are blotch/tiger stripe and mosaic which are not related to disease, mould or shrivelled seeds, according to NSW DPI senior research scientist Dr Jenny Wood.
“The 2019/20 Australian Pulse Trading Standards state that ‘tiger striping’ is not classified as defective, however it can look similar to diseased or damaged seeds,” Dr Wood said.
“Additionally, they detract from the clean and uniform appearance preferred by our export customers, so may be discriminated against in the market.
“Mosaic markings are classified as defective, but generally occur at a very low percentage within harvested crops.
“Seed defects from weather damage such as bruising from hail, discolouration/staining and sprouting are classified as defective and will be more prone to cracked seed coats and splitting of seed during harvest and subsequent handling.”
The four-year project was, in part, triggered by reports of some chickpea crops that had very noticeable blotch/tiger striping in central Queensland in 2012, as well as the fact that seed quality downgrading due to pre-harvest weather damage has posed a significant issue in some years.
The project involved field trials, controlled experiments and laboratory evaluations to determine the causes of chickpea seed defects. Several recommendations from this work have now been implemented into the PBA chickpea breeding program to enhance their screening for this defect.
The challenge is that the seed marking defects are only triggered under certain environments, so are not always observed. We now want to develop genetic tools that can be implemented earlier in the breeding cycle and improve selection regardless of the environment.
A grower survey was conducted to ascertain the scale and impact of chickpea defects at delivery during the 2017 season.
The survey found that, of the respondents, 55 per cent suffered discounted or rejected chickpea deliveries due to defects, and for half of these growers these penalties were imposed for more than 50 per cent of their crop.
Defects for which growers were penalised included mould, stained, poor colour, shrivelled, green and foreign material and many growers were penalised for more than one defect.
“While many growers were penalised for mould in 2017, there were reports that seed markings like blotch/tiger stipe and mosaic markings were sometimes mistakenly classified as mould,” Dr Wood said.
“Mistakes like this at grain receival are costly to growers, as the tolerance for mould is much lower than for poor colour.”
The size of the discount varied widely but tended to range between $10 and $100 per tonne. Additionally, many growers then faced costs associated with additional seed cleaning/grading, delivery delays/costs and flow on logistical/opportunity costs including subsequent harvest delays.
“Assuming that grower responses to this survey can be extrapolated across the whole Australian chickpea industry, the total cost of chickpea defects to the Australian chickpea growers in 2017 averaged $143 million which equated to an average of 16 per cent of the gross value of Australian chickpeas,” Dr Wood said.
Key considerations to help growers minimise the incidence of seed defects include:
- To reduce the likelihood of weather damaged, stained and sprouted defective seed, time harvest (and desiccation, if used) to avoid rainfall on mature/dry crops if possible to minimise seed loss (pod drop, shattering, cracked seeds) and risk of price penalties from quality loss (cracked seeds, weather damaged, stained and sprouted).
- Time harvest (and desiccation, if used), aiming to harvest when seed is at 14 per cent moisture content. This will maximise seed weight and therefore yield. But do not harvest at moisture contents higher than 14 per cent as this is the maximum allowed due to risk of seed spoilage and mould during storage.
- Ensure combine harvester settings are optimised for every crop to minimise harvest loss, capture the best quality seed and to remove immature green and small shrivelled seeds.
- Avoid storage of grain when fresh green seeds are present as this increases the likelihood of mould developing during storage. Desiccation prior to harvest will help reduce this. However, desiccation with glyphosate should not be used on crops that are to be kept for seed, as it reduces seed germination. Only use recommended registered chemicals.
- If weather damage occurs, do not retain this seed for planting as it will have lower germination and viability. Always test seed prior to planting.
- Avoid sowing blotch/tiger stripe marked seeds as this may increase the risk of marked seeds at harvest
- The environmental triggers of seed markings still need to be confirmed, however results suggest that avoiding early sowing of chickpeas in environments where blotch/tiger stripe markings are known to occur may help growers minimise the risk of this defect in harvested grain.