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Rural Industries Research & Development Corporation
An Evaluation of Lucerne Varieties for Seed Yield and Strategies to Enhance Seed Production
By Dr Ross W DownesOctober 2002
RIRDC Publication No 02/099 RIRDC Project No IPB-1A
This research program was conducted by Dr Ross Downes, Innovative Plant Breeders,1998-2001, to evaluate lucerne varieties for seed yield and to investigate strategies to enhance seed productivity.
Using the best available agronomic management practices on farms, it was proposed to identify lucerne varieties with the highest seed production. To ensure that this research program was of direct benefit to the lucerne-seed industry, studies were conducted in commercial fields, with supplementary investigations in nurseries and glasshouses.
Findings
Crop establishment and management
Seed yield is determined by the product of two components: number of stems and yield per stem.
• The number of stems in a seed production field is affected by crop establishment, losses due to disease, moisture stress and management.
• Differences in stand or plant population between different fields can have a large effect on variation in yield.
• Yield per stem is determined by the number of pods set which depends on flowers being tripped, and the number of seeds per pod which depend on pollination and fertilisation.
• These components are affected by management, weather, pollinators and varietal characteristics.
Varietal performance
Performance of some varieties is more stable than others under both irrigated and dry land conditions.
Some varieties produce higher yields than others Varieties are variable and contain a proportion of plants with poor seed yield potential Trials in seed production districts can assess seed yield potential and longevity of varieties.
Breeding
There is sufficient variation in lucerne varieties for seed yield to be increased substantially by selection and breeding.
With superior varieties, adequate stand and good management, yields of one tonne per hectare with a value of $3000 should be achieved, a three fold increase over current yields and returns.
Pollination
• Observations during the 2000 season revealed no difference in seed yield in crops in locations close to, and remote from hives.
• Bees were present in crops, collecting nectar without tripping the flowers, and were therefore transferring very little pollen between flowers.
• Bees were seen to be actively collecting pollen from couch grass and weeds and not from lucerne.
Many plants in currently available varieties have flowers which trip automatically and their frequency can be increased by selection and breeding.
Rain during the flowering period affects pollination and fertilisation and can reduce yield potential substantially The risk of rain reducing yield can be minimised by staggering crops to ensure that they pass through the sensitive flowering phase at different times.
Irrigation practices
When overhead irrigation was used there was evidence of reduced numbers of seeds per pod, reflecting lack of fertilisation of ovules.
Seed yield per stem is similar in spring dry land crops , and summer crops which are irrigated four or five times using 600 mm of water.
More efficient water use would save water to allow a three-fold increase in area irrigated.
Spring irrigated seed crops, have the potential to use only 200 mm water.
Implications
Crop establishment and management
Seed yield is determined by the product of number of stems and yield per stem.
Effective crop establishment is essential.
Superior grazing management is needed to avoid plant losses and resowing costs.
Plant diseases such as lucerne yellows cause loss of stand and should be controlled.
Management of both beneficial and destructive insects is important.
Specialist independent crop monitors can provide valuable advice to growers.
Selection of varieties
There is variation in performance of varieties within and between farms.
Plant stand, timing of irrigation, soil characteristics and other management practices have a bearing on varietal performance.
Some varieties were more variable in performance than others and some consistently produced higher yields.
Seed yield and longevity can be assessed in trials.
Breeding
There is sufficient variation in lucerne varieties for seed yield to be increased substantially by selection and breeding.
With superior varieties and good management, yields of one tonne per hectare with a value of $3000 should be achieved, a three fold increase over current yields and returns of $1000/ha.
Growers already achieving 1 tonne/ha can also expect substantial gains.
Pollination
Honey bees as pollinators costs the industry $600,000/year.
The cost effectiveness practice of using honey bees as pollinators is of doubtful value.
Irrigation practices
Seed yield per stem is similar in dry land crops in spring and summer crops which are irrigated four or five times using 600 mm of water.
Spring irrigated seed crops use considerably less water than summer crops More efficient water use would provide a three-fold increase in area irrigated and an increase in returns of seed produced three-fold to $45 million.
Spring crops avoid seed wasp attack which currently reduces export returns by $5million/year.
Recommendations
Crop establishment and management
Growers should take care in sowing to obtain a dense stand of plants Rotational grazing should be used to retain stand Effective treatments for insect and disease attack should be used Crop monitors should be employed to advise on appropriate management strategies Disease resistant varieties should be planted to minimise losses and maintain stand
Selection of Varieties
Varieties should be evaluated for seed production as well as for fodder production For reliable results varieties should be included in seed yield trials for three years and in diverse sites Trials should be conducted by independent operators
Management of Pollination
Seed growers should evaluate effectiveness of honey bees in tripping flowers Seed growers should consider benefits of honey bees against cost of $600,000 per year Potential of leaf-cutter bees to increase yield should be costed Growers should seek varieties with automatic tripping to remove need for pollinating insects
Breeding New Varieties
Breeders should select varieties for increased seed yield Development of varieties with high levels of automatic tripping should be undertaken to reduce cost and unreliability of pollinators Varieties with multiple resistances should be bred to reduce stand loss Germplasm should be evaluated to reduce weather losses in mature crops awaiting harvest
Evaluation of irrigation practices
Dry land seed crops should
be considered to complement irrigated crops Irrigated spring seed crops
should be evaluated to conserve water and reduce seed wasp losses Water
use efficiency in spring and summer seed crops should be examined Growers
should consider having crops flower and mature at different times to spread
loss risk Water stress to stimulate flowering should be evaluated as a
management tool Possible detrimental effects of overhead watering at flowering
time should be examined
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