More efficient breeding of drought resistant peanuts in India and Australia

• International Crops Research Institute for the Semi Arid Tropics, India
• Indian Council of Agricultural Research, India

Peanut is one of the most drought-tolerant of all grain legumes, and is therefore grown in many of the world's semi-arid cropping regions. It is a particularly important crop in India, which is the world's largest producer. In Australia, most of the crop is grown in Queensland; its production and market potential are expanding.
The Indian crop is mainly grown under rainfed conditions, which means that production is inherently variable. The final yield of the plant is greatly affected by lack of available water during the growth phase. In Australia, this can also be a problem. In both countries the situation is exacerbated by high evaporation rates and the low water-holding capacity of the soils on which much of the growth takes place.
So a high-yielding cultivar that continues to produce well under drought conditions is a priority to enable stability of production. That is why much research for the last decade has attempted to improve performance by selecting plants with good pod yield under adverse conditions. As well as spending time testing plants in large-scale trials under different conditions, a study of plant physiology has revealed the features of the plant that correlate best with drought tolerance.
The previous work had developed low-cost, rapid and easily measured indicators for three significant physiological features of drought-tolerance (amount of water transpired (T), water-use efficiency (W) and harvest index (HI)), thus allowing their potential quantification in large numbers of breeding populations. This project therefore aimed to implement and apply this physiological knowledge to test whether indirect selection using the trait approach could improve the efficiency of selection in large-scale peanut breeding programs.

This project was designed to test whether using the trait approach (indirect selection) could improve the efficiency of selection. In other words, would physiological traits be more effective and efficient indicators than direct selection for pod yield alone?

Scientists first selected elite parents with high levels of drought resistance traits, identified using the trait-based approach drawn from the ACIAR project 'Selection for water use efficiency in food legumes'. A crossing and selection program with these parents then took place at four sites in India and one in Queensland, used either a trait or empirical approach to determine if efficiencies in selection and rate of genetic progress were achievable. Plants were exposed to stressed and non-stressed conditions.
The researchers also made a quantitative assessment of costs and benefits, comparing indirect selection methods with conventional methods (based on yield) to see which gave the most cost-effective results for producing drought-resistant cultivars. They also undertook an economic analysis to predict likely returns from the research.

Both the empirical and trait selection methods were able to select out genotypes under water limited/non-limiting conditions that yielded significantly higher than local check varieties (e.g. from 10-30% higher, depending on location). Although there were only small differences in the efficiency of selection (i.e. rate of genetic progress) between trait and empirical approaches, there was clear evidence that the trait approach was able to identify high-yielding genotypes, with high levels of WUE, which can be assumed to have yield benefits in extreme water stress environments. Thus a strategy of parent selection via the trait approach is recommended to ensure high and stable levels of drought resistance traits (or other target traits) are available in the parental material.

In the extension phase of the project the scientists found that they could refine methods of selection, but they believed the key finding of their data analysis was the need to more accurately measure the key physiological traits. Failure to do will mean lower heritability for traits and consequent reductions in potential gains from a trait-based approach.
In India, progeny were developed that significantly out-yielded locally adapted varieties in each of the country's main peanut-growing regions, in both rainy (rain-fed) and post-rainy (irrigated) seasons. The adoption of higher yielding, more drought tolerant genotypes will improve grower returns and thereby allow better stability of production in drought years. A number of the collaborating ICAR institutions are keen to further test and evaluate the elite ACIAR project selections. They have included the advanced lines in local State evaluation testing programs and in the ICAR All India Coordinated Project for Groundnut (AICORPG) trials conducted throughout the entire country.
In Kingaroy, Australia the Indian germplasm used in the crosses did not appear to be the best choice for local agronomic conditions, and the hybrids did not perform as well as local varieties such as Streeton and Conder, which are highly adapted to a water limited environment. There were however a number of promising selections identified, especially those with ultra-short maturity and high yield potential, which will have definite advantages for Australian peanut breeding program and peanut growers seeking early maturing variety options (for drought and aflatoxin escape). The Australian peanut industry however has strict quality specifications, and these promising lines will now enter the core breeding program as parents for future recombination with lines with more acceptable quality characteristics.
An economic analysis of the benefits of the ACIAR research in developing elite peanut genotypes revealed that in India the adoption (25% after 10 years) of a variety with an average yield advantage of 137 kg/ha (kernel) over the best local check variety would yield economic benefits equivalent to a Net Present Value of 71,970 Lakh Rp ($A287 million) in the 10 years following release of the variety.
Project scientist Mrs M. Asalatha was successful in winning an ACIAR John Allwright fellowship to study for her PhD at the University of Queensland. Four Indian project scientists visited Australian institutions and studied advanced statistical techniques relating to analysis of multi-environment variety trials. Significant among the many papers, articles and other published material arising from the research was the production of ACIAR Proceedings No. 112, 'Breeding of Drought Resistant Peanuts'.