SATrends Issue 53                                                                                                                 April 2005

1.Boon to Sterility Mosaic Resistance
top 

Sterility mosaic (SMD) caused by an eriophyd mite-transmitted Pigeonpea sterility mosaic virus (PPSMV) is the major disease of pigeonpea in the Indian subcontinent. SMD is responsible for yield loss of worth >US$300 million. Plants infected at an early stage of the crop growth result in 0-10% flowering. Late infection results in 40-70% flowering, and poor quality seed.

Various isolates of PPSMV occur in India, which could be broadly grouped as ‘B' and ‘P' types. The B-types are highly virulent and can overcome host-plant resistance selected against P-types. The B-types occur in northern and southern regions, and P-types occur in central regions of India. Host-plant resistance to B-type isolates is scarce and very few pigeonpea genotypes withstand infection. Among these, pigeonpea variety ICP7035, a landrace selected in 1973 from Madhya Pradesh, India, possesses the best resistance against PPSMV.

Since 1973, ICP7035 was evaluated against >10 PPSMV isolates and the genotype was resistant to all. SMD resistance in ICP7035 is highly stable because it is resistant to PPSMV as well as its vector, Aceria cajani. Additionally, ICP7035 is tolerant to fusarium wilt and Alternaria blight. It is a medium duration variety and each plant produces about 90-110 pods per plant. Each pod contains 5 seeds. Fresh seeds are bold (9-12 mm diameter) and suitable as a vegetable. Compared to other varieties, ICP7035 seeds contain the highest percent of digestible carbohydrates, vitamins and micronutrients. Green pod yield ranges between 4500 - 5200 kg ha -1 under irrigated conditions. Dehulled dried seeds (grain) measuring 5-7 mm in diameter are suitable for Dhal (decorticated split seeds). Grain yield ranges between 1200 to 1600 kg ha -1 and 100 dried seed weighs 18 g and contain 19.6% protein, 27.4% dietary fiber and 33% starch and is rich in copper, magnesium and phosphorous.

  ICP7035: A dual-purpose SMD resistant pigeonpea variety. (A) Pod bearing plant; (B) Fresh pods for vegetable purpose; (C) Dried grain; (D) Split seeds (Dhal).

ICP7035 has been released for cultivation in Fiji as Kamica, where it is popularly grown for vegetable purposes and for export to the Caribbean and USA. In 2004, it was released in the Peoples Republic of China as Guimu-4 , where it is used for vegetable, grain and soil conservation purposes. ICRISAT, together with the University of Agriculture Sciences-Bangalore, is releasing this variety in SMD endemic areas of Southern Karnataka, India. Farmers are happy. There is rapid diffusion of this genotype and increasing adoption rates over the last two years in Southern Karnataka. ICRISAT has produced breeder quality seed of this genotype for supply to farmers and seed multiplication agencies.

For further information contact p.lavakumar@cgiar.org or k.saxena@cgiar.org or f.waliyar@cgiar.org

2.Rhythm and blues of sorghum
top 

Researchers have described the importance of the photoperiod-sensitivity of West African sorghum varieties since the sixties. The date of sowing depends on the date of the first rainfall, which varies from year to year. The date of the last rainfall however, is more predictable. Interestingly, landraces of a region flower more or less at the same time, towards the end of the rainy season, and mature on residual soil moisture. Timing is tricky. Grain from early flowers may get damaged by mold, birds or insects, whereas late-flowering varieties are attacked by sorghum midges, or risk exhaustion of soil water before grain filling is complete. Consensus holds that the change in the photoperiod, the only certain environmental signal for the passage of the seasons, is responsible for the timing of the flowering.

Studies conducted by ICRISAT/CIRAD on local landraces in Bamako since 2000 have shown other characters related to photoperiod-sensitivity. When plants are sown before July, a sudden and very strong decrease in the development and growth rhythms is seen after the appearance of the 20 th leaf – new leaves take double the time to emerge, and this coincides with the beginning of jointing. Consequently, the rate of stem growth is reduced by a half when compared with plants sown in August, or with a non photoperiod-sensitive cereal, such as maize.

The agronomical change confers on sorghum crucial adaptability to the African savannahs. First, the reduced rate of growth induces an equivalent reduction in the mineral demand to build the plant tissues. In poor soils with low mineral concentrations, this represents an evident advantage. Second, slow stem growth allows roots to grow deeper and colonize a larger volume of soil, thereby accessing a larger mineral and water reserve. Third, it avoids drought stresses that occurs at the end of the rainy season, and permits leaves of plants sown early to produce and transfer biomass during the phase of grain filling, which lasts one month after the end of the rainy season .

Therefore, farmers of West Africa are wise to sow these well-adapted landraces as soon as possible in the rainy season. The challenge for agronomists and breeders is to discover if it is possible to increase the grain production of these plants without changing their life-cycle, and taking into account the limits on mineral and water availability during the grain filling phase.

For more information contact b.clerget@cgiar.org

3. Boost from Basins
top 

Conservation agriculture sounds like old hat, but its breathing new life into African smallholder farming. Broadly, it's a suite of land and crop management practices to improve productivity, profitability, and sustainability. ICRISAT is working with NGO partners in Zimbabwe to promote an easy-to-implement conservation agriculture package, ideally suited to smallholder farmers in drought-prone areas. The program is supported by the Department for International Development, UK.

The central component in the package is the planting basin. Seeds are planted not along the usual furrow, but in small basins – simple pits, about 15 cm across and 15 cm deep. These basins can be dug without having to plough the field – remember that the majority of smallholder farmers struggle to plough their fields because they lack draft animals.

 
Rainwater basins, and resulting healthy crop stand on left

The principle is straightforward: rather than spreading nutrients and water uniformly over the field, concentrate them in the basins to maximize yield for a given level of inputs. Basins are prepared during the dry season, when demands on family labor are relatively low. When the rains begin, the basins are soon flooded with water – if you plant now, you are ensured of good germination and a healthy crop stand, even if a dry spell follows.

The basin is combined with other crop/soil management practices:

  • Use of crop residues: spreading residues over the field protects against loss of topsoil, and enriches the soil with nutrients.
  • Fertilizer microdosing: even small quantities of fertilizer – as little as half a Coke bottle cap-full per basin – can dramatically increase yields, provided you know how. The trick is to concentrate the fertilizer near the plant (eg, in the basins), and apply it at the right time (the 5-6 leaf stage).
  • Manure treatment: manure is ‘cured' or partly composted for a few weeks before application, to minimize nutrient loss and improve effectiveness.

The basin technology was field-tested last season. This year it is being scaled out across 16 districts in the drier areas of Zimbabwe. Farmers are establishing and managing demonstration plots. Community interest is growing rapidly. But one concern still remains – will farmers invest the labor needed, first for basin preparation and then for weed control (an essential part of the package)? There is an acute shortage of labor in most smallholder communities, not only during the cropping season but also in the off-season (when family members are away, working). The project partners believe the problem can be licked – and so do farmers and community leaders, who have seen the results.

For more information contact s.twomlow@cgiar.org

4. Rustics rev up the response
top 

ICRISAT scientists and students have tested the possibility of using non-formal instruction methods to strengthen the capacity of rural youth in information facilitation processes. Over the last four months, the ICRISAT group also tested the capacity of trained local youth to play the role of supporters or intermediaries in agricultural extension.

The test took place in Addakal in Mahbubnagar District (AP State, India). ICRISAT had conducted an information needs assessment and found that there were gaps in timely access to extension information. An online approach to Q&A between farmers and experts was set up at the rural information hub in Addakal, which is connected to the Internet. A question from a farmer was logged into an online content management system (in Telugu language) and an expert studied it and responded. Nearly all the questions were related to pest and disease problems. It turned out that practically all the questions lacked the contextual information, which the experts needed to provide satisfactory responses. The Q&A therefore went into circles, making the average time for generating a satisfactory response about six days.

Mrs Chandrakala, who knows her pesticides

To reduce the number of information cycles and the time taken in general, ICRISAT provided training on basic notions in soil health, water management and pest management to youth at the rural hub. A group of three individuals received this training for three days at a stretch on-site, and were further given learning opportunities online. Prepared thus, the young operators at the hub and associated villages started adding supplementary and contextual information to questions from the farmers. Over a period two months, the cycling time started to decline, and reached a level of twelve hours in three months. Farmers now are able to get satisfactory responses to their questions the following day. The service is finding a wider following. Satyanarayana Reddy, a farmer in this area, says that he earlier went by whatever advice the pesticide dealer gave him. He believes he receives much better advice now, which is backed by good reasoning. Chandrakala, a woman farmer, is now able to distinguish between various pesticides and their precise uses.

The experiment shows that a blend of non-formal learning approaches with access to ICT can make a difference in the way extension information is available in a typical rural context in India.

For more information contact s.dixit@cgiar.org or G Dileepkumar at vasat@cgiar.org