The International Crops Research Institute for the Semi-Arid Tropics (1CRISAT) genebank in India holds the world's largest collection of 21,594 pearl millet germplasm accessions from 50 countries including 6529 landraces from ten Asian countries. Gap analysis using passport and characterization data and geographical information system tools revealed 134 distinct districts of 14 provinces in India and 12 districts of Punjab province in Pakistan as the major geographical gaps. Different methods of identifying geographical gaps used in the study indicated Chittoor, Karimnagar, Nizamabad, Prakasam and Warangal in Andhra Pradesh; Raigarh in Chattisgarh; Dewas and Rewa in Madhya Pradesh; Buldana and Hingoli in Maharashtra; Malkangiri, Nabarangapur, Naupada and Sundergarh in Orissa; Bhilwara, Chittaurgarh and Kota in Rajasthan; Thiruvallur and Vellore in Tamil Nadu; and Auraiya, Chandauli, Chitrakoot, Gonda, Gorakhpur, Hamirpur, Kushinagar, Mau, Shrawasti and Sonbhadra in Uttar Pradesh as common geographical gaps in India. A total of 208 distinct districts in 12 provinces were identified as gaps in diversity for one or more traits. Among all districts, Beed, Latur and Osmanabad in Maharashtra, India, for all traits; Rajanpur, Muzaffargarh, Multan and Lodhran for panicle length and Chakwal and Sargodha for panicle width in Pakistan; and southern parts of North Yemen and Lahiz provinces in Yemen were identified as gaps in the diversity. In India, Warangal in Andhra Pradesh; Rewa in Madhya Pradesh; Hingoli in Maharashtra; Vellore in Tamil Nadu; and Auraiya, Chandauli, Chitrakut, Gorakhpur and Mau in Uttar Pradesh were identified as gaps in diversity for one or more traits and found common to geographical gaps identified. In Pakistan, Lodhran, Multan and Muzaffargarh were identified as gaps common to probability and diversity methods. Area for exploration should be decided prior to launch of the collection mission in consultation with local government officials and extension officers, who are known to have knowledge in pearl millet cultivation in the identified districts. It is suggested to collect the complete passport data including georeference information while collecting the germplasm.

The ICRISAT genebank, Patancheru, India holds 22,211 pearl millet germplasm accessions from 50 countries, including 19,063 landraces. Among these, 15,904 landraces that were geo-referenced are either thermo-sensitive (52.5%), or photoperiod-sensitive (45.6%), or insensitive to both temperature and photoperiod (2%). Latitude ranges of 10–15°N with 39.6% and 15–20°S with 13.1% of total accessions are the important regions for pearl millet germplasm. A study on climate data of the germplasm collection sites revealed that most accessions from latitudes ranging from 10 to 20° on both sides of the equator were highly sensitive to longer photoperiod (>12.5 h) and/or lower temperature ( < 12°C). Accessions that originated in locations at higher latitudes (>20–35°) on both the hemispheres exhibited low sensitivity to both photoperiod and low temperature, as they were exposed to such climates during their evolution. The accessions that are insensitive to both photoperiod and temperature were few but they originated from locations spread across all latitudes, although the highest numbers were from mid-latitudes (15–20°) in both hemispheres. As germplasm accessions are sensitive to climatic variables such as temperature and photoperiod, recording of location-specific geo-reference data while collecting the germplasm, which can help to elucidate the sensitivity of accessions to temperature and photoperiod, is emphasized. Critical evaluation of photoperiod-sensitive accessions that are late flowering for forage production and the photoperiod-insensitive early-maturing accessions for grain production, multiple cropping and development of parental lines with synchronized flowering for the development of hybrids is suggested.

Kwe Kwe in Midlands of Zimbabwe were identified as gaps common to geographic area and diversity for some or the other traits. For a successful germplasm collection mission to fill the gaps identified, planning should be made in advance in collaboration and consultation with NARS, local government officials and extension officers. It is suggested to collect the complete passport data including georeference information while collecting the germplasm.

The genebank at ICRISAT, Patancheru, India conserves a total of 19,063 pearl millet landraces from latitudes ranging from 33.008 in the Southern Hemisphere (SH) to 34.378 in the Northern Hemisphere (NH). In the present study, the NH was found to be the major region for growing pearl millet landraces (80.5%). More landraces were found at lower latitudes (, 208) in both hemispheres than at higher latitudes. The latitude range of 108-158 in the NH and 158-208 in the SH were found to be important source regions for the prevalence of pearl millet, with 39.6% and 13.1% in the world collection of landraces, respectively. Landraces from lower-latitude regions on either side of the equator varied widely for all traits. Landraces from the 58 -108N latitude region flowered late and grew tall in the rainy and post-rainy seasons and produced more tillers. Landraces from the 108 -158N latitude region produced few tillers and had long and thick panicles with larger seeds. Long-bristled bird-resistant landraces were considerable at latitudes of 108-158S and 208-258S. The minimum temperature at the collection sites was found to be one of the important factors for determining the patterns of the prevalence of pearl millet across the latitudes. Late-maturing, tall and high-tillering landraces from lower-latitude regions were better sources for fodder production. Earlymaturing landraces producing long and thick panicles with large seeds from mid-latitude regions (158-208) in both hemispheres were useful for developing high-yielding cultivars. Using the latitudinal patterns of diversity in pearl millet landraces, missions may be launched to explore high-diversity, under-collected and threatened areas for the collection of materials of interest at latitudes of 158-208.

The genebank at ICRISAT conserves the largest collection of 23,092 pearl millet germplasm accessions originating in 52 countries. A total of 15,979 landraces originating in 34 countries and having geographic coordinates of the collection sites were selected to investigate the geographical distribution of pearl millet traits and diversity in the collection. Results revealed adaptation of pearl millet to latitudes ranging between 33.00°S and 36.91°N. Landraces with early flowering (33-40 days) were predominant in Pakistan, Ghana, Togo and India; with very late flowering (121-159 days) in Sierra Leone and the Central African Republic; with short plant height (80-100 cm) in India, Zambia and Sudan; with tallness (401-490 cm) in Chad, Burkina Faso, Nigeria and the Central African Republic; with high tillering (11-35) in India and Yemen; with high panicle exsertion (11-29 cm) in Ghana, Chad, India and Yemen; with long panicles (75-135 cm) in Nigeria and Niger; with thick panicles (41-58 mm) in Namibia, Togo and Zimbabwe and those with large seeds (16-19 g 1000 seeds-1) were predominant in Togo, Benin, Ghana and Burkina Faso. Collections from Ghana for flowering (36-150 days), Burkina Faso for plant height (80-490), India and Yemen for total (1-35) and productive (1-19) tillers per plant, Niger for panicle exsertion (-45 to 21.0), panicle length (9-135 cm) and thickness (12-55 mm) and Zimbabwe for 1000 seed weight (3.5-19.3 g), were found as important sources for trait diversity. Launching collection missions for trait-specific germplasm is suggested to enrich the world collection of pearl millet at ICRISAT genebank for diversity.